Karl Fischer Titration
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shambhoiKarl Fischer Titration
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shambhoiIntroduction
The methods used to analyze moisture content in substances range from
the loss-on-drying method to physical, electrical and optical systems.
Moisture content measurement by means of Karl Fischer reagents is now
widely employed as the only reliable chemical method.
Today the method is widely accepted as a moisture content measurement
system for both chemicals and manufactured products. It has been
adopted as an international standard by the International Standards
Organization (ISO), as an American Standard Testing Method (ASTM) in the
United States, and is also included in the German DIN standards and the
British BS system. The method has also been incorporated into Japanese
standards, including the Japanese Industrial Standards (JIS) and Japanese
Agricultural Standards (JAS). It is also included in Japanese pharmaceutical
practice, the official food additive manual, and the Japan Petroleum Institute
Standards.
Development of Karl Fischer Reagents
The German scientist Karl Fischer (1901-1958) first revealed his new
reagent to the world in a paper [NOTE 1] published in 1935. A mixture of
iodine, sulfur dioxide, pyridine and methanol, it was named after its inventor.
As shown in the following formula, Karl Fischer reagents react selectively to
water in specific amounts. Mitchell & Smith subsequently carried out a
detailed study of the reaction [NOTE 2] and published findings that
indicated a reaction of 1 mole of iodine to 1 mole of water. This basic
reaction formula remains in use today.
H2 OI 2 SO 2 3 P y 2 Py HI Py SO 3
Py SO3CH3OH Py HSO4CH3
In recent years, however, the Karl Fischer reaction mechanism has been
studied on a more theoretical level. A published paper [NOTE 3] shows that
the pyridine acts simply as a buffer and that it is not essential to the
reaction. The following reaction formula, in which pyridine is expressed as a
base, has been put forward.
H2OI2SO23BaseCH3OH 2Base HIBase HSO4CH3
Note: Base = Amin. "Base" is sometimes shown as RN.
Characteristics of the Karl Fischer Titration Method
The measurement of moisture content using Karl Fischer reagents is
superior to other methods such as loss-on-drying, distillation and infrared
absorption, or to electrolysis and other electrical methods, for the following
reasons:
(1) The absolute amount of moisture can be determined without a
working curve (in the case of coulometric titration). Moisture
content can be determined accurately, even where moisture is
present at levels of only a few ppm.
(2) Measurements can be taken over short periods of time.
(3) Measurements can be taken using small samples (from a few
mg to a few gm).
(4) The method can be used with liquid, solid and gaseous
samples.
(5) The method is suitable for unstable substances that can alter
when heated.
Mitsubishi Chemical Corporation and Karl Fischer Reagents
Mitsubishi Chemical Corporation recognized early on the advantages of the
Karl Fischer reagent, when it was introduced into Japan in the postwar era.
The company began to investigate this in 1950. It subsequently developed
Karl Fischer reagent SS, a single solution with stable titer that could be used
by anyone in factory research or analytical laboratories. It also developed
and supplied a variety of dehydrating solvents for use with various types of
samples. In addition, Mitsubishi Chemical Corporation developed simple
methods for measuring the moisture content of various substances and
manufactured products. With each new methodology, the company
endeavored to promote the use of the Karl Fischer titration method through
papers for scientific symposiums and society journals (about 60 to date).
In 1985, Mitsubishi Chemical Corporation developed a new Karl Fischer
reagent without the pyridine odor. The new pyridine-free products were
named the "S-Series". The company continues to respond to the needs of its
customers. In 1992, it added the X-Series products, which do not contain
carbon tetrachloride or chloroform, to its range of coulometric reagents.
This manual has been written to provide basic information on Karl Fischer
reagents and analytical methods. As we want this manual to have
immediate application, we have used the Q&A approach to make it easy to
find needed information. We hope that this manual will become a useful
reference guide and one that will serve to build and improve knowledge of
our range of Karl Fischer reagent products.
(1) Fischer, K.; Angew. Chem., 48,394 (1935).
(2) Smith, D.M., Bryant. W.M.D., Mitschell; J.; J.Am.Chem.Soc., 61,2407
(1939).
(3) Verhoef, J.C.; J. Electroanal.Chem., 71,305 (1976), 75,705 (1977).
March 2004
CONTENTS
Capter I: Basic Knowledge
I-1 Questions & Answers about Karl Fischer Reagents
1. Karl Fischer Titration
11
11
Q1 :What are the other methods currently avaikable for the
measurement of moisture content?
Please explain how
these differ from karl fischer titration? 11
Q2 :Please explain briefly how moisture content is measured
using Karl Fischer reagents? 11
Q3 :Could you outline the principle and procedures involved
14
involumetric titration?
Q4 :Please outline the principles and procedures involved in
coulometric titration.
16
Q5 :What is the moisture vaporization method, and when is it
19
used?
2. Karl Fischer Reagent Products
22
Q6 :Wha volumetric titration reagents are available?
Please explain the types of reagents and their uses, and the
methods employed. 22
Q7 :What coulometric titration reagents are there?
Please
explain the types of reagents and their uses, and the
33
methods employed.
3. Applicability of Karl Fischer Titration
37
Q8 :Whaat substances is Karl Fischer titiration suitable for?
37
Q9 :What is interference in the context of the Karl Fischer
titiration?
Please explain what is meant by interference
reactions. 39
Q10:Please outline any methods that can be used to suppress
interference reactions so that Karl Fischer titration can be
employed. 43
4. Procedures for Karl Fischer Titiration
45
Q11:How should we actually carry out volumetric titration?
Please describe the preparations and procedures involved.
45
Q12:How can we actually measure moisture content using
coulometric titration? Please describe the preparations and
51
procedures involved.
Q13:Sampling procedures aro one of the most important aspects
of moisture content measurement.
What are the specific
54
methods and equipment invokved?
5. Officiak Testing Methods and Documentation
59
Q14:Karl Fischer titiration is classed as an official testing method.
59
What Japanese standards have been adopted?
Q15: Please provide some example of the international
standards(ISO)and foreign standards that have been adopted
63
foe the Karl Fischer titration method.
Q16:What reference works aare there concerning Karl Fischer
measurement methods? 65
6. Important Informatiom about Handling and Using Karl Fischer
Reagents 67
Q17:Are there any safety requirements or other precautions that
should be followed when using Karl Fischer reagents? 67
Chapter II Applications Part 1
II-1 Organic Compounds
1.Hydrocarbons
71
72
2.Halogenated Hydrocarbons
74
76
3.Alocohols
4.Ethers
78
5.Phenols
80
6.Ketones
82
7.Aldehydes
85
8.Organic Acids
9.Esters
89
91
10.Organic Acid Salts
93
11.Organic Hydrates
94
12.Amines
96
100
13.Amides, Anilides
14.Nitriles, Cyanohydrins
101
102
15.Hydrazines
16.Other Nitrogenous Compounds
18.Acid Chlorides
103
105
17.Acid Anhydrides
105
19.Quinones
106
20.Peroxides
107
21.Sulfur Compounds
69
108
II-2 Inorganic Compounds
112
1.Metals and Simple Substances
113
2.Inorganic Acids
115
3.Hydroxides
118
4.Oxides
119
121
5.Halides(halogenides)
123
6.Carbonates, Bicarbonates
7.Sulfates, Sulfites
125
8.Other Salts
127
9.Inorfanic Gases
129
Chapter III Applications-2
III-1.Industrial Products
1.Fertilizers
131
133
133
2.Agricultural Chemicals
3.Glasss/Ceramics
135
136
4.Liquefied Petroleum Gases
5.Coals, Tars
6.Petroleum Products
7.Plastics
138
141
143
147
8.Rubber, Rubber Products, Compounding Agents
9.Fibers, Papers
10.Dyestuff Intermediates
11.Pigments
12.Paints
150
152
153
155
156
13.Printing Inks and Imaging Materials
14.Adhesives
15.Soaps and Detergents
16.Cosmetics
158
159
161
163
17.Chemicals & Materials for Electronic Equipment and Electrical Parts
III-2.Foodstuffs
165
167
1.Food Additives and Flavorings
167
2.Cereals and Dried Vegetables
171
3.Sugars and Condiments
4.Confectionery
173
174
5.Dairy Products, Fat Products
176
6.Goument Foods, etc.
III-3.Pharmaceuticals
180
1.Biochemical Products
2.Pharmaceuticals
178
180
182
3.Chinese Herbal Medicines, Biological Tissue, etc.
III-4.Minerals and Natural Products
1.Minerals
184
186
186
2.Natural Products
189
Chapter IV List of Karl Fischer Reagents
191
Chapter V Summary of Selection Procedures for Karl
199
Fischer Reagents
Chapter VI Index
201
Capter I: Basic Knowledge
Capter I: Basic Knowledge
10
Chapter I: Basic Knowledge
Chapter I: Basic Knowledge
I-1. Questions & Answers about Karl Fischer Reagents
1. Karl Fischer Titration
Q1
What are the other methods currently available for the measurement of
moisture content? Please explain how these differ from Karl Fischer
titration?
There are many ways of measuring moisture content. Methods based on
new principles are still being announced. The following table lists the
primary methods in current use. Karl Fischer titration is regarded as the
most useful of these methods by virtue of its wide applicability and its
capacity to measure absolute values. It is the focus of continuing research.
Measurement method
Measuring range
Applications
Interfering substances
Karl Fischer titration
A few ppm - 100%
gases,liquids, solids Oxidizing,reducing substances
Drying
0.01%
solids
Volatile substances, unstable substances
Azeotropic distillation
0.05%
liquids
Volatile water-soluble substances
Colorimetric method
0.1-a few %
solids, liquids
Colored substances
Infrared absorption
0.01-a few %
gases, liquids, solids Alcohol,amine, etc.
Gas chromatography
ppm-a few %
gases, liquids
Substances with the same retention capacity
Dew point method
ppm-a few %
gases
Condensable substances
Electrolysis
1-1000ppm
gases
ROH, RCHO, NH3, HF
0.3%-a few %
Electric resistance
(Conductimetric method)
gases, liquids
Conductive substances
Dielectric constant method
1-a few %
gases, liquids
Substances with high dielectric ratios
Neutron scattering method
a few %
solids
Substances containing hydrogen
gases
Substances that
react with sensing membranes
Quartz oscillation method 1-1000ppm
Q2
Please explain briefly how moisture content is measured
using Karl Fischer reagents?
1. Methods
There are two methods based on the use of Karl Fischer reagents, or Karl
Fischer titration, to measure moisture content.
11
I-1. Questions & Answers about Karl Fischer Reagents
(1) Volumetric titration
(2) Coulometric titration
Your choice should reflect a proper understanding of each method. It is also
essential to use the appropriate reagent in each case. The following table
compares the characteristics of each method.
Item
Volumetric titration
Coulometric titration
Principle
A method of volumetric analysis used to
determine moisture content from the
titrated amount of Karl Fischer reagent
Iodine produced through electrolytic
oxidation undergoes a KF reaction with
water. Moisture content is determined by
measuring the amount of electricity
required to the point where excess
iodine is produced.
Titration reagents
Karl Fischer reagent and titration solvent
(dehydrated solvent)
Anolyte and catholyte
Characteristics
1) Since a Karl Fischer reagent is used as 1) The factors measured are current and
the titration agent, the titer must be
time. Since electrons act as the titration
known in advance.
agent, a standard solution is not
2) A wide range of reagents can be used
required. The method allows
as various dehydrating agents are
measurement of absolute quantities
available.
based on the Faraday constant.
3) The method can be used to measure 2) The same anolyte can be used
moisture content across a wide range.
repeatedly.
However, it is not suitable at the
3) The method is effective for measuring
microgram level.
minute amounts of water. Electricity
can be measured in tiny increments,
so it is possible to measure water in
quantities of a ug
2. Titration Equipment
With Karl Fischer titration, electrical detection methods are used to
determine the end point. It is important to use the following types of titration
equipment.
Volumetric titration : Automatic volumetric moisture meter
Coulometric titration : Automatic coulometric moisture meter
There are now convenient automatic moisture measurement systems
designed for ease of operation.
As Karl Fischer reagents are affected by atmospheric moisture, an airtight
titration cell must be used.
For your information
1. Unlike standard volumetric analysis, it is not possible with Karl Fischer
titration simply to fill a buret with Karl Fischer reagent and add it one drop
12
Chapter I: Basic Knowledge
at a time to a flask or beaker that is exposed to the air. Since Karl Fischer
instantly reacts with atmospheric moisture, the end-point would never be
reached.
2. At present there is no method that allows the color change at the endpoint of Karl Fischer titration to be detected visually. The only method is
to detect minute amounts of surplus iodine electrically.
! Helpful hint -1
How is the end-point detected electrically?
The volumetric and coulometric titration systems currently on the market
employ controlled current voltage detection (constant-current polarization
voltage detection). A constant current of 1-30uA is applied to two platinum
electrodes, and the end-point is detected by measuring the voltage
(polarization voltage) between the electrodes. If the titration solution has a
relatively high water content, a polarization voltage of 300-500mV will be
produced. The voltage varies according to the type of solvent used and the
sample. In general, high voltages are produced in the case of substances
with low conductivity, such as hydrocarbons.
As the Karl Fischer titration continues and the end-point approaches, the
voltage will suddenly drop to 10-50mV. With volumetric analysis, the endpoint is deemed to have been reached after the voltage has remains at this
level for a specific period of time. With commercially available titration
systems, the period is 30-60 seconds. With coulometric analysis, an endpoint voltage is specified, and the end-point is reached when the voltage
falls below that level.
13
I-1. Questions & Answers about Karl Fischer Reagents
Q3
Could you outline the principle and procedures involved in
volumetric titration?
[Principle]
Karl Fischer titration is a volumetric analysis method that takes advantage of
the fact that iodine contained in Karl Fischer reagents reacts quantitatively
and selectively with water, as shown in the following formula.
I2
SO2
H 20
3Base
CH3OH 2Base HI
Base HSO4CH3
The quantification is based on the stoichiometrical principle that 1 mole of
iodine (254g) reacts with 1 mole of water (18g). In practice, the titer of a Karl
Fischer reagent is expressed as a water equivalent. Unlike normal
volumetric analysis methods, the concentration of iodine is not shown. For
example, Mitsubishi Chemical's SS-X Karl Fischer reagent is adjusted so
that 1ml will react with approximately 3mg of water, which means that the
solution contains approximately 42mg of iodine and has a 3mg titer. Once
the water equivalent of a Karl Fischer reagent is known, it is possible to
determine moisture content from the amount used (titrated).
Memo "Titer"
This value is used to determine the quantity of a substance from the amount of
reagent titrated. It shows the equivalent amount of water per unit of volume and
is usually expressed as mgH20/ml.
[Procedures]
a) A dehydrated solvent suitable for the sample is placed in a flask attached
to an automatic volumetric moisture meter (Figure 1).
b) The Karl Fischer reagent is titrated until all water has been eliminated
from the titration flask. (It is not necessary at this time to read the amount
titrated.) The titer of the Karl Fischer reagent is determined using water,
etc.
c) The sample is added.
d) The Karl Fischer reagent, the titer of which (mgH20/ml) has now been
determined, is titrated until the end-point is reached. The end-point is
detected electrically by means of a detection circuit built into the titration
system.
e) Moisture content is determined from the amount titrated according to the
14
Chapter I: Basic Knowledge
following formula:
Moisture content (%)=
Titration quantity (ml) titer (mgH2O/ml)
Sample quantity (g) 1000
100
Measurement system
Buret
Drying tube
Sample
injection port
Automatic
switching valve
Detection
electrode
Drying tube
Titration
nozzle
Titration
bath flask
Rotor
Magnetic stirrer
Karl Fischer reagent
Control system
Display/recording system
Detection
unit
Control
unit
Recording
Display
Figure 1: Automatic Volumetric Moisture Titration System
15
I-1. Questions & Answers about Karl Fischer Reagents
Q4
Please outline the principles and procedures involved in
coulometric titration.
[Principle]
With coulometric titration, electrolytic oxidation is achieved by adding the
sample to an iodide ion solution, instead of the iodine contained in the Karl
Fischer reagent and used as the titration agent for volumetric titration. As
shown in the following formula, electrolytic oxidation produces iodine at the
anode. The electrolytic solution immediately begins to act as a Karl Fischer
reagent and reacts with the water in the sample. At the end of the process,
the excess iodine can be detected electrically.
2I- - 2e I2
According to Faraday's laws, the iodine is produced in proportion to the
quantity of electricity. This means that the water content can immediately be
determined from the Coulombs required for electrolysis. To produce 1 mole
of iodine requires 96485 x 2 Coulomb {current (amperes) x time (seconds)}.
Since 1 mole of iodine reacts with 1 mole of water, the amount of electricity
required to cause a reaction with 1mg of water will be as follows.
96485
2/18020 = 10.71 Coulombs
This means that if electrolysis takes 1 second with a current of 107mA, the
amount of water can be quantified as 10ug. Normally, titration systems sold
over the counter carry out electrolysis at 300-400mA. This design allows
titration at the rate of about 30ug per second.
Memo " Faraday's Laws"
The laws relate to electrolysis.
(1) The mass of an electrolyzed substance deposited on an electrode is
proportionate to the amount of electricity.
(2) The quantity of a substance deposited by a given amount of
electricity is proportionate to its chemical equivalent weight.
Faraday constant = 96485 C/mol
16
Chapter I: Basic Knowledge
[Procedures]
a) Electrolyte solutions (Aquamicron AX and CXU) are introduced into the
anode and cathode chambers of an electrolysis cell (Figure 3) attached
to an automatic coulometric moisture meter (Figure 2).
b) An electrolytic current is passed through the anolyte as it is stirred in the
anode chamber. All water is removed from the electrolysis cell by
producing iodine until the end-point is reached. (It is not necessary at this
time to read the amount titrated.)
c) The sample is then introduced, and the electrolysis process is started
again.Coulometric titration is continued until the end-point is reached.
The end-point is detected electrically by means of a detection circuit built
into the titration system.
d) Moisture content is automatically calculated from the amount of electricity
required for electrolysis in the automatic coulometric moisture meter. The
amount of water is expressed in ug units.
Moisture content (ppm) =
Measured value (ug)
Quantity of sample (g)
Drying tube
Measurement
system
Electrolysis
cell
Titration bath
Sample
injection port
Cathode
chamber
Detection
electrode
Anode
chamber
Catholyte
Cathode
Power source
for electrolysis
current
Anode
Detection
unit
Diaphragm
Anolyte
Display
Control unit
Rotor
Magnetic stirrer
Recording
Figure 2: Automatic Coulometric Moisture Meter
17
I-1. Questions & Answers about Karl Fischer Reagents
(8)
(7)
(1) Anode chamber
(2) Cathode chamber
(3) Anode
(4) Cathode
(5) Diaphragm
(6) Rotor
(7) Drying tube for anode chamber
(8) Drying tube for cathode chamber
(9) Stopper
(10) Sample injection port
(11) Drain cock
(12) Detection electrode
(2)
(9)
(10)
(1)
(4)
(12)
(11)
(3)
(5)
(6)
Figure 3: Electrolysis Cell
! Helpful hint - 2
Are there any criteria to guide the choice between volumetric and
coulometric titration?
The following factors should be taken into account when making this
decision.
(1) Using the characteristics of coulometric titration
The need to check titer is eliminated, since it is not necessary to
standardize the Karl Fischer reagent. This feature is very useful for
reducing the work involved in everyday analysis tasks.
(2) Moisture content as a criterion
Coulometric titration should be used if the moisture content is 1% or
lower. It is especially useful for measuring moisture content at the ppm
level within tolerances of a few ppm.
Coulometric titration can still be used if the moisture content is higher
than about 1%, but it is necessary to use small samples, and analysis
results will be influenced by weighing error. Normally volumetric titration
is used in such cases.
(3) Electrode reactions
Coulometric titration is not used for substances that react with
18
Chapter I: Basic Knowledge
electrodes, such as anilines, diamines and some phenols. Volumetric
titration is carried out using a suitable dehydrated solvent.
(4) Solids that do not dissolve in electrolyte
Solids that do not dissolve in organic solvents can reduce current
efficiency by obstructing electrodes and diaphragms. In principle,
coulometric titration should be avoided in such cases. Use volumetric
titration with a suitable dehydrated solvent, or the moisture vaporization
method.
Q5
What is the moisture vaporization method, and when is it
used?
[Outline]
The moisture vaporization method is used to measure samples of solids that
cannot be dissolved in dehydrated solvents or electrolytes, or samples that
include interfering substances. The moisture content is vaporized by
heating the sample in a flow of dried nitrogen gas. It is then captured in a
dehydrated solvent or electrolyte and subjected to Karl Fischer titration.
Either coulometric or volumetric titration is used.
This method is commonly used with natural substances, such as minerals
and rocks, and with macromolecules such as polymers and rubber. New
areas of use include electronic materials, including printed circuit boards
and wafers, and printing materials, such as toners. This method is also
useful for petroleum products containing additives, such as lubricants.
Convenient moisture vaporization systems are available commercially to suit
various purposes. They can be connected to either volumetric or
coulometric titration systems and used to measure moisture content.
19
I-1. Questions & Answers about Karl Fischer Reagents
[Procedures]
a) Solid samples
i) Nitrogen gas (or air) is first passed through a drying tube (filled with
silica gel or phosphorus pentoxide, etc.) and then supplied at a rate of
approximately 300ml/min. to an oven that is maintained at a suitable
temperature for vaporization.
ii) The sample boat is placed in the heating tube and exposed to the flow of
nitrogen gas to ensure that the heating system is free of moisture.
iii) The sample is immediately placed in the sample boat and inserted into
an oven that is maintained at the required temperature.
iv) The vaporized moisture is absorbed into a dehydrated solvent in a
titration flask (or into an electrolyte in an electrolysis cell).
v) The absorbed water is subjected to Karl Fischer titration.
Vaporization unit
Measurement unit
Drying tube
Carrier gas
Exhaust vent
Temperature regulation
system
Oven
Screw lid
Push rod
Sample boat
Thermocouple
Blowing tube
Heating tube
Oven
Measureme
nt system
Detection electrode
Sample injection port
Ribbon heater
Flowmeter
Magnet
Titration solvent or anolyte
Titration flask or electrolysis cell
Nitrogen
Drying tube
Carrier gas supply unit
Figure 4: A Moisture Vaporization System (for Solid Samples)
b) Liquid samples, such as lubricating oils
i) Approximately 20ml of a base oil (mineral oil, vacuum pump oil, etc.) is
placed in the heating unit of a moisture vaporization system and heated
to 100-150C.
ii) The moisture content of the base oil is totally removed by introducing a
flow of dried nitrogen gas into the moisture vaporization system at the
rate of approximately 300ml/min.
iii) 1-10g of the sample is added to the base oil, which is now free of
moisture.
iv) The vaporized moisture is absorbed into a dehydrated solvent in a
titration flask (or into an electrolyte in an electrolysis cell).
v) The absorbed water is subjected to Karl Fischer titration.
20
Chapter I: Basic Knowledge
Flowmeter
Electrolysis cell
Titration system
Moisture vaporization system
Oven
Temperature regulation system
Nitrogen gas
(300ml/min.)
Drying agent (silica gel, etc.)
Figure 5: A Moisture Vaporization System (for Lubricating Oils)
! Helpful hint - 3
How can we check for accuracy when a moisture vaporization apparatus is
added to the system?
The accuracy of capture is an important concern, since moisture vaporized
in the moisture vaporization apparatus is carried through the heating tube
and blowing tube by means of dried nitrogen gas before being absorbed
into a dehydrated solvent (or into an electrolyte in an electrolysis cell). The
capture ratio (recovery ratio) can be checked using the following three
methods.
(1) Using water
With the water method, which is usually the simplest, 5 or 10ul (5 or
10mg) of water is placed directly into the sample boat using a
microsyringe (capacity: 10ul).
(2) Sodium tartrate dihydrate method (theoretical moisture content:
15.66%)
When using this method, the sodium tartrate dihydrate must first be dried
at 105 C.
(3) Glass capillary pipette method
The glass capillary pipette method is simple and is suitable for checking
amounts in the order of 1,000ug. Glass capillary pipettes are commonly
used in biotechnology fields, and their capacities are extremely precise.
They provide an easy way to obtain a required volume of water by
means of the capillary phenomenon.
Reference:Bunseki, p587, 1995
21
I-1. Questions & Answers about Karl Fischer Reagents
2. Karl Fischer Reagent Products
Q6
What volumetric titration reagents are available? Please explain
the types of reagents and their uses, and the methods employed.
Mitsubishi Chemical Corporation has a range of products to suit every
purpose. Its products can be broadly divided into the following four
categories.
Mitsubishi
Karl Fischer Reagents
Titrant
Can be used in various titer according to anticipated
moisture content
Mitsubishi Dehydrated Solvents
They are suitable as titration solvents for the Karl Fischer
reaction, to dissolve or disperse a sample in order to extract
water.
Mitsubishi Standard Water Methanol
This is used to determine the titer of a Karl Fischer reagent.
The type used depends on the titer. Water methanol can also
be used a titration agent for back titration.
Mitsubishi Standard Liquid
This is used to determine the titer of a Karl Fischer reagent.
Karl Fischer reagents and dehydrated solvents have traditionally been
available in both pyridine types and pyridine-free types, which do not have
the pyridine odor. There is no significant difference in performance between
the two types, and they can be used interchangeably.
22
Chapter I: Basic Knowledge
1. Karl Fischer Reagent SS-Z, SS
Initially the titer of Karl Fischer reagents was unstable, and it was necessary
to use them in the extremely inconvenient form of binary solutions.
Mitsubishi Chemical was the first manufacturer in the world to perfect a
single solution version, which it called "Karl Fischer Reagent SS". In the 50
years since that time, Mitsubishi Chemical has continued to enhance and
expand its technology, and today enjoys an excellent reputation for its
superior products.
Mitsubishi Chemical has also developed Karl Fischer Reagent SS-Z, which
is pyridine-free and does not contain chloroform or methyl cellosolve. Users
can choose from an extensive product range, as listed below.
Product
Titer
Applications
Packaging
10mg
Samples with high moisture
content (40% or higher)
8-12mg/ml
Foodstuffs, Cosmetics
Detergents, etc
500ml bottles
SS-Z
5mg
General normal
samples
4.5-5.5mg/ml
General samples, Organic
solvents
500ml, 1L
bottles
SS-Z
SS
3mg
3mg
General normal
samples
2.5-3.5mg/ml
General samples, Organic
solvents
500ml bottles
SS-Z
SS
1mg
1mg
Samples with low moisture
content (0.1% or lower)
0.7-1.2mg/ml
Organic solvents, Petroleum
products, Gas products
500ml bottles
SS
Purpose
Karl Fischer Reagent SS-Z:
Pyridine-Free and Methyl Cellosolve-Free Types
Instead of pyridine, Karl Fischer SS-Z contains a solid amine. As a result,
the product is free of the pyridine odor. All the ingredients required to
implement Karl Fischer reactions stoichiometrically are included in a single
solution. The product is available in either 5mg/ml, 3mg/ml or 1mg/ml titer.
23
I-1. Questions & Answers about Karl Fischer Reagents
[Characteristics]
a) The titer is stable.Even when stored properly under air-tight conditions,
Karl Fischer reagents tend to lose titer due to self-reaction. With SS-Z,
the titer remains extremely stable and changes at less than 0.05% per
day even when stored at room temperature.
b) SS-Z is suitable even for moisture titration of ketones, which have an
interfering effect.SS-Z does not contain methanol, which reacts with
ketones. The moisture content of ketones can be measured easily by
using SS-Z in combination with the Dehydrated Solvent KTX. (For
aldehydes, use SS in combination with CP or PP Dehydrated Solvent).
c) SS-Z Karl Fischer reagent is available in three titers to suit samples with
different moisture contents. The 3mg/ml product is generally regarded
as a standard type and should be used first.
KarFischer Reagent SS: Pyridine Type
Karl Fischer Reagent SS is the traditional product containing pyridine. Its
performance is similar to that of Karl Fischer Reagent SS-Z. It is available in
a titer of 10mg/ml, making it suitable for samples with a high moisture
content.
For Your Information
Mitsubishi Chemical's series of Karl Fischer reagents are supplied in brown
glass bottles sealed with lids containing packing. Provided that the bottles
are sealed, they can be stored for long periods with only a minimal decline
in titer due to moisture absorption. Once the seal is broken, however,
moisture absorption could cause titer to decline unless storage conditions
are optimal. Care should be taken to close caps tightly.
Karl Fischer Reagent SS is a high-titer product and maintains a stable titer
over long periods. Depending on the storage environment, however, minute
amounts of sediment may be observed. This has no effect on the
effectiveness of the reagent, which can be still used.
24
Chapter I: Basic Knowledge
! Helpful hint - 4
What is the difference between traditional pyridine products and nonpyridine products?
Pyridine-free types use another amine in place of pyridine as the base.
Pyridine requires special handling because of its strange odor. Pyridine-free
products use a liquid or solid amine with a high boiling point in place of
pyridine.
Apart from the base, the composition of pyridine-free types is virtually the
same as traditional products, and safety requirements are identical.
Furthermore, it has been confirmed that the performance of pyridine-free
types is not significantly different from that of traditional types.
The speed of the Karl Fischer reaction varies according to the pH of the
titration liquid, the concentration of sulfur dioxide, the type of organic
solvent used, the amount of sample added, and changes in the matrix. It is
not possible to generalize about the relative speeds of traditional and
pyridine-free products, which should be considered on a case-by-case
basis.
2. Mitsubishi Dehydrated Solvents
Moisture content measurement using Karl Fischer Reagent SS or SS-X
involves the extraction of moisture from a liquid, solid or gaseous sample
into a dehydrated solvent from which all moisture has been removed,
followed by titration. Ideally, titration solvents should have low moisture
content and contain no impurities. However, it is extremely troublesome and
time-consuming to refine solvents through distillation and dry them before
each use. Mitsubishi Chemical has solved this problem by developing a
range of dehydrated solvents so that a solvent suitable for each type of
sample will always be available.
In terms of applications, dehydrated solvents can be broadly categorized
into those used to dissolve samples and those used to prevent interference
reactions. These are shown in the following table. Users should select a
solvent that is suitable for the samples.
25
I-1. Questions & Answers about Karl Fischer Reagents
(1) Mitsubishi Dehydrated Solvents for Use in Dissolving Specimens
A commonly used titration solvent is methanol, which has a large polarity
and considerable capacity to extract water. However, a titration solvent
to which other solvents have been added is desirable for substances
that do not readily dissolve in methanol. Mitsubishi Chemical offers a
range of blended solvents to suit user requirements. Please choose the
type that is suitable for the characteristics of the sample. With some
exceptions, most of the products are blended at 0.2mg/ml or lower.
Principal ingredients
Methanol
Methanol
Chloroform
Methanol
Formamide
Methanol
Ethylene glycol
Name
GEX (pyridine-free)
MS
ML
OL II (pyridine-free)
CM
SU (pyridine-free)
FM
ME
Use
Packaging
General samples
500ml bottles
Petroleum products
Oils and fats
Sugars, proteins
Food additives
Gases
Inorganic salts
500ml bottles
500ml bottles
500ml bottles
Dehydrated Solvents GEX and MS
The solvent most commonly used to extract water from samples is methanol.
The main ingredients of Dehydrated Solvents GEX and MS is methanol that
has been thoroughly dehydrated. In general, these products can be used
immediately to measure moisture content. In addition, a reaction accelerator
has been added to make the reaction between Karl Fischer reagent and
water occur more rapidly than with ordinary methanol. This allows
measurements to be taken quickly and with a clear titration end-point.
[Uses]
Organic solvents (n-heptane, cyclohexane, xylene, toluene, benzene, ethyl
acetate, N,N-dimethylformamide, etc.), inorganic chemicals, pesticides,
pharmaceutical products, fertilizers, synthetic detergents, refrigerants,
foodstuffs, etc.
26
Chapter I: Basic Knowledge
[Characteristics]
a) Minute amounts of water can be measured accurately.
b) The reaction between water and the Karl Fischer reagent occurs rapidly.
c) The end-point can be readily determined and measured over a short
period of time.
d) By first adding salicylic acid, it is possible to measure the moisture
content of amines (strong basicity).
Reference: Muroi, K., Ono, M., Bunseki Kagaku 20, 975 (1971).
Dehydrated Solvents OL II and CM
Dehydrated Solvents OLII and CM are mixtures of dehydrated chloroform
and dehydrated methanol, to which a reaction accelerant has been added.
Applications include petroleum-related JIS and ASTM tests. These
dehydrated solvents are ideal as solvents for petroleum products. They can
also be used to dissolve resins, pharmaceutical products, rubber and other
substances and can sometimes be used as titration solvents for these items.
[Characteristics]
a) Petroleum products, resins and adhesives dissolve well in these products.
b) The reaction between water and the Karl Fischer reagent occurs faster
than with ordinary solvent mixtures.
c) The end-point can be readily determined and measured over a short
period of time.
[Applications]
Crude oil, electrical insulating oil, refrigerator oil, diesel oil, naphtha,
gasoline, resins, adhesives, pharmaceutical products (caffeine, lecithin,
ointments), printing inks, etc.
Dehydrated Solvents SU and FM
In the past the moisture content of sugars and foodstuffs was measured
through drying at normal or low pressures. Measurement required long
periods of time with these methods, however, and samples were frequently
affected by heat decomposition. These drawbacks meant that the results did
not always reflect the true moisture content. Measurements could not easily
be taken even with the Karl Fischer method, since there was no suitable
extraction solvent. Dehydrated Solvents SU and FM developed by Mitsubishi
27
I-1. Questions & Answers about Karl Fischer Reagents
Chemical are mixtures of dehydrated formamide and dehydrated methanol,
to which a reaction accelerant has been added. Substances that dissolve
well in the main ingredient, formamide, include casein, glucose, starch and
lignin. These solvents are therefore ideal for use in the extraction of moisture
from sugars and foodstuffs.
[Characteristics]
a) Sugars and protein dissolve well in these products.
b) The reaction between water and the Karl Fischer reagent occurs rapidly.
c) The end-point can be readily determined and measured over a short
period of time.
[Applications]
Sugars (sugar, drops, caramel, butter sweets, black sugar sweets, malt
syrup, syrup), gelatin (medical capsules, etc.), nucleic acid food additives,
pharmaceutical products, dried vegetables, cereals, animal feeds, wool, etc.
Reference: Muroi, K., Tsutsui, C., Koizumi, H., Nihon Shokuhin Kogyo
Gakkaishi 16, 39 (1969).
Dehydrated Solvent ME
The moisture content of gases can be measured indirectly using the
physical or physical-chemical characteristics of water (see Q1), or by means
of the Karl Fischer method, which involves a direct reaction with the water.
The Karl Fischer method is the more reliable, since the water is captured
directly. It is widely used as the standard method and has been included in
the JIS system and other systems.
Dehydrated Solvent was created as a moisture capturing solvent for use with
gases. It is a mixture of dehydrated methanol and dehydrated ethylene
glycol, to which a reaction accelerant has been added. Moisture content can
be measured easily and accurately by passing a certain amount of gas
through about 100ml of Dehydrated Solvent ME, followed by immediate
titration using a Karl Fischer reagent.
Similar measurements can be obtained with a solvent prepared simply by
mixing Dehydrated Solvent GEX or MS with propylene glycol in the ratio of
3:1 (by volume).
28
Chapter I: Basic Knowledge
[Characteristics]
a) The moisture content in gases can be captured completely, and there is
minimal vaporization of the solvent even when large volumes of gas are
passed through it.
b) The reaction between water and the Karl Fischer reagent occurs rapidly.
c) The end-point can be readily determined and measured over a short
period of time.
[Applications]
Inorganic gases (hydrogen, nitrogen, oxygen, argon, helium, etc.)
hydrocarbons (ethylene, acetylene, propylene, propane, butane, etc.)
Vaporization solvent for plastics, minerals, greases, lubricants, etc. Also
excellent for use with inorganic salts, which dissolve readily in this product.
Reference: Muroi, K., Ono, M., Sekiyu Gakkaishi [Journal of Japan
Petroleum Society] 11 (No. 6), 440 (1968).
K. Muroi, Bunseki Kagaku 20, 975 (1971).
(2) Dehydrated Solvents used to Prevent Interference Reactions
Aldehydes or ketones that include active carbonyls cause interference
reactions by reacting with methanol to produce water (see Q8). To
prevent such reactions and measure moisture content accurately, it is
necessary to use a dehydrated solvent designed for use with ketones.
The same dehydrated solvent can be used with lower carboxylic acid,
which causes a similar reaction. Reactivity varies according to the
specific substance and users should be aware that there are limitations
on the size of the samples that can be measured.
Principal ingredients of solvent
Name
Use
KTX(pyridine-free) Ketones
Propylene carbonate
Diethylene glycol monoethyl ether
Lower carboxylic acid
Chloroform
CP
Ketones
Propylene carbonate
Lower carboxylic acid
Silicone oils
Pyridine
PE
Special-purpose
Ethylene glycol
paints and varnishes
Pyridine
PP
Aldehydes
Propylene glycol
Packaging
500ml bottles
500ml bottles
500ml bottles
500ml bottles
29
I-1. Questions & Answers about Karl Fischer Reagents
Dehydrated Solvents KTX and CP
The method usually employed to measure the moisture content of
substances that react with alcohol, such as ketones and silicon oils, involves
the use of glycolic solvents which show relatively low reactivity, where
generally used, at low temperatures. Dehydrated Solvent KTX is a pyridinefree titration solvent produced by mixing dehydrated propylene carbonate
and diethylene glycol monoethyl ether. It should always be used in
conjunction with Karl Fischer Reagent SS-Z. It cannot be used with
aldehydes.
The main ingredients of Dehydrated Solvent CP are chloroform and
propylene carbonate. With this blended solvent, the moisture content of
substances such as ketones, aldehydes (except acetaldehydes) and
silicone oils can be measured easily at room temperature.
[Characteristics]
a) These solvents limit interference reactions with methanol, allowing
ketones, aldehydes (except acetaldehydes), carboxylic acid, etc., to be
measured at room temperature.
b) These products can be used with aminobenzene group and are
especially suitable for direct titration of aniline.
c) These products can be used to measure trace moisture in silicone oils.
[Applications]
Acetone, methyl ethyl ketone, methyl isobutyl ketone, etc.
Propionaldehyde, butyraldehyde, crotonaldehyde, etc.
Aniline, cresidine, toluidine, anisidine, etc.
Silicone oils
Dehydrated Solvent PE
Dehydrated Solvent PE is a mixture of dehydrated pyridine and dehydrated
ethylene glycol, to which a reaction accelerator has been added. It is used
at the amount of no more than 15ml of sample to 30ml of PE, accompanied
by direct titration using Karl Fischer Reagent SS. With this product it is
possible to suppress the interference reaction that is caused by ketones and
to measure moisture content accurately. The solubility of piridine, which is
one of the main ingredients, also allows the product to be used for special
applications, such as paints.
30
Chapter I: Basic Knowledge
[Characteristics]
a) This solvent allows direct titration of ketones and lower carboxylic acid.
b) PE can be used as a titration solvent for paints, varnishes, etc.
c) With this product the reaction between water and the Karl Fischer reagent
occurs rapidly.
d) The end-point can be readily determined and measured over a short
period of time.
[Applications]
Acetone, cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, acetic
acid, paints, varnishes, etc.
Reference: Muroi, K., Ogawa, K, Bunseki Kagaku 12, 963 (1963).
Dehydrated Solvent PP
Dehydrated Solvent PP is a mixture of dehydrated pyridine and dehydrated
propylene glycol. As a result of work carried out by Mitsubishi Chemical in
relation to active aldehydes, which present the greatest problem in terms of
accurate measurement of moisture content, it is now possible to suppress
two interference reactions (see Q9) and achieve precise measurement
through direct titration with Karl Fischer Reagent SS, simply by adding no
more than approximately 1ml of sample to 25ml of Dehydrated Solvent PP.
In the case of acetaldehydes, which are the most active, about 5ml of
sample is added to 25ml Dehydrated Solvent PP. The resulting mixture is
then expelled with dried nitrogen and titrated.
[Characteristics]
This solvent allows direct titration of active aldehydes.
[Applications]
Acetaldehydes, n-butyraldehyde, iso-butyraldehyde, propionaldehyde,
crotonaldehyde, other higher aldehydes
Reference: Muroi, K., Bunseki Kiki 3 (No.11), 40 (1965).
31
I-1. Questions & Answers about Karl Fischer Reagents
3. Standardization Reagents of Karl Fischer reagents
The titer of Karl Fischer Reagent SS-Z and SS can be standardized using
water, standard water-methanol, standard water solution and sodium tatrate
dihydrate. The most commonly used methods are those involving water,
standard water-methanol and standard water solution. Standard watermethanol is also used as a titration agent for back titration. The following
three standard water-methanol and standard water solution products are
available.
Product
Application
Standard water-methanol
2.0mg/ml
Standardization of Karl
Fischer reagents with titer
of 3~10mg/ml, reverse
titration
Standardization of Karl
Fischer reagents with
potency of 1mg/ml
Standardization of Karl
Fischer reagents with titer
of 1~10mg/ml
Standard water-methanol
0.5mg/ml
Aquamicron standard
water 10mg
Packaging
250ml bottles
250ml bottles
10-ampoule cases
a) Standard water-methanol must be stored in such a way that it cannot
absorb moisture from the atmosphere.
b) Once the seal is broken the moisture content may change because of
atmospheric humidity.
The product should be re-standardized before use as a back titration.
! Helpful hint -5
Why is salicylic acid used to suppress the interference reaction caused by
amines with strong basicity (pKa9 or higher)?
Interference reactions are observed when amines with strong basicity (pKa9
or higher) undergo direct Karl Fischer titration. Consequences of these
reactions can include unstable end points and higher than normal analytical
readings. To suppress these reactions, samples are first treated with acids
to reduce the basicity. Traditionally, acetic acid was used, but this tended to
trigger a reaction producing esters. Other problems include the fact that
acetic acid itself has a high moisture content. Studies concerning the use of
salicylic acid yielded promising results and the following advantages were
identified.
32
Chapter I: Basic Knowledge
a) No esterification reaction during normal titration.
b) Since methanol can be used as the titration solvent, Karl Fischer titration
yields good results.
c) Salicylic acid has a low moisture content.
The fact that salicylic acid is a solid, is a drawback. However, preparation
simply involves the measurement of about 10g of salicylic acid into a titration
flask and the addition of 50ml of Dehydrated Solvent GEX (or MS), then
stirring until dissolved. Up to 70mmol of amines can be measured with 10g
of salicylic acid.
Q7
What coulometric titration reagents are there? Please explain the
types of reagents and their uses, and the methods employed.
Mitsubishi Chemical Corporation offers a range of coulometric titration
reagents to suit user requirements. These products can be broadly
categorized into the following four types.
General-purpose
electrolytes (two types)
These are general-purpose reagents for use with normal
samples.
Ketone electrolyte (one type)
This is used with ketones and lower carboxylic acid, etc.
Check solution (one type)
This product is used for end point checking.
Standard liquid (two types)
This reagent is used to check the moisture meters used in
coulometric titration.
Advice to Users
Electrolytes are of two types; anolyte, which is placed in the anode chamber
of the electrolysis cell, and catholyte, which is placed in the cathode
chamber. Both these products form one pair.
33
I-1. Questions & Answers about Karl Fischer Reagents
Characteristics of the Aquamicron Series
When using the Aquamicron Series of electrolytes it is important to
understand the following characteristics of the products.
a) Very small quantities of water (about 10ug) can be measured
accurately.
b) Titration procedures are very simple.
c) Measurements can be carried out quickly (1-10 minutes).
d) It is not necessary to assess the titer of the reagent.
e) The reagent can be used repeatedly.
f) The composition of the solvents has been enhanced to make them
suitable for immediate use with various samples. This eliminates the
troublesome task of adding other solvents.
1. General-Purpose Electrolytes
The general-purpose Aquamicron Series of products are ideally constituted
to facilitate Karl Fischer reactions with solvents, including methanol and
propylene carbonate. Sample solubility is excellent, and even trace amounts
of moisture can be extracted and titrated coulometrically with ease. These
products also offer superior reagent stability, which is the most important
requirement when measuring minute amounts of water. This means that
measurements can be taken with good reproducibility.
The Aquamicron Series is suitable for a wide range of products including
aromatics and other organic solvents, petroleum products, inorganic
products and gas products.
They are also the ideal reagents for the water vaporization method. A
particularly convenient feature is the fact that they can be used immediately
without the need to add other solvents. Aquamicron products have an
excellent reputation for use in day-to-day moisture measurement for plastics
and other solid samples.
Product
Pyridine-free, chloroform-free
Aquamicron AX
Aquamicron CXU
Pyridine-free
Aquamicron AS
Aquamicron CXU
34
Type
Packaging
Anolyte
Catholyle
500ml glass bottles
5ml ampoules (10 per case)
Anolyte
Catholyle
500ml glass bottles
5ml ampoules (10 per case)
Chapter I: Basic Knowledge
2. Electrolytes for use with Ketones
Ketones are used as industrial solvents and for many other purposes.
Specially prepared Aquamicron products that do not contain methanol must
be used for ketones because they trigger an interference reaction with the
methanol in general-purpose Aquamicron products. The same specially
prepared products are also excellent for use with lower carboxylic acid,
which causes an esterification reaction with methanol.
Aquamicron products prepared for use with ketones can also be used with
usual chemical substances such as alcohols. They should not be used with
non-polar hydrocarbons or halogenated hydrocarbons which have low
permittivity.
Product
Pyridine-free,
chloroform-free
Aquamicron AKX
Aquamicron CXU
Type
Anolyte
Catholyle
Packaging
500ml glass bottles
5ml ampoules (10 per case)
[Applications]
Acetone, methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, silicon
oils, acetic acid, dichloroacetic acid, etc.
Reference: Muroi, K., Fujino, H., Sekiyu Gakkaishi [Journal of Japan
Petroleum Society] 26, 97 (1983).
35
I-1. Questions & Answers about Karl Fischer Reagents
3. Check Solution P
Check Solution P is a solution of organic solvent containing a trace amount
of water (approximately 4mg/ml). It is used to adjust the end point of
coulometric titration by providing surplus water when free iodine is produced
in the electrolytes. It can also be used for day-to-day inspections of
coulometric titration systems. Since methanol is not used as the organic
solvent, this product can also be used with both general-purpose
Aquamicron products and products prepared for use with ketones.
Moisture Content
Packaging
100ml glass bottles with septum caps
3.8-4.2mgH 2 O/ml
[Method of Use]
A red tinge in the anolyte solution indicates the presence of free iodine.
Normally, the measurement of moisture content cannot be initiated. In such
cases, Check Solution P is added to the anolyte as required (until the red
tinge disappears) to supply surplus water and turn all of the iodine into
iodide ions. The end point for the anolyte solution can be fine-tuned by
adding Check Solution P in 100ul increments until the red tinge disappears.
Titration is then started.
Check Solution P can also be used for day-to-day verification of moisture
meter. This is done by precisely measuring the moisture content of the
Check Solution P itself.
4. Water Standard Solution
Aquamicron Water Standard Solution is a water solution containing a
standard amount of water. It is used to verify coulometric moisture meters
and to determine the titer of KF reagents when used in volumetric moisture
meters. The following products are available.
Product
Application
Packaging
Aquamicron Water Standard 0.2mg Verification of moisture meters 5ml ampoules (10 per case)
(coulometric titration)
Aquamicron Water Standard 1mg Verification of moisture meters 5ml ampoules (10 per case)
(coulometric titration)
Aquamicron Water Standard 10mg Determination of titer of KF reagents 8ml ampoules (10 per case)
(volumetric titration)
36
Chapter I: Basic Knowledge
3. Applicability of Karl Fischer Titration
Q8
What substances is Karl Fischer titration suitable for?
One of the most useful characteristics of Karl Fischer titration is its extremely
wide range of applications.
Organic
compounds:
Karl Fischer titration can be used with almost all compounds.
Inorganic compounds:
The scope of application is limited for a number of reasons,
including the fact that inorganic compounds are generally
difficult to dissolve in organic solvents and the fact that many
react with Karl Fischer reagents. For this reason, the
measurement of moisture content in inorganic compounds is
commonly carried out using either the drying method or
other procedures. However, the Karl Fischer method is
useful for compounds that contain volatile substances and
for compounds that are amenable to thermal decomposition.
The following are typical compounds that can be measured directly.
1. Organic compounds
(1) Hydrocarbons
Saturated hydrocarbons, unsaturated hydrocarbons, aromatic
hydrocarbons
(2) Alcohols
Monohydric alcohols, polyhydric alcohols, phenols
(3) Ethers
(4) Acids
Monobasic acids, polybasic acids, sulfonic acids, hydroxy acids, amino
acids
(5) Esters
Organic acid esters, inorganic acid esters, carbamate esters
(6) Aldehydes
Formaldehyde, chloral
(7) Ketones
37
I-1. Questions & Answers about Karl Fischer Reagents
Normal ketones, diisopropyl ketone, benzophenone, benzoin, alizarin,
quinalization, dibenzalacetone, camphor, etc.
(8) Acetals RCH(OR')2
(9) Acid anhydrides (RC=O)2O
(10) Peroxides
Dialkyl peroxide
(11) Nitrogen compounds
Amines (pKa9 or lower)
Aminoalcohols
Amides RCONH2
Nitriles RCN
Azo compounds RN=NR'
Imines RCHNR' Cyanhydrine RCH(OH)CN
Oximes R2C=N'OH
Lactam NH(CH2)nCO
Isocyanide compounds
Nitroso compounds R2N-N=O, nitro compounds RN02
Cyanic acid derivatives HOC=N
Hydroxamic acid RC-NH
O OH
Anilides C6H5NHCOR
Purines, proteins
(12)Halogenated hydrocarbons
(13)Halogenated acyls
(14)Sulfur compounds
Thioether RSR, disulfides RSSR, thiocyanate compounds RSCN,
isothiocyanates RNCS, thioesters RCOSR
2. Inorganic compounds
(1) Organic salts and their hydrates
Sodium acetate, potassium oxalate, sodium tartrate, Ammonium acetate,
barium acetate, lead acetate, ammonium oxalate, etc.
(2) Inorganic salts and their hydrates
Alkaline salts of strong acids, sulfates, acidic sulfates, disulphates,
dithionates, phosphates (I), phosphates (II)
(3) Acids
Sulfur dioxide, hydriodic acid, hydrochloric acid, hydrofluoric acid,
nitric acid, sulfuric acid (92% or lower), phosphoric acid
(4) Chelate compounds
Cobalt complexes
(5) Polytungsten salts
38
Chapter I: Basic Knowledge
Q9
What is interference in the context of the Karl Fischer titration?
Please explain what is meant by interference reactions.
Karl Fischer reagent reacts selectively with water, but its other constituents
may react with substances other than water. In such cases, titration may fail
to reach an end point, or an abnormal amount of Karl Fischer reagent may
be consumed, leading to negative or positive errors in the analysis values.
This type of phenomenon is called an interference reaction. It is necessary
to be aware of this problem when using Karl Fischer titration.
Interference reactions can be broadly divided into the following two types.
Reactions with iodine (or iodide ions)
Reactions with other ingredients of Karl Fischer reaction (mainly
methanol, sulfur dioxide)
The following are examples of substances that cause interference, and
descriptions of the reactions that occur.
1. Reactions with iodine (or iodide ions)
The Karl Fischer method is a form of non-aqueous oxidation-reduction
titration. Since the reaction betwen Karl Fischer reagent and water is a kind
of iodometry, it is subject to interference by substances that trigger an
oxidation-reduction reaction with iodine and iodide ions. Samples containing
substances that react with iodine and iodide ions will therefore produce
positive errors in measurements, while those that contain iodine produced
through the oxidation of hydriodic acid, which is a reactive substance, will
produce a negative error.
(1) Substances that consume iodine (reduction reaction) and
cause a positive error
These are substances that react directly with free iodine in the Karl Fischer
reagent. Because they consume iodine, they have the same effect as water,
which means that the analysis results will be correspondingly higher.
1.1 Organic compounds
(a) Thiol (mercaptan), thiourea and their nitrogen substitutes
2RSH+I2 RSSR+2HI
(b) Hydrazine hydrochloride
Hydrazine hydrochloride reacts on a mole by mole basis
with iodine.
(c) Thio acid
39
I-1. Questions & Answers about Karl Fischer Reagents
2RCSSH+I 2 RCSSSSCR+2HI
(d) Vinyl ether and 2,3-dihydofurane, dihydroprane
ROCH=CH2+I2+R'OH ROCH(OR')CH2I+HI
(e) Ascorbic acid (Vitamin C)
(f) Amines and aminoalcohols (pKa9 or higher)
These consume iodine gradually.
1.2 Inorganic compounds
(a) Ammonia
This reacts with iodine to produce nitrogen iodide
NH3+3I2 NI3+3HI
(b) Hydroxylamines
2NH2OH+3I2+2SO2+2CH3OH 6HI+2HSO4CH3+N2
(c) Ferric chloride
Iron(III) salt causes the following reaction, with the result
that only 5.5 molecules of water are titrated.
FeCl3 6H2O+5.5I2+6SO2+6CH3OH
FeI2+9HI+3HCl+6HSO 4CH3
(d) Metal oxides
Manganese dioxide, ferric oxide and lead dioxide react with
Karl Fischer reagent. However, the reaction is not
quantitatively constant, since these substances do not
dissolve readily in the reagent.
MnO2+I2+2SO2+2CH3OH MnI2+2HSO4CH3
However, interference does not occur with hydrogen
peroxide, sodium peroxide, barium peroxide, pottasium
persulfate or ammonium persulfate, since these substances
react selectively with sulfur dioxide.
H2O2+SO2 H2SO4
Na2O2+SO2 Na2SO4
(e) Weak acids and oxides
Boric acid, metaboric acid, boron oxide and arsenic trioxide
all react with Karl Fischer reagent.
H3BO3+3I2+3SO2+6CH3OH 6HI+3HSO4CH3+B(OCH3)
HBO2+2I2+2SO2+5CH3OH 4HI+2HSO4CH3+B(OCH3)
As2O3+3I2+3SO2+3CH3OH 2AsI3+3HSO4CH3
(f) Salts
In general, the weakly acidic salts of alkaline metals react
with Karl Fischer reagent in the same way as oxides.
Carbonates, bicarbonates, sulfites and pyrosulfites react in
approximately constant amounts.
K2CO3+I2+SO2+CH3OH 2KI+CO2+HSO4CH3
KHCO3+I2+SO2+CH3OH KI+HI+SO2+HSO4CH3
Na2SO3+I2+CH3OH 2NaI+HSO 4CH3
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Chapter I: Basic Knowledge
Na2S2O5+I2+CH3OH 2NaI+SO 2+HSO4CH3
Sodium tetraborate (Na 2B 4O 7) and sodium metaarsenite
react in approximately the same quantities as shown in (d).
The following are examples of salts that cause nonquantitative reactions with Karl Fischer reagent, and salts
for which the reaction mechanism is not fully understood.
Na2CrO4 H2O, Mg(NH4)2(CrO4)2 6H2O, (NH4)2Cr2O7, Na2S
9H2O, 20MoO3 2H3PO4 48H2O, ZrOCl2 8H2O, ZrO(NO3)
2H2O, Al2O(OOCCH3)2 4H2O
(g) Reducing agents
When strong reducing agents are titrated, the amount of
moisture will be higher. Stannous chloride and sodium
thiosulfate react with Karl Fischer in approximately constant
quantities.
SnCl2 2H2O+3I2+2SO2+2CH3OH
SnI4+2HCl+2HI+2HSO4CH3
2Na2S2O3 5H2O+11I 2+10SO2+10CH3OH
2NaI+Na2S4O6+20HI+10HSO 4CH3
Sodium sulfide also reacts with iodine.
Na2S+I2 2NaI+S
(2) Substances that produce iodine (oxidation reactions) and cause a
negative error
(2.1) Organic compounds
(a) Dichloroisocyanuric acid
Iodine is freed through the oxidation of hydriodic acid.
(b) Quinone
Iodine is freed through the oxidation of hydriodic acid.
(c) Peroxy acid
Iodine is freed through the oxidation of hydriodic acid.
RC(O)OOH+2HI I2+H2O+CH3COOH
(d) Peroxides (diasyl)
Iodine is freed through the oxidation of hydriodic acid
(C6H5COO)2+2HI I2+2C6H5COOH
(2.2) Inorganic compounds
(a) Chlorine
Iodine is freed through the oxidation of hydriodic acid
Cl2+2HI I2+2HCl
(b) Oxidizing agents
Moisture content appears lower when strong oxidizing are
measured.
41
I-1. Questions & Answers about Karl Fischer Reagents
(3) Substances that react with hydriodic acid and produce water
Metal oxides and hydroxides.
Oxides and hydroxides of alkaline metals and alkaline earth metals react
in approximately constant quantities with the hydriodic acid in Karl
Fischer reagent.
MO+2HI MI2+H2O
M(OH)2+2HI MI2+2H2O
NaOH+HI NaI+H 2O
CaO+HI CaI2+H2O
e.g. MgO, ZnO, Ag2O, HgO, Cu2O, LiOH, KOH, Ba(OH)2, etc.
However, weakly acidic oxides react much less.
Substances that do not react at all include Al2O3, CuO, NiO
and PbO.
Oxides that react in constant amounts dissolve completely in the Karl
Fischer at the titration end point, but Ni and Al compounds do not
dissolve.
2. Other Substances that react with ingredients of Karl
Fischer Reagents
If methanol is used as the solvent for Karl Fischer reagent and the titration
solvent, the following interference reactions will occur. In the case of
aldehydes, there will be interference resulting from reactions with both sulfur
dioxide and water.
(1) Carbonyl compounds
The following reactions with alcohol cause interference by producing
water, leading to high analysis results. Frequently, the end point will
never be reached.
R2CO+2ROH R2C(OR)2+H2O
RCHO+2ROH RCH(OR)2+H2O
In addition to these reactions, aldehydes also capture water through the
following interference reaction. This results in low analysis results.
C6H5N SO2+RCHO+H2O C6H5NHSO3CH(OH)R
(2) Lower carboxylic acids and their derivatives
Formic acid, acetic acid, monochloroacetic acid and dichloroacetic acid
trigger an esterification reaction with methanol at room temperature (20
C) or higher. This reaction causes interference by gradually producing
water.
CH3COOH+CH 3OH CH3COOCH 3+H2O
Formic acid in particular is not suitable for Karl Fischer titration.
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Chapter I: Basic Knowledge
(3) Silanol and silanol derivatives
If methanol is present during Karl Fischer titration, the silanol in silicon
oils will trigger the following interference reaction.
R3SiOH+I2+SO2+2CH3OH R3SiOCH3+2HI+CH 3SO4H
Q10
Please outline any methods that can be used to suppress
interference reactions so that Karl Fischer titration can be employed.
The countermeasures used to suppress interference depend on the type of
interference reaction.
Basically,
Karl Fischer titration cannot be used with substances that
cause oxidation/reduction reactions. Special preliminary processes
must therefore be used to convert these substances into other
substances before titration.
Where substances react with methanol, Karl Fischer titration is carried
out under conditions that do not involve the use of methanol.
With Karl Fischer Reagent SS-Z and SS, methanol is not used as the
solvent, so it is possible to measure the water content in carbonyl
compounds and other substances simply by using the reagent in
conjunction with a dehydrated solvent formulated for use with
ketones. These expanded range of uses greatly enhances the value
of these products.
In the case of interference substances that do not change when
heated, it is possible to carry out Karl Fischer titration by using a water
vaporization system.
With substances that have strong basicity, such as amines, it is
possible to use Karl Fischer titration if the substances are first
neutralized by adding acid.
Specific examples are shown in the following tables. Individual researchers
should optimize their approaches on the basis of these examples.
43
I-1. Questions & Answers about Karl Fischer Reagents
1. Substances requiring special treatment
Compound
Treatment
Ammonia
Ferric salts
Hydrazine derivatives
Hydroxylamine salts
Thiol (mercaptan)
Sulfuric acid
Thio acid
Thiourea
Add acetic acid.
Add 8-Hydroxyquinoline.
Add acetic acid.
Add sulfur dioxide:pyridine solution (1:1).
Prevent interference by adding olefins (octene, etc.).
If the sulfuric acid is 92% pure or higher, add a large
surplus of pyridine and titrate it as a salt.
Prevent interference by adding olefins (octene, etc.).
Prevent interference by adding olefins (octene, etc.).
2. Using Karl Fischer reagents with interference substances
With ketones, aldehydes, lower carboxylic acid and amines with strong
basicity, titration should be carried out using the Karl Fischer reagent in
conjunction with the reagents shown below.
Substance
Reagent Used
Volumetric titration
Karl Fischer
Reagent SS-Z
Karl Fischer
Reagent SS
Karl Fischer
Reagent SS-Z
Karl Fischer
Reagent SS
Dehydrated Solvent KTX
Karl Fischer
Reagent SS-Z
Karl Fischer
Reagent SS
Karl Fischer
Strong-base amines
(pKa9 and above) Reagent SS-Z
Karl Fischer
Reagent SS
Dehydrated Solvent KTX
Ketones
Aldehydes
Low-grade
carboxylic acid
Coulometric titration
Aquamicron AKX
Aquamicron CXU
Dehydrated Solvent CP
Dehydrated Solvent KTX
Dehydrated Solvent CP
Dehydrated Solvent PP
Aquamicron AKX
Aquamicron CXU
(suitable only for
certain aromatic
aldehydes)
Aquamicron AKX
AquamicronCXU
Dehydrated Solvent CP
Dehydrated Solvent GEX Aquamicron AX
+ salicylic acid
+ salicylic acid
Dehydrated Solvent MS Aquamicron CXU
+ salicylic acid
Note:Do not use Karl Fischer SS with Dehydrated Solvent KTX.
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Chapter I: Basic Knowledge
Measuring Moisture Content of Strong-Base Amines
Put 10g of salicylic acid into a titration flask (electrolysis cell).
Add 50ml of Dehydrated Solvent GEX or MS (100ml in the case
of Aquamicron AX) and mix together. Add the sample (amine)
after dehydrating it with Karl Fischer reagent. Then initiate Karl
Fischer titration. The amount of sample that can be measured
will vary according to the type of amine.
4. Procedures for Karl Fischer Titration
Q11
How should we actually carry out volumetric titration?
Please describe the preparations and procedures involved.
To measure moisture content by means of volumetric titration, you will first
need to prepare the following items.
Titration
agent: Karl Fischer Reagent SS-Z (or SS)
(It is necessary to assess the titer before use.)
Titration solvent: Select the dehydrated solvent to suit the samples.
A Karl Fischer volumetric titration system
(Reagents manufactured by Mitsubishi Chemical can be used with
any commercially available system.)
Next, the amount of the sample is determined according to the anticipated
moisture content.
In general, one of the following three methods of titration are used. The
procedures for each are explained below.
(1) Direct titration
(2) Back titration
(3) Water vaporization
1. Sample Size
It is important to determine the size of the sample according to the moisture
content. If there is excessive moisture, Karl Fischer reagent will be wasted,
and if there is too little, there will be significant effect on titration error and
the results will lack precision. The following table can be used as a guide
when determining the appropriate amount of sample in relation to
anticipated moisture content. The figures shown here assume that the Karl
Fischer reagent has a titer of 3mg/ml. If the titer is different, it will be
necessary to adjust the figures accordingly.
45
I-1. Questions & Answers about Karl Fischer Reagents
Anticipated moisture content (%)
Amount of Sample (g)
0.1 or lower
0.1-0.5
0.5-1
1-5
5-10
10-50
50 or higher
10-20
5
2
0.5
0.3
0.1
0.03
2. Direct titration (standard method)
This is the standard and most commonly used method of volumetric titration.
The sample is dissolved in a dehydrated solvent and titrated with Karl
Fischer reagent. Titration is carried out in a sealed system isolated from the
atmosphere.
[Procedures]
a) Place 25-50ml of dehydrated solvent in a thoroughly dried flask.
b) Titrate the Karl Fischer reagent SS-Z to the end point to remove all
moisture.(This procedure is known as "pre-titration". It is not necessary to
read the titration volume at this stage.)
c) Measure out the sample (A, g) according to the anticipated moisture
content and immediately place it in a titration flask.
d) Titrate to the end point (B, ml) using Karl Fischer SS-Z for which the titer
(F, mg/ml) is known, stirring continuously.
e) Calculate the moisture content (W, %) according to the following formula.
W=
BxF
x 100
A x 1000
3. Back Titration
In the case of solid samples that cannot readily be dissolved in dehydrated
solvents, moisture is extracted by stirring for a specific period. An excess of
Karl Fischer reagent is then added and the sample is left for a specific
period to allow the moisture to react thoroughly with the reagent. The excess
Karl Fischer reagent is then subjected to back titration using standard
water/methanol solution.
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Chapter I: Basic Knowledge
[Procedures]
a) All moisture is removed from the dehydrated solvent using the procedures
described in the previous section.
b) The sample (A', g) is immediately placed in a titration flask.
c) A specific amount (C, ml) of excess Karl Fischer reagent SS-Z (titer
F'mg/ml) is then added and the sample is stirred for the required period of
time.
d) The sample is then titrated to the end point (D, ml) using a standard
water/methanol solution (titer f, mg/mg).
e) Moisture content (W', %) is calculated according to the following formula.
W' =
(C x F')-(D x f )
x 100
A' x 1000
4. Moisture Vaporization Method
The moisture vaporization method is used with solid samples that do not
readily dissolve in dehydrated solvents, or for samples that cause
interference reactions. Moisture vaporization is carried out using a
commercially available moisture vaporization system in combination with a
volumetric titration system.
[Procedures]
a) An oven is maintained at a temperature suitable for vaporizing the
moisture content of the sample. Nitrogen gas, which has previously been
passed through a drying tube, is passed through the moisture
vaporization system at the rate of approximately 300ml/min.
b) The titration system is dehydrated by means of pre-titration in the titration
system in a flow of nitrogen gas.
c) The sample is then quickly transferred to a sample boat and placed in an
oven that has been maintained at the required temperature.
d) The vaporized water is absorbed into a dehydrated solvent (GEX, MS or
ME).
e) Karl Fischer titration is then carried out according to the direct titration
method.
Note:Dehydrated solvent GEX or MS should be used in a mixture
consisting of one part of propylene glycol to three parts of
dehydrated solvent by volume.
47
I-1. Questions & Answers about Karl Fischer Reagents
5. Determining Titer
The titer of the Karl Fischer reagent SS-Z (or SS) that is placed in the titration
system must always be determined before use. Karl Fischer reagent SS-Z
(or SS) is very stable and needs to be tested only once a week, provided
that the bottle is kept airtight. Where particularly high accuracy is required,
titer should be checked daily. Titer can be determined using one of the
following four methods.
Using pure water
Using standard water solution
Using standard water/methanol solution
Using sodium tartrate dihydrate
The characteristics of these methods and the procedures for using them are
described below.
(1) Using pure water
This method is the most accurate, since the standard for determining titer is
water itself. The drawback with this method is the difficulty of measuring
small amounts of water accurately. A microsyringe is used for conveying the
water. It is convenient to use a commercially available dropping bottle with a
small dripping pipette. Each drop from the pipette is 20-30mg.
[Procedures]
The amount of water obtained should be 10-30mg. The procedures are the
same as for direct titration. The following calculation formula is used.
F=S/T
Where F: Titer (mgH2O/ml)
S: Amount of water obtained (mg)
T: Amount of Karl Fischer reagent required for titration (ml)
(2) Using standard water solution
With this method, a standard water solution with a guaranteed value is used
in place of water. Where the value of the standard water solution is around
10mg/g, approximately 1g is obtained. The following calculation formula is
used.
F=S x K/T
Where F: Titer (mgH2O/ml)
S: Amount of standard water solution obtained (g)
K: Guaranteed value of standard water solution (mgH2O/g)
T: Amount of Karl Fischer reagent required for titration (ml)
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Chapter I: Basic Knowledge
(3) Using standard water/methanol solution
Standard water/methanol solution is a standard water solution for which the
moisture content has been accurately determined. It is especially suitable
for determining the titer of Karl Fischer Reagent SS-Z (or SS). The moisture
content is shown in the label (e.g. 2.02mgH2O/ml).
[Procedures]
a) 25-50ml of dehydrated solvent GEX (or MS) is placed in a titration flask.
b) Karl Fischer Reagent SS-Z (or SS) is titrated to the end point to remove all
moisture content. (It is not necessary to read the titration value at this
stage.)
c) 5-10ml of standard water/methanol solution is taken and added to the
dehydrated solvent in the titration flask.
d) The Karl Fischer Reagent SS-Z (or SS) that is to be assessed is titrated.
e) Titer is calculated from the titration volume according to the following
formula.
F=A x f/B
Where F: Titer of Karl Fischer Reagent SS-Z (or SS) (mgH2O/ml)
A: Amount of standard water/methanol solution obtained (ml)
f : Titer of standard water/methanol solution (mgH2O/ml)
B: Amount of Karl Fischer Reagent SS-Z (or SS) titrated (ml)
Note:Standard water/methanol solution has the same expansion
coefficient as methanol. If it is used at a temperature that is
significantly different from the assessment temperature shown
on the label (20C), it will be necessary to correct the volume
(ml) of standard water/methanol solution used.
(4) Using sodium tartrate dihydrate
Sodium tartrate dihydrate is the most stable of the hydrate standard
substances in relation to changes in atmospheric humidity. It has a
theoretical moisture content of 15.66%. The low solubility of commercially
available sodium tartrate dihydrate means that large amounts cannot be
obtained. The amount for 50ml of methanol would be about 200mg or less.
Users should be aware that the crystal size of commercially available
products may vary. If the crystals are too small they may scatter when
added, leading to errors.
49
I-1. Questions & Answers about Karl Fischer Reagents
[Procedures]
The amount of sodium tartrate dihydrate obtained should be around 150mg.
The procedures are the same as for direct titration.
The following calculation formula is used.
F=m x 0.1566/V
Where F: Titer (mgH2O/ml)
m: Amount of sodium tartrate dihydrate obtained (mg)
V: Amount of Karl Fischer reagent required for titration (ml)
! Helpful hint -6
Why does a solution that reached the titration end point change color if it is
left standing?
If a solution is left standing for a period after it has reached the titration end
point, it will turn yellow and will start to consume Karl Fischer reagent again.
Conversely, it may turn the reddish brown color associated with overtitration.
This phenomenon results from contamination by external moisture, and from
the free iodine from the iodide in the solution through the action of ultraviolet
rays and oxygen.
50
Chapter I: Basic Knowledge
Q12
How can we actually measure moisture content using coulometric
titration? Please describe the preparations and procedures involved.
To measure moisture content by means of coulometric titration, you will first
need to prepare the following items.
Electrolytes:
Aquamicron series
To ensure proper functioning, it is essential to use the correct
anolyte-catholyte combination.
A Karl Fischer coulometric titration system
(Aquamicron series products manufactured by Mitsubishi
Chemicals can be used with most commercially available
systems.)
Next, the size of the sample is determined according to the anticipated
moisture content.
There are actually two coulometric titration methods.
(1) Direct titration
(2) Moisture vaporization
1. Sampling amounts
Coulometric titration is suitable for the measurement of trace quantities of
moisture. Sample size is an important consideration as excessive quantities
will extend the time required for analysis.
Normally a sample containing 0.1-5mg of water is used. The guidelines in
the following table assume that the appropriate moisture content range for
coulometric titration is 1% or lower. This is not to say that coulometric
titration cannot be used for samples with a moisture content above 1%. In
such cases, however, the need to obtain samples in extremely small
quantities will increase measurement errors, leading to problems with
accuracy. If possible, volumetric titration should be used in such cases.
Anticipated moisture content (%)
Sample quantity (g)
0-0.05
0.05-0.1
0.1-0.2
0.2-0.5
0.5-2.0
5-10
2
1
0.5
0.1
2. Obtaining a Sample
A carefully dried syringe (1-10ml) should be used. First, flush the syringe 2-3
times with the sample substance. Next, the amount required for the sample
should be taken. A piece of silicon rubber should be attached to the end of
the syringe needle, and the syringe should then be weighed precisely.
The silicon rubber should then be removed, and the sample inserted into the
51
I-1. Questions & Answers about Karl Fischer Reagents
system. The rubber should then be replaced, and the syringe weighed
again. The difference in weights should be equal to the weight of the
sample.
3. Combination of Aquamicron Products
General use
Anolyte
Catholyte
Aquamicron AX or
Aquamicron AS
Aquamicron CXU
With ketones
Aquamicron AKX
Aquamicron CXU
4. Direct Titration
This method is suitable for liquid, solid or gaseous substance that can be
dissolved in Aquamicron. Direct titration should not be used for insoluble
solid samples since these may clog the membranes or affect the efficiency
of the current.
[Procedures]
a) Approximately 100ml of anolyte (Aquamicron AX, AS or AKX) is placed in
an electrolyte cell (Figure 3) that has been carefully dried.
b) The entire contents of a catholyte ampoule (Aquamicron CXU, 5ml) is
placed in the catholyte chamber.
c) An electrolytic current is applied to the anode-cathode while it is stirred to
produce iodine and trigger the Karl Fischer reaction in order to remove all
water from the electrolysis cell. (It is not necessary to read the moisture
content at this stage.)
d) The sample is introduced into the electrolysis cell and coulometric titration
is then carried out until the end point.
e) Moisture content is calculated according to the following formula.
W1=M/S
or
W2=M x 100/(Sx106)
Where W1: Moisture content (ppm)
W2: Moisture content (%)
M: Measurement value (gH2O)
S: Amount of sample (g)
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Chapter I: Basic Knowledge
Silicon rubber
Electrolysis cell
Figure 6: Sampling Syringe
Catholyte chamber
Anolyte chamber
Figure 7: Sample Injection System
5. Moisture Vaporization
With this method, the coulometric titration system is used in conjunction with
a moisture vaporization system. Approximately 150ml of anolyte
(Aquamicron AX or AS) is placed in an electrolysis cell. Two ampoules
(10ml) of catholyte (Aquamicron CXU) are used.
The condition for moisture vaporization should be optimized for the
particular sample. Detailed instructions for various types of samples are
provided later in this manual.
53
I-1. Questions & Answers about Karl Fischer Reagents
Q13
Sampling procedures are one of the most important aspects of moisture content
measurement. What are the specific methods and equipment involved?
At a room temperature of 25C with 50% humidity, the moisture content of
the atmosphere is 0.01mg per 1ml. Depending on the procedures used,
moisture (humidity) may infiltrate the electrolysis cell (or titration flask),
adhere to the equipment used to obtain samples, or adhere to or dissolve in
the sample. It is important to be aware of this possibility as it can lead to
error.
It is also essential to vary sample quantities in accordance with individual
characteristics and moisture content. It is convenient to use commercially
available sampling equipment of the types shown in Figures 9-17. These are
designed to allow samples to be varied according to the particular
circumstances. The procedures for using this equipment are described
below.
1. Liquid Samples
Equipment used with liquid samples includes micro-syringes, syringes,
pipettes and dropper bottles.
(1) Micro-syringes
Micro-syringes are used to obtain specific amounts of water, substances
with a high moisture content, or check solutions for coulometric titration.
Products are available commercially with capacities of 10, 25, 50 and 100ul.
The needle should be as long as possible. Most commercial products have
50mm needles. The following precautions should be taken when using
micro-syringes.
a) Where possible, avoid using the full stroke of the micro-syringe when
measuring the sample. We recommend using 2/3 or less of the stroke.
(This is because the plunger could be contaminated by atmospheric
moisture.)
b) Dry the micro-syringe thoroughly. After the micro-syringe has been
washed with an organic solvent (methanol, etc.) with a low boiling point, it
should be thoroughly dried in a flow of dried nitrogen, etc., and then
placed in a drier.
c) Flush the micro-syringe 2-3 times with the sample.
d) When adding the sample, push the plunger down quickly to ensure that
no sample remains on the tip of the needle.
Sometimes samples are tested by weight using the same procedures as
with syringes. The weight of the sample normally should be determined from
measurements of volume and relative gravity (or density).
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Chapter I: Basic Knowledge
(2) Syringes
These are used for most liquid samples. Glass syringes are most commonly
used, however plastic products (disposable) are also convenient. The most
commonly used commercial products are 1, 2, 5 and 10ml syringes. General
procedures for using syringes are described below.
a) After carefully drying the syringe (figure 6), flush it two or three times with
small amounts of the sample. Then draw in the required amount of the
sample.
b) Attach a piece of silicon rubber to the needle and weigh the syringe.
c) Remove the silicon rubber and insert the syringe needle through the
stopper attached to the side valve of the titration cell (Figure 8). Inject the
sample.
d) Pull out the syringe needle and weigh it accurately with the piece of
silicon rubber attached to the needle.
e) The difference between the two weights is the weight of the sample.
Cap nut
Silicon washer
Common fitting
Figure 8: Stopper
(3) Pipettes
Because a stopper cannot be used with a pipette, the side stopper (or
sample injection stopper) must be removed. With the stopper removed the
experiment is exposed to the air and the results must be corrected for the
infiltration by atmospheric moisture by conducting a blank test for the same
period of time that the flask was open. The method is unsuitable, therefore,
for the coulometric titration used to measure trace amounts of moisture.
The weight of the sample is determined by separate measurement of the
relative gravity (or density). We recommend the use of syringes wherever
possible.
(4) Dropper bottle
Dropper bottle (Figure 9) are used for water or for samples with a high
moisture content. They are especially convenient for measuring water when
determining the titer of Karl Fischer Reagent SS-Z (or SS) using water. With
commercially available products, the pipettes produce droplets of about
30mg each.
55
I-1. Questions & Answers about Karl Fischer Reagents
[Procedures]
a) After carefully drying the dropper bottle, introduce the sample. Attach the
pipette and extract the sample.
b) Accurately weigh all the equipment.
c) Remove the pipette from the dropper bottle and titrate the titration solvent.
d) Replace the pipette on the dropper bottle and weigh the equipment
accurately.
e) The difference between the two weights is the weight of the sample.
(5) Dropper bottle (for high-viscosity substances)
This equipment (Figure 10) is used for samples with the viscosity of treacle.
Procedures are the same as in (4) above.
Figure 9: Dropper bottle
Figure 10: Dropper bottle
(for high-viscosity substances)
2. Solid Samples
The appropriate method must be selected with reference to the varying
characteristics and forms of solid samples. There are commercial products
that are suitable for each method and it is convenient to use these.
As the sample insertion aperture on the titration flask must be opened to
insert the sample, a blank test must be carried out to adjust for the time
while the flask is open. In general, the following procedures are used.
a) Obtain the required amount of sample using a thoroughly dried sampling
bottle.
b) Accurately weigh the sampling bottle.
c) Remove the stopper of the sample insertion aperture on the titration flask
and quickly insert the sample.
d) Close the stopper and record the time that stopper was open. (The lid
should be opened for exactly the same period of time during the blank
test.)
e) Weigh the sampling bottle.
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Chapter I: Basic Knowledge
(1) Upright solid sampling bottle
An upright solid sampling bottle (Figure 11) is used for ordinary
powdered, granular or lumpy samples. This type of sampling bottle is
used frequently.
(2) Angled solid sampling bottle
A drawback with upright sampling bottles is that the sample must be
shaken to some extent to make it drop to the bottom. The angled bottle
solves this problem by means of a half-rotational bend that allows the
sample to fall (Figures 12, 13). The angled-neck bottle is especially
suitable for plastic pellets.
(3) Trace solid sampling bottle
This container (Figure 14) is used to obtain extremely small amounts of
samples with a high moisture content. It is suitable for powdered
samples.
(4) Syringe-type sampling bottle
The syringe-type sampling bottle (Figure 15) is used for consolidated
powders and viscous solids. The sample is drawn into the syringe by
pulling out the plunger, and then expelled the contents into the system by
pushing in the plunger.
(5) Sampling bottle for semi-solids
This container (Figure 16) is used for high-viscosity samples, such as
greases. The sample is first taken onto the sampling spoon (A), which is
then weighed together with the bottle (B). Next, the sample is inserted
into the titration flask together with the sampling spoon. The spoon is
stirred for a period to allow the sample to dissolve. On completion of the
measurement the sampling spoon is returned to the sampling bottle,
which is then weighed. The difference between the two weights is the
weight of the sample.
Figure 11:
Upright Sampling Bottle
Figure 12:
Angled Sampling Bottle
Figure 13:
Angled-neck Sampling Bottle
57
I-1. Questions & Answers about Karl Fischer Reagents
Figure 14: Trace Sampling Bottle
Sample
Figure 15: Syringe-Type Sampling Bottle
Figure 16:
Semi-Solid Sampling Bottle
3. Liquefied Gas Samples
A dual-aperture pressurized sampling bottle and stainless steel pipes are
used. Commercial products are available to suit specific purposes and
these are recommended.
The key requirement for sampling is to ensure that the liquid phase is
introduced into the dehydrating solvent (or electrolyte). Errors may result if
only the gaseous phase is introduced. Also, the entire amount of sample
must be added. The general procedures are summarized below.
a) Position the gas bottle upright or at an angle.
b) Connect a pipe between the gas bottle and the sampling bottle.
c) Introduce the liquid phase into the sampling bottle.
d) Keep the amount of the sample to 80% or less of the vessel's capacity
and determine the weight.
Injection needle
Extension pipe
Figure 17: A Typical Sampling Bottle
58
Chapter I: Basic Knowledge
Gas vent
Aquamicron CXU
Aquamicron AX
Electrolysis cell
Figure 18: Example of an Injection Assembly
5. Official Testing Methods and Documentation
Q14
Karl Fischer titration is classed as an official testing
method. What Japanese standards have been adopted?
Karl Fischer Reagent SS-Z (or SS), dehydrating solvent, and the Aquamicron
series of products all conform with Japanese standards and can be used
with confidence.
1. Japanese Industrial Standards (JIS)
JIS
Name of Standard
C2101
K0068
K0113
Testing methods for electrical insulating oils.
Test methods for water content of chemical products
General rules for methods of potentiometric, amperometric,
coulometric, and Karl-Fischer titrations
Carbon tetrachloride
K0068,K0113
Ammonium nitrate
K0068
Trichloroethylene
K0068,K0113
K1422
K1424
K1508
Cited Standards
59
I-1. Questions & Answers about Karl Fischer Reagents
K1521
K1522
K1527
K1530
K1557
K2211
K2220
K2234
K2242
K2275
K2436
K2437
K2438
K3351
K3362
K4101
K4108
K4109
K4112
K4127
K4129
K4132
K4137
K4148
K4153
K4156
K4809
K6724
K6759
K6910
M8001
M8211
K8231
60
Perchloroethylene
Isopropyl alcohol
Ethylene glycol
Propylene glycol
Testing method of polyether for polyurethane
Refrigerating machine oils
Lubricating grease
Engine antifreeze coolants
Heat treating oils
Crude oil and petroleum products
- Determination of water content
Naphthalene, anthracene, carbazole
Phenols
Pyridine bases
Glycerines for industrial use
Testing methods for synthetic detergent
General testing methods for organic intermediates
Nitrobenzenes
Aminobenzenes
N-Substituted anilines
Benzoic acid
Naphthol
1-Naphthylamine
Anisidine
Dinitrobenzenes
Diphenylamine
Nitrophenols
Analytical methods of explosives
Vinyl Acetate
Testing methods for acrylonitrile
Testing methods for phenolic resins
General testing methods for reagent chemicals
Iron ores-Method for determination of combined water content
Method for determination of combined water
in manganese ores
K0068,K0113
K4101
K4101
K4101
K0068
K2275
K2275
K0068
K3362
K0113
K0068,K0113
K0068,K0113
K0068,K0113
K0068
K0068
K0113
K0113
K0113
K0113
K0113
K0113
K0113
K0113
K0113
K0113
K0113
K0113
Chapter I: Basic Knowledge
2. Japan Pharmaceutical Codex (Revision 14)
General Test Method 27: Moisture Content Test (Karl Fischer Method)
The items listed in the Pharmaceutical Codex that stipulate the use of
moisture content testing by means of Karl Fischer reagent are as follows.
Item
Tolerance (sample amount)
Aspirin aluminum
Aminophylline
Isopropanol
Quinine ethylcarbonate
Ethosuximide
Suxamethonium chloride
Suxamethonium chloride for injection
Berberine chloride
Benzalkonium chloride
Thiamine hydrochloride
Anhydrous citric acid
Clofibrate
Cyclophosphamide
Distigumine bromide
Dextromethorphan hydrobromide
Isosorbide dinitrate
Hydroxyzine pamoate
Potassium guaiacolsulfonate
Metothrexate
Mercaptopurin
Folic acid
Riboflavin sodium phosphate
Protirelin tartrate
Terbutaline sulfate
Chlorobutanol
4.0% (0.15g)
7.9% (0.3g)
0.7%w/v (2ml)
3.0% (0.5g)
0.5% (2g)
8.0-10.0% (0.4g)
10.0% (0.4g)
15.6% (0.3g)
15.0%
5.0% (0.5g)
0.5% (2g)
0.2% (5g)
5.5-7.0% (0.5g)
1.0% (1g)
4.0-5.5% (0.2g, back titration)
1.5% (0.3g)
3.0% (1g)
3.0-4.5% (0.3g)
12.0% (0.2g, special method)
10.0-12.0% (0.2g, back titration)
8.5% (0.2g, special method)
10.0% (0.1g, back titration)
4.5% (0.2g)
0.5% (1g)
6.0% (0.2g)
61
I-1. Questions & Answers about Karl Fischer Reagents
Sorbitan sesquioleate
Propylene glycol
Polysorbate 80
Sodium lauryl sulfate
Polyvinyl pyrrolidone K25
Polyvinyl pyrrolidone K30
Polyvinyl pyrrolidone K90
Macrogol 400
Macrogol 1500
Macrogol 4000
Macrogol 6000
Berberine tannate
0.5% (1g)
0.5% (2g)
3.0% (1g, back titration)
5.0% (0.5g)
5.0% (1.0g)
5.0% (1.0g)
5.0% (1.0g)
1.0% (2g)
1.0% (2g)
1.0% (2g)
1.0% (2g)
6.0% (0.7g)
3. Notes to Official Food Additive List (7th ed., 1999)
General Test Method 17: Moisture Content Test (Karl Fischer Method)
The Karl Fischer method is stipulated for the following food additives.
Item
Tolerance
5'-Inosinic acid sodium salt
5'-Uridine acid sodium salt
Citric acid (anhydrous)
Disodium glycyrrhizate
5'-Cytidine acid sodium salt
Sucrose fatty acid ester
Sodium dehyroacetate
Folic acid
5'-Calcium ribonucleotide
5'-Sodium ribonucleotide
29.0% or lower (0.15g, back titration)
26.0% or lower (0.15g, back titration)
0.5% or lower (2g)
13.0% or lower (0.2g, back titration)
26.0% or lower (0.15g, back titration)
4.0% or lower (back titration)
8.3-10.0% or lower (0.3g, back titration)
8.5% or lower (0.2g, back titration)
23.0% or lower (0.15g, back titration)
27.0% or lower (0.15g, back titration)
4. Japan Petroleum Institute Standards
Test for water in liquid petroleum products (Karl Fischer Method)
JPI-5S-14-76
62
Chapter I: Basic Knowledge
5. Japan LPG Association Standards
Moisture Content Test Method in LPG: Karl Fischer Method
JLPGA-S-02-99
6. Japan Agricultural Standards (JAS)
Vegetable Oils (Karl Fischer Method, moisture content 0.2% or lower) (1969)
Q15
Please provide some examples of the international standards (ISO) and foreign
standards that have been adopted for the Karl Fischer titration method.
Listed below are some examples of standards established by the
International Organization for Standardization (ISO) and the American
Society For Testing and Materials. The BS (U.K.) and DIN (Germany)
systems are also based on these standards.
1. General Testing Methods
(1) Volumetric titration
ISO 760-1978
Determination of water - Karl Fischer method (General method)
ASTM E203-01
Water using Karl Fischer reagent
(2) Coulometric titration
ASTM E1064-92
Water in organic liquids by coulometric Karl Fischer titration
2. Individual Standards
ASTM D1364-95
Water in volatile solvents (Fischer reagent titration method)
ASTM D1533-96
Water in insulating liquids (Karl Fischer reaction method)
ASTM D1631-94
Water in phenol and related materials by the iodine reagent method
ASTM D1744-92
Water in liquid petroleum products by Karl Fischer reagent
ASTM D3277-95
Moisture content of oil-impregnated cellulosic insulation
ASTM D3466-85
Water content of trichlorotrifluoroethane
63
I-1. Questions & Answers about Karl Fischer Reagents
ASTM D3621-84
Water in acetate esters
ASTM D4017-96
Water in paint and paint materials by Karl Fischer method
ASTM D4377-93
Water in crude oils (Karl Fischer) titration
ASTM E700-79
Water in gases using Karl Fischer reagent
ISO 2097: 1972
Glycerols for industrial use - Determination of water content - Karl
Fischer method
ISO 2514: 1974
Acetaldehyde for industrial use - Determination of water content - Karl
Fischer method
ISO 2596: 1994
Iron ores - Determination of hygroscopic moisture in analytical
samples - Gravimetric and Karl Fischer methods
ISO 2753: 1973
Urea for industrial use - Determination of water content - Karl Fischer
method
ISO 3699: 1976
Anhydrous hydrogen fluoride for industrial use - Determination of
water content - Karl Fischer method
ISO 4317: 1991
Surface-active agents and detergents - Determination of water content
- Karl Fischer method
ISO 5381: 1983
Starch hydrolysis products - Determination of water content - Karl
Fischer method
ISO 5791: 1978
Ammonium nitrate for industrial use - Determination of water content Karl Fischer method
ISO 6191: 1981
Light olefins for industrial use - Determination of traces of water - Karl
Fischer method
ISO 7105: 1985
Liquefied anhydrous ammonia for industrial use - Determination of
water content - Karl Fischer method
ISO 7335: 1987
Iron ores - Determination of combined water content - Karl Fischer
method
ISO 10101-1-3: 1993
Natural gas - Determination of water by the Karl Fischer method Part 1: Introduction
64
Chapter I: Basic Knowledge
Part 2: Titration procedure
Part 3: Coulometric titration
ISO 10362-2: 1994
Cigarettes - Determination of water in smoke condensates - part 2:
Karl Fischer method
ISO 11817: 1994
Roasted ground coffee - Determination of moisture content - Karl
Fischer method
Q16
What reference works are there concerning Karl Fischer
measurement methods?
The following is a list of basic references concerning Karl Fischer titration. It
consists mainly of works written by members of the Mitsubishi Chemical
Corporation research team.
1. Mitchell & Smith: Aquametry, 2nd Edition, Part 3 (1980).
2. Funasaka, W., Muroi, M., Suibun no Teiryo [Measuring Moisture Content]
II: Karl Fischer Method (out of print).
Bunseki Raiburari 14 [Analysis Library 14], published by Tokyo Kagaku
Dojin(1969).
3. General Introductions
Muroi, K., "Karu Fissha Ho ni Yoru Suibun no Sokuteiho" [Measuring
Moisture Content Using the Karl Fischer Method] (in Keisoku Gijutsu
[Measurement Technology], 3, 49, 1977).
Muroi, K., "Bunseki Kagaku ni Okeru Mizu" [Water in Chemical Analysis],
(in Bunseki [Analysis] 2, 74, 1979).
4. Papers Concerning Pyridine-Free Types
Kato, H., Ono, M., Kuwata, S.:
(1) "New Karl Fischer Volumetric Reagent Composed of a Base" (in Bunseki
Kagaku 35, 91, 1986).
(2) "Determination of Moisutre by Karl Fischer Coulometric Reagent
Composed of New Bases" (in Bunseki Kagaku 33, 638, 1984).
(3) "Determination of Moisture in Ketones and Lower Carboxylic Acids by
New Karl Fischer Coulometric Reagent"(in Bunseki Kagaku 34, 147,
1985).
65
I-1. Questions & Answers about Karl Fischer Reagents
(4) "Determination of Moisture in Amines by New Karl Fischer Coulometric
Titration"
(in Bunseki Kagaku 34, 805, 1985).
Memo "Outline of official testing methods in other countries"
ISO:
The International Organization for Standardization (ISO) was
established to promote the discussion and adoption of global
standards with a view to facilitating the international exchange
of goods and services and to developing cooperation in the
spheres of intellectual, scientific, technological and economic
activity. Formally established in 1947, ISO has its headquarters
in Geneva, Switzerland. JIS is currently reviewing its standards
with the aim of making them compatible with these international
standards.
ASTM: The American Society For Testing Materials (ASTM) is an
American organization dedicated to science and technology. It
was formed in 1898 to standardize specifications and test
methods, etc., for industrial materials. It has published
numerous ASTM standards which include testing methods.
BS:
British Standards (BS) are standards established by the British
Standards Institution, which was founded in 1901.
DIN:
Industrie Normen (DIN) are standards established by the
Deutsches Institut fur Normung, which was renamed in 1975 to
match the name of the standards.
66
Chapter I: Basic Knowledge
6. Important Information about Handling and Using Karl Fischer Reagents
Q17
Are there any safety requirements or other precautions
that should be followed when using Karl Fischer reagents?
In addition to handling requirements related to the characteristics of Karl
Fischer reagents, there are precautions to be taken in relation to safety and
hygiene. It is important to fully understand both sets of requirements.
1. Safety and Hygiene Requirements
1) Never drink the reagent or inhale it's vapor.
2) Avoid skin contact. If the reagent does come in contact with the skin,
wash it off with soap, etc., and rinse well with water.
3) If reagent splashes into an eye, flush the eye immediately with water, for
at least 15 minutes. The eye should be checked by an eye specialist.
4) Make sure that the room is adequately ventilated when handling Karl
Fischer reagents.
5) Keep the reagents away from naked flames.
6) Observe general rules for handling reagents, including the following.
Organic Solvent Poisoning Prevention Regulations
Injury Prevention Rules For Specified Chemical Substances, etc.
Poisonous and Deleterious Substances Control Law
Fire Prevention Law (hazardous substances)
The regulations vary according to the specific type of reagent. For
detailed information, contact the Mitsubishi Chemical Corporation.
2. Handling Requirements
(1) General Requirements
a) Sampling bottles and other equipment must be dried thoroughly before
use. During testing, take care to prevent contamination by atmospheric
moisture. The following paper includes detailed information about the
prevention of moisture contamination.
Muroi, M., "Measuring Trace Moisture Content Using the Karl
Fischer Method - With Particular Emphasis on the Influence of
Atmospheric Moisture and the Prevention Thereof" (in Bunseki
Kagaku 12, 858, 1963)
b) Check to find out if the sample will cause an interference reaction. If the
sample is one where the interference reaction can be prevented, take the
appropriate steps to do so.
67
I-1. Questions & Answers about Karl Fischer Reagents
c) Store Karl Fischer reagents at or below room temperature and in a
location that is not exposed to the light. Seal bottles to prevent the
absorption of moisture.
(2) Volumetric Reagents
a) Refer to the relevant sections for information about points that require
particular care during volumetric titration, such as changes over time in
the titer of Karl Fischer Reagent SS-Z (or SS), the titer of standard watermethanol and the evaluation procedures.
b) Avoid the following combination when using volumetric reagents;
Karl Fischer Reagent SS and Dehydrating Solvent KTX
Karl Fischer Reagent SS-Z and Dehydrating Solvent CP
(3) Coulometric Titration
a) The analytical capability of Aquamicron AX and AS anolytes is
approximately 800-1,000mgH 2O per 100ml of anolyte. However, if a
sample is added in stages so that the total amount exceeds 150ml, the
sample will have an effect that causes a gradual decline in current
efficiency. This may lead to inaccurate results. In such cases, discard all
the reagent and begin again with fresh reagent.
b) The analytical capability of Aquamicron CXU catholyte is approximately
130-150mgH2O per 5ml of catholyte. With prolonged use, however, the
reagent will gradually turn light brown and then dark brown. If the color
begins to change, the reagent should be completely removed, with a
pipette, etc., and replaced with fresh reagent. Do not add fresh reagent to
discolored reagent.
68
Chapter II: Applications - 1
Chapter II: Applications - 1
69
II-1 Organic Compounds
70
Chapter II: Applications - 1
Chapter II: Applications - 1
This section is a summary of technical knowledge accumulated by
Mitsubishi Chemical Corporation over many years. This information is
included as a guide for those actually using Karl Fischer titration to measure
the moisture content of individual compounds. There are specific examples
for both organic and inorganic compounds.
II-1. Organic Compounds
Karl Fischer titration is the ideal method for measuring the moisture content
of organic compounds. With very few exceptions, it is suitable for almost all
compounds. Measurement is straightforward, as organic compounds can
generally be dissolved in the solvents used with Karl Fischer reagents.
The section of Basic Knowledge gave an overview of the range of
applications, grouped into those that can be measured directly, those that
cause interference but which can be measured after modification, and those
that cause interference. Refer to the relevant parts of the manual for
essential information on the reactive functional groups that cause
interference.
In the Section on Applications, we will describe specific Karl Fischer titration
methods for individual compounds, together with examples that illustrate key
factors to be taken into account when actually using these methods. Of
course, it is impossible to cover every type of substance, so users should
refer to the examples for similar compounds when establishing the
conditions for moisture measurements.
Important!
Some of the examples refer to earlier reagent products.
The latest products are those named as the "reagents to
use". There may be exceptional cases in which
measurements cannot be carried out as shown in the
tables. Users should choose the most appropriate type of
reagent and measurement method.
71
II-1. Organic Compounds
1. Hydrocarbons
Key Points
Hydrocarbons can be measured readily using standard procedures.
Both volumetric and coulometric titration can be used. Moisture content
tends to be very low, however, because of the low water solubility of
hydrocarbons and because of their low water absorption capacity. For
this reason, coulometric titration is suitable.
In the case of volumetric titration, standard dehydrated solvents are
used. Solubility may be inadequate with long-chain hydrocarbons, but
moisture content can be measured through dispersal extraction after
sufficient stirring. Dehydrated solvents formulated for use with oils can
be used to enhance solubility with good effect.
Substances with low moisture content can be measured accurately
using Karl Fischer Reagent SS-Z (or SS) with a low titer.
With coulometric titration, the sample is added directly to the electrolyte
solution (anolyte). Measurement is carried out after dissolution or
dispersal.
In the case of olefins, double bonding may cause interference. using
the electrolyte solution (anolyte), the interference can be lowered.
Examples of substances that can be measured directly:
Ethylene, propylene, butadiene, propane, butane (see the discussion on
industrial LPG in Chapter III: Applications 2, III-1).
Pentane, 2,4-dimethyl pentane, 2,2-methyl pentane, 2,2,4-trimethyl pentane,
octane, 3-methylhexane, decane, octadecane, 2-pentene, dipentene, 1,3pentadiene, isooctane, cyclopentane, methyl cyclopentane, cyclohexane,
methyl cyclohexane, cyclohexene, benzene, toluene, xylene, ethyl benzene,
mesitylene, styrene, naphthalene, diphenyl, decalin, hexamethyl benzene,
anthracene, phenanthrene
72
Chapter II: Applications - 1
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
General-use Dehydrated Solvent GEX (or MS)
Substance
n-Hexane
Benzene
Toluene
Xylene
Dehydrated
solvent
Sample
quantity (g)
General-use
6.5870
8.7206
8.5511
4.3511
"
"
"
(2) Coulometric titration
Reagents used: Aquamicron AX (or AS)
Aquamicron CXU
Substance
n-Pentane
n-Hexane
Isooctane
n-Decane
n-Dodecane
Ligroin
Cyclohexene
1-Hexene
1-Decene
1-Tetradecene
Benzene
Toluene
Xylene
Naphthalene
25-50ml
Measurement
Moisture
value (mg)
content (ppm)
0.25
0.78
0.45
0.72
38
89
53
165
100ml
5ml
Sample quantity
(g)
Measurement value
(g)
Moisture content
(ppm)
2.5775
1.8828
3.4600
2.0480
2.1048
2.1315
2.2335
0.7600
0.7475
1.5460
2.5297
2.5151
2.4930
1.7755
48
37
89
54
63
124
69
54
30
21
334
380
174
129
19
20
26
26
30
58
31
71
40
14
132
151
70
73
All liquid samples can be measured continuously up to 20-50ml, using
approximately the same amounts as shown in the table.
Note: It is convenient to use a syringe-type sampling bottle for
naphthalene. Refer to JIS K2436 for details of the test method.
73
II-1. Organic Compounds
2. Halogenated Hydrocarbons
Key Points
The behavior of halogenated hydrocarbons is similar to that of
hydrocarbons. Measurements can be carried out using standard
procedures without problems.
Both volumetric and coulometric titration can be used, but coulometric
titration is recommended because of the minute amounts of moisture
included in these substances.
In the case of volumetric titration, standard dehydrated solvents are
used. Halogenated hydrocarbons dissolve well in methanol, but
solubility may become inadequate if the substance is added
continuously. With sufficient stirring, however, it will be possible to
extract and measure the moisture content. An effective way of
enhancing solubility is to use dehydrated solvents formulated for use
with oils.
Substances with low moisture content can be measured accurately
using Karl Fischer Reagent SS-Z (or SS) with a low titer.
For coulometric titration, the sample is added directly to the electrolyte
solution (anolyte). Measurement is carried out after dissolution or
dispersal.
There is no interference, even in the case of substances such as vinyl
chloride, with double bonding. Direct titration can be used in the same
way.
Because of the processes used in their production, halogenated
hydrocarbons sometimes contain trace amounts of free chlorine. This
causes interference through the oxidation of iodide ions to produce free
iodine. As a result, the moisture measured will be reduced in proportion
to the amount of free iodine. This can be prevented by using
Dehydrated Solvent MS as the titration solvent, and by agitating the
solution thoroughly before the Karl Fischer titration, to render the free
chlorine inactive. This is because of the reaction between amine and
sulfur dioxide in the dehydrated solvent, as shown in the following
formula.
Cl2+SO2+2CH3OH+2C 5H5N
C5H5NHCl+C5H5NHSO4CH3+CH3Cl
Reference: Muroi, M., Bunseki Kagaku 16, 1061 (1967)
"Determination of Water in Subtances Containing Active
Chlorine by Karl Fischer Titration"
74
Chapter II: Applications - 1
Examples of substances that can be measured directly:
Methyl chloride, vinyl chloride, methylene chloride, methylene iodide,
chloroform, carbon tetrachloride, iodoform, ethyl iodide, ethylene bromide,
ethylidene bromide, 6-chloropropylene, 1,4-dichloro-2-butene,
bromobenzene, iodobenzene,chloronaphthalene, bromonaphthalene
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
General-use Dehydrated Solvent GEX (or MS)
Substance
Chloroform
Carbon Tetrachloride
1,2-Dichloroethane
1,1,2-Trichloroethane
Chlorobenzene
Dehydrated
solvent
Sample
quantity (g)
General-use
14.4999
15.7825
6.1605
14.0776
10.9400
"
"
"
(2) Coulometric titration
Reagents used: Aquamicron AX (or AS)
Aquamicron CXU
25-50ml
Measurement
Moisture
value (mg)
content (ppm)
1.60
0.49
1.48
0.74
0.71
110
31
240
53
65
100ml
5ml
Substance
Sample quantity
(g)
Measurement value
(g)
Moisture content
(ppm)
Methylene chloride
Ethylene chloride
Chloroform
1,1,1-Trichloroethane
1,1,2,2-Tetrachloroethane
Carbon tetrachloride
Chlorobenzene
Methylene bromide
Ethylene bromide
Bromoform
1-Bromotetradecane
1-Bromohexadecane
Tetrabromoethane
Methyl iodide
Ethy iodide
Hexadecyl bromide
3.7445
3.5193
4.1721
3.7146
7.9300
4.4559
3.1038
2.4660
2.2125
2.6518
2.0400
1.0255
2.9079
2.3104
1.9392
1.0067
62
244
332
380
3553
101
207
715
202
1747
168
52
478
476
337
50
17
70
80
102
430
22
67
290
91
659
75
51
164
206
174
50
75
II-1. Organic Compounds
3. Alcohols
Key Points
The moisture content of alcohols can be measured easily using direct
titration. End-points are stable and highly accurate analytical results are
attainable. Both volumetric and coulometric titration can be used.
In the case of volumetric titration, the sample is dissolved in a generaluse dehydrated solvent and titrated. Alcohols dissolve very well in this
type of solvent and there should not be any problems. Solubility may be
inadequate with higher alcohols (such as stearyl alcohol). In such cases
it is appropriate to use dehydrated solvents formulated for use with oils.
Propargyl alcohol interferes with the titration by reacting with the Karl
Fischer reagent.
For coulometric titration, the sample is dissolved in the electrolyte
solution (anolyte). Titration will be prolonged if samples have a high
moisture content (2% or above). We recommend either the reduction of
the sample quantity, or the use of volumetric titration.
Examples of substances that can be measured directly:
-Monohydric alcoholsMethanol, ethanol, isopropanol, alkyl alcohol, n-, iso-, tert-butanol, isoamyl
alcohol, 2-methyl-4-butanol, 2,4-dimethyl-3-pentanol, decanol, dodecanol,
octadecanol, geraniol, citronellol, cyclohexanol, borneol, terpinenol, benzyl
alcohol, cholesterol
-Polyhydric alcoholsEthylene glycol, 1,2-propanediol, 1,3-propanediol, glycerine, 1,4-butanediol,
1,4-butenediol, 2-methyl-1, 3-propanediol, diethylene glycol, pentaerythritol,
D-mannitol, D-sorbitol
76
Chapter II: Applications - 1
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
General-use Dehydrated Solvent GEX (or MS)
Substance
Dehydrated
solvent
Sample
quantity (g)
Methanol
Ethanol
n-Butanol
Ethylene glycol
Propylene glycol
Diphenyl carbinol
General-use
3.8240
2.2102
3.9210
5.5002
5.1726
0.5953
"
"
"
"
"
25-50ml
Measurement
Moisture
value (mg)
content (ppm)
0.43
3.33
0.49
0.46
0.78
0.33
112
1507
125
84
151
554
Samples can be measured continuously up to 20-50ml using
approximately the same quantities as those shown in the table.
(2) Coulometric titration
Reagents used: Aquamicron AX (or AS)
Aquamicron CXU
100ml
5ml
Substance
Sample quantity
(g)
Measurement value
(g)
Moisture content
(ppm)
Ethanol
n-Propanol
i-Propanol
i-Butanol
tert-Butanol
n-Amyl alcohol
Benzyl alcohol
Ethylene glycol
Propylene glycol
Ethylene glycol monoethyl ether
2-Ethyl hexanol
Undecanol
Glycerin
2.1936
2.2488
2.2244
2.2361
2.1829
4.1200
2.9511
3.1536
2.9381
2.6777
0.8310
0.8240
0.7572
3026
1291
590
1043
1315
3024
280
539
1212
639
282
63
930
1379
574
265
467
602
722
95
171
412
239
339
76
1228
Samples can be measured continuously up to 20-50ml using
approximately the same quantities as those shown in the table.
77
II-1. Organic Compounds
4. Ethers
Key Points
The moisture content of ethers can be measured readily using direct
titration. End-points are stable and highly accurate analytical results are
obtainable. The behavior of ethers is similar to that of hydrocarbons.
Both volumetric and coulometric titration can be used.
With volumetric titration, the sample is dissolved in a general-use
dehydrated solvent and measured. Solubility may be inadequate with
ethers that have a high carbon number. In such cases we recommend
the use of dehydrated solvents formulated for use with oils.
In the ether group, the following compounds need special care:
Substances that have double bonding and cause interference - Vinyl
ether (Note 1)
For coulometric titration, add the sample to the electrolyte solution
(anolyte) and take the measurement. With most ethers, measurement
can be carried out without difficulty. With propylene oxide, however,
there is a limit to the quantity of sample that can be added (Note 2).
Examples of substances that can be measured directly:
Dimethyl ether, diethyl ether, isopropyl ether, ethylene oxide, tetramethylene
oxide, methyl carbitol, diethylene glycol, ethylene glycol dimethyl ether,
diphenyl ether, dioxane, tetrahydrofuran
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
General-use Dehydrated Solvent GEX (or MS)
Substance
Dehydrated
solvent
Sample
quantity (g)
-Butyrolactam
Dioxane
Tetrahydrofuran
Propylene oxide
Ethyl vinyl ether
n-Butyl vinyl ether
2,3-Dihydrofuran
General-use
5.6364
4.9618
2.4548
4.3472
0.1833
0.1657
0.2647
78
"
"
"
"
"
"
25-50ml
Measurement
Moisture
value (mg)
content (ppm)
1.18
1.13
2.96
3.09
0.59
0.10
0.65
209
228
1206
711
3200
600
2400
Chapter II: Applications - 1
(2) Coulometric titration
Reagents used: Aquamicron AX (or AS)
Aquamicron CXU
100ml
5ml
Substance
Sample quantity
(g)
Measurement value
(g)
Moisture content
(ppm)
Isopropyl ether
Ethylene glycol monoethyl ether
Diethylene glycol Monoethyl ether
Diethylene glycol Ethyl ether
Dioxane
Tetrahydrofuran
-Butyrolactam
2-Methyl tetrahydrofuran
Propylene oxide
2.0613
2.7175
2.8298
4.5130
2.9090
0.8278
3.1256
4.3290
1.7117
430
653
1094
3961
120
923
507
944
1217
208
240
387
878
41
1115
162
218
711
Note 1: Vinyl ether causes interference by reacting with the Karl Fischer
reagent to produce iodoacetal in accordance with the following
formula.
ROCH=CH2+I2+R'OH ROCH(OR')CH 2I+HI
The same type of interference occurs with 2,3-dihydrofuran and
dihydropyran.
Corrected titration method:
Add a small amount of the sample (0.5g or less) to 50ml of
Dehydrated Solvent CP and titrate this with Karl Fischer
reagent. If the amount added is greater than 0.5g, an
interference reaction will gradually occur.
79
II-1. Organic Compounds
Note 2: It proved possible to add propylene oxide in three amounts of
1.7g (total: 5.1g). Thereafter the analytical readings rose until
finally, an end point was not reached.
With volumetric titration, it proved possible to add 50g and
measure this directly without any problems.
5. Phenols
Key Points
With most phenols the moisture content can be measured directly. As a
general rule there are no limitations with volumetric titration, but it is
important to be aware that limitations do exist in the case of coulometric
titration.
With volumetric titration, the sample is dissolved in a general-use
dehydrated solvent in the same way as for alcohols, before undergoing
Karl Fischer titration. Solubility is not a problem.
Aminophenols cannot be measured in methanol because of
interference reactions. Measurements can be taken, however, by using
a titration solvent prepared by adding salicylic acid to Dehydrated
Solvent MS (see "12. Amines"). The size of the sample used in such
cases should not exceed 2g.
In the case of coulometric titration, anodic oxidation produces a
precipitate that adheres to the anode. The resulting contamination of
the electrode precludes normal electrode performance and reduces the
efficiency of the current. An end point cannot be reached with
hydroquinone and aminophenols. This kind of interference is common
with coulometric titration, and care should be taken when using the
method. In tests carried out by Mitsubishi Chemical Corporation,
however, measurements have proved possible under controlled
conditions, as follows.
To 100ml of Aquamicron AX,
a) approximately 1g of phenol is added to begin with.
b) The total cumulative quantity added is approximately 5g. If there is
too much phenol the efficiency of the current will decline and
gradually lead to higher analytical values.
80
Chapter II: Applications - 1
Examples of substances that can be measured directly:
Phenol, catechol, resorcinol, pyrogallol, guaiacol, picric acid, o-cresol, pcresol, 5-methyl resorcinol, eugenol, p-tert-butyl catechol, -naphthol, naphthol
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
General-use Dehydrated Solvent GEX (or MS)
Substance
Phenol
m-Cresol
Dehydrated
solvent
Sample
quantity (g)
Measurement
value (mg)
General-use
1.9139
2.6048
1.94
1.92
"
(2) Coulometric titration
Reagents used: Aquamicron AX (or AS)
Aquamicron CXU
Substance
Phenol
m-Cresol
o-Cresol
2,6-Xylenol
25-50ml
Moisture
content (%)
0.101
0.074
100ml
5ml
Sample quantity
(g)
Measurement value
(g)
Moisture content
1.8906
2.0319
0.6042
1.4616
1241
242
3048
1737
656ppm
119ppm
0.504%
0.119%
81
II-1 Organic Compounds
6. Ketones
Key Points
If the Karl Fischer reagent and the titration solvent contain methanol,
ketones react with the methanol (ketal bonding) as shown in the
following formula. As it produces water this causes an interference
reaction.
R2CO+2CH3OH R2C(OCH 3)2+H2O
This may increase the time needed to reach the end point, or may mean
that it is never reached. Excessively high moisture readings are among
other phenomena that can adversely affect accuracy and precision.
However, Karl Fischer titration can be carried out if the following
counteracting steps are taken.
a) Use a Karl Fischer reagent and titration solvent that do not contain
methanol.
b) The degree of interference varies according to the type of ketone
compound.Determine the size of the sample to use with reference to
the specific type of compound.
In general, acetone and cyclohexanone show the strongest reactivity
among the aliphatic ketone compounds and reactivity decreases in
proportion to the carbon number. Aromatic ketone compounds are
reported to be less reactive than the aliphatics. Either volumetric or
coulometric titration can be used with these ketones, but a reagent
formulated for ketones should be chosen.
Karl Fischer Reagent SS-Z (or SS) is used for volumetric titration. It
contains absolutely no methanol and can be used safely with ketones.
Use Dehydrated Solvent KTX (or CP), which is formulated for ketones.
For coulometric titration, use a combination of Aquamicron AKX/CXU.
Reference: (1)Reference: Muroi, M, et al., J. Japan Petrol. Inst.,26, 97
(1983)."Determination of Water in Ketones and Silicone Oils
by Karl Fischer Titration Method"
(2) Kato, H.: "Determination of Moisture in Ketones and Lower
Carboxylic Acids by New Karl Fischer Coulometric Reagent"
(in Bunseki Kagaku 34, 147, 1984).
82
Chapter II: Applications - 1
Examples of substances that can be measured directly:
The following inactive carbonyl compounds can be added to methanol
(Dehydration Solvent GEX, MS) and measured directly.
Di-isopropyl ketone, camphor, benzophenone, deoxybenzoin, benzyl,
benzoin, alizarin, quinalizarin, ninhydrin
For other substances, use a ketone-type reagent.
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Ketone-type Dehydrated Solvent KTX (or CP, PP) 25-50ml
Substance
Dehydrated
solvent
Sample
quantity (g)
Measurement
value (mg)
Moisture
content (%)
Acetone
Acetylacetone
Methyl ethyl ketone
Methyl isobutyl ketone
Cyclohexanone
Acetophenone
Furfural
Diacetone alcohol
Ketone-type
1.4616
1.8327
2.2490
2.2779
0.8839
2.0562
0.5799
1.8455
3.31
1.46
1.13
0.44
0.80
3.58
5.94
3.33
0.23
0.080
0.050
0.019
0.090
0.17
1.02
0.18
"
"
"
"
"
"
"
Note: Dehydrated Solvent KTX should be used in combination with
Karl Fischer Reagent SS-Z, and Dehydrated Solvents CP and
PP with Karl Fischer Reagent SS.
A feature of Dehydrated Solvents KTX and CP is that they can be used to
take measurements at normal temperatures. This is particularly convenient
as interference can be suppressed and measurements made without
regulating the reaction temperature.
Dehydrated Solvent KTX must always be used with a pyridine-free Karl
Fischer Reagent SS-Z. A normal end point will not be achieved if Karl
Fischer Reagent SS is used.
In general, the interference state of ketones is ascertained through the
continuous addition of reagent. When the analytical reading begins to
appear abnormally high, it should be assumed that interference has begun.
Beyond that point, analytical readings must be discarded.
83
II-1 Organic Compounds
(2) Coulometric titration
Reagents used: Aquamicron AKX
Aquamicron CXU
Substance
Acetone
Methyl ethyl ketone
Methyl isobutyl ketone
Acetylacetone
Acetophenone
Cyclopentanone
Cyclohexanone
Diacetone alcohol
2-Methoxy-2-methyl-4 -pentanone
100ml
5ml
Sample quantity Measurement value MoistureContent
(g)
(%)
(g)
0.3954
0.4141
0.8010
0.9760
0.5451
0.4955
0.3117
0.9602
1.8963
907
464
102
683
215
1090
635
217
81
0.229
0.112
127ppm
0.700
394ppm
0.220
0.204
226ppm
043ppm
Measurable
amount (ml)
10
15
15
15
15
5
2
It is important to be aware of patterns of blank current (also described as
"background" or "drift" current) in the moisture meter. If a gradual rise in the
blank current causes the end point to fluctuate, it will not be possible to
obtain accurate analytical results. In such cases the electrolyte must be
replaced.
84
Chapter II: Applications - 1
7. Aldehydes
Key Points
If the Karl Fischer reagent and the titration solvent contain methanol,
aldehydes react with the methanol (acetal bonding) as shown in the
following formula. As it produces water, this causes an interference
reaction.
RCHO+2CH 3OH RCH(OCH 3)2+H2O
This may cause end point fluctuation, or may mean that the end point is
never reached. Other phenomena include excessively high moisture
readings.
As shown in the following formula, aldehydes may also react with an
ingredient in the Karl Fischer reagent (sulfur dioxide), causing an
interference reaction that consumes water (bisulfite addition) and
reduces the moisture content reading.
C5H5NSO2+RCHO+H2O C5H5NHSO3CH(OH)R
Furthermore, since aldehydes are more reactive than ketones, the
reaction speed will vary considerably according to the specific
aldehyde involved. Because of these complex problems it is very
difficult to obtain accurate analytical readings for aldehydes.
In general, Karl Fischer titration can be carried out if the following
counteracting steps are taken.
a) Use a Karl Fischer reagent and titration solvent that do not contain
methanol.
b) Keep the size of the sample used for titration to a minimum to
suppress the reaction that consumes water.
c) Acetaldehydes are highly reactive and must be titrated under special
conditions.These are described later in this manual.
With coulometric titration, sulfur dioxide in the electrolytic solution
causes interference that leads to low moisture readings. Although an
end point may be reached the analytical reading is unlikely to be
accurate and using this method is difficult. In practice, this method
should never be used with acetaldehydes.
Reference: Muroi, K, et al., Bull. Chem. Soc. Japan, 38,1176 (1965).
"The Determination of the Water Content in Acetaldehyde by
Means of Karl Fische Reagent"
85
II-1 Organic Compounds
Examples of substances that can be measured directly:
The following inactive carbonyl compounds can be dissolved in a generaluse dehydrated solvent and measured directly.
Formaldehyde,
chloral
However, these substances tend to react with methanol at room temperature
(above 25C) and we recommend a titration method whereby the sample is
dissolved in a ketone-type dehydrated solvent.
[Examples of Measurement]
(1) Volumetric titration
Reagents used:Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent KTX (or CP)
25-50ml
Substance
Dehydrated
solvents
Sample
Quantity (g)
Measurement
Value (mg)
Moisture
Content (%)
n-Butyraldehyde
Isobutyraldehyde
Crotonaldehyde
Propionaldehyde
Formalin
Chloral hydrate
Ketone-type
0.4020
0.3952
0.4239
0.2014
0.0328
0.1752
3.56
0.96
0.67
7.36
17.42
19.27
0.886
0.243
0.158
3.65
53.1
11.0
"
"
"
General-use
"
Note: Dehydrated Solvent KTX should be used in combination with
Karl Fischer Reagent SS-Z, and Dehydrated Solvent CP with
Karl Fischer Reagent SS.
Measuring moisture content in acetaldehydes
Given the intensity of the interference reaction that occurs with
acetaldehydes, Dehydrated Solvent PP should be used as it contains no
pyridine-sulfur dioxide. The following guidelines should apply.
If the acetaldehyde has a high moisture content, 0.2ml samples can be
measured. If the moisture content is less than about 0.2%, however, the
sample will be too small and this method cannot be used. Accordingly,
when measuring trace amounts of moisture, 5-10ml of sample should be
added to 5ml of Dehydrated Solvent PP in the apparatus shown in the
diagram. The sample should be vaporized using dried nitrogen during the
titration.
86
Chapter II: Applications - 1
1) Sampling
Attach a piece of silicon rubber to the needle of a carefully dried syringe
(capacity: 5-10ml, needle length: approx. 10cm). Place the syringe in a dry
polyethylene bag and store it in a refrigerator. Remove the thoroughly chilled
syringe from the refrigerator, together with a sample container (fitted with a
metal sampling stopper) that has also been stored in the refrigerator. Insert
the needle of the syringe into the metal stopper and extract some of the
sample. Flush the syringe twice with the sample. On the third occasion,
extract 5-10ml of sample.
2) Titration
Pour 5ml of Dehydrated Solvent PP into a titration flask (capacity: approx.
50ml), as shown in the diagram. Place the flask in a water bath at a
temperature of 20-25 C. Add dried nitrogen to the titration flask through a
three-way cock (E) at a rate of approximately 0.9l/min. Titrate with Karl
Fischer Reagent SS until the end point is reached. Stop the agitation of the
Dehydrated Solvent PP and the nitrogen flow. Insert the syringe through one
of the holes in the three-way valve (E) until the tip of the needle reaches the
surface of the Dehydrated Solvent PP. Inject the sample immediately. Start
the agitation of the Dehydrated Solvent PP and the nitrogen flow. At the
same time, titrate to the end point, using Karl Fischer Reagent SS to drive off
the vaporized acetaldehyde.
A: 50ml titration flask
B: Water bath
C: Magnetic stirrer
D: Platinum electrode
E: Three-way valve
F: Nitrogen drying tube
(phosphorus pentaoxide)
G: Karl Fischer Reagent SS
H: Standard water/methanol
buret
I: Drying tube
J: Nitrogen vent
K: Sampling point
Figure 19: Acetaldehyde Moisture Titration System
87
II-1 Organic Compounds
Examples:
No
Measurement(mg)
(mg)
(%)
Sample amount Measurement
(ml)
(ml)
1
2
3
4
5
1
3
5
7
10
0.14
0.41
0.65
1.06
1.32
0.42
1.23
1.95
3.17
3.95
0.053
0.052
0.050
0.050
0.050
Note: Titer of Karl Fischer reagent: 3.00mg/ml
(2) Coulometric titration
Reagents used: Aquamicron AKX
Aquamicron CXU
Substance
Sample quantity
(g)
Benzaldehyde
Salicylaldehyde
3-Phenylpropionaldehyde
Chloral hydrate
0.5205
0.6257
0.5435
0.0441
88
100ml
5ml
Measurement value
(g)
343
751
1467
4916
Moisture Content
(%)
660ppm
0.120
0.270
11.1
Chapter II: Applications - 1
8. Organic Acids
Key Points
With most organic acids, moisture content can be measured directly
and easily. If a dehydrated solvent with methanol as its main ingredient
is used, however, interference will occur as the result of an esterification
reaction between methanol and lower carboxylic acids such as formic
acid, acetic acid and adipic acid. These reactions produce water and
will be evidenced by a delayed end point or an unusually high
analytical result.
Esterification reactions vary, depending on the individual acid. Formic
acid shows a strong esterification reaction and will react very quickly
with methanol. Reactivity lessens as the carbon number increases.
Normally, during volumetric titration, propionic acid will not trigger
interference attributable to an esterification reaction. Aromatic
carboxylic acid is another substance that does not cause interference
related to esterification.
Interference can also result from a reaction with iodine. Formic acid
appears to be affected by the oxidation of iodine and L-ascorbic acid
reacts quantitatively with Karl Fischer reagent.
For volumetric titration, a ketone-type dehydrated solvent is used with
lower carboxylic acids. A general-use dehydrated solvent can be used
with higher carboxylic acids and aromatic carboxylic acid. If problems
are encountered with the methanol solubility of substances with high
carbon numbers, a dehydrated solvent formulated for oils (such as
stearic acid) should be used.
For measurements based on coulometric titration, a ketone-type of
anolyte is used with the lower carboxylic acids. Coulometric titration
cannot be used for formic acid, however, as an end point cannot be
reached. A general-use electrolyte can be used with higher carboxylic
acids and aromatic carboxylic acid.
Examples of substances that can be measured directly:
Acetic acid, mono-, di-, trichloroacetic acid, trifluoroacetic acid, propionic
acid, acrylic acid, methacrylic acid, trimethylacetic acid, caproic acid,
stearic acid, oleic acid, linolenic acid, cyclohexane carboxylic acid,
cyclohexyl acetic acid, camphoric acid, abietic acid, 3,5-dinitrobenzoic
acid, cinnamic acid, anisic acid, benzilic acid, 2,4-dichlorophenoxy acetic
acid, benzoic acid
89
II-1 Organic Compounds
Polybasic acids
Oxalic acid, malonic acid, maleic acid, succinic acid, diglycolic acid, adipic
acid, sebacic acid, nitrilotriacetic acid, phthalic acid, terephthalic acid
Sulfonic acids
Benzenesulfonic acid, toluenesulfonic acid, xylenesulfonic acid,
naphthalenesulfonic acid, sulfanilic acid
Hydroxy acids
Glycolic acid, -hydroxybutyric acid, citric acid, tartaric acid, hydroxycaproic acid, -hydroxyadipic acid, , -dihydroxyadipic acid,
ricinoleic acid, salicylic acid
Amino acids
Glycine, leucine, sarcosine, valine, aspartic acid, iminodiacetic acid,
creatine, asparagine, methionine, phenylalanine, glutamic acid
[Examples of Measurement]
(1) Volumetric titration
Reagents used:Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent KTX (or CP)
Dehydrated Solvent OL II (or CM)
25-50ml
Substance
Dehydrated
solvents
Sample
quantity (g)
Measurement
value (mg)
Moisture
content (%)
Acetic acid
Monochloroacetic acid
Dichloroacetic acid
Propionic acid
Salicylic acid
Oxalic acid
Stearic acid
Ketone-type
4.8365
1.0110
0.7817
4.9670
3.5186
0.1211
2.4937
07.86
02.70
00.86
10.92
00.85
35.19
00.42
00.16
00.27
00.11
00.22
00.024
29.1
00.017
"
"
General-use
"
"
Oil-type
Note: Dehydrated Solvent KTX should be used in combination with
Karl Fischer Reagent SS-Z, and Dehydrated Solvent CP with
Karl Fischer Reagent SS.
90
Chapter II: Applications - 1
(2) Coulometric titration
Reagents used: Aquamicron AKX (or AX)
Aquamicron CXU
Substance
Electrolyte
Sample
quantity(g)
Formic acid
Acetic acid
Propionic acid
Dichloroacetic acid
Salicylic acid
Stearic acid
Oxalic acid
Ketone-type
1.2200
1.0500
0.9930
1.5630
1.6222
2.1418
0.0222
"
"
"
General-use
"
"
100ml
5ml
Measurement
Moisture
value (g)
content (ppm)
Not measurable
0687
1321
1313
0341
0130
6645
0655
1330
0840
0210
0061
29.9%
9. Esters
Key Points
Esters are substances for which moisture content can be measured
very easily using standard Karl Fischer titration procedures. There are
no significant interference reactions and behavior is similar to that of
hydrocarbons. Both volumetric and coulometric titration can be used
without any problem.
For volumetric titration, a general-use dehydrated solvent is used.
Solubility will be a problem with long-chain aliphatic esters and a
dehydrated solvent formulated for oils is recommended.
With coulometric titration, measurements are carried out by adding the
sample directly to the electrolyte (anolyte).
Examples of substances that can be measured directly:
Esters
Methyl formate, ethyl formate, methyl acetate, ethyl acetate, aryl formate,
methyl acrylate, methyl methacrylate, ethyl malonate, methyl valerate, methyl
adipate, methyl sebacate, methyl glycolate, 2,3-butylene di-acetate, ethyl
citrate, cyclohexyl acetate, methyl benzoate, methyl salicylate, phenyl
acetate
Inorganic esters
Ethyl carbonate, ethyl chlorocarbonate, butyl nitrite
91
II-1 Organic Compounds
Lactones
-butyrolactone
Carbamic acid esters
Methyl carbamate, ethyl carbamate
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS)
Dehydrated
solvent
Sample
quantity (g)
General-use
0.9467
4.3557
2.8098
5.6364
Substance
Methyl acetate
Ethyl acetate
Methyl acrylate
-Butyrolactam
"
"
"
(2) Coulometric titration
Reagents used: Aquamicron AX (or AS)
Aquamicron CXU
Substance
Methyl acetate
Methyl isoamyl
n-Butyl acetate
Isopropyl isovalerate
Di-isopropyl malonate
Benzyl benzoate
92
25-50ml
Measurement
Moisture
value (g)
content (ppm)
2.15
0.86
5.31
1.18
2224
197
1890
210
100ml
5ml
Sample quantity
(g)
Measurement value
(g)
Moisture content
(ppm)
2.5250
0.8548
2.4589
0.9186
1.0740
1.5825
3.1695
105
1280
195
1256
449
319
512
42
1494
79
1367
418
202
162
Chapter II: Applications - 1
10. Organic Acid Salts
Key Points
Since organic acid salts containing water of crystallization dissolve
readily in methanol, their moisture content can be measured easily
using a general-use dehydrated solvent. In the case of organic acid
salts that do not contain water of crystallization, moisture content can
be measured by dissolving or dispersing the substances in a generaluse dehydrated solvent. As these substances are solids with a high
moisture content, we recommend measurement using volumetric
titration.
The organic salt sodium tartrate dihydrate was formerly sed as a
standard reagent for determining the titer of Karl Fischer reagents for
use in volumetric titration.
Examples of substances that can be measured directly:
Organic acid salts containing water of crystallization
Barium acetate, cadmium acetate, cobalt acetate, lead acetate, magnesium
acetate, nickel acetate, sodium acetate, zinc acetate, uranyl acetate, sodium
citrate, lithium citrate, calcium lactate, calcium malonate, sodium
naphthionate, ammonium oxalate, potassium oxalate, calcium propionate,
sodium succinate, sodium benzoate, sodium tartrate
Organic acid salts without water of crystallization
Ammonium acetate, sodium adipicate, potassium hydrogen tartrate,
ammonium citrate, sodium formate, sodium phthalate, zinc stearate
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS)
25-50ml
93
II-1 Organic Compounds
Substance
Dehydrated
solvent
Sample
quantity (g)
Measurement
value (mg)
Moisture
content (%)
Sodium L-aspartate
Lithium citrate
Sodium citrate
Ammonium acetate
Cadmium acetate
Magnesium acetate
Lithium acetate
Sodium acetate
Sodium napthionate
Calcium lactate
Oxalic acid
Manganese benzoate
Calcium stearate
General-use
0.0841
0.0354
0.0812
1.2884
0.2750
0.1918
0.1003
0.0678
0.0731
0.2003
0.0825
0.0862
0.2046
04.32
08.73
10.08
06.44
37.07
64.27
04.13
10.75
05.85
58.39
23.58
09.45
05.98
05.140
24.700
12.400
00.500
13.500
33.500
11.500
15.800
22.800
29.200
28.600
11.000
02.920
"
"
"
"
"
"
"
"
"
"
"
Oil-type
11. Organic Hydrates
Key Points
Since organic hydrates are solids, measurements can normally be
carried out directly using volumetric titration. For measurements using
volumetric titration, these substances can be dissolved or dispersed in
a general-use dehydrated solvent. As with organic acid salts,
volumetric titration is generally recommended for organic hydrates.
Water of crystallization is not always stable in organic hydrates and
moisture content frequently varies with reference to temperature and
humidity. Cyanuric acid, in particular, tends to lose most of its water of
crystallization.
Examples of substances that can be measured directly:
Pyromellitic acid, L-asparagine, creatine, L-histidine, dextrose, L-rhamnose,
raffinose, chloral hydrate, ninhydrin, alloxan, piperazine, o-phenantholine,
brucine, brucine sulfate
94
Chapter II: Applications - 1
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS)
Substance
Dehydrated
solvents
Chloral hydrate
Hydrazine hydrate
General-use
"
25-50ml
Sample quantity Measurement
(g)
value (mg)
0.1752
0.0732
19.27
25.68
Moisture
content (%)
11.0
35.1
95
II-1 Organic Compounds
12. Amines
Key Points
Some amines exhibit unusual behavior during Karl Fischer titration. That
behavior falls into two categories; that caused by basicity and that
caused by other chemical interference reactions. The titration
conditions must be modified in accordance with the nature of the
behavior that is involved.
In terms of basicity, substances can be divided into two groups using
benzylamine with a pKa value of 9.4 (Ka=2.4 x 10 -5) as the dividing line.
1) Amines below pKa9.4
Titration can be carried out without difficulty using standard procedures
and behavior is comparable with hydrocarbons. In the case of
volumetric titration, the substances are dissolved in a general-use
dehydrated solvent and titrated directly. With coulometric titration, the
sample is introduced into a general-use electrolyte (anolyte) and titrated
directly.
2) Amines with strong-basicity (above pKa9.4)
Aside from the Karl Fischer reactions with water, interference reactions
caused by the strong basicity of these substances gradually consume
the Karl Fischer reagent and are known to cause the following
phenomena.
a. Poor end point stability
b. Failure to reach end point
c. Abnormally high analytical results
To suppress these interference reactions, the substances must be
neutralized with acids before titration and the Karl Fischer titration
system must be kept in a state that is close to neutrality. Salicylic acid is
normally used for this purpose as it causes almost no esterification
reaction with titration solvents which have methanol as their main
ingredient. If acetic acid is used, the esterification reaction must be
suppressed by chilling the system to 15 C or below during the Karl
Fischer titration.
For volumetric titration the titration solvent is prepared by dissolving 10g
of salicylic acid in 50ml of Dehydrated Solvent GEX (or MS).
For coulometric titration the electrolyte is prepared by dissolving 10g of
salicylic acid in 100ml of general-use electrolyte (anolyte).
Note:Up to 70mmol of amine can be neutralized with 10g of
salicylic acid. This is why titration is normally carried out
continuously with a quantity that corresponds to a sample of
70mmol.
96
Chapter II: Applications - 1
Substances that react with electrodes or cause other interference
reactions
Coulometric titration cannot be used for substances that react with
electrodes, such as aniline, toluidine, diamines and aminophenol.
With substances such as aniline or toluidine, the end point will not be clear if
methanol is used as the titration solvent for volumetric titration. Volumetric
titration is possible, provided that Dehydrated Solvent CP is used. Diamines
cause an interference reaction with iodine, with the result that the end point
is never reached.
Reference:(1) Muroi, K. et al., "Measuring Trace Moisture Content in
Amines Using the Karl Fischer Method" (in Bunseki Kiki
[Analytical Equipment] 8, 374, 1969).
(2) Kato, H. et al., "Determination of Moisture in Amines by Karl
Fischer Coulometric Titration" (in Bunseki Kagaku 34, 805
(1985).
Examples of substances that can be measured directly using standard
methods:
Pyridine, 2-aminopyridine, 2-picoline, quinoline, pyrrole, imidazole, triazine,
triazole, indole, carbazole, benzothiazole, N,N-dimethylaniline,
diphenylamine, 2-pyridyl ethanol, 4-pyridyl ethanol
Examples of substances that require neutralization with acid:
Trimethylamine, ethylamine, diethylamine, triethylamine, propylamine,
isopropylamine, 3-methoxypropylamine, butylamine, di-isobutylamine, disec-butylamine, dipentylamine, hexylamine, N,N-dimethylcyclohexylamine,
dicyclohexylamine, benzylamine, pyrrolidine, piperidine, piperazine,
morpholine, ethanolamine, N,N-dimethylethanolamine, diethanolamine,
triethanolamine, di-isopropanolamine, tri-isopropanolamine, Tris
(hydroxymethyl) aminomethane
Examples of substances that require a methanol-free titration solvent:
Aniline, toluidine, anisidine, naphthylamine
97
II-1 Organic Compounds
[Examples of Measurement]
(1) Volumetric titration --neutralization using salicylic
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS) approx. 50ml
Salicylic acid
approx. 10g
Substance
Dehydrated
solvents
General-use+Salicylic acid
n-Butylamine
Diethylamine
"
Diethanolamine
"
Piperidine
"
Tri-n-butylamine
"
Di-isopropyl amine
"
2-Methylaminopyridine
"
Triethanolamine
"
N-Ethyl morpholine
"
N,N-Dimethyl benzylamine
"
N-Ethyl aniline
"
Aniline
Ketone-type
Sample
quantity(g)
Measurement
value (mg)
Moisture
content (%)
0.7335
0.7234
1.0240
0.9034
1.6367
1.5010
1.0520
1.1240
0.9050
0.9000
0.9580
1.0185
1.45
1.02
2.62
1.00
1.27
1.21
0.47
0.70
0.88
1.55
0.55
1.49
0.200
0.140
0.260
0.110
0.077
0.081
0.120
0.170
0.260
0.170
0.057
0.150
Note:Salicylic acid crystals are bulky and difficult to handle. To
overcome this problem, place 10g of salicylic acid in an empty
titration flask and add Dehydrated Solvent GEX. The salicylic
acid will dissolve readily and can be rendered moisture-free
through a Karl Fischer titration that prepares for the main
titration.
(2) Coulometric titration
Reagents used: Aquamicron AX (or AS)
100ml
or with approx. 10g of Salicylic acid added
Aquamicron CXU
5ml
98
Chapter II: Applications - 1
Substance
pKa
i-Propylamine
n-Butylamine
n-Hexylamine
Diethylamine
Di-i-propylamine
Di-n-butylamine
Triethylamine
Tri-n-propylamine
Tri-n-butylamine
3-Dimethylamino propionitrile
Cyclohexylamine
Monoethanolamine
Diethanolamine
Triethanolamine
2-Diethylaminoethanol
1,3-Diaminopropane
1,2-Propane diamine
Pyrrolidine
Piperidine
4-Benzyl piperidine
Piperazine
Pyrrole
N-Methyl morpholine
Benzylamine
N,N-Dimethyl benzylamine
2-Amino-3-picoline
2-Methyl aminopyridine
o-Toluidine
m-Toluidine
p-Anisidine
m-Aminophenol
Dimethyl aminomethyl phenol
N,N-Dimethyl-p-toluidine
Aniline
N,N-Diethyl aniline
o-Chloro-aniline
2-Anilinoethanol
10.6
10.6
10.6
11.0
11.1
11.3
10.7
10.7
10.9
6.9
10.6
9.5
9.0
7.8
9.4
11.3
11.2
10.3
7.7
9.4
8.9
6.7
6.7
4.4
4.7
5.3
4.2
7.9
5.6
4.6
6.6
2.6
4.0
Sample quantity Measurement
(g)
value (g)
0.694
0.732
0.766
0.707
0.722
0.760
0.726
0.753
0.778
0.870
0.867
0.269
1.097
1.124
0.884
0.218
0.861
0.997
0.200
0.967
0.905
0.268
0.900
1.031
1.052
0.986
0.937
0.938
1.213
1.085
321
2440
496
989
931
3231
5582
1159
626
2635
1741
614
1199
1870
2757
1471
Cannot be measured
Cannot be measured
3971
6314
210
3104
1907
452
1042
2621
1280
Cannot be measured
Cannot be measured
Cannot be measured
Cannot be measured
1606
494
Cannot be measured
102
361
2614
Moisture
content (%)
463ppm
0.333
648ppm
0.140
0.129
0.425
0.769
0.154
805ppm
0.303
0.201
0.228
0.109
0.166
0.312
0.675
0.461
0.633
0.105
0.321
0.211
0.169
0.116
0.254
0.122
0.163
527ppm
109ppm
298ppm
0.241
99
II-1 Organic Compounds
13. Amides, Anilides
Key Points
The moisture content of amides and anilides can be measured easily
using standard methods. Amides behave in the same way as weakbasicity amines. Both volumetric and coulometric titration can be used.
For volumetric titration, use either a general-use or an oil-type
dehydrated solvent, depending on the solubility of the sample.
In the case of coulometric titration, the sample is added directly to the
electrolyte (anolyte).
Examples of substances that can be measured directly:
Formamide, acetamide, malonamide, dimethyl formamide, urea, ethylene
urea, biuret, acetyl urea, alloxan, benzamide, salicylamide, acetanilide,
propionanilide
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS)
25-50ml
Substance
Dehydrated
solvents
Sample
Quantity (g)
Measurement
Value (mg)
Moisture
Content (%)
Formamide
N,N-Dimethyl formamide
Urea
Acetanilide
Stearamide
General-use
2.2307
2.6466
2.5000
4.9110
3.6953
1.71
3.28
1.40
10.35
0.15
0.077
0.124
0.056
0.211
0.004
100
"
"
"
Oil-type
Chapter II: Applications - 1
(2) Coulometric titration
Reagents used: Aquamicron AX (or AS)
Aquamicron CXU
Substance
Sample quantity
(g)
Formamide
N,N-Dimethyl formamide
Acetamide
N,N-Dimethyl acetamide
Oleylamide
Erucamide
2.1173
2.6484
4.6866
1.1590
2.1790
3.8854
100ml
5ml
Moisture Content
(ppm)
Measurement value
(g)
1510
552
314
707
78
148
713
208
067
612
036
038
14. Nitriles, Cyanohydrins
Key Points
Nitriles have weak basicity and can be measured easily using standard
methods. Reliable moisture measurement is also possible with
cyanohydrins. Both volumetric and coulometric titration can be used.
For volumetric titration, a general-use dehydrated solvent is used. For
coulometric titration, the sample is added directly to the electrolyte
(anolyte).
Examples of substances that can be measured directly:
Acetonitrile, aminoacetonitrile, acrylonitrile, sebaconitrile, methylene
aminoacetonitrile, adiponitrile, acetone cyanhydrin, formaldehyde
cyanohydrin, acrolein cyanohydrin acetate
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS)
Substance
Acetonitrile
25-50ml
Dehydrated
solvents
Sample
Quantity (g)
Measurement
Value (mg)
Moisture
Content (%)
General-use
2.1687
3.22
0.148
101
II-1 Organic Compounds
(2) Coulometric titration
Reagents used: Aquamicron AX (or AS)
Aquamicron CXU
Sample quantity
(g)
Substance
Acetonitrile
Acrylonitrile
100ml
5ml
Measurement value
(g)
0.7691
0.0800
822
295
Moisture Content
(ppm)
1070
3690
15. Hydrazines
Key Points
Iodine oxidation causes hydrazine derivatives to react with Karl Fischer
reagent as shown in the following formula.
2C6H5NHNH2+2I23HI+C6H5NH2 HI+C6H5NN=N
Karl Fischer titration is possible also with acidic solvents. Moisture
content can be measured without this reaction if the sample is first
dissolved in an excess of acetic acid (approx. 2g of sample in 25ml of
acetic acid).
The moisture content of dinitrophenyl hydrazine and benzoyl hydrazine
can also be measured accurately if the sample is dissolved in acetic
acid and then titrated. Hydrazine hydrochloride reacts with iodine on a
mole-for-mole basis, but hydrazine sulfate does not react with Karl
Fischer reagent and can be dissolved in methanol for titration.
In the case of hydrazine compounds, volumetric titration is the only
method that can be used. Coulometric titration is not suitable.
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS) approx.
Titrate after cooling to 15C or lower.
Substance
Hydrazine
102
Dehydrated
solvents
Sample
Quantity (g)
Measurement
Value (mg)
General-use
0.0296
0.84
50ml
Moisture
Content (%)
2.85
Chapter II: Applications - 1
Substance
Sample moisture
(%)
Semicarbazide hydrochloride
Phenylhydrazine hydrochloride
0.390.00
0.370.01
content (%)Amount added
Measurement value
Added moisture
2.52
2.50
2.50
2.53
16. Other Nitrogenous Compounds
Key Points
Both volumetric and coulometric titration can be used directly for other
nitrogenous compounds. For volumetric titration, the substance is
dissolved in a general-use dehydrated solvent and titrated. If a
substance is difficult to dissolve its solubility can be improved with the
addition of another solvent.
Coulometric titration is carried out using a general-purpose electrolyte
and in accordance with standard procedures.
Examples of substances that can be titrated directly:
Lactam, Imines
-Caprolactam, benzal-n-butylimine
Cyanohydrine
Formaldehyde cyanohydrin, acetone cyanhydrin, acrolein cyanohydrines
Azo-, azole compounds
p-Aminoazobenzene, diazoaminobenzene, benzotriazole
Isocynates, nitroso compounds
1-Naphthyl isocynate, phenyl isocyanate, N-nitrosodiphenylamine
Nitro compounds
Nitromethane, nitroglycerine, 2-nitropropane, m-dinitrobenzene, 3,5dinitrobenzoic acid
Oximes, hydroxamic acids
Acetone oxime, dimethylglyoxime, butylaldoxime, hepta-aldoxime,
cyclohexanone oxime
Cyanic acid derivatives
Cyanamides, dicyanamides, cyanuric acid, melamine
Amidines
Guanidine nitrate
103
II-1 Organic Compounds
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS)
Substance
Dehydrated
solvents
Nitromethane
Nitroethane
1-Nitropropane
m-Nitroaniline
p-Nitrophenol
o-Nitro-p-chloroaniline
m-Dinitrobenzene
2,4-Dinitrotoluene
-Caprolactam
N-Methyl pyrrolidine
m-Nitro-p-toluidine
p-Dichloro nitrobenzene
General-use
"
"
"
"
"
"
"
"
"
*1
*2
Sample
Quantity (g)
5.6235
2.0672
1.8575
2.3233
0.9844
0.9209
1.0835
1.9935
1.5336
3.1519
2.1785
10.1400
25-50ml
Measurement
Value (mg)
0.99
4.63
2.75
1.26
11.30
0.30
0.15
0.06
3.22
2.14
0.45
0.78
Moisture
Content (%)
0.018
0.22
0.15
0.054
1.15
0.033
0.014
0.003
0.21
0.068
0.021
0.008
*1: Dehydrated Solvent MS 25ml + dinitromethane 10ml
*2: Dehydrated Solvent MS 25ml + dichloromethane 10ml
(2) Coulometric titration
Reagents used: Aquamicron AX (or AS)
Aquamicron CXU
Substance
Nitromethane
Nitroethane
1-Nitropropane
2-Nitropropane
p-Nitrophenol
m-Nitroaniline
m-Nitro-p-toluidine
o-Nitro-p-chloroaniline
N-Vinyl pyrrolidone
-Caprolactam
Isocyanate
Sample quantity
(g)
1.1312
10237
0.9757
1.0338
0.5196
1.5120
2.0193
1.0060
1.0675
0.6448
3.3597
100ml
5ml
Measurement value
(g)
993
2224
1324
816
5507
875
404
295
340
1290
95
Moisture Content
(ppm)
879
0.217%
0.136%
789
1.06%
579
200
293
319
0.200%
028
In all cases, samples can be measured up to a volume of 20-50ml, as shown
in the table.
104
Chapter II: Applications - 1
17. Acid Anhydrides
Key Points
Acid anhydrides and acylates can be measured directly using
volumetric titration. The sample is subjected to Karl Fischer titration
after it has been dissolved in either a general-use dehydrated solvent or
a compound solvent made up of one part pyridine to four parts
methanol by volume.
Examples of substances that can be titrated directly:
Acid Anhydrides
Acetic anhydride, propionic anhydride, butyric anhydride, n-valeric
anhydride, succinic anhydride, benzoic anhydride, phthalic anhydride
18. Acid Chlorides
Key Points
The following acid chlorides cause interference through oxidation of the
hydriodic acid in Karl Fischer reagent and the release of free iodine. For
this reason, water content is measured using volumetric titration as
follows.
To suppress the interference, neutralize the sample by adding 1-3g of
the sample to a methanol solvent that includes 20% pyridine/sulfur
dioxide (SO 2 32g/pyridine 100ml). Then carry out the Karl Fischer
titration.
1) Potassium dichloroisocyanurate
C3N3O3Cl2K+2SO 2+3C5H5N+CH3OH
C3N3OH(OCH3)2+C5H5NHCl+KCl+2C 5H5NHSO4CH3
2) Aryl sulfonyl chloride
ArSO2Cl+CH3OH+C5H5N ArSO3CH3+C5H5NHCl
Coulometric titration cannot be used because of the interference.
Examples of substances that can be titrated directly:
Acid Chlorides
Propionyl chloride, butyryl chloride, valeryl chloride, caproyl chloride, capryl
chloride, stearoyl chloride, benzoyl chloride
105
II-1 Organic Compounds
[Examples of Measurement]
(1) Volumetric titration
Reagents used:Karl Fischer Reagent SS
Dehydrated Solvent MS + SO2/pyridine solvent 25-50ml
Substance
Sample quantity
(g)
Measurement value
(mg)
Moisture Content
(%)
Potassium dichloroisocyanurate
p-Toluene sulfonyl chloride
p-Chlorobenzene sulfonyl chloride
Toluene 2,4-disulfonyl chloride
p-Ethylbenzene sulfonyl chloride
Methanesulfonyl chloride
1.0228
1.0541
1.0059
0.8721
1.6708
2.9444
2.45
0.82
1.20
2.18
0.54
2.10
0.24*
0.078
0.12**
0.25
0.032
0.071
*: Drying method 0.23%
**: Infrared method 0.14%
19. Quinones
Key Points
Quinones interfere with the titration through the oxidation of hydriodic
acid, which is produced from a reaction between water and Karl
Fischer reagent, to produce free iodine. For this reason, direct titration
is impossible. Instead, an indirect method based on water vaporization
is used.
Either volumetric or coulometric Karl Fischer titration can be used. Refer
to the section on Basic Knowledge for information on the water
vaporization method.
[Examples of Measurement]
(1) Water vaporization - Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS) + PG (3:1) 50-100ml
Substance
Heating
temperature (C)
Sample
quantity (g)
Measurement
value (mg)
Moisture
content (%)
Naphthoquinone (wet)
Naphthoquinone (dry)
p-Quinone
160
160
130
0.1185
2.2096
3.5710
7.62
0.82
0.15
6.43
0.037
0.0042
106
Chapter II: Applications - 1
20. Peroxides
Key Points
As shown in the following formula, peroxides react with the sulfur
dioxide in Karl Fischer reagent. In general, however, there is no
interference.
ROOH+SO2 RHSO4
It is important to ensure that there is always an adequate excess of
sulfur dioxide.
Acetyl peroxide is highly reactive and causes interference by releasing
iodine through the oxidation of hydrogen iodide.
(CH3COO)2+2HI 2CH3COOH+I2
Other substances may also cause interference if there is insufficient
sulfur dioxide. Dialkyl peroxides (R-OO-R) are not reactive and have no
effect on Karl Fischer titration. Diacyl peroxides (RCO-OO-OCR) cause
interference through the oxidation of hydrogen iodide as shown in the
following formula.
RCO-OO-OCR+HI 2RCOOH+I 2
Examples of substances that can be measured directly:
Di-tert-butyl peroxide (this substance causes an exothermic reaction when
titrated with Karl Fischer reagent, but moisture content can be measured
accurately), diethyl peroxide, lauryl peroxide, triacetone peroxide
107
II-1 Organic Compounds
21. Sulfur Compounds
Key Points
The moisture content of most sulfur compounds, including sulfides,
disulfides, thiocyanic acid and sulfonic acid, can be measured by
means of direct titration using standard procedures. As with
hydrocarbons, these compounds have a tendency to slow the rate of
the reaction between water and Karl Fischer reagent, so they should
always be measured in excess methanol.
For volumetric titration, the substances are measured after they have
been dissolved in a general-use dehydrated solvent.
For coulometric titration, the sample is added directly to a general-use
electrolyte (anolyte).
The only substances that cause interference are mercaptan, thiourea,
thioacetic acid and dithio acid. These consume Karl Fischer reagent by
reacting with iodine as shown in the following formulae.
2RSH+I2 RSSR+2HI
2RCSSH+I 2 RCSSSSCR+2HI
Before these substances can be titrated, they must be neutralized using
special procedures.
Dimethyl sulfoxide (DMSO) exhibits unusual behavior. Karl Fischer
titration appears to move toward a stable end point without any
difficulty, but with sequential addition of the sample the moisture
content declines with each analysis. It is important to note that the
presence of DMSO reduces the percentage of water recovered.
Examples of substances that can be measured directly:
Sulfides
Carbon disulfide, allyl sulfide, n-butyl sulfide, n-butyl disulfide, thiophene,
benzothiophene
Thiocyanates, etc.
Ethyl thiocyanate, ethylene thiocyanate, n-butyl thiocyanate, ethyl
isothiocyanate, 1-naphthyl isothiocyanate, ethyl thioacetate, benzothiazole,
1-acetyl-2-thiourea, methyl isothiourea
108
Chapter II: Applications - 1
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS) 25-50ml
Substance
Dehydrated
solvent
Sample
quantity (g)
Carbon disulfide
Dimethyl sulfoxide
General-use
6.3050
3.0721
"
(2) Coulometric titration
Reagents used: Aquamicron AX (or AS)
Aquamicron CXU
Substance
Dimethyl sulfoxide
Benzothiophene
Sample quantity
(g)
Measurement
Moisture
value (mg)
content (ppm)
0.62
0.92
098
298
100ml
5ml
Measurement value
(g)
1.0773
1.1633
784
158
Moisture Content
(ppm)
728
136
Measuring the Moisture Content of Mercaptan
Interference caused by mercaptan can be eliminated by reacting an active
olefin such as octene with the sample using boron trifluoride as the catalyst.
BF3
RSH+R'CH=CHR' R'CH(SR)CH2R'
a) Reagent
Solution of boron trifluoride and ethyl ether (BF3 45%)
or Solution of boron trifluoride and acetic acid (100gBF3/l)
Isooctene, glacial acetic acid, pyridine
b) Measurement method
Put 5-10ml of glacial acetic acid into a 250ml measuring flask. Add the
sample making sure that the amount of mercaptan does not exceed 15
millimoles. Next, add 3ml of boron trifluoride/ethyl ether solution or 10ml of
boron trifluoride/acetic acid solution and 6ml of isooctene. Mix well and
leave for about 30 minutes at room temperature. Carefully add 5ml of
pyridine and then titrate the solution with Karl Fischer reagent. Using the
same procedures, obtain a dummy test result for the reagent. Subtract this
from the titration value to determine the moisture content. However, the
reagent used should always be thoroughly dehydrated.
(JACS., 62, I (1940))
109
II-1 Organic Compounds
Note:An error will occur at the rate of 0.3ppm of water for every 1ppm
of sulfur in the mercaptan. If the mercaptan content is low, an
accurate measurement of the moisture content can be obtained
by adjusting the measurement value.
Reference:JISK2275 Crude oil and petroleum products - Determination of
water content
Test Examples
content (%)
Added moisture
Observed moisture(%)
Moisture
(%)
Sample
Ethyl mercaptan
Isopropyl mercaptan
Butyl mercaptan
Isoamyl mercaptan
Hexyl mercaptan
Heptyl mercaptan
Benzyl mercaptan
Thiophenol
2-Thionaphthol
Thioglycollic acid
6.30
6.30
3.05
2.85
1.85
4.60
2.80
1.35
6.95
0.70
0.90
0.85
0.40
0.15
0.70
0.25
0.25
0.05
3.85
6.35
6.25
3.05
2.90
1.85
4.60
2.80
1.35
7.00
Other Substances that Cause Interference
It may not be possible to obtain a clear end point with thiourea as it reacts
with iodine. This is because thiourea triggers tautomerism and interconverts
to isothiourea, which causes the same reaction as mercaptan.
NH2
S=C
NH2
110
NH2
HSC
NH
Chapter II: Applications - 1
1-Phenyl-2-thiourea, 1, 3-diphenyl thiourea and thiobenzamide also react in
the same way as thiourea. However, N-methyl thiourea and 1-acetyl-2thiourea can be titrated directly without causing a reaction.
When thioacetatic acid is titrated directly, it reacts quantitatively with Karl
Fischer reagent and consumes 1 mole of iodine per mole. Dithio acid
causes a similar quantitative reaction. This interference can be prevented by
taking the following preliminary steps.
First, add an equivalent amount of n-butanol to the sample and treat it with
olefin using boron trifluoride as the catalyst. It appears that the butyl
mercaptan produced in this way combines with the olefin as shown in the
following formulae.
CH3COSH+C4H9OH CH3COOH+C4H9SH
RCSSH+C4H9OH RCSOH+C4H9SH
If excess butanol is used it will react with the acid during titration and
produce ester and water. The results must be corrected to allow for this.
111
II-2. Inorganic Compounds
II-2. Inorganic Compounds
Interference reactions are more common with inorganic compounds than
with organic compounds. Refer to the comments on interference in Q9 of the
section on Basic Knowledge. Also, the moisture vaporization method is used
more often because there are a number of substances that cannot be
dissolved in the titration solvents. For each substance, it is essential to
consider whether or not to use the moisture vaporization method (heat
vaporization system). In addition, when taking measurements careful
consideration must be given to the way in which moisture is present
(adhesion water or compounded water).
112
Chapter II: Applications - 1
1. Metals and Simple Substances
Key Points
Since these substances are solids and cannot be dissolved in
methanol, they are normally measured using the moisture vaporization
method. The sample is powdered in preparation for the measurement.
During this preliminary process it is important to prevent absorption of
humidity or dissipation of the moisture content.
For volumetric titration, it is possible to disperse the sample in
dehydrated solvent and carry out Karl Fischer titration directly.
However, the moisture vaporization method is normally used.
With coulometric titration the presence of insoluble substances, such as
powdered metal, interferes with the electrode reaction. Other causes of
interference include membrane blockage. For these reasons,
coulometric titration cannot be used directly.
In most cases the moisture vaporization method is effective with these
samples. Because moisture content is commonly low, Karl Fischer
titration is carried out using the coulometric method. The heating
temperature for moisture vaporization is 100-250C. If necessary, the
process can be carried out at temperatures of 600-700C.
113
II-2. Inorganic Compounds
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS) 25-50ml
Substance
Dehydrated
solvent
Sample
quantity (g)
Measurement
value (mg)
Moisture
content (%)
Aluminum paste
Powdered aluminum + oil
Powdered tungsten
Titanium
Sulfur
Ferrite
General-use
0.2524
0.5968
4.2880
0.4541
1.1710
0.3121
00.83
00.15
00.71
10.97
00.47
11.11
0.329
0.075
0.017
2.42
0.042
3.56
"
"
"
"
"
(2) Coulometric titration
Reagents used: Aquamicron AX (or AS)
Aquamicron CXU
Substance
Aluminum paste
Powdered aluminum
Powdered metal (Cd)
"
Powdered metal (zinc)
Powdered silicon
Powdered cobalt alloy
Powdered brass
Copper wire
Powdered lead tin
Nickel
Powdered sulfur
Red phosphorus
Ferrite
114
150ml
10ml
Heating
Temperature (C)
Sample
quantity (g)
Measurement
value (g)
Moisture
content (%)
110
600
110
250
250
700
200
250
200
400
250
100
180
700
0.2646
3.3284
0.2572
0.1494
3.8345
0.0537
2.3461
1.5277
2.4454
9.9006
1.0724
2.3143
0.2036
0.0774
3831
524
354
787
35
1252
563
1951
332
531
316
151
1470
3034
1.45
157ppm
0.138
0.527
9ppm
2.33
240ppm
0.128
136ppm
54ppm
295ppm
65ppm
0.722
3.92
Chapter II: Applications - 1
2. Inorganic Acids
Key Points
The following problems arise when methanol is used as the titration
solvent for inorganic acids.
1) The pH of the Karl Fischer titration system is shifted to the acid side.
This lowers the reaction rate.
2) An esterification reaction occurs with acids at high temperatures.
This produces water, raising the measurement value.
To suppress these interference reactions the sample should be
neutralized with an amine, such as pyridine, before Karl Fischer
titration.
Since these substances commonly have a high moisture content,
volumetric titration is used. It is convenient to use Dehydrated Solvent
MS (manufactured by Mitsubishi Chemical). As this product contains a
relatively high percentage of pyridine as a reaction accelerant, it is not
necessary to add more pyridine.
In the case of hydrogen chloride gas, moisture is condensed in special
apparatus at -78C. The main constituent, hydrogen chloride, is then
separated so that the condensed water can be dissolved in pyridinemethanol and titrated.
Reference:Muroi, Ono: Microchem.J., 18,234 (1973)
"Determination of Trace Moisture in Hydrogen Chloride Gas by
Karl Fischer Titration."
Examples of test methods
1) Sulfuric acid
Concentrated sulfuric acid (95% or higher) causes an esterification
reaction in methanol and produces water. By adding 50ml of Dehydrated
Solvent MS and using a small sample (approx. 0.5g or less), it is possible
to carry out direct titration without any interference reaction.
2) Nitric acid
The reagent nitric acid can be titrated directly by adding about 0.3g of
sample to 50ml of Dehydrated Solvent MS. In the case of fuming nitric
acid, the sample will have to be neutralized with pyridine.
115
II-2. Inorganic Compounds
3) Hydrochloric acid
The reagent hydrochloric acid can be titrated directly by adding about
0.03g of sample to 50ml of Dehydrated Solvent MS.
4) Hydrofluoric acid
The reagent hydrofluoric acid can be titrated directly by adding about
0.03g of sample to 50ml of Dehydrated Solvent MS.
However, as hydrofluoric acid erodes glass parts of the titration cell and
the electrodes, teflon-coated parts should be used.
5) Hydrocyanic acid
The reagent hydrocyanic acid can be dissolved in Dehydrated Solvent
MS for direct titration.
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS) 25-50ml
Substance
Dehydrated
solvent
Sample
quantity (g)
Measurement
value (mg)
Moisture
content (%)
97% Sulfuric acid
92% Sulfuric acid
Nitric acid
Nitric acid (85%)
Hydrochloric acid (38%)
Hydrofluoric acid (48%)
Hydrocyanic acid
Phosphoric acid (85%)
General-use
0.2423
0.1145
0.0360
0.1155
0.0379
0.0368
0.3888
0.0533
07.69
08.74
35.04
16.87
23.67
18.96
05.56
07.85
03.17
07.63
97.30
14.60
62.50
51.50
01.43
14.70
"
"
"
"
"
"
"
Hydrogen chloride gas
Hydrogen chloride gas reacts with Karl Fischer reagent and cannot be
titrated directly. The moisture content is titrated after condensation in a trap
at -78C, using the following procedures.
a) To ensure that the system is free of moisture, nitrogen gas that has first
been dried with silica gel and phosphorus pentaoxide is passed inside
titration flask D in the direction L M y at a rate of approximately
0.5l/min. (The moisture content of the nitrogen that passed through the
system is titrated.)
116
Chapter II: Applications - 1
b) Titration flask D is cooled to -78C in a methanol dry ice cooling bath.
c) Immediately after the nitrogen flow has been stopped, the sample gas is
passed into titration flask D in the direction A M y at a rate of
approximately 0.5l/min.
d) When 5~20l of gas has passed through the system, the three-way cock is
switched to allow nitrogen to flow into titration flask D in the direction L
M y for about one minute to drive out all of the sample gas.
e) The flow of nitrogen is then stopped and 20ml of a 1:1 pyridine/methanol
solution is introduced from B to flush out the water that has condensed in
E.
f) Titration flask D is removed from the methanol dry ice cooling bath. When
the flask has returned to room temperature, the water captured in the
pyridine/methanol solution is titrated.
g) A dummy value is established from 20ml of pyridine/methanol solution
using the same procedures. Moisture content is determined by
subtracting this value from the titration result.
Hydrogen
chloride gas
Dried
nitrogen gas
Hydrogen
chloride gas
Nitrogen gas
A:Flowmeter for hydrogen
chloride gas
B: Solvent injection port
C: Cooling bath
D: Titration flask
E: Condensing tube
F: Nitrogen supply tube
G: Platinum electrode
H: Stirrer bar
I: Buret protector
J: Buret for KF reagent
K. Back-up titration flask
L,M,N: Three-way stop cocks
O,P: Drying tubes
Figure 20: Titration Apparatus for Hydrogen Chloride Gas
117
II-2. Inorganic Compounds
Test Examples
Gas flow rate
(l/min.)
Volume
(l)
0.3
0.4
0.5
0.6
0.7
0.8
20
20
20
20
20
20
Measurement value Moisture content
(mg)
(ppm)
0.44
0.43
0.45
0.40
0.38
0.33
12.6
12.4
12.8
11.5
10.4
09.4
Note:Karl Fischer Reagent SS with a titer of 0.35mg/ml was used.
(At present there is no reagent with this titer.)
3. Hydroxides
Key Points
Metallic hydroxides generally react with the iodine in Karl Fischer
reagent in accordance with the following formula. In particular, alkaline
metal and alkaline earth hydroxides (strong basicity) react quantitatively
and rapidly.
M(OH) 2+2HI MI2+H2O
For example, lithium hydroxide, sodium hydroxide, potassium hydroxide
and barium hydroxide all produce water and react immediately with
Karl Fischer reagent. For this reason, direct titration cannot be used.
Moisture content is measured using the moisture vaporization method.
[Examples of Measurement]
(1) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS) 150ml
Aquamicron CXU
10ml
118
Chapter II: Applications - 1
Substance
Calcium hydroxide
"
Magnesium hydroxide
Nickel hydroxide
"
Heating
temperature(C)
Sample
quantity (g)
Measurement
value (g)
Moisture
content (%)
110
900
150
150
600
0.6375
0.0289
0.4956
0.1222
0.1092
2953
6708
670
1797
22098
0.463*
23.2**
0.135*
1.47*
20.2**
Note:*Adhesion water, ** bonded water
4. Oxides
Key Points
Metallic oxides generally react with the iodine in Karl Fischer reagent in
accordance with the following formula. In particular, alkaline metal and
alkaline earth oxides (strong basicity) react quantitatively and rapidly.
MO+2HI MI2+H2O
A number of substances, such as magnesium oxide, zinc oxide, silver
(I)oxide, mercury (I) oxide and copper (I) oxide, react with Karl Fischer
reagent in accordance with the formula below.
ZnO+I 2+SO2+CH3OHZnI2+HSO4CH3
Manganese dioxide reacts with Karl Fischer reagent as shown below.
Lead dioxide and red lead cause similar reactions.
MnO2+I2+2SO2+2CH2OHMnI2+2HSO 4CH3
As a result, direct titration is not possible and moisture content is
measured using the moisture vaporization method. For measurement
using moisture vaporization, the heating temperature for normal
adhesion water is set at 100~200C.
119
II-2. Inorganic Compounds
[Examples of Measurement]
(1) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS)
150ml
Aquamicron CXU
10ml
Substance
Zinc oxide
Aluminum oxide
"
Antimony oxide
Cadmium oxide
Gadolinium oxide
Calcium oxide
"
Silicon oxide
Copper (I) oxide
"
Copper (II) oxide
Titanium oxide
Nickel oxide
Bismuth oxide
Magnesium oxide
Manganese oxide
Iron (III) oxide
"
Red iron oxide
"
120
Heating
temperature(C)
Sample
quantity (g)
Measurement
value (g)
Moisture
content (%)
200
200
700
150
250
800
100
800
250
110
700
700
300
250
100
130
750
200
500
200
700
2.1892
1.4522
0.7433
1.9930
0.7301
0.1192
1.3610
0.2526
0.1295
0.4958
0.3140
0.6090
0.3858
0.9014
2.5479
0.2773
0.1382
0.5168
0.5353
0.4209
0.4079
1715
1801
1581
211
228
977
261
1862
1313
654
4734
2366
3691
1135
182
906
6650
1460
1729
1751
2076
783ppm
0.124
0.213
106ppm
312ppm
0.820
192ppm
0.737
1.010
0.132
1.510
0.389
0.957
0.126
71ppm
0.327
4.810
0.283
0.323
0.416
0.509
Chapter II: Applications - 1
5. Halides (halogenides)
Key Points
As a general rule, halides do not cause interference and can be
measured directly. Also, some halides can be dissolved in titration
solvents and titrated with either volumetric or coulometric titration.
Volumetric titration is carried out using a general-purpose dehydrated
solvent. If a substance cannot be dissolved or causes interference, the
moisture vaporization method is used. Care needs to be taken when
taking samples as many of these substances absorb humidity very
readily.
Some substances, such as ammonium chloride, sodium chloride,
potassium chloride, potassium iodide and cerium iodide, occlude their
moisture content during crystallization. The extent of this effect is
reported to be 0.1~0.3%. Since these salts generally dissolve readily in
formamide, moisture content can be measured using a dehydrated
solvent formulated for sugars as the titration solvent.
Reference:Solubility of salts in formamide (g/100g)
NaCl
KCl
NH4Cl
9.33
6.31
11.05
Nal
Kl
62.7
62.5
Alkaline earth halides crystallize as hydrates. Substances that can be
measured without major problems include magnesium chloride 6hydrate, calcium chloride 2-hydrate, strontium chloride 6-hydrate, and
barium chloride 2-hydrate. The same is true of bromides and iodides.
Potassium fluoride (anhydride and 2-hydrate) is soluble and can be
measured without any difficulty. Calcium fluoride is insoluble and its
moisture content cannot be measured through direct titration.
Similar measurement procedures can be used for substances such as
aluminum chloride 6-hydrate, manganese (II) chloride 4-hydrate, cobalt
chloride 6-hydrate, cadmium chloride 2.5-hydrate and tin (IV) chloride
5-hydrate. However, care is needed with the following salts as their
water does not react with iodine on a mole-for-mole basis.
With copper (II) chloride 2-hydrate, only 1.5 mole of water is measured.
CuCl2 2H2O+1.5I2+2SO2+2CH3OHCuI+2HCl+2HI+2HSO 4CH3
With iron (III) chloride 6-hydrate, only 5.5 mole of water can be
measured.
FeCl 3 6 H2O+5.5I2+6SO2+6CH3OHFeI2+3HCl+9HI+6HSO 4CH3
Tin (II) chloride 2-hydrate is a powerful reducing agent. Direct
measurement is not possible as it reduces the iodine in Karl Fischer
reagent.
SnCl 2 2 H 2 O +3I2+2SO2+2CH3OHSnI4+2HCl+2HI+2HSO 4CH3
121
II-2. Inorganic Compounds
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS) 25-50ml
Substance
Dehydrated
solvents
Sample
quantity (g)
Measurement
value (mg)
Aluminum chloride 6-hydrate
Potassium chloride
Magnesium chloride 6-hydrate
Magnesium chloride anhydride
Lithium chloride
Manganese chloride
Strontium chloride
Vanadium chloride
Barium chloride
Lithium chlorate
Dried lithium chlorate
Sodium iodide
General-use
0.0331
0.5178
0.0554
0.6703
0.1004
0.0759
0.0412
0.0766
0.5933
0.1053
0.0783
3.3707
15.17
1.37
30.04
3.01
5.11
27.94
16.75
18.10
86.92
13.77
2.13
1.63
"
"
"
"
"
"
"
"
"
"
"
(2) Coulometric titration
Reagents used: Aquamicron AX (or AS)
Aquamicron CXU
Sample
Aluminum chloride 6-hydrate
Manganese chloride
Lithium chloride
Sulfur hexafluoride
45.8
0.26
54.2
0.45
5.09
36.8
40.6
23.6
14.7
13.1
2.72
0.048
100ml
5ml
Sample quantity
(g)
Measurement value
(g)
Moisture content
(%)
0.0166
0.1607
0.0932
10.29
7490
0700
4780
0230
45.100
00.436
05.130
22ppm
(3) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS)
150ml
Aquamicron CXU
10ml
122
Moisture
content (%)
Chapter II: Applications - 1
Substance
Potassium chloride
"
Lithium chloride
Cesium iodide
Sodium iodide
Barium fluoride
Aluminum fluoride
Zinc fluoride
Heating
temperature(C)
Sample
quantity (g)
Measurement
value (g)
Moisture
content (%)
100
750
200
200
400
800
800
500
0.9903
1.0021
0.1035
9.5975
2.9079
0.5323
0.6244
0.8577
1056
3044
5117
18
1510
291
55
596
0.107
0.304
4.940
2ppm
519ppm
547ppm
88ppm
695ppm
6. Carbonates, Bicarbonates
Key Points
Direct measurement is not possible with carbonates and bicarbonates
as they react with Karl Fischer reagent and cause interference. The
degree of interference depends on the solubility of each substance. For
example, alkaline metal carbonates and bicarbonates react as shown in
the formulae below.
K2CO3+I2+SO2+CH3OH2KI+CO2+HSO4CH3
KHCO3+I2+SO2+CH3OHKI+HI+CO 2+HSO4CH3
Direct measurement is possible with calcium carbonate. Since it does
not dissolve in dehydrated solvent it is dispersed and the moisture
content extracted. This is only possible with volumetric titration.
Direct measurement is not possible with sodium bicarbonate and the
moisture vaporization method is also unsuitable as the substance
releases water when heated. In general, for carbonates that are stable
when heated, the moisture content is measured using the moisture
vaporization method.
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX, OL II (or MS, CM) 25-50ml
123
II-2. Inorganic Compounds
Substance
Dehydrated
solvent
Sample
quantity (g)
Measurement
value (mg)
Moisture
content (%)
Calcium carbonate
Calcium carbonate
General-use
Oil-type
1.0272
1.0053
1.86
1.63
0.181
0.162
Note:The end point was more stable with an oil-type dehydrated
solvent.
(2) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS)
150ml
Aquamicron CXU
10ml
Substance
Calcium carbonate
"
Potassium carbonate
Sodium carbonate
Barium carbonate
"
Basic magnesium carbonate
Manganese carbonate
"
Heating
temperature(C)
Sample
quantity (g)
Measurement
value (g)
Moisture
content (%)
100
600
200
180
300
700
250
110
600
0.1223
0.0975
0.6278
0.2004
0.6761
0.8437
0.0249
0.0334
0.0466
623
1554
1712
4099
805
1103
3605
1723
3699
0.509
1.58
0.273
2.05
0.119
0.131
14.5
5.16
7.94
Measuring the moisture content of sodium bicarbonate
Sodium bicarbonate is used in fire extinguishers and various other applications. Even
trace amounts of moisture can lead to problems during storage or use. It is difficult to
measure moisture content accurately using the conventional sulfuric acid dessicator
method, so the Karl Fischer titration method is used together with a moisture
extraction-correction technique as described below.
Approximately 100g of sample is taken in a 500ml separating funnel. To this, 130ml of
dehydrated methanol is added. The mixture is stirred well and then left to stand.
When the sample and methanol have separated, 50ml of liquid is extracted and
placed in the titration flask of a Karl Fischer titration system, and titrated. The small
quantity of sample dissolved in the extracted liquid is titrated by neutralization
titration, and the moisture content is determined by correcting the Karl Fischer
titration result.
Reference:N.G. Leavitt, C.B. Robert: Anal.Chem., 26,1367 (1954).
124
Chapter II: Applications - 1
7. Sulfates, Sulfites
Key Points
Differences in reactivity to Karl Fischer reagent mean that the choice of
direct titration method must be made with reference to the individual
substance. In most cases we recommend the measurement of moisture
content using the moisture vaporization method. Sulfates crystallize as
hydrates. In general, hydrates with six or more molecules of water of
crystallization dissolve in methanol and remain in solution during
titration. This means that they can be measured directly using a
general-purpose solvent. Some examples of this type of substance are
listed below.
Na 2 SO 2 10H 2 O, MgSO 4 7H 2 O, NiSO 4 6H 2 O, ZnSO 4 7H 2 O,
Al2(SO2)2 18H2O,KAl(SO4)2 12H2O, FeSO4 (NH4 )2SO4 6H2O
Water is strongly bonded in zinc sulfate 1-hydrate and manganese
sulfate 1-hydrate and cannot be measured. Karl Fischer titration cannot
be used for calcium sulfate 2-hydrate at normal room temperatures as
the water is released very slowly. Total moisture content can be
measured by using the moisture vaporization method at a temperature
above 200 C. Copper sulfate causes interference by oxidizing
hydrogen iodide, the reactive substance in Karl Fischer reagent. This
reaction frees 0.5 moles of iodine.
CuSO4+2HI CuI+0.5I2+H2SO4
As the resulting free iodine acts as a reagent, the measurement results
will be low. In general, the weakly acidic salts of alkaline metals react in
the same way as oxides.
Sulfites and pyrosulfites react quantitatively. Sodium sulfite and sodium
pyrosulfite react as shown in the following formulae.
Na2SO3+I2+CH3OH 2NaI+HSO 4CH3
Na2S2O5+I2+CH3OH 2NaI+SO 2+HSO4CH3
Accordingly, the moisture vaporization method is used with these salts.
125
II-2. Inorganic Compounds
[Examples of Measurement]
(1) Moisture vaporization - Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS) 50-100ml
Substance
Heating
temperature(C)
Sample
quantity (g)
Measurement
value (mg)
Moisture
content (%)
Sodium metabisulfite
Potassium metabisulfite
Gypsum
150
150
250
0.1926
0.2215
0.2060
11.39
3.85
14.76
5.91
1.74
7.17
(2) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS)
150ml
Aquamicron CXU
10ml
Substance
Sodium dithionite
(Sodium hydrosulfite)
Sodium sulfite
Aluminum sulfate
100C dried
200C dried
Sodium sulfate
Calcium sulfate
"
"
126
Heating
temperature(C)
Sample
quantity (g)
Measurement
value (g)
Moisture
content (%)
200
0.4796
2671
00.557
250
4.0301
247
61ppm
700
700
250
200
600
900
0.0229
0.0515
3.1305
0.0521
0.0684
0.0612
8787
8139
375
3310
4337
3868
38.400
15.800
120ppm
06.3500
06.3400
06.3200
Chapter II: Applications - 1
8. Other Salts
Key Points
Some salts react with Karl Fischer reagent and others do not. Direct
measurement is possible with salts that do not react with Karl Fischer
reagent and that can be dissolved or dispersed in a titration solvent. As
a general rule, moisture content can be determined easily by using the
moisture vaporization method. First, however, it is necessary to take the
heating temperature into consideration because of the need to check
for such factors as intramolecular dehydration. Procedures for the
various types of salts are described below.
Nitrates can be measured directly using volumetric titration. A generalpurpose dehydrated solvent is used. Depending on the solubility of the
substance, a solvent formulated for sugars may be used. Examples of
substances for which this method is suitable include ammonium nitrate,
sodium nitrate, potassium nitrate, chromium nitrate, cobalt nitrate and
mercury (I) nitrate.
Sodium nitrite cannot be measured directly as it reacts quantitatively
with Karl Fischer reagent as shown in the following formula.
NaNO2+0.5I 2+SO2+CH3OH NaI+NO+HSO4CH3
Chromates and bichromates also react with Karl Fischer reagent, but
the reactions are not quantitative. Potassium permanganate is insoluble
and will not react. Sodium tetraborate produces a similar reaction with
boric acid, and direct measurement is not possible.
Na2B4O7+7I2+7SO2+19CH3OH2NaI+12HI+7HSO 4CH3+4B(OCH3)3
Sodium arsenite reacts in the same way with oxides (anhydrous
arsenites.)
NaAsO2+2I2+SO2+2CH3OH NaI+AsI3+2HSO4CH3
Primary phosphates can be measured directly using volumetric titration.
The behavior of secondary phosphates reflects their weak basicity, but
they do not cause any significant interference. Tertiary phosphates
cause interference because of their strong basicity and they must be
neutralized with acid before Karl Fischer titration.
127
II-2. Inorganic Compounds
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS)
25-50ml
Substance
Dehydrated
solvent
Sample
quantity (g)
Measurement
value (mg)
Di-ammonium hydrogen phosphate
Sodium nitrate
Sodium nitrate
General-use
0.1511
2.1116
2.2079
3.94
2.46
2.73
"
Sugar-type
Moisture
content (%)
2.61
0.116*
0.124**
Note:* Partially insoluble. ** Soluble
(2) Moisture vaporization - Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS) 50-100ml
Substance
Heating
temperature(C)
Sample
quantity (g)
Measurement
value (mg)
Moisture
content (%)
Sodium metasilicate
200
0.1039
41.52
40.0
(3) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS)
150ml
Aquamicron CXU
10ml
Substance
Aluminum nitrate
Sodium nitrate
"
Sodium tripolyphosphate
"
"
Di-ammonium hydrogen phosphate
Tri-sodium phosphate
Magnesium hypophosphite
128
Heating
temperature(C)
Sample
quantity (g)
Measurement
value (g)
Moisture
content (%)
700
130
400
100
150
250
110
150
180
0.0200
2.0903
0.4948
1.1821
1.1219
1.1523
0.0960
0.0342
0.0338
08853
00721
01501
01555
06044
End point
02568
18449
13640
44.300
345ppm
00.303
00.132
00.539
not reached
02.680
53.900
40.400
Chapter II: Applications - 1
9. Inorganic Gases
Key Points
The moisture content of non-condensing gases, such as nitrogen,
oxygen and hydrogen, is captured by passing the sample gas through
a titration solvent or electrolyte.
Karl Fischer titration is then carried out. It is necessary, therefore, to
obtain and assemble equipment which includes pipes for the sample
gases and gas meters. Metal pipes should be used at the injection
ports. Pipes made of vinyl chloride or other plastics should be avoided
as these absorb atmospheric moisture.
For volumetric titration, an absorption solution is prepared by mixing a
general-use dehydrated solvent with propylene glycol in a ratio of 3:1.
For short periods, general-use dehydrated solvent can be used alone.
In such cases, changes in the quantity of the titration solvent, caused
by volatilization, must be monitored carefully.
For substances with low moisture content, accurate measurements can
be obtained by using a low-titer Karl Fischer reagent.
Because of the minute amounts of moisture in inorganic gases, we
recommend coulometric titration.
[Examples of Measurement]
(1) Volumetric titration
Place 150ml of dehydrated solvent in a titration flask. Titrate the Karl Fischer
reagent to the end point to remove all moisture. Next pass the sample gas
through the dehydrated solvent in the titration flask at a rate of 0.2-0.5l/min.
The flow of gas should be measured using a gas meter. Stop the flow of gas
(A) after the amount of water absorbed into the dehydrated solvent has
reached 5-50mg. Titrate (Bml) immediately using a Karl Fischer reagent with
a known titer (FmgH20/ml). Calculate the moisture content (W%) according
to the following formulae.
W (Vol%) =
W (Wt%) =
760
(273t)
B F 1.244
P
273
A 100
B F
P
273
A
760
273 t
M
1000
22.4
100
100
129
II-2. Inorganic Compounds
Here,
P: Atmospheric pressure (mmHg) at time of measurement
t: Temperature of gas at time of measurement (C)
M: Molecular weight of sample gas
Sample gas
Hydrogen
Nitrogen
Oxygen
Sample quantity (l)
Titration quantity
(ml)
Moisture content
(v/v%)
10.0
30.0
30.0
2.21
0.38
3.09
0.030
0.0017
0.014
Note:Using Karl Fischer Reagent SS (titer: 1mg/ml)
Reference:Muroi, K., Bunseki Kagaku [Analytical Chemistry] 10, 847
(1961).
"Determination of a Micro-quality of Water in Gaseous Sample
by the Karl Fischer Method"
(2) Coulometric titration
Inject 150ml of Aquamicron AX into the anode chamber of an electrolytic cell
fitted with a gas adapter. Inject 10ml of Aquamicron CXU into the cathode
chamber. Apply an electrolytic current to the Aquamicron AX while stirring,
and use coulometric titration to remove all water from the system. Next, pass
the sample gas into the electrolytic cell via the gas adapter at a rate of 0.30.5l/min. Use a gas meter to measure the volume of the gas flow. Stop the
flow of gas after the amount of water absorbed into the Aquamicron AX has
reached 0.1-5mg. Immediately, carry out coulometric titration to the end
point and calculate the moisture content.
Sample gas
Nitrogen
Oxygen
Hydrogen
Argon
130
Sample quantity (l)
Titration quantity
(g)
Moisture content
(v/vppm)
20
20
20
20
475
171
099
028
31.6
11.4
6.8
1.9
Chapter III: Applications - 2
Chapter III: Applications - 2
131
III-1. Industrial Products
132
Chapter III: Applications - 2
Chapter III: Applications - 2
In this section we provide some actual examples of the use of Karl Fischer
titration with chemical products, other industrial products, foodstuffs,
pharmaceuticals and other substances.
III-1. Industrial Products
Most general chemical and industrial products consist of organic or
inorganic compounds, either singly or as mixtures. This means that for many
products moisture content can be determined using Karl Fischer titration.
Because of the wide variety of substance characteristics and forms,
however, it is important to choose the most appropriate measurement
method with reference to the substances that make up each product. In this
chapter we give actual examples of moisture measurement for as many
products as possible.
1. Fertilizers
Key Points
Single-salt fertilizers, such as ammonium sulfate, ammonium chloride,
ammonium nitrate, urea and potassium chloride, can be either
dissolved or dispersed in a general-use dehydrated solvent for Karl
Fischer titration. Other substances, such as synthetic fertilizers
containing urea, should be dispersed in a general-use dehydrated
solvent in preparation for Karl Fischer titration. The moisture content of
synthetic fertilizers that do not contain urea can be measured using the
moisture vaporization method.
Coulometric titration can be used only in conjunction with moisture
vaporization.
Moisture vaporization is sometimes effective with fertilizers, but account
must be taken of the fact that some ingredients in compound fertilizers,
such as urea, ammonium phosphate and single superphosphate, break
down when heated to certain temperatures.
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS) 25-50ml
133
III-1. Industrial Products
Substance
Ammonium sulfate
Ammonium chloride
Sodium nitrate
Ammonium nitrate
Urea
Potassium chloride
Urea+ammonium nitrate
Urea+ammonium sulfate
+ammonium phosphate
Chemical fertilizer
High-grade chemical fertilizer
Sample quantity Measurement value
(g)
(mg)
Moisture Content
(%)
Heating loss method
(%)
5.1321
5.0541
2.5784
5.0635
2.5089
2.5113
2.5213
2.5055
0.70
1.80
15.60
5.01
1.40
8.80
23.75
33.75
136ppm
356ppm
0.605
0.099
558ppm
0.350
0.942
1.35
0.016
0.044
0.59
0.080
0.060
0.36
0.94
1.30
0.4920
0.1500
14.63
5.34
2.97
3.56
2.23
3.30
(2) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS)
150ml
Aquamicron CXU
10ml
Substance
Ammonium sulfate
Chemical fertilizer
High-grade chemical fertilizer
134
Heating Temperature Sample Quantity
(C)
(g)
100
100
100
0.6294
0.0998
0.0929
Measurement Value Moisture Content
(g)
(%)
2827
2000
3539
0.449
2.00
3.81
Chapter III: Applications - 2
2. Agricultural Chemicals
Key Points
Direct Karl Fischer titration is possible for substances that can be
dissolved in dehydrated solvent. Samples of main ingredients and other
products can be dissolved in a general-use dehydrated solvent and
titrated directly. Powders that include fillers and other substances
should be stirred for a while in a general-use dehydrated solvent. The
moisture content can then be fully extracted and titrated.
Alternatively, the moisture vaporization method can be used.
However, chloropicrin is oxidative and causes interference by freeing
iodine.
Substances that may react with Karl Fischer reagent include copper
powders, mercury powders, copper-mercury powders, zineb granules
and arsenate-lime powders. The normal moisture vaporization method
is suitable for agricultural chemicals in solid form. Adhesion water can
be measured at 100-150 C. The heating temperature should be
determined in accordance with the individual substance.
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS)
Substance
Sample Quantity Measurement value Moisture Content
(g)
(mg)
(%)
Chloropicrin
3.3387
0.31
0.0093
Kitazine-P
Insecticide
Captan
Namekat
Powdered sulfur
1.0875
5.1263
0.2394
0.1437
1.0222
2.27
3.51
6.64
5.69
5.93
0.2090
685ppm
2.7700
3.9600
0.5800
(2) Coulometric titration
Reagents used: Aquamicron AX (or AS)
Aquamicron CXU
25-50ml
Remarks
Turns brown
immediately after
end point
Insoluble
100ml
5ml
135
III-1. Industrial Products
Sample quantity Measurement value Moisture content
(g)
(g)
(%)
Substance
IBP*
1.0260
2210
0.215
*:O,O-Diisopropyl-S-benzylthiophosphate
(3) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS)
150ml
Aquamicron CXU
10ml
Substance
Heating Temperature Sample Quantity
(C)
(g)
TPN (Daconil)
Zineb (Diefar)
Namekat
Captan
Bryeslin powder
100
110
110
110
150
0.4867
0.1021
0.1314
0.0679
0.1109
Measurement Value Moisture Content
(g)
(%)
0241
1459
6606
1914
4822
495ppm
1.43
5.03
2.82
4.35
Captan: N-Trichloromethylthio-4-cyclohexene-1,2-dicarboximide
TPN: Tetrachloroisophthalonitrile
Zineb: Zinc ethylenebisdithiocarbamate
3. Glass/Ceramics
Key Points
Because glass, ceramics and similar substances do not dissolve in
organic solvents, both volumetric titration and coulometric titration are
used in combination with moisture vaporization.
The heating temperature and other conditions for moisture vaporization
must be determined with reference to the type of sample. Particular
care is required with glass as it will melt at certain temperatures and
adhere to the sample boat used in the moisture vaporization method.
Up to about 600C, adhesion can be stopped if the boat is covered with
aluminum foil.
Direct titration is not possible with cement. The moisture content of
cement is chemically bonded, while the oxides in cement cause
interference by reacting with Karl Fischer reagent to produce water. The
usual method is to carry out moisture vaporization at 800-1,000 C,
followed by Karl Fischer titration.
136
Chapter III: Applications - 2
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS)
Substance
Porous glass powder
25-50ml
Sample quantity Measurement Value Moisture Content Vaporization method
(g)
(mg)
(%)
(%)
0.1589
2.50
1.56
(2) Moisture vaporization - Volumetric titration
Reagents used:Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS) + PG (3:1)
Substance
Hydrated cement
1.55
50-100ml
Heating temperature Sample quantity Measurement Value Moisture Content
(C)
(g)
(mg)
(%)
700
0.1291
19.85
15.3
(3) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS) 150ml
Aquamicron CXU
10ml
Substance
Glass wool
Lead glass (powder)
Fluorine glass
Phosphate glass
Porous glass (powder)
Sealer
Glass
Ceramics (powder)
IC ceramics
Cement
Cellite (dried)
Heating temperature Sample quantity Measurement Value Moisture Content
(C)
(g)
(g)
(ppm)
200
400
700
800
300
800
600
130
800
800
180
0.5127
0.7471
0.9856
0.2757
0.2062
2.2730
1.0121
2.5429
6.7010
0.3102
0.1721
196
811
79
285
3199
339
34
2974
222
2219
128
382
0.109%
080
0.103%
0.155%
149
034
0.117%
033
0.715%
743
137
III-1. Industrial Products
4. Liquefied Petroleum Gases
Key Points
Liquefied petroleum gases, such as propane and butane, can be
added directly to dehydrated solvents or electrolytes and subjected to
Karl Fischer titration, using either the volumetric or coulometric
methods. Coulometric titration is most suitable, since liquefied
petroleum gases usually contain only trace amounts of moisture.
To obtain accurate measurements of moisture content, it is important to
add the sample in the liquid phase. In particular, allowance must be
made for a marked tendency for fluctuations in the moisture content of
samples at around the 50ppm level. Be sure to inject the entire sample
into the sampling bottle. For details of the methods used,
refer to the LPG Testing Method Standards of the Japan LPG
Association.
Reference:Muroi, K. et al., "Rapid Determination of Water in LPG by
KarlFischer Method" J. Japan Petroleum Institute 11, 440
(1968).
Sampling Method
Liquid-phase samples are obtained as follows.
(1) Place the canister containing the gas upside-down or on an angle.
Connect a high-pressure sampling bottle to the canister outlet using a
hose designed for this purpose (Figure 22).
(2) Open valves A and B of the sampling bottle. Next, gradually open the
valve on the canister, allowing a small amount of the gas to vaporize.
Release the gas through the sampling bottle.
(3) Close valve B, and open the valve on the canister to release the sample
into the sampling bottle.
Note:The sample can be moved into the sampling bottle by opening
and closing valve B, repeatedly. Do not fill the bottle completely
with liquid sample. Always keep the sample below 80% of the
volume and leave some vapor space.
138
Chapter III: Applications - 2
(4) Close valve A and the valve on the canister. Remove the hose. Weigh
the sampling bottle, and then attach a syringe needle to valve B (Figure
21).
Syringe needle
Extension pipe
Figure 21: Sampling bottle and hose
Figure 22:Obtaining a sample from a
gas canister
Titration Method
Coulometric titration (or volumetric titration) is carried out as follows.
(1) First place 150ml of anolyte (or 100ml of general-use dehydrated
solvent) in an electrolytic cell and use coulometric titration (or Karl
Fischer Reagent SS-X) to remove all moisture.
(2) Introduce the syringe needle through the side port of the electrolytic cell
(or titration flask) until it reaches the bottom of the cell (or titration flask),
as shown in Figure 23.
Gas vent
Aquamicron CXU
Aquamicron AX
Electrolytic cell
Figure 23: Injecting the sample (coulometric titration)
139
III-1. Industrial Products
(3) Gradually open valve B while stirring the anolyte (or general-use
dehydrated solvent). Inject the sample for 10-15 minutes (at a rate of
about 1g/min.).
Note:The sample will gasify as it is injected and it will escape through
the upper vent valve into a draft chamber, or to the outside air.
(4) Withdraw the syringe from the sampling bottle.
(5) Weigh the sampling bottle. Subtract this weight from the weight before
the injection of the sample to determine the weight of the sample.
(6) Titrate the moisture absorbed into the anolyte (or general-use
dehydrated solvent) to the end point, using coulometric titration
(volumetric titration).
(7) Calculate the moisture content using the following formulae.
For coulometric titration:
Moisture content (ppm) = measurement value (g)/sample quantity (g)
For volumetric titration
Moisture content (ppm) =
Titration volume(ml) Titer(mgH2O/ml)
100
sample quantlty (g) 1000
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS)
Substance
LPG
Propane
Methyl chloride
Vinyl chloride
Sulfur dioxide
Aerosol
Sample quantity
(g)
Titration quantity
(mg)
Moisture content
(ppm)
25.1
29.0
18.3
15.7
53.1
27.4
1.40
1.11
4.95
7.41
17.6
1.18
56
38
271
475
331
35
(2) Coulometric titration
Reagents used: Aquamicron AX (or AS)
Aquamicron CXU
140
100ml
150ml
10ml
Chapter III: Applications - 2
Substance
Sample quantity
(g)
LPG
Ethylene
Propane
Butadiene
Flon gas R113
Spray cans
Titration quantity
(g)
23.24
40.06 L
6.50
16.63
7.97
6.26
Moisture content
(ppm)
253
55
280
120
234
1008
11
1.7
43
7.2
29
161
5. Coals, Tars
Key Points
The moisture content of coals is normally measured using a moisture
vaporization system. Measurements can be obtained using either
volumetric or coulometric titration.
Tars are subjected to Karl Fischer titration using the moisture
vaporization system designed for oils.
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX, OL II (or MS, CM)
Substance
Brown coal
Coal tar
Dehydrated
solvents
Sample Quantity
(g)
General-use
Oil-type
0.0389
0.1619
25-50ml
Measurement Value Moisture Content
(mg)
(%)
4.38
7.30
11.3
04.5
(2) Moisture vaporization - Volumetric titration
Reagents used: Karl Fischer Reagent SS-X (or SS)
Dehydrated Solvent GEX (or MS) + PG (3:1) 50-100ml
Substance
Powdered coal
Heating Temperature Sample Quantity
(C)
(g)
150
0.1262
Measurement Value Moisture Content
(mg)
(%)
5.76
4.56
141
III-1. Industrial Products
(3) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS) 150ml
Aquamicron CXU
10ml
Substance
Brown coal
Powdered coal
Coal tar
Coke
Pitch tar
142
Heating Temperature Sample Quantity
(C)
(g)
110
130
150
500
180
0.0497
0.2509
0.1114
0.0448
0.4892
Measurement Value Moisture Content
(g)
(%)
5456
1188
4718
1813
335
11.0
0.473
4.24
4.05
685ppm
Chapter III: Applications - 2
6. Petroleum Products
Key Points
Karl Fischer titration is an excellent method for the measurement of
trace moisture in petroleum products. Karl Fischer titration has been the
standard test method for the Petroleum Society since 1976, and it
became a Japan Industrial Standard in 1982.
As moisture is generally present only in trace quantities in petroleum
products, coulometric titration is presently in widespread use.
Coulometric titration is carried out by adding a sample, such as
insulating oil, refrigerating machine oil, transformer oil, kerosene or
diesel oil, to an electrolyte.
The sample is added 5-10ml at a time. Though some substances fail to
dissolve and may cloud the solution, their moisture content can be
measured once they are thoroughly dispersed.
For volumetric titration, the substance is dissolved in a dehydrated
solvent formulated for oils. Karl Fischer titration can then be carried out
directly. Silicon oils can be titrated directly by adding samples to a
ketone-type dehydrated solvent.
Some additives, such as antioxidants, cause interference reactions with
Karl Fischer reagent. If lubricants (e.g. gasoline engine oils and diesel
engine oils) and other products contain such substances, Karl Fischer
titration must be carried out using an oil-type moisture vaporization
system.
Dissolve greases that do not contain interference substances in oil-type
dehydrated solvent and titrate directly. For those that do contain
interference substances, Karl Fischer titration should be carried out
indirectly using a moisture vaporization system.
Petroleum products occasionally contain trace amounts of mercaptan
or hydrogen sulfide. These react with Karl Fischer reagent. They react
quantitatively with iodine on a mole for mole basis, however, so
provided that the amount of mercaptan or the hydrogen sulfide content
is known, moisture content can be determined accurately through
adjustment of the titration result.
2RSH+I2 2RSSR+2HI
H2S+I2 2S+HI
As shown in the above formulae, 1ppm of sulfur in mercaptan or
hydrogen sulfide is equivalent to 0.28ppm and 0.56ppm of moisture
content, respectively.
143
III-1. Industrial Products
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX, OL II (or MS, CM)
Substance
Industrial gasoline
Aviation gasoline
Kerosene
Diesel oil
Heavy oil
Crude oil
Transformer oil
Refrigerating machine oil
Rust preventive oil
Compressor oil
Air filter oil
Heat treatment oil
Hydraulic oil
Rolling oil
Hydraulic actuation oil
Rotary pump oil
Aviation oil
Fluoride oil
Liquid paraffin
Asphalt
Cutting oil
Grinding oil
Wax
Brake oil
144
Quantity
Dehydrated solvents Sample(g)
Oil-type
"
"
"
"
"
"
"
"
"
"
"
"
"
"
"
"
"
"
"
"
"
"
General-use
20.0
20.0
20.0
20.0
1.0805
1.5023
20.0
20.0
20.0
15.0
20.0
20.0
20.0
20.0
20.0
30.0
15.0
20.0
30.0
5.0
15.0
15.0
0.1001
1.0555
25-50ml
Measurement Value Moisture Content
(mg)
(ppm)
0.42
0.30
1.22
1.66
27.88
5.41
0.52
1.24
1.80
3.60
1.96
1.10
0.30
1.08
0.84
0.30
1.50
0.34
0.45
0.95
1.58
2.01
4.72
1.27
21
15
61
83
2.58%
0.360%
26
62
90
240
98
55
15
54
42
10
100
17
15
190
105
134
4.72%
0.120%
Chapter III: Applications - 2
Substance
Quantity
Dehydrated solvents Sample(g)
Measurement Value Moisture Content
(mg)
(ppm)
[Insulating oil]
Mineral oil
Oil-type
Alkylbenzene 2-1
"
Alkylbenzene 2-2
"
Alkylbenzene 2-3
"
Polybutene 3-1
"
Polybutene 3-2
"
Polybutene 3-3
"
Alkyl naphthalene 4-1
"
Alkyl naphthalene 4-2
"
Alkyl diphenyl ethane
"
Silicon oil
Ketone-type
8.8431
8.5784
8.7058
8.3116
8.1933
6.8850
5.9730
9.2462
9.3594
9.4135
9.6343
0.20
0.17
0.55
0.23
0.14
0.19
0.11
0.15
0.14
0.38
0.37
23
20
63
28
17
28
18
16
15
40
38
(2) Moisture vaporization - Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS) + PG (3:1) 50-100ml
Substance
Gasoline engine oil
Diesel engine oil
Marine engine oil
Marine cylinder oil
Cap grease
JIS 1-1
JIS 2-2
Fiber greases
JIS 2-3
JIS 2-4
Graphite greases JIS 1-1
JIS 2-1
Heating Temperature Sample Quantity
(C)
(g)
150
150
150
150
120
140
140
140
140
120
Measurement Value Moisture Content
(mg)
(%)
0.66
0.94
1.04
1.91
2.39
4.20
0.39
0.43
1.89
1.11
4.3793
5.5145
5.4998
5.4565
1.0865
1.0776
1.0112
1.0523
1.0519
1.0219
(3) Coulometric titration
Reagents used: Aquamicron AX (or AS)
Aquamicron CXU
0.015
0.017
0.019
0.035
0.220
0.390
0.039
0.041
0.180
0.109
100ml
5ml
145
III-1. Industrial Products
Substance
Sample Quantity
(g)
Gasoline
Naphtha
Kerosene
Heavy oil
Rolling oil
Aviation oil
Refrigerating machine oil
Actuation oil
Brake oil
Liquid paraffin
Electric insulating oils
Alkylbenzene
3.9353
0.7280
0.7940
4.4103
4.3029
2.5869
2.4350
4.2943
2.9758
8.6600
4.1460
4.3132
Measurement Value Moisture Content
(g)
(ppm)
351
117
27
286
233
270
101
387
904
130
77
73
89
161
34
65
54
104
42
90
304
15
19
17
(4) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS)
150ml
Aquamicron CXU
10ml
Substance
Diesel oil
Heavy oil
C heavy oil
Mineral oil
Turbine oil
Rolling oil
Aviation oil
Engine oil
Gasoline engine oil
Diesel engine oil
Gear oil
Cutting oil
Actuation oil
Grinding oil
Turbine oil
Brake fluid
Hydraulic oil
Rust preventive oil
Machine oil (paraffin)
Machine oil (naphthene)
Crude oil
Wax
146
Heating Temperature Sample Quantity
(C)
(g)
130
110
150
130
130
110
130
130
180
130
130
150
130
150
130
150
130
130
130
130
130
150
4.0973
4.4278
0.3820
4.5434
8.4001
4.3029
3.3879
0.9133
4.6133
4.3132
2.6322
1.7824
4.2394
1.7166
4.4632
2.9758
4.3793
1.7590
4.3941
4.5122
0.4156
0.7235
Measurement Value Moisture Content
(g)
(ppm)
241
290
2188
273
296
233
328
908
168
1298
244
134
98
186
149
904
392
532
263
274
1506
8
59
66
0.573%
60
35
54
97
994
36
301
93
75
23
108
33
304
90
303
60
61
0.362%
11
Chapter III: Applications - 2
7. Plastics
Key Points
Plastics reach high temperatures during the molding process and trace
amounts of moisture can cause bubbling or seriously affect the
performance of a plastic by reducing its molecular weight through
pyrolysis. This means that moisture management is a very important
aspect of the drying processes for plastics. Karl Fischer titration is the
ideal method for measuring trace moisture content in plastics. The
moisture vaporization method permits accurate and relatively fast (1030 minutes) determination of moisture content.
When using the moisture vaporization method, it is important to set the
heating temperature with reference to the type of plastic. The optimal
temperature range must be determined for each plastic. The generally
accepted view is that plastics should be heated to around melting
point. Figure 24 provides guidelines on the appropriate heating
temperatures
[If the analytical result is low]
If the heating temperature is too low, moisture vaporization will be delayed
and the analytical time will be longer. The measurement process may end
before the moisture has been vaporized, leading to a low analytical result.
The result may also be low if vaporized moisture is absorbed by additives or
degraded plastic constituents that have condensed in the tubes of the
moisture vaporization system.
[If the analytical result is high]
Plastics that contain OH bases, such as polyvinyl alcohol, phenol resin and
polyvinyl acetate, may produce high readings if the heating temperature is
too high. It may be impossible to complete titration in some cases. Such
phenomena appear to be caused by the formation of water through heating.
Moisture content of urea resin cannot be measured normally at temperatures
above 120C because ammonia produced through the breakdown of urea
resins reacts with iodine. Melamine resins appear to cause interference in
the same way.
147
III-1. Industrial Products
Sample
Melting
point (C)
Heating temperature (C)
120
160
200
240
Ionomer resins
Polymethyl methacrylate
Urethane resins
Epoxy resins
183
120-150
ABS resins
6-Nylon
225
6,6-Nylon
267
Urea resins
Phenol resins
Low-density polyethylene
108-120
Polyethylene terephthalate
248-260
Polybutylene terephthalate
218-219
Polyvinyl chloride
200-210
Polyoxymethylene
175-180
Polycarbonate
222-230
Polystyrene
Polypropylene
Polyvinyl alcohol
230
168-170
245
Polyvinyl butyral
Melamine resin
Polytetrafluoroethylene
320-330
Polyimide
Ethylene-vinyl acetate
copolymers
Figure 24: Optimal Moisture Vaporization Temperature Ranges for Plastics
Reference:Kato, H. et al.: Kobunshi Kako, 35, 584 (1986).
Muroi, K. et al.: Bunseki Kagaku, 11, 351 (1962).
148
280
Chapter III: Applications - 2
[Examples of Measurement]
(1) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS)
150ml
Aquamicron CXU
10ml
Substance
Polyethylene
Cross-linked polyethylene
Polypropylene
Vinyl chloride
Vinyl acetate
Ethylene vinyl acetate copolymer
Polyvinyl alcohol
Polyvinyl butyral
Polystyrene
Styrol foam
Polyester
PET
PBT
Polycarbonate
Polyacetal
Phenol resins
6-Nylon
6,6-Nylon
Metacrylic resins
ABS resins
Urea resins
Fluorine resins
Epoxy resins
Polyol
Urethane
Heating Temperature Sample Quantity
(C)
(g)
180
180
160
130
130
180
150
180
180
130
230
230
250
250
200
200
230
250
250
200
110
160
120
150
180
3.7702
1.2786
2.3185
0.9815
1.5925
0.4743
0.1392
0.5641
2.7896
0.2892
2.4615
4.6003
1.2020
1.0830
1.5227
0.1142
0.2211
0.0492
1.6017
0.8455
0.4898
2.4470
0.4142
1.0286
1.4886
Measurement Value Moisture Content
(g)
(ppm)
67
145
97
412
1549
1005
3739
1486
965
218
512
171
223
972
2181
5227
3007
1200
1337
2073
3587
18
2360
1258
3136
18
113
42
420
973
0.212%
269
0.263%
345
753
208
37
186
898
0.143%
4.58%
1.36%
2.44%
835
0.245%
0.732%
7
0.570%
0.122%
0.211%
149
III-1. Industrial Products
8. Rubber, Rubber Products, Compounding Agents
Key Points
The qualities of rubber are adversely affected by the presence of
moisture in raw materials or in compounding agents. Moisture content
can be measured accurately, quickly (10-20 minutes) and conveniently
by combining moisture vaporization with coulometric titration.
Hints:
1. The sample should weigh between 0.5g and 1g.
2. The heating temperature for moisture vaporization should be 130-200C.
Direct titration is not possible with vulcanization accelerators and
antioxidants as these react with Karl Fischer reagent to release iodine.
The moisture content of carbon black cannot be measured through
direct titration as the end point cannot be determined.
Reference:Muroi, K. et al.: Journal of Japan Rubber Institute, 52, 61
(1979).
[Examples of Measurement]
(1) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS)
150ml
Aquamicron CXU
10ml
Substance
[Rubber]
NBR (nitrile-butadiene rubber)
SBR (styrene--butadiene rubber)
CR (chloroprene rubber)
Butyl rubber
Silicon rubber
EPR (ethylene propylene rubber)
Natural rubber
[Rubber products]
Rubber caps
Power cable rubber
Oil seal rubber
Tire rubber
Silicon rubber
150
Heating Temperature Sample Quantity
(C)
(g)
Measurement Value Moisture Content
(g)
(%)
150
150
130
150
200
180
150
0.8001
1.2264
1.4352
1.9435
0.1657
3.4106
0.6374
2554
0475
1148
0894
2081
1001
1734
000.319
387ppm
800ppm
460ppm
001.25
293ppm
000.272
150
130
150
200
200
0.6121
0.0977
0.3228
0.5031
0.4937
3158
0871
1661
2635
1199
000.516
000.892
000.515
000.524
000.243
Chapter III: Applications - 2
Sample
80
100
Heating temperature (C)
120 130
150 160
180
200
Raw rubber
NR
SBR
BR
CR
NBR
Vulcanization accelerants
OBS
D
DM
CZ
TT
Antioxidants
DMBPPD
IPPD
Stearic acid
Zinc oxide
Paraffin wax
Carbon black
Sulfur
Process oil
Figure 25: Optimal Heating Temperature Range for Raw Rubber and
Compounding Agents
Reference:Muroi, K. et al.: Journal of Japan Rubber Institute, 52, 61
(1979).
151
III-1. Industrial Products
9. Fibers, Papers
Key Points
Because samples of fibers and paper do not dissolve in dehydrated
solvent, moisture content is measured using moisture vaporization
followed by Karl Fischer titration (volumetric or coulometric).
A heating temperature of 130-150 C is appropriate for moisture
vaporization. Moisture content in samples of these substances typically
reaches several per cent. The following guidelines are suggested for
sample quantities.
1) Volumetric titration: 0.5g
2) Coulometric titration: 0.05-0.1g
Reference:Muroi, K. et al., "Determination of Water Content in Electric
Insulating Papers by the Karl Fischer Method" in Bunseki
Kagaku 30, 624 (1981).
[Examples of Measurement]
(1) Moisture vaporization - Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS) + PG (3:1) 50-100ml
Substance
Bakelite paper
Condenser paper
Pressed board paper
Filter paper
Heating Temperature Sample Quantity
(C)
(g)
150
150
150
230
Measurement Value Moisture Content
(mg)
(%)
0.5111
0.4955
0.6646
0.1700
(2) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS)
150ml
Aquamicron CXU
10ml
152
34.70
36.74
49.29
08.82
6.80
7.42
7.42
5.19
Chapter III: Applications - 2
Substance
Kraft paper
Synthetic paper
Woodfree paper
Machine-made paper
Photocopy paper
Oil paper
Paper tape
Cellotape
Copy paper
Cellulose (paper)
Acrylic fibers
Polyester
Chemical fibers
Wool
Absorbent cotton
Heating Temperature Sample Quantity
(C)
(g)
150
150
150
150
150
180
150
150
150
150
110
180
180
150
150
0.0663
0.0563
0.0201
0.0948
0.0665
0.0526
0.2057
0.0741
0.8160
0.0500
0.2396
0.2177
0.0497
0.0838
0.0631
Measurement Value Moisture Content
(g)
(%)
3840
2910
0722
4793
3099
3160
4892
6975
2553
3057
2653
0430
2596
7225
4379
5.79
5.17
3.59
5.06
4.66
6.01
2.38
9.41
0.313
6.11
1.07
0.198
5.22
8.62
6.94
10. Dyestuff Intermediates
Key Points
Many dyestuff intermediates are solids and must be dissolved in
solvents. Most Japanese Industrial Standards stipulate volumetric
titration. These standards should be taken into account when setting
conditions for the moisture content test methods that should be used
with individual compounds.
To raise the solubility of specific substances in the dehydrated solvent
used for the volumetric titration, it may be necessary to add other
solvents, such as those listed below, to the methanol. It should also be
noted that special solvents are sometimes used with amines.
Volumetric titration solvents and the main compounds for which they
are used
1) Dehydrated Solvent MS (or GEX)
2) Dehydrated Solvent CP : anilines, o-anisidines, p-cresidines, p chloroanilines
CP+acetic acid : p-anisidines, p-phenetidines,
m-aminophenols
3) Dehydrated Solvent PE : Peri acid
153
III-1. Industrial Products
4) Dehydrated Solvent MS+pyridine : metanilic acid,
o-toluenesulfonamide, C-acids
5) Dehydrated Solvent MS+dichloromethane : nitro compounds,
some chloro compounds
Coulometric titration can be used. However, interference reactions
make it unsuitable for some substances (* e.g. anilines and other
electrode-reactive substances).
Substances for which coulometric titration cannot be used
Anilines, p-anisidines, m-aminophenols, p-chloroanilines, p-toluidines,
metanilic acid
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX, KT (or MS, CP) 25-50ml
Substance
Dehydrated solvents
p-Toluidines
p-Anisidines
p-Phenetidines
m-Aminophenols
Anthranilic acid
Diphenyl amine
2-Aminonaphthalene
-1-sulfonic acid
Sodium naphthionate
J-acid
Carbonyl J-acid
m-Nitroaniline
p-Nitrophenol
1-Hydroxy-2-naphthoicacid
Anilines
5-Amino-2-chlorotoluene
-4-sulfonate(C-acid)
CP+acetic acid (2:1)
154
Sample Quantity
(g)
Measurement Value Moisture Content
(mg)
(ppm)
"
"
2.9253
2.0115
1.1072
1.0152
1.0164
8.3429
0.5290
0.89
0.46
1.68
0.29
0.11
0.25
1.62
304
229
0.152%
286
108
30
0.306%
"
"
"
"
"
"
Ketone-type
MS+pyridine (5:1)
0.0593
0.1051
0.2062
1.5089
0.9844
2.0959
2.1601
1.9911
13.45
5.88
6.15
0.95
11.30
0.54
1.92
0.09
22.7
5.60%
2.98%
630
1.15%
258
889
45
"
"
"
General-use
Chapter III: Applications - 2
(2) Coulometric titration
Reagents used: Aquamicron AX (or AS)
Aquamicron CXU
100ml
5ml
Substance
Electrolyte
Sample Quantity
(g)
Measurement Value Moisture Content
(g)
(ppm)
Anthranilic acid
Diphenyl amine
2-Aminonaphthalene-1sulfonic acid(Tobias acid)
Sodium naphthionate
8-Amino-2-naphthalene
sulfonic acid(Peri acid)
m-Aminophenol
General-use
"
"
1.1934
4.0630
0.5500
370
104
1721
310
026
0.313%
"
"
0.0514
0.0561
11653
4260
22.7%
7.59%
Ketone-type
0.4592
117
255
11. Pigments
Key Points
Most pigments are insoluble in titration solvents and cannot be titrated
directly. In particular, direct titration should be avoided with inorganic
pigments which react with Karl Fischer reagent.
The moisture content of any pigment can be measured quickly (10-30
minutes) and accurately using the conventional drying method based
on moisture vaporization. Either volumetric or coulometric titration can
be used, depending on the moisture content.
(1) Moisture vaporization - Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS) + PG (3:1) 50-100ml
Substance
Zinc white
Titanium oxide
Prussian blue
Red iron oxide
Chrome yellow
Aluminum powder
Antimony oxide
Calcium carbonate
"
Barium carbonate
Heating Temperature Sample Quantity
(C)
(g)
300
200
200
300
300
400
300
100
600
500
3.1135
1.0405
0.4002
3.0021
2.9988
5.0211
3.5011
2.1111
1.0050
3.1009
Measurement Value Moisture Content
(mg)
(%)
3.73
4.16
22.17
10.21
8.40
1.00
3.85
10.77
16.18
4.03
0.120
0.400
5.540
0.340
0.280
199ppm
0.110
0.510
1.610
0.130
155
III-1. Industrial Products
(2) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS)
150ml
Aquamicron CXU
10ml
Substance
Cuprous oxide
"
Titanium oxide
Yellow pigment
Red pigment
Barium carbonate
Heating Temperature Sample Quantity
(C)
(g)
230
700
200
230
200
500
0.3651
0.1497
1.0378
0.1949
0.0415
3.1009
Measurement Value Moisture Content
(g)
(%)
2959
1953
3631
2028
2370
4.30
0.810
1.300
0.350
1.040
5.710
0.130
12. Paints
Key Points
Moisture content in paints causes bubbling, condensation and lumps in
painted surfaces. Moisture measurement is, therefore, very important
for quality management.
Drying methods cannot be used as there is a risk that other constituents
will vaporize with the water. Distillation is also unsuitable because it
takes too long, and because many paints include hydrophilic
substances that are difficult to separate. As a result, Karl Fischer
titration has been chosen as the moisture measurement method for
paints and it is stipulated as a Japanese industrial Standard (K5407).
Paints include a variety of film-forming substances as well as various
other ingredients such as enamels with pigments and varnishes, some
of which may react with Karl Fischer reagent.
The possibility that some of these substances will cause an interference
reaction is something that must be checked in advance.
JIS K5407 (testing method for paint constituents) stipulates both
volumetric and coulometric titration. The level of moisture content in
paints is generally within the range for either method. If a product
contains a number of substances that will not dissolve in solvents,
volumetric titration should be used in preference to coulometric titration.
For volumetric titration, the sample must be dissolved or dispersed in a
suitable solvent in preparation for Karl Fischer titration. A ketone-type
dehydrated solvent is excellent for samples that contain ketones. If a
sample contains other substances that cause interference reactions,
Karl Fischer titration should be used in combination with moisture
vaporization. Either volumetric or coulometric titration can be used in
156
Chapter III: Applications - 2
such cases.
Because of the high viscosity of most paints, it is difficult to obtain a
sample and inject it into a titration cell. Select equipment that matches
the characteristics of the sample, such as a thick needle (2mm
diameter), a sampling spoon or a glass rod.
(now, JIS K5407 is abolished.)
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent OL II, KT (or CM, CP) 25-50ml
Substance
Dehydrated
solvents
Oil-type
Epoxy resin paints
Fluoroethylene resin paints
"
Paints
"
Paint thinners (incl.MEK)
Ketone-type
Melamine varnish
"
Sample Quantity
(g)
0.6645
1.0017
0.9953
4.8894
0.1504
Measurement Value Moisture Content
(mg)
(%)
0.43
647ppm
1.11
0.111
4.97
0.499
4.33
886ppm
1.09
0.725
(2) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS)
150ml
Aquamicron CXU
10ml
Substance
Enamel
Paints
Lacquer paint
Powder paint
Epoxy resin paint
Fluoroethylene resin paint
Polyester paint
Liquid varnish
Melamine varnish
Heating Temperature Sample Quantity
(C)
(g)
150
130
200
180
150
180
150
300
110
0.1388
1.3175
0.0650
0.4513
2.2101
1.0507
0.1931
0.1122
0.1894
Measurement Value Moisture Content
(g)
(%)
1902
0742
2798
1395
1454
1170
0978
1934
1324
1.37
563ppm
4.30
0.309
658ppm
0.111
0.506
1.73
0.699
157
III-1. Industrial Products
13. Printing Inks and Imaging Materials
Key Points
Volumetric titration is used for printing inks and imaging materials. Inks
in particular may have a high moisture content. Samples can be
obtained in small quantities and directly dissolved or dispersed in
dehydrated solvent for Karl Fischer titration. Coulometric titration is
commonly used in conjunction with moisture vaporization for samples
that cannot be dissolved in solvent or that contain interference
substances.
Because of the high viscosity of many inks, it may be difficult to obtain a
sample and inject it into a titration cell. Select equipment that matches
the characteristics of the sample, such as a thick needle (2mm
diameter), a sampling spoon or a glass rod.
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX, KTX, OL II (or MS, CP, CM) 25-50ml
Substance
Dehydrated
solvents
Sample Quantity
(g)
Printing ink
Offset ink
Metallic ink
Oil-based ink
Water-based ink
Emulsion ink
Inkjet ink
Gravure ink
[Printing ink pigment]
Carmine 6B
Lake red
Copper phthalophenone yellow
Benzidine yellow
[Ink raw materials]
Acrylates
Epoxy resins
Phenolic novolak
Photosensitive resins
Toners
General-use
Oil-type
0.4511
1.0834
0.3172
0.1768
0.0209
0.0561
0.0372
0.4125
5.85
4.33
1.66
22.83
17.51
31.75
27.34
1.38
1.30
0.400
0.523
12.9
83.8
56.6
73.5
0.335
0.4606
0.4174
0.5640
0.6273
3.28
0.71
0.74
0.74
0.712
0.170
0.131
0.118
0.6104
0.8443
0.7655
0.0315
0.1374
1.54
4.80
3.87
6.90
1.02
0.252
0.569
0.506
21.9
0.742
158
"
"
"
"
"
Ketone-type
Oil-type
"
"
"
General-use
Oil-type
"
"
Ketone-type
Measurement Value Moisture Content
(mg)
(%)
Chapter III: Applications - 2
(2) Moisture vaporization - Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS) + PG (3:1) 50-100ml
Substance
Emulsion inks
Water-based ball-pen inks
Heating Temperature Sample Quantity
(C)
(g)
200
200
0.0626
0.0338
Measurement Value Moisture Content
(mg)
(%)
34.78
18.68
55.7
55.3
14. Adhesives
Key Points
The moisture content of adhesives ranges from minute to high, so both
volumetric and coulometric titration are used. For volumetric titration,
the sample is dissolved or dispersed in a suitable solvent. Moisture
vaporization is used for substances that are totally insoluble.
Coulometric titration can be carried out directly in the case of
substances that dissolve in electrolytes. Moisture vaporization is used
for samples that are even slightly insoluble.
Adhesives are very viscous and instant adhesives solidify quickly when
exposed to air. Because of these and other characteristics, a number of
samples are very difficult to handle and sampling equipment must be
selected with reference to the attributes of each sample. If the viscosity
of the product allows it to be sampled in a syringe, use a thick needle
(2mm diameter). For substances with higher viscosity, use a sampling
spoon or glass rod. Special procedures are needed for instant
adhesives.
Refer to the following document.
Reference:Muroi, K. et al., "Determination of Minute Traces of Water in
Cyanoacrylate Adhesive Compositions by the Coulmetric Karl
Fischer Titration Method Using the Anodic Electrolytic for
Ketones" in Journal of the Japan Adhesive Society 21, 186
(1985).
159
III-1. Industrial Products
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent OL II, KTX (or CM, CP)
Substance
Dehydrated
solvents
Sample Quantity
(g)
Porcelain adhesives
Aluminum adhesives
Woodworking bonds
Construction putties
Rubber-metal adhesives
Adhesives
Oil-type
1.5001
0.5508
0.0785
0.2324
0.6883
4.4427
"
"
"
Ketone-type
"
25-50ml
Measurement Value Moisture Content
(mg)
(%)
1.65
3.75
46.70
1.78
3.14
0.79
00.110
00.681
59.500
00.766
00.456
178ppm
(2) Moisture vaporization - Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS) + PG (3:1) 50-100ml
Substance
Pastes
Woodworking bonds
Construction putties
Heating Temperature Sample Quantity
(C)
(g)
150
200
250
Measurement Value Moisture Content
(mg)
(%)
0.4960
0.0546
0.8479
01.59
32.24
02.33
00.321
59.100
00.275
(3) Coulometric titration
Reagents used: Aquamicron AX (or AS), AKX 100ml
Aquamicron CXU
5ml
Substance
Electrolyte
Epoxy resins
Isocyanate hardeners
Bonds
Cyanoacrylates
Adhesives
General-use
"
"
ketone-type
"
Sample Quantity
(g)
Measurement Value Moisture Content
(g)
(ppm)
0.5112
1.5368
0.9403
1.9786
2.3736
(4) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS)
150ml
Aquamicron CXU
10ml
160
1507
098
524
430
430
295
064
557
217
181
Chapter III: Applications - 2
Substance
Epoxy resins (powder)
Isocyanates (principal)
Silicon bonds
Aluminum adhesives
Pastes
Porcelain adhesives
Sealing compounds
Heating Temperature Sample Quantity
(C)
(g)
250
180
210
200
150
180
230
0.7074
0.3079
0.4800
0.2670
0.3230
0.9336
0.4367
Measurement Value Moisture Content
(g)
(%)
1080
0941
0909
1180
0954
0964
1218
0.153
0.306
0.189
0.442
0.295
0.103
0.279
15. Soaps and Detergents
Key Points
Because soaps and detergents generally have a high moisture content,
volumetric titration is used. The moisture vaporization method is used
for metallic soaps, some of which cause interference.
Direct coulometric titration can be used for samples that will dissolve in
electrolyte.
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX, OL II(or MS,CM) 30-50ml
161
III-1. Industrial Products
Substance
Dehydrated
solvents
Cosmetic soap
Oil-type
Soft soap
General-use
Facial soap
"
Cleansers
"
Shampoo
"
Alkyl benzene sulfonate
"
ABS detergents
"
Laundry detergents
"
High-grade alcohol detergents
"
Liquid detergent
"
Anionic surfactants
"
Cationic surfactants
"
Nonionic surfactants
"
Amphoteric surfactants
"
Polyglycerine
"
Sample Quantity
(g)
Measurement Value Moisture Content
(mg)
(%)
0.0863
0.2133
0.0549
0.0391
0.0353
0.2551
0.0345
0.0707
0.1366
0.0453
0.5323
3.0084
3.0155
1.0295
1.5572
09.61
41.59
10.84
21.36
27.68
02.29
26.23
06.03
81.41
20.54
10.86
01.84
01.48
11.43
05.45
11.500
19.500
19.800
54.600
78.400
00.897
76.000
08.600
59.900
45.400
02.040
612ppm
491ppm
1.110
0.350
(2) Moisture vaporization - Volumetric titration
Reagents used:Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS) + PG (3:1) 50-100ml
Substance
Cosmetic soaps
Facial soaps
Alkyl benzene sulfonate
ABS detergents
Laundry detergents
Cleansers
Heating Temperature Sample Quantity
(C)
(g)
200
180
150
130
180
200
0.0739
0.0998
0.1870
0.0303
0.0690
0.0503
(3) Coulometric titration
Reagents used: Aquamicron AX (or AS)
Aquamicron CXU
Substance
Soaps
Shampoos
162
Sample Quantity
(g)
0.2934
0.0209
Measurement Value Moisture Content
(mg)
(%)
07.65
19.76
01.69
22.80
05.84
27.47
100ml
5ml
Measurement Value Moisture Content
(g)
(%)
01314
16073
00.448
76.900
10.400
19.800
00.904
76.000
08.460
54.600
Chapter III: Applications - 2
(4) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS)
150ml
Aquamicron CXU
10ml
Substance
Detergents
Soaps
Cleansers
Heating Temperature Sample Quantity
(C)
(g)
180
150
600
0.0324
0.4901
0.0330
Measurement Value Moisture Content
(g)
(%)
5084
1517
2475
15.700
00.310
07.500
16. Cosmetics
Key Points
Creams, emulsions, rinses, hair tonics, lotions and other cosmetics
have high moisture content. Accordingly, volumetric titration is the main
method used with these items. When carrying out the volumetric titration
it is convenient to use a high-titer Karl Fischer reagent. An oil-type
dehydrated solvent is used for products with a high oil content, such as
creams. A general-purpose dehydrated solvent is used for hair tonics
and lotions.
Coulometric titration can also be used. However, the high moisture
content of these products means that titration will be prolonged, even
with small samples. For this reason, volumetric titration should be used
whenever possible.
Sampling devices should be selected carefully. Viscous products such
as creams should be sampled with a sampling spoon and dissolved
directly in the dehydrated solvent.For lotions and similar products, a
sampling flask with pipette is convenient. For cosmetics that will not
dissolve in dehydrated solvent, volumetric or coulometric titration
should be used in combination with moisture vaporization.
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX, OL II (or MS, CM) 25-50ml
163
III-1. Industrial Products
Substance
Cream
Emulsion
Rinse
Nourishing cream
Cleansing cream
Cold cream
Hair tonic
Hair treatments
Dehydrated
solvents
Sample Quantity
(g)
Oil-type
0.1072
0.1011
0.1151
0.0281
0.0454
0.0556
0.0409
0.0328
"
"
"
"
"
General-use
"
Measurement Value Moisture Content
(mg)
(%)
61.21
74.61
88.39
12.72
15.00
14.09
17.33
16.92
57.1
73.8
76.8
45.3
33.0
25.3
42.4
51.6
(2) Moisture vaporization - Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS) + PG (3:1) 50-100ml
Substance
Mascara
Essence
Heating Temperature Sample Quantity
(C)
(g)
150
150
0.0262
0.0660
(3) Coulometric titration
Reagents used: Aquamicron AX (or AS)
Aquamicron CXU
Substance
Cream
Cleansing cream
Emulsion
Cream lotion
Sample Quantity
(g)
0.0364
0.0416
0.0330
0.0153
Measurement Value Moisture Content
(mg)
(%)
13.53
43.42
51.6
65.8
100ml
5ml
Measurement Value Moisture Content
(g)
(%)
23089
11188
28611
11580
63.4
26.9
86.7
75.7
(4) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS)
150ml
Aquamicron CXU
10ml
Substance
Lip cream
Cream lotion
164
Heating Temperature Sample Quantity
(C)
(g)
180
180
0.0722
0.0180
Measurement Value Moisture Content
(g)
(%)
04871
13600
06.75
75.60
Chapter III: Applications - 2
17. Chemicals & Materials for Electronic Equipment and Electrical Parts
Key Points
Materials for electronic equipment and electrical parts are made of
mixed or composite materials. They vary widely in terms of both the raw
materials and their form. The methods used to measure moisture
content must be selected with reference to the characteristics of each
item. These items generally have a low moisture content and many are
insoluble in solvents. For this reason, moisture content is measured
using moisture vaporization and coulometric titration.
Chemical products such as liquid crystals, photoresists and capacitor
electrolytes can be dissolved in dehydrated solvents or electrolytes.
This means that they can be titrated directly using volumetric or
coulometric titration.
Chemical substances may be either liquid or solid. For viscous liquids,
a syringe with a 2mm diameter needle should be used.
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX, OL II (or MS, CM) 25-50ml
Substance
Capacitor electrolyte
Liquid crystal
Photoresist
Dehydrated
solvents
Sample Quantity
(g)
General-use
0.0454
1.0998
1.0823
"
Oil-type
(2) Coulometric titration
Reagents used: Aquamicron AX (or AS)
Aquamicron CXU
Substance
Liquid crystal
Photoresist
Sample Quantity
(g)
1.0504
0.5578
Measurement Value Moisture Content
(mg)
(%)
3.67
0.23
3.23
8.080
209ppm
0.298
100ml
5ml
Measurement Value Moisture Content
(g)
(%)
196
998
187ppm
0.179
165
III-1. Industrial Products
(3) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS)
150ml
Aquamicron CXU
10ml
Substance
Liquid crystal
Photoresist
Capacitor
IC chip
Silicon wafer
Printed circuit board
Polycarbonate disk
166
Heating Temperature Sample Quantity
(C)
(g)
180
180
260
250
700
200
230
2.2303
1.7653
0.1194
0.6872
4.1167
0.0976
0.4430
Measurement Value Moisture Content
(g)
(%)
0248
0334
0217
1709
0029
1303
0678
111ppm
189ppm
0.182
0.249
007ppm
1.340
0.153
Chapter III: Applications - 2
III-2. Foodstuffs
The food category encompasses a wide range of substances with varying
properties.
It includes agricultural, livestock and marine products and processed
products, as well as food additives. The moisture content of these items also
varies widely. It is necessary, therefore, to select the most appropriate
sample handling procedures and measurement method for each individual
product.
Test methods for foodstuffs are mostly stipulated in the JAS standards. In
most cases moisture content is measured using heating and drying
methods, but Karl Fischer titration is specified for some items. In the case of
chemically defined foodstuffs, such as sugars and additives, Karl Fischer
titration can be applied using the same methods as for normal chemicals.
Food items with complex structures, such as cereals and meats, contain not
only adhesion moisture but also moisture incorporated within cells.
Measurement results for these items are provided for your information.
Because many food items do not dissolve in organic solvents, the moisture
vaporization method is used extensively. However, foodstuffs commonly
become unstable when heated, and water may be formed as substances
break down. Care must be taken, therefore, when setting analytical
conditions.
1. Food Additives and Flavorings
Key Points
Food additives are substances used in the manufacture, processing
and preservation of foodstuffs. There are many types with varying
attributes. Most are solid, but those that dissolve in dehydrated solvents
or electrolytes can be titrated directly using Karl Fischer titration.
However, it is necessary first to determine whether or not interference
substances are present. Direct titration should be avoided in the case
of insoluble substances, and the moisture vaporization method is
recommended. As the moisture content of these substances is
generally high, volumetric titration is used.
However, coulometric titration can also be used if the sample quantity is
kept small.
When using moisture vaporization, it is necessary to set the
measurement conditions after determination of the heating temperature.
Official specifications for food additives commonly stipulate the loss-ondrying method, so conformance with that method should be checked.
167
III-2. Foodstuffs
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX, SU (or MS, FM) 25-50ml
Substance
[Flavorings]
Flavor
Orange powder
Palm lemon
Strawberry powder
[Condiments]
Sodium citrate
Sodium 5'-inosinate
Sodium glutamate
Yeast extract
[Emulsifiers]
Sorbitan fatty acid ester
[Sweeteners]
Potassium glycyl rhizinate
Maltitol
Sorbit
Aspartame
[Preservatives]
Sorbic acid
Potassium sorbate
Sodium benzoate
[Strengtheners]
Thiamine hydrochloride
Calcium lactate
[Acidulants]
Malic acid
Citric acid
[Water-retaining emulsifying stabilizer]
Sodium chondroitin sulfate
168
Dehydrated
solvents
Sample Quantity
(g)
General-use
0.0228
0.2623
0.0765
0.2789
10.93
5.01
7.08
3.69
48.0
1.91
9.25
1.33
"
"
0.1711
0.0802
0.1303
0.0810
20.97
20.65
13.38
2.84
12.3
25.7
10.3
3.65
General-use
2.0962
2.95
0.141
General-use
Sugar-type
0.1652
0.1891
0.4317
0.0535
12.45
25.77
2.71
1.33
7.54
13.6
0.628
2.49
"
"
1.0059
1.0489
1.0787
1.14
0.53
6.89
0.113
505ppm
0.639
General-use
Sugar-type
0.2321
0.0475
9.89
13.75
4.26
28.9
General-use
"
1.0382
0.1044
2.52
9.23
0.243
8.84
Sugar-type
0.0483
4.49
9.30
"
Sugar-type
"
General-use
Sugar-type
"
"
General-use
Measurement Value Moisture Content
(mg)
(%)
Chapter III: Applications - 2
(2) Moisture vaporization - Volumetric titration
Reagents used: Aquamicron SS-Z (or SS) 150ml
Dehydrated Solvent GEX (or MS) + PG (3:1) 50-100ml
Substance
[Flavorings]
Cheese powder
Vanilla powder
Yoghurt powder
Strawberry powder
Orange powder
Palm lemon
[Strengtheners]
Calcium lactate
Heating Temperature Sample Quantity
(C)
(g)
Measurement Value Moisture Content
(mg)
(%)
130
130
130
050
150
180
0.1915
0.1161
0.0984
0.3188
0.2943
0.0630
12.34
4.70
8.47
4.25
6.01
5.68
200
0.0513
14.50
(3) Coulometric titration
Reagents used: Aquamicron AX (or AS)
Aquamicron CXU
Substance
Sample Quantity
(g)
Sodium 5'-inosinate
Sodium citrate
Sorbic acid
Potassium sorbate
Sodium benzoate
Malic acid
Saccharin
0.0524
0.0785
0.9221
1.0728
1.0179
1.0728
0.0921
6.44
4.05
8.61
1.33
2.04
9.02
28.3
100ml
5ml
Measurement Value Moisture Content
(g)
(%)
13467
9649
1048
411
6463
2471
12813
25.7
12.3
0.114
383ppm
0.635
0.230
13.9
(4) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS)
150ml
Aquamicron CXU
10ml
169
III-2. Foodstuffs
Substance
[Condiments]
Sodium glutamate
Sodium glutamate
Disodium succinate
Trisodium citrate
Yeast extract
Sodium 5'-guanylate
Sodium 5'-inosinate
[Sweeteners]
Saccharin
Aspartame
[Preservatives]
Sorbic acid
Potassium sorbate
Sodium benzoate
[Strengtheners]
Calcium citrate
[Acidulants]
Malic acid
[Quality enhancers]
Sodium polyphosphate
[Water-retaining emulsifying stabilizer]
Sodium chondroitin sulfate
170
Heating temperature Sample Quantity
(C)
(g)
Measurement Value Moisture Content
(g)
(%)
80
180
120
200
80
200
200
1.1071
0.0484
0.0536
0.1071
0.0391
0.0249
0.0165
358
4739
21575
13056
1446
4744
4256
323ppm
9.79
40.3
12.2
3.70
19.1
25.8
150
150
0.0648
0.0426
8869
1001
13.7
2.35
160
160
160
1.0252
1.0139
1.0259
3495
341
6456
0.341
336ppm
0.629
150
0.0940
12257
105
1.0389
2132
0.205
130
2.0194
4988
0.247
150
0.0440
4182
9.50
13.0
Chapter III: Applications - 2
2. Cereals and Dried Vegetables
Key Points
Volumetric titration is suitable for cereals and starches which have a
high moisture content (approximately 10%). If the sample is in powder
form it can be dispersed in dehydrated solvent, allowing the moisture
content to be extracted for direct Karl Fischer titration. When using a
dehydrated solvent with sugars, solubility is sometimes enhanced if the
temperature is raised to 40-45 C before titration. The moisture
vaporization method is suitable for the many items that do not dissolve
in solvents. Care needs to be taken with the heating temperature for
moisture vaporization. Temperatures in the 130-180 C range are
commonly used. High temperatures may cause various phenomena,
including discoloration, abnormal results or failure to reach an end
point. In such cases the measurement must be repeated at a lower
temperature.
Moisture vaporization should be used with coulometric titration. Cereals
cannot be titrated directly as they do not dissolve in electrolytes.
Cereals are sometimes sampled after preliminary processing (e.g.
pulverization).
Care is needed to avoid moisture vaporization or absorption during
these processes.
Volumetric titration is the principal method used for dried vegetables.
The sample is added to the dehydrated solvent and stirred well for a
period of 5-10 minutes before direct titration. Moisture vaporization is
used when the moisture content cannot be fully extracted from samples
in this way. Karl Fischer titration can be carried out using either the
volumetric or coulometric methods. As moisture content tends to be
high, however, volumetric titration is usually preferable.
The precautions stipulated for moisture vaporization in connection with
cereals also apply to dried vegetables.
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX, SU (or MS, FM) 25-50ml
171
III-2. Foodstuffs
Substance
Dehydrated
solvents
Sample Quantity
(g)
Apple powder
Dried carrot powder
Dried onions
Dried tomato powder
Sweet potato starch
Corn flour
Soy protein
Corn starch
Wheat
Soy protein
Soy flour
Potato powder
General-use
0.0989
0.1231
0.0366
0.1309
0.1885
0.0627
0.0574
0.1612
0.0635
0.0756
0.0692
0.0721
"
"
"
"
"
"
Sugar-type
"
"
"
Sugar-type (45C)
Measurement Value Moisture Content
(mg)
(%)
2.16
3.74
2.81
3.07
31.10
6.06
4.09
21.15
9.05
5.43
5.26
5.80
2.19
3.04
7.68
2.35
16.50
9.67
7.13
13.10
14.30
7.18
7.60
8.04
(2) Moisture vaporization - Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS) + PG (3:1) 50-100ml
Substance
Corn starch
Maize
Wheat flour
Corn flour
Devil's-tongue flour
Apple powder
Dried onions
Soy flour
Heating Temperature Sample Quantity
(C)
(g)
150
130
180
180
130
110
070
150
0.1103
0.0529
0.0826
0.1421
0.1270
0.1647
0.0457
0.0719
Measurement Value Moisture Content
(mg)
(%)
13.77
6.34
13.10
53.65
11.30
3.60
3.44
5.33
12.5
12.0
15.9
37.8
8.90
2.19
7.53
7.41
(3) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS)
150ml
Aquamicron CXU
10ml
Substance
Corn starch
Wheat
Malt
Maize
Wheat flour
Soy protein
Potato powder
172
Heating Temperature Sample Quantity
(C)
(g)
150
150
110
150
130
150
110
0.0490
0.0524
0.0764
0.0482
0.0659
0.0463
0.0602
Measurement Value Moisture Content
(g)
(%)
6409
7498
4530
7009
6382
3337
4876
13.10
14.30
5.93
14.50
9.68
7.21
8.10
Chapter III: Applications - 2
3. Sugars and Condiments
Key Points
Sugars are dissolved in a sugar-type dehydrated solvent and titrated.
Volumetric titration is used. If a substance is slow or difficult to dissolve
the solvent can be heated (up to 50C) and titrated. (If the temperature
exceeds 50C the formamide in the sugar-type dehydrated solvent will
gradually break down. The Karl Fischer reagent will be consumed in
small amounts leading to uncertainty about the end point.)
Condiments are normally dispersed in general-use dehydrated solvent.
This is followed by extraction and titration. If the ingredients of a
particular item give it a high sugar content, a sugar-type dehydrated
solvent is used. An oil-type dehydrated solvent is used for products with
a high fat content.
Moisture vaporization should generally be avoided for sugars as these
tend to break down when heated. Moisture vaporization is unnecessary
for condiments, since in almost all cases moisture content can be
measured using direct titration. When using the moisture vaporization
method the optimal heating temperature must be determined first.
Changes in the sample could lead to errors.
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX, SU, OL II (or MS, FM) 25-50ml
Substance
Wasabi paste
Roast meat gravy
Soy sauce
Soup powder
Bonito stock
Sugar syrup
Powdered miso
Glucose
White sugar
Maltose
Malt syrup
Soup
Refined sugar
Soup stock
Granulated sugar
Mayonnaise
Dehydrated
solvents
Sample Quantity
(g)
General-use
"
"
"
"
"
"
Sugar-type
"
"
"
"
Sugar-type (40C)
Sugar-type (40C)
Sugar-type (45C)
Oil-type
0.0465
0.0187
0.0265
0.0754
0.1475
0.0691
0.1228
1.1052
0.2550
0.0695
0.0505
0.0322
0.4729
0.4363
2.8133
0.1425
Measurement Value Moisture Content
(mg)
(%)
10.23
10.66
17.55
2.89
7.48
40.56
3.79
1.64
3.51
3.56
12.49
19.87
4.04
5.66
0.71
28.93
22.0
57.0
66.2
3.83
5.07
58.7
3.09
0.148
1.38
5.12
24.9
61.7
0.854
4.22
252ppm
20.3
173
III-2. Foodstuffs
(2) Moisture vaporization - Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS) + PG (3:1) 50-100ml
Substance
Heating Temperature Sample Quantity
(C)
(g)
Soup powder
Wasabi paste
Soy sauce
Mayonnaise
090
110
200
200
Measurement Value Moisture Content
(mg)
(%)
0.0824
0.0522
0.0399
0.1408
03.70
11.68
24.07
28.61
04.49
22.40
60.30
20.30
(3) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS) 150ml
Aquamicron CXU
10ml
Substance
Heating Temperature Sample Quantity
(C)
(g)
Sugar
Spices
130
130
0.4853
0.0412
Measurement Value Moisture Content
(g)
(%)
3669
5830
01.98
14.20
4. Confectionery
Key Points
Because sugar is the main ingredient of confectionery, these items are
dissolved in a sugar-type dehydrated solvent for titration. Volumetric
titration is used.
Coulometric titration is normally avoided as these products will not
dissolve in electrolytes. The moisture vaporization method is also in
some cases unsuitable as heating causes sugars to break down and
produce water.
Caramels, candies and similar items are titrated after they have been
dissolved in a sugar-type dehydrated solvent that has been heated (up
to 45C). (If the temperature exceeds 45C the formamide in the sugartype dehydrated solvent will gradually break down. The Karl Fischer
reagent will be consumed in small amounts and this will lead to
uncertainty about the end point.) The moisture vaporization method can
be used for snack-type confectionery.
174
Chapter III: Applications - 2
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent SU (or FM) at 40C 25-50ml
Substance
Sample Quantity
(g)
Malt syrup
Candy
Drops
Milk caramel
Cream caramel
Chocolate
Wafers
Chocolate cream
Chocolate emulsifier
Chewing gum
Corn snack
0.0505
0.1893
0.2674
0.2869
0.1206
0.3153
0.5500
0.0999
0.2527
0.2978
0.2217
Measurement Value Moisture Content
(mg)
(%)
12.59
5.78
5.77
23.42
9.93
3.18
12.76
12.13
5.83
5.63
3.24
24.90
3.05
2.16
8.16
8.24
1.01
2.32
12.10
2.31
1.89
1.46
(2) Moisture vaporization - Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS) + PG (3:1) 50-100ml
Substance
Potato chips
Biscuits
Corn snacks
Heating Temperature Sample Quantity
(C)
(g)
130
130
130
Measurement Value Moisture Content
(g)
(%)
0.1814
0.3821
0.2462
3.73
12.72
3.44
2.06
3.33
1.40
(3) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS)
150ml
Aquamicron CXU
10ml
Substance
Small rice crackers
Heating Temperature Sample Quantity
(C)
(g)
130
0.0377
Measurement Value Moisture Content
(g)
(%)
2776
7.36
175
III-2. Foodstuffs
5. Dairy Products, Fat Products
Key Points
Because of their high moisture content, most dairy products are titrated
directly using the volumetric method. A sugar-type dehydrated solvent
is normally used as the titration solvent. However, products that have
fats as their principal ingredients, such as butter, are dissolved in an oiltype dehydrated solvent for titration. When volumetric titration is used
for fat products they are dissolved in an oil-type dehydrated solvent.
The moisture content of vegetable oils, which contain little water, can be
measured more accurately using coulometric titration.
If a product will not dissolve readily in the electrolyte, the addition of
chloroform to the anolyte (equivalent to 20% by volume of anolyte) will
allow the substance to dissolve for repeat titrations.
The moisture vaporization method can be used for samples of these
types. However, the conditions must be determined with care. As a
general rule, a heating temperature in the 110-180C range is used.
[Examples of Measurement]
(1) Volumetric titration
Reagents used:Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX, OL II, SU (or MS, CM, FM) 25-50ml
Substance
Powdered milk
Dehydrated
solvents
Sample Quantity
(g)
Measurement Value Moisture Content
(mg)
(%)
General-use
0.0572
2.64
Cream cheese
"
0.0485
25.04
51.6
Natural cheese
"
Sugar-type
0.1143
72.16
63.1
1.0888
30.55
Condensed milk
"
0.0730
19.42
26.6
Fresh cream
"
0.1142
16.74
14.7
Powdered cheese
"
0.1269
5.43
"
Oil-type
0.1067
18.59
17.4
4.6163
0.51
110ppm
Butter
"
0.0303
4.25
14.0
Margarine
"
0.0970
15.49
16.0
Milk powder
Meat extract
Rapeseed oil
4.56
2.81
4.28
Sugar-type dehydrated solvent should be heated to 40 C before use in
titration.
176
Chapter III: Applications - 2
(2) Moisture vaporization - Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS) + PG (3:1) 50-100ml
Substance
Cream cheese
Natural cheese
Meat extract
Margarine
Heating Temperature Sample Quantity
(C)
(g)
130
130
180
150
0.1147
0.0898
0.0705
0.1281
(3) Coulometric titration
Reagents used: Aquamicron AX (or AS)
Aquamicron CXU
Substance
Powdered milk
Butter
Cheese
Palm oil
Sesame oil
Soy bean oil
Salad oil
Sample Quantity
(g)
0.2071
0.0422
0.0142
0.3189
0.9017
4.5118
2.7354
Measurement Value Moisture Content
(mg)
(%)
59.14
57.00
12.17
19.97
51.6
63.5
17.3
15.6
100ml
5ml
Measurement Value Moisture Content
(g)
(%)
5852
5845
5840
0303
0534
0029
0394
02.83
13.90
41.10
950ppm
592ppm
51ppm
144ppm
(4) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS)
150ml
Aquamicron CXU
10ml
Substance
Powdered milk
Cheese
Heating Temperature Sample Quantity
(C)
(g)
110
130
0.0648
0.0217
Measurement Value Moisture Content
(g)
(%)
2953
8982
4.56
41.4
177
III-2. Foodstuffs
6. Gourmet Foods, etc.
Key Points
Volumetric titration is normally used for gourmet foods because of their
high moisture content. They are dissolved in a sugar-type dehydrated
solvent and subjected to Karl Fischer titration. If a product will not
dissolve readily the solvent can be heated to 40 C. An oil-type
dehydrated solvent is used for high-fat foods. A general-purpose
dehydrated solvent may be used for some samples. If the moisture
content cannot be extracted fully using these solvents, Karl Fischer
titration is used in conjunction with moisture vaporization. Either
volumetric or coulometric titration can be used in such cases.
In the case of coulometric titration, direct titration should be avoided
because of problems with the solubility of samples.
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX, SU, OL II (or MS, FM, CM) 25-50ml
Substance
Dehydrated
solvents
Sample Quantity
(g)
Powdered egg yolk
Dried beer yeast
Coffee
Cocoa
Juice powder
Raw coffee beans
Tea
Gelatine
Soy milk
Curry roux
General-use
0.0610
0.0820
0.1287
0.3632
0.4695
0.0574
1.0516
0.0170
0.0663
0.1353
178
"
Sugar-type
"
"
Sugar-type (40C)
Sugar-type (40C)
Sugar-type (40C)
Oil-type
"
Measurement Value Moisture Content
(mg)
(%)
2.96
3.02
3.87
5.60
4.07
5.45
5.80
2.59
57.26
4.57
4.85
3.68
3.01
1.54
0.867
9.49
0.552
15.2
86.4
3.38
Chapter III: Applications - 2
(2) Moisture vaporization - Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS) + PG (3:1) 50-100ml
Substance
Coffee beans
Dried beer yeast
Curry roux
Heating Temperature Sample Quantity
(C)
(g)
130
200
130
Measurement Value Moisture Content
(mg)
(%)
0.1919
0.0840
0.1217
4.11
8.86
4.31
02.14
10.6
03.54
(3) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS)
150ml
Aquamicron CXU
10ml
Substance
Coffee
Raw coffee beans
Cocoa
Hops
Beet
Gelatine
Heating Temperature Sample Quantity
(C)
(g)
090
150
110
130
130
180
0.1282
0.0555
0.2486
0.0189
0.0913
0.0114
Measurement Value Moisture Content
(g)
(%)
3229
5012
3973
1536
7669
1790
02.52
09.03
01.60
08.14
08.40
15.70
179
III-3 Pharmaceuticals
III-3. Pharmaceuticals
In this field, Karl Fischer titration is the most effective tool for precise
moisture content measurement. Moisture content tends to be high, ranging
from a few percent up to a few tens of percent. For this reason, volumetric
titration is generally used.
The examples in this section show the application of Karl Fischer titration to
biochemical and pharmaceutical products. Where the chemical ingredients
of these products are known direct titration can be used as it is possible to
determine whether or not interference will occur.
Even if products cause interference, they can still be measured using
moisture vaporization and Karl Fischer titration, provided that they remain
stable when exposed to heat.
Special pharmaceutical items are listed in the Japanese Pharmacopoeia.
Aside from volumetric titration, the coulometric titration and moisture
vaporization methods can also be used. This chapter gives examples based
on the actual implementation of these methods.
1. Biochemical Products
Key Points
Sugar-type dehydrated solvents are generally used when applying
volumetric titration to biochemical products such as amino acids,
nucleic acids, sugars, enzymes and lipids. Even substances that do not
dissolve in general-use dehydrated solvents can be titrated directly
using a general-use dehydrated solvent, provided that the moisture
content of the sample can be extracted adequately.
Direct coulometric titration is not suitable as many samples cannot be
dissolved in the anolytes used for this type of titration. Coulometric
titration is carried out using the moisture vaporization method. Some
samples break down at certain heating temperatures and there must be
careful consideration of the temperature used for moisture vaporization.
L-cystime and vitamin C react with Karl Fischer reagent and cannot be
titrated directly. Care is needed with general vitamin preparations that
include vitamin C since these can also cause interference reactions.
(Vitamin C reacts quantitatively with iodine. If the amount of vitamin C
included in a sample is known, then the moisture content can be
determined by adjusting the results. Refer to the Basic Knowledge
section for more information.) Moisture vaporization is used with these
substances.
180
Chapter III: Applications - 2
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX, SU (or MS, FM) 25-50ml
Substance
Dehydrated
solvents
L-alanine
General-use
Potassium asparaginate
"
Glycylglycine
"
Vitamin B12
"
Vitamin B1 hydrochloride
"
ATP
Sugar-type
Citidine (5') diphosphocholine sodium
"
Dextran
"
Chlorella
"
Yeast extract
"
Cyclodextrin
"
Sample Quantity
(g)
0.5316
0.1026
0.2882
0.1452
0.2321
0.0750
0.0466
0.0901
0.0550
0.0810
0.0386
Measurement Value Moisture Content
(mg)
(%)
0.13
5.29
0.24
11.27
9.89
6.55
1.92
5.93
3.54
0.95
1.55
245ppm
5.16
833ppm
7.76
4.26
8.73
4.12
6.58
6.44
3.58
4.02
(2) Moisture vaporization - Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS) + PG (3:1) 50-100ml
Substance
Adenosine triphosphate
Heating Temperature Sample Quantity
(C)
(g)
200
Measurement Value Moisture Content
(mg)
(%)
0.0430
3.28
8.41
(3) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS)
150ml
Aquamicron CXU
10ml
Substance
L-alanine
Sodium asparaginate
Glycylglycine
L-cystine
Dextran
Vitamin preparations
Vitamin C
Vitamin B12
Chlorella
Yeast extract
Yeast nucleic acid
Heating Temperature Sample Quantity
(C)
(g)
150
180
130
130
180
110
100
130
150
80
200
0.7408
0.0366
0.2765
0.1123
0.0457
0.1211
0.1264
0.0403
0.0659
0.0391
0.0230
Measurement Value Moisture Content
(g)
(%)
56
2020
70
796
3093
2235
1275
3128
4180
1446
5875
076ppm
5.52
253ppm
0.709
6.76
1.85
1.01
7.76
6.34
3.70
25.5
181
III-3 Pharmaceuticals
2. Pharmaceuticals
Key Points
The Japanese Pharmacopoeia (7th revision) designates Karl Fischer
methodology as the general testing method for 28 pharmaceutical
products. In addition to volumetric titration, the coulometric titration and
moisture-vaporization methods have also been specified. Normally,
samples are placed in a general-use dehydrated solvent and stirred for
a period before titration. Alternatively, surplus Karl Fischer reagent may
be added to the solution, which is then stirred for a period and reverse
titrated with standard water-methanol. Depending on the solubility of the
sample, a sugar-type or oil-type dehydrated solvent should be used.
The chemical constituents of pharmaceutical products are usually
known so it is possible to determine in advance whether or not a
particular product is suitable for Karl Fischer titration. Coulometric
titration is convenient when only a limited amount of sample can be
obtained (such as when a substance is too valuable to use more than a
few milligrams), or when moisture content is low. The moisture
vaporization method is used when it is difficult to draw the moisture into
the dehydrated solvent, or when interference would occur.
As with other types of substances, the heating temperature must be
selected with care.
Moisture vaporization should be used only after careful consideration.
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent SU(or MS, FM)
182
25-50ml
Chapter III: Applications - 2
Substance
Dehydrated
solvents
Aminophylline
General-use
Digitalis
"
Antibiotics
"
Gibberellin methyl ester
"
Berberine chloride
"
Glutathione
"
Aspirin aluminum
"
Carbetapeten citrate
"
Chlorobutanol
"
Patenol
"
Erythromycin lactobionate
"
Rutin
"
Libotite
Sugar-type
Hemin
"
Phosphomycin Ca
"
Pantechinan
"
Sodium aspartate
Sugar-type (40C)
Throat drops
" (40 C)
Sample Quantity
(g)
0.2115
0.3502
0.1245
0.2005
0.0433
0.2713
0.1638
0.3053
0.0896
0.1243
0.0431
0.1202
0.1337
0.1838
0.1533
0.1375
0.0543
0.2970
Measurement Value Moisture Content
(mg)
(%)
8.90
5.46
8.35
3.31
4.23
11.51
2.33
0.13
4.35
0.13
1.43
11.36
31.18
1.47
14.65
28.30
5.77
10.79
4.21
1.56
6.71
1.65
9.55
4.24
1.42
0.043
4.85
0.10
10.3
9.45
23.3
0.800
9.49
20.6
10.6
3.63
(2) Moisture vaporization - Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS) + PG (3:1) 50-100ml
Substance
Phosphomycin Ca
Potassium xanthogenate
Heating Temperature Sample Quantity
(C)
(g)
250
150
0.1142
0.5009
(3) Coulometric titration
Reagents used: Aquamicron AX (or AS)
Aquamicron CXU
Substance
Albumin
Polypeptide
Aminophylline
Sample Quantity
(g)
0.2236
0.0037
0.0427
Measurement Value Moisture Content
(mg)
(%)
10.58
02.42
9.260
0.483
100ml
5ml
Measurement Value Moisture Content
(g)
(%)
0693
0316
1795
0.310
8.540
4.200
183
III-3 Pharmaceuticals
(4) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS)
150ml
Aquamicron CXU
10ml
Substance
Albumin
Glutathione
Berberine chloride
Bufferin
Aspirin aluminum
Synthetic penicillin
Heating Temperature Sample Quantity
(C)
(g)
110
110
150
130
150
150
0.1818
0.4208
0.0288
0.0662
0.1715
0.0837
Measurement Value Moisture Content
(g)
(%)
0578
1635
2735
2645
2332
2616
0.318
0.389
9.560
4.000
1.360
3.130
3. Chinese Herbal Medicines, Biological Tissue, etc.
Key Points
Either a general-use or a sugar-type dehydrated solvent is used for
chinese herbal medicines. In general, however, these products are
difficult to dissolve. This means that insufficient moisture is extracted
and accurate analytical results cannot be obtained. The moisture
vaporization method is used for this reason. The heating temperature
must be considered carefully as heating can cause some products to
change color or break down.
In the examples shown, biological tissue was dispersed in a generaluse dehydrated solvent and subjected to Karl Fischer titration.
Similar procedures should be used for capsules and other items.
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX, SU (or MS, FM) 25-50ml
184
Chapter III: Applications - 2
Substance
Pills (heart tonic)
Muscle
Brain
Blood serum
Pancreas
Bile acid
Licorice powder
Crude drugs
Capsules
Soft capsules
Dehydrated
solvents
Sample Quantity
(g)
General-use
0.1356
0.1018
0.0994
0.0916
0.6645
0.9185
0.1111
0.0608
0.0697
0.0528
"
"
"
"
"
"
Sugar-type
" (40 C)
C)
(40
"
Measurement Value Moisture Content
(mg)
(%)
8.86
75.74
77.23
83.90
33.36
15.15
9.91
18.80
9.81
5.09
6.53
74.4
77.7
91.6
5.02
1.65
8.92
30.9
14.1
9.64
(2) Moisture vaporization - Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS) + PG (3:1) 50-100ml
Substance
Pills (heart tonic)
Crude drugs
Medicinal wafers
Capsules
Toothpaste
Black hair
Blond hair
Heating Temperature Sample Quantity
(C)
(g)
110
130
150
170
200
200
200
Measurement Value Moisture Content
(mg)
(%)
0.2215
0.0532
0.0776
0.0726
0.2069
0.0726
0.1583
14.51
16.46
12.82
10.14
64.33
08.09
18.38
06.55
30.90
16.50
14.00
31.10
11.10
11.60
(3) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS)
150ml
Aquamicron CXU
10ml
Substance
Crude drugs
Licorice powder
Cinnamon
Mint
Soft capsules
Gelatine capsules
Heating Temperature Sample Quantity
(C)
(g)
130
130
130
110
150
150
0.0961
0.0439
0.0620
0.0428
0.0463
0.0201
Measurement Value Moisture Content
(g)
(%)
1254
3977
3464
2411
4463
3262
1.30
9.06
5.59
5.63
9.64
16.2
185
III-4. Minerals and Natural Products
III-4. Minerals and Natural Products
This chapter provides examples of the use of Karl Fischer titration to
measure the moisture content of mineral substances such as rock, sand and
iron ore. As these substances are not soluble in solvents the moisture
vaporization method is, of course, used in most cases. Particular care must
be taken with reference to the heating temperature as water of composition
can cause problems.
Natural products vary widely and it is possible to present only a few
examples here.
Refer to these when determining the analytical conditions.
1. Minerals
Key Points
With the traditional drying methodology, substances like ores and rock
tended to oxidize. Measurement had to take place over long periods of
time and the results were frequently inaccurate. By combining moisture
vaporization with Karl Fischer titration moisture content can be
measured quickly and accurately.
Karl Fischer titration can be carried out using either volumetric or
coulometric methods. Volumetric titration is generally used for
substances with a high moisture content. Since minerals commonly
occur in lumps or granular form, samples must first be crushed into
suitably fine grains. During this process care is needed to prevent
moisture vaporization into, or absorption from the atmosphere.
With minerals, problems can arise not only with water of adhesion but
also with water of composition (water of crystallization). Fractional
measurement is achieved using the moisture vaporization method. The
heating temperature is set between 100 and around 200C for water of
adhesion, and between 500 and 1,000 C when measuring water of
composition. Thus, the temperature for moisture vaporization is set
according to both the type of sample and the purpose of the
measurement.
A commercially available dual-system heating oven provides a
convenient way of obtaining accurate fractional measurements of water
of adhesion and water of composition.
Reference: JIS M8211 "Iron Ores-- Method for Determination of
Combined Water Content"
186
Chapter III: Applications - 2
[Examples of Measurement]
(1) Volumetric titration
Reagents used:Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS) 25-50ml
Substance
Soil
Dried soil
Powdered quartz
Dehydrated
solvents
Sample Quantity
(g)
General-use
0.0508
0.0858
1.6711
"
"
Measurement Value Moisture Content
(mg)
(%)
23.63
04.21
00.94
46.500
04.910
00.056
(2) Moisture vaporization - Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS) + PG (3:1) 50-100ml
Substance
Rocks
Clay
"
Soil
Iron ore
Limestone
Cement
Ferrite
Coal
Amphibole
Black mica
Kaolin
Talc
Bentonite
Manganese ore
Heating Temperature Sample Quantity
(C)
(g)
900
110
700
200
750
700
800
200
180
1000
1000
800
1000
800
750
0.0798
0.8837
0.1033
0.0483
0.5638
0.2462
1.5555
0.8967
1.0022
1.0283
1.1005
0.1414
0.2003
0.1135
0.2313
Measurement Value Moisture Content
(mg)
(%)
13.11
34.46
14.99
22.88
13.58
0.84
11.20
9.20
33.47
16.04
25.75
19.94
14.40
18.61
24.29
16.4
03.90
14.5
47.2
02.41
00.34
00.720
01.03
03.34
01.56
02.34
14.1
07.19
16.4
10.5
187
III-4. Minerals and Natural Products
(3) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS) 150ml
Aquamicron CXU
10ml
Substance
Black mica
Amphibole
Rocks
Silica
Casting sand
"
Clay
Soil
Talc
"
Sintered ore
Manganese ore
"
Iron ore
Powdered quartz
"
188
Heating Temperature Sample Quantity
(C)
(g)
1000
1000
700
900
110
900
110
180
200
900
750
110
750
750
200
900
0.0733
0.2167
0.1176
0.0476
1.5238
1.1927
0.0520
0.0736
0.4579
0.1871
0.0985
0.1700
0.0185
0.1115
1.1064
0.8052
Measurement Value Moisture Content
(g)
(%)
1716
3391
6331
2333
1515
6688
2048
3747
843
9512
65
833
1922
2653
564
937
002.340
01.560
05.380
04.900
994ppm
00.561
03.940
05.090
00.184
05.080
660ppm
00.490
10.400
02.380
510ppm
00.116
Chapter III: Applications - 2
2. Natural Products
Key Points
Natural products vary widely and the appropriate Karl Fischer titration
should be selected to suit the particular sample. Direct titration is used
for substances that dissolve in dehydrated solvent or that are unstable
when heated. If the sample is stable when heated, use the moisture
vaporization method. The heating temperature must be considered
carefully when using that method. If the temperature is too high the
breakdown of the substance could lead to interference. (For example,
the end point may not be reached, or the analytical results that are
obtained may be abnormally high.)
Karl Fischer titration can be carried out using either volumetric or
coulometric methods, but volumetric titration is probably more suitable
since natural products tend to have a high moisture content.
[Examples of Measurement]
(1) Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX, KTX, SU (or MS, CM,FM) 25-50ml
Substance
Dehydrated
solvents
Sample Quantity
(g)
Silver fir leaves
Tree roots
Pollen
Pine resin
Rosin
General-use
0.0462
0.0279
0.0071
1.0106
0.7388
"
Sugar-type
Ketone-type
"
Measurement Value Moisture Content
(mg)
(%)
3.12
2.53
0.64
0.74
6.15
6.76
9.07
9.0
0.073
0.832
(2) Moisture vaporization - Volumetric titration
Reagents used: Karl Fischer Reagent SS-Z (or SS)
Dehydrated Solvent GEX (or MS) + PG (3:1) 50-100ml
Substance
Pine resin
Heating Temperature Sample Quantity
(C)
(g)
130
1.6708
Measurement Value Moisture Content
(mg)
(%)
0.83
0.050
189
III-4. Minerals and Natural Products
(3) Coulometric titration
Reagents used: Aquamicron AX (or AS)
Aquamicron CXU
Substance
Raw lacquer
Processed lacquer
Sample Quantity
(g)
0.0247
0.1211
100ml
5ml
Measurement Value Moisture Content
(g)
(%)
14.00
3466
03.15
3810
(4) Moisture vaporization - Coulometric titration
Reagents used: Aquamicron AX (or AS)
150ml
Aquamicron CXU
10ml
Substance
Silver fir leaves
Tree roots
190
Heating Temperature Sample Quantity
(C)
(g)
130
100
0.0541
0.0189
Measurement Value Moisture Content
(g)
(%)
3800
1723
7.02
9.12
Chapter IV: List of Karl Fischer Reagents
Chapter IV: List of Karl Fischer Reagents
191
List of Karl Fischer Reagents
192
Chapter IV: List of Karl Fischer Reagents
Volumetric Titration Reagents
The requirements for volumetric titration are a Karl Fischer reagent, standard
water-methanol to assess the titer and a dehydrated solvent in which to
dissolve or disperse the sample.
Mitsubishi Chemical Corporation has an extensive range of reagents
suitable for all levels of moisture content. Choose the combination of
products that is most suitable for your particular purpose.
Karl Fischer Reagent SS Series (Pyridine-Type)
The SS Series has enjoyed an excellent reputation for quality and
performance for many years.
Product
Karl Fischer
Reagent SS
(Mitsubishi)
Standard
Packaging
Uses
Titer
500ml
General-use
2.5-3.5mgH2O/ml glass bottles This titration preparation can be
used for a wide range of purposes.
Titer
8-12mgH2O/ml
500ml
High moisture content
glass bottles This product allows quick, accurate
measurement of moisture content
over about 40% in foodstuffs,
cosmetics, etc.
Titer
500ml
Low moisture content
0.7-1.2mgH2O/ml glass bottles This product is suitable for
measuring moisture content below
100ppm in organic solvents,
electrical insulating oils,
gases, etc.
Dehydrated
Solvent MS
Moisture content
0.2mgH2O/ml or
lower
Dehydrated
Solvent ML
Moisture content
0.2mgH2O/ml or
lower
500ml
General-use (*recommended
glass bottles product)
Suitable for organic solvents,
inorganic chemicals, agricultural
chemicals, pharmaceuticals,
fertilizers, detergents, foodstuffs,
etc.
500ml
General-use
glass bottles Suitable for organic solvents,
inorganic chemicals, agricultural
chemicals, pharmaceuticals,
fertilizers, detergents, foodstuffs,
etc.
193
List of Karl Fischer Reagents
Product
Dehydrated
Solvent CM
Standard
Moisture content
0.3mgH2O/ml or
lower
Packaging
Uses
500ml
Oil-type
glass bottles Suitable for naphtha, gasoline,
diesel oil, heavy oil, electrical
insulating oil, oils and fats
(hardened oil, margarine, etc.), etc.
Dehydrated
Solvent CP
Moisture content
0.5mgH2O/ml or
lower
500ml
Ketone-type (*recommended
glass bottles product)
For ketones, silicon oils, acetic acid
and other lower carboxylic acids,
aldehydes (except acetaldehydes),
anilines, etc.
Dehydrated
Solvent PE
Moisture content
0.2mgH2O/ml or
lower
500ml
Ketone-type
glass bottles For ketones, silicon oils, acetic acid
and other lower carboxylic acids,
aldehydes (except acetaldehydes),
anilines, etc.
Dehydrated
Solvent PP
Moisture content
0.2mgH2O/ml or
lower
500ml
Aldehyde-type
glass bottles Acetaldehydes, propionaldehydes,
butyraldehydes, etc.
Dehydrated
Solvent FM
Moisture content
0.2mgH2O/ml or
lower
500ml
Sugar-type
glass bottles Sugars, proteins, gelatine,
additives, animal feeds, etc.
Dehydrated
Solvent ME
Moisture content
0.2mgH2O/ml or
lower
500ml
For gaseous samples
glass bottles Nitrogen, etc.
Mix Dehydrated Solvent MS with propylene glycol (PG) in a 3:1 ratio (e.g. MS90ml:
PG30ml) when using a moisture vaporization system.
Standard Reagents for Titer Assessment
Mitsubishi Chemical Corporation supplies two types standard watermethanol products that include a known amount of water. These products
are used to assess the titer.
Select the product according to the titer of the Karl Fischer reagent that you
are using. These standard reagents are also convenient for use in back
titration.
194
Chapter IV: List of Karl Fischer Reagents
Product
Standard
Water
Methanol
(Mitsubishi)
Standard
Packaging
Uses
Moisture content: 250ml
Used to assess titer of Karl Fischer
2.00.04
glass bottles reagents(3-10mgH20/ml)
mgH2O/ml
Moisture content: 250ml
Used to assess titer of Karl Fischer
0.50.02
glass bottles reagents (1mgH20/ml)
mgH2O/ml
Karl Fischer Reagent SS-Z Series (Pyridine/Chloroform-Free Type)
Mitsubishi's SS-Z range of titration products is free of both pyridine and
chloroform.
These products are kind to both people and the environment.
Karl Fischer Reagent SS-Z is a volumetric titration reagent that contains
neither chloroform nor methyl cellosolve. It is also free of pyridine so there is
almost no odor.
A low-toxicity solvent system has been used to develop a product that is
kind to both people and the environment while providing the same
performance as earlier products.
These products can be used with existing moisture content measuring
systems. Combine them with the dehydrated solvent that is appropriate for
the sample.
Product
Karl Fischer
Reagent
SS-Z
(Mitsubishi)
Dehydrated
Solvent GEX
Dehydrated
Solvent OLX
Dehydrated
Solvent OL II
Standard
Packaging
Uses
Titer
500ml, 1L
General-use
4.5-5.5mgH2O/ml glass bottles This titration preparation can be
used for a wide range of purposes.
500ml
Low moisture content
Titer
0.7-1.2mgH2O/ml glass bottles This titration preparation is suitable
for samples with low moisture
content.
Moisture content: 500ml
General-use
0.2mgH2O/ml or glass bottles Suitable for organic solvents,
lower
inorganic chemicals, agricultural
chemicals, pharmaceuticals,
fertilizers, detergents, foodstuffs,
etc.
Moisture content: 500ml
Oil-type
0.5mgH2O/ml or glass bottles Suitable for naphtha, gasoline,
lower
heavy oil, electrical insulating oil,
oils, etc.
Moisture content: 500ml
Oil-type (*includes chloroform)
0.3mgH2O/ml or glass bottles Suitable for naphtha, gasoline,
lower
heavy oil, electrical insulating oil,
oils and fats, etc.
195
List of Karl Fischer Reagents
Product
Dehydrated
Solvent KTX
Standard
Packaging
Uses
Moisture content: 500ml
Ketone-type
0.2mgH2O/ml or glass bottles For ketones, silicon oils, acetic acid
lower
and other lower carboxylic acids,
aldehydes (except acetaldehydes),
etc.
Dehydrated
Solvent SU
Sugar-type
Moisture content: 500ml
0.2mgH2O/ml or glass bottles Sugars, proteins, gelatine,
lower
additives, animal feeds, etc.
Mix Dehydrated Solvent GEX with propylene glycol (PG) in a 3:1 ratio
(e.g. GEX90ml:PG30ml) when using a moisture vaporization system.
Coulometric Titration Reagents
Coulometric titration reagents consist of anolytes which are placed in the
anode chamber and catholytes which are placed in the cathode chamber.
These products have a worldwide reputation for excellent performance and
can be used in all manufacturers' coulometric titration systems. A generaluse product and a ketone-type product (for ketones, lower carboxylic acids,
silicon oils, etc.) are available. These products can be used with
Aquamicron CXU catholyte.
These products are kind to both people and the environment. They contain
no carbon tetrachloride, methyl cellosolve, pyridine or chloroform.
Aquamicron Series
Product
Aquamicron
AX
(anolyte)
Aquamicron
CXU
(catholyte)
Standard
Packaging
Uses
General-use
Moisture content: 500ml
0.15mgH2O/ml or glass bottles Used with organic solvents,
lower
inorganic chemicals, petroleum
products, gases, and a wide range
of other substances.
Moisture content: 5ml
0.6mgH2O/ml or ampoules/10
lower
per case
Aquamicron
AKX
(anolyte)
Aquamicron
CXU
(catholyte)
Moisture content:
0.15mgH2O/ml or
lower
Moisture content:
0.6mgH2O/ml or
lower
196
500ml
Ketone-use
glass bottles Ketones, silicon oils, lower
carboxylic acids, etc.
5ml
ampoules/10
per case
Chapter IV: List of Karl Fischer Reagents
Single-Solution Coulometric Titration Reagent
Aquamicron FLS is a single-solution coulometric titration reagent. It should
be used in single-solution electrolytic cells without diaphragm.
Use this product in combination with single-solution electrolytic cells.
This product is kind to both people and the environment. It contains no
carbon tetrachloride, methyl cellosolve, pyridine or chloroform.
Product
Aquamicron
FLS
Standard
Packaging
Uses
Moisture content: 500ml
Used for moisture vaporization
0.15mgH20/ml or glass bottles method.
lower
Organic solvents.
Using Single-Solution Karl Fischer Titration
As the single-solution coulometric titration version of Karl Fischer titration has
not been adopted as an official method (JIS, etc.), it should be regarded
only as a convenient methodology. (It may not be possible to use this
product in some types of equipment.)
Aquamicron Solid Water Standard
Product
Aquamicron
Solid Water
Standard
Standard
Packaging
Uses
Moisture content: 10g
For evaluation a moisture meter with
3.830.05%
glass bottles a water vaporizer.
Aquamicron Standard Solution
Mitsubishi Chemical Corporation has traditionally supplied standard watermethanol as a standard reagent for assessing titer. Recently we have begun
to sell a new product which has been developed in response to growing
awareness of the importance of day-to-day management needs. It also
reflects the demand for products that are easy to use and manage.
This product is the result of long years of experience in the fields of
production technology and moisture measurement technology. For added
peace of mind, it is also environmentally friendly thanks to the use of lowodor, low-toxicity solvents.
197
List of Karl Fischer Reagents
Product
Titer
Aquamicron
0.2mgH2O/g
water
Standard 0.2mg
Packaging
Uses
5ml
Used to check the accuracy of
ampoules/10 coulometric titration systems.
per case
Aquamicron
1mgH2O/g
water
Standard 1mg
Aquamicron
10mgH2O/g
water
Standard 10mg
5ml
ampoules/10
per case
8ml
ampoules/10
per case
Used to check the accuracy of
coulometric titration systems.
Used to assess the titer of KF
reagents used in automatic
volumetric titration systems.
Mitsubishi Check Solution P
This end-point adjustment solution can be used with both general-use and
ketone-type products. It can also be used for day-to-day management of
coulometric moisture measurement systems.
Product
Check
Solution P
(Mitsubishi)
198
Moisture Content
Packaging
Uses
3.8~4.2mgH2O/ml 100ml glass Used when the presence of free iodine
bottles with in the anolyte has caused reddishseptum caps brown discoloration. Add a suitable
amount to restore a water surplus.
Normally a 100l microsyringe is used.
The readiness of a coulometric moisture
measurement system for normal use
can be checked periodically by
measuring a specific volume of Check
Solution (e.g. 100l).
ChapterV: Summary of Selection Procedures for Karl Fischer Reagents
Expected moisture
content 1% or lower?
Sample
NO
Volumetric
titration
YES
YES Expected moisture NO
content 40% or
lower?
Coulometric
titration
SS-Z
1,3,5mg/ml
NO
SS
10mg/ml
NO
Liquid or gas?
YES
Moisture
vaporization
Soluble in
dehydrated
solvent?
Liquid or gas?
Interference
reaction with KF
reagent?
Interference YES
reaction with KF
reagent?
Soluble in
methanol?
Change in
anolyte pH?
YES
Interference YES
reaction with
sulfur dioxide?
NO
NO
YES
YES
YES
pH change in
titration solvent?
Moisturevaporization
Interference
reaction with
methanol?
YES
NO
NO
NO
Soluble in
chloroform?
NO
NO
Add salicylic
acid
Interference
reaction with
methanol?
NO
YES
Add salicylic
acid
Soluble in
formamide?
YES
YES
Aquamicron
AX/CXU
Aquamicron
AX/CXU
Aquamicron
AX/CXU
Aquamicron
AKX/CXU
GEX
MS
GEX
MS
OLX, OL II
CM
SU
FM
KTX
CP
PP
GEX + PG
MS+PG
Plastics
Inorganics
Minerals
General samples
Amines
Ketones
Lower carboxylic acid
Aromatic aldehydes
Amines
General samples
Petroleum
products
Sugars
Ketones
Aldehydes
Solids
199
Chapter VI: Index
Chapter VI: Index
201
Index
202
Chapter VI: Index
A:
Abietic acid 89
Absorbent cotton 153
ABS resin 148,149
Acetaldehyde 86
Acetamide 100,101
Acetanilide 100
Acetic acid 89,90,91
Acetic anhydride 105
Acetone 84,101
Acetone cyanhydrin 101,103
Acetone oxime 103
Acetonitrile 101,102
Acetophenone 83,84
Acetylaceton 83,84
Acetylene 29
Acetyl peroxide 107
Acetyl thiourea 108,111
Acetylurea 100
Acrolein cyanohydrin acetate 101
Acrylic acid 89
Acrylic fiber 153
Acrylonitrile 101,102
Actuation oil 146
Adenosine 5'-triphosphate disodium 181
Adhesive 159,160
Adipic acid 89,90
Adiponitrile 101
Aerosol 140
Air filter oil 144
(L-)Alanine 181
Albumin 183,184
Alizarin 83
Alkyl alcohol 76
Alkylbenzene 145,146
Alkyl benzene sulfonate 162
Alkyl diphenyl ethane 145
Alkyl naphthalene 145
Alloxan 94,100
Aluminum chloride 121,122,133
Aluminum fluoride 123
Aluminum nitrate 128,133
Aluminum oxide 120
Aluminum paste 114
Aluminum powder 155
Aluminum sulfate 126,133
Amino acid 180
Aminoacetonitrile 101
(p-)Aminoazobenzene 103
( -)Aminocapronitrile 101
(5-)Amino-2-chlorotoluene-4sulfonate(C-acid) 154
(2-)Aminonaphthalene-1-sulfonic acid
154,155
(m-)Aminophenol 80,97,99,153,154
Aminophylline 183
(2-)Amino-3-picoline 99
(2-)Aminopyridine 97
Ammonia
40
Ammonium acetate 93,94
Ammonium chloride 121,133,134
Ammonium citrate 93
Ammonium nitrate 127,133,134
Ammonium oxalate 93
Ammonium phosphate 133
Ammonium sulfate 133,134
Amphibole 187,188
(n-)Amyl alcohol 77
Aniline 97,98,99,153,154
(2-)Anilinoethanol 99
Anisic acid 89
Anisidine (p-anisidine) 97,99,153,154
Anthracene 72
Anthranilic acid 154,155
Antibiotics 183
Antimony oxide 120,155
Antioxidant 143,150,151
Apple powder 172
Argon 130
Arsenic trioxide 40
Aryl formate 91
Ascorbic acid 40
Asparagine 90,94
Aspartame 168,170
Aspartic acid 90
Asphalt 144
Aspirin aluminum 183,184
Aviation oil 144,146
203
Index
B:
Bakelite paper 152
Barium acetate 93
Barium carbonate 124,155,156
Barium chloride 121,122
Barium fluoride 123
Barium hydroxide 118
Barium peroxide 40
Basic magnesium carbonate 124
Beer yeast 178,179
Beet 179
Bentonite 187
Benzal-n-butylimine 103
Benzaldehyde 88
Benzamide 100
Benzene 72,73
Benzenesulfonic acid 90
Benzidine yellow 158
Benzilic acid 89
Benzoic anhydride 105
Benzoin 83
Benzophenone 83
Benzothiazole 97,108
Benzothiophene 108,109
Benzotriazole 103
Benzoyl chloride 105
Benzoyl hydrazine 102
Benzyl alcohol 76,77
Benzylamine 96,97,99
Benzyl benzoate 92
Benzyl mercaptan 110
(4-) Benzyl piperidine 99
Berberine chloride 183,184
Bile acid 185
Biscuit 175
Bismuth oxide 120
Biuret
100
Blood serum 185
Boric acid 40
Borneol 76
Boron oxide 40
Brain
185
Brake oil 144,146
Brass 114
Bromobenzene 75
Bromoform 75
(1-) Bromohexadecane 75
204
Bromonaphthalene 75
(1-) Bromotetradecane 75
Brown coal 141,142
Brucine 94
Brucine sulfate 94
Bryeslin powder 136
Bufferin 184
Butadiene 72,141
Butane 72,138
(1,4-) Butanediol 76
(iso-)Butanol 76,77
(n-) Butanol 76,77
(tert-) Butanol 76,77
(1,4-) Butenediol 76
Butter 176,177
(n-) Butyl acetate 92
Butyl aldoxime 103
(n-) Butylamine 97,98,99
(p-tert-) Butyl catechol 81
(n-) Butyl disulfide 108
(2,3-) Butylene diacetate 91
Butyl mercaptan 110
Butyl nitrite 91
Butyl rubber 150
(n-) Butyl sulfide 108
(n-) Butyl thiocyanate 108
(n-) Butyl vinylether 78
(n-) Butyraldehyde 86
Butyric anhydride 105
(-) Butyrolactam 78,79,92
(-) Butyrolactone 92
Butyryl chloride 105
C:
C-acid 154
Cadmium (powdered metal) 114
Cadmium acetate 93,94
Cadmium chloride 121
Cadmium oxide 120
Caffeine 27
Calcium carbonate 123,124,125
Calcium chloride 121
Calcium citrate 170
Calcium fluoride 121
Calcium hydroxide 119
Calcium lactate 93,94,168,169
Calcium malonate 93
Calcium oxide 120
Chapter VI: Index
Calcium propionate 93
Calcium stearate 94
Calcium sulfate 125,126
Camphoric acid 89
Camphor 83
Candy 174,175
Capacitor 165,166
Caproic acid 89
( -) Caprolactam 103,104
Caproyl chloride 105
Capryl chloride 105
Capsule 184,185
Captan 135,136
Caramel 174,175
Carbazole 97
Carbetapeten citrate 183
Carbon black 150,151
Carbon disulfide 108,109
Carbon tetrachloride 75
Carbonyl J-acid 154
Catechol 81
Cellite 137
Cellotape 153
Cellulose 153
Cement 136,137,187
Ceramics 136,137
Cereals 171
Cerium iodide 121
Cesium iodide 123
Cheese 169,176,177
Chemical fiber 153
Chemical fertilizer 134
Chewing gum 175
Chloral
86,88
Chloral hydrate 86,88,94,95
Chlorella 181
Chlorine 74
(p-) Chloroaniline 99,153,154
Chlorobenzene 75
(p-) Chlorobenzene sulfonyl chloride
106
Chlorobutanol 183
Chloroform 75
Chloronaphthalene 75
Chloropicrin 135
Chloroprene rubber 150
(6-) Chloropropylene 75
Chocolate 175
Cholesterol 76
Chrome yellow
155
Chromium nitrate 127
Cinnamic acid 89
Cinnamon 185
Citric acid 90,168
Citronellol 76
Clay 187,188
Cleanser 162,163
Coal 141,142,187
Coal tar 141,142
Cobalt acetate 93
Cobalt alloy 114
Cobalt chloride 121
Cobalt nitrate 127
Cocoa 178,179
Coffee 178,179
Coke 142
Compressor oil 144
Condiment 168,170,173
Confectionery 174
Copper (II) chloride 121
Copper (I) oxide 119,120
Copper (II) oxide 120
Copper phthalophenone yellow 158
Copper sulfate 125
Copper wire 114
Copy paper 153
Corn starch 172
Cosmetics 163
Cream 163,164
Creatine 90,94
(p-) Cresidine 153
(m-) Cresol 81
(o-) Cresol 81
(p-) Cresol 81
Crotonaldehyde 86
Crude drug 185
Crude oil 144,146
Cuprous oxide 156
Curry roux 178,179
Cutting oil 144,146
Cyanamide 103
Cyanuric acid 94,103
Cylinder oil 144,145
Cyclodextrin 181
Cyclohexane 72,73
Cyclohexane carboxylic acid 89
205
Index
Cyclohexanol 76
Cyclohexanone 83,84
Cyclohexanone oxime 103
Cyclohexene 72,73
Cyclohexyl acetate 91
Cyclohexyl acetic acid 89
Cyclohexylamine 99
Cyclopentane 72
Cyclopentanone 84
(L-) Cystine 181
D:
(n-) Decane 72,73
Decanol 76
Decalin 72
73
(1-) Decene
Deoxybenzoin 83
Detergent 161,163
Dextran 181
Dextrose 94
Diacetone alcohol 83,84
(1,3-) Diaminopropane 99
Di-ammonium hydrogenphosphate 128
Diazoaminobenzene 103
Dichloroacetic acid 89,90,91
(2,4-) Dichlorophenoxy acetic acid 89
(1,4-) Dichloro-2-butene 75
(1,2-) Dichloroethane 75
(p-) Dichloronitrobenzene 104
Dicyanamides 103
Dicyclohexylamine 97
Diesel oil 143,144,146
Diesel engine oil 145
Diethanolamine 97,98,99
Diethylamine 97,98,99
(2-) Diethylaminoethanol 99
Diethyl peroxide 107
(N,N-) Diethylaniline 99
Diethylene glycol 76,78
Diethylene glycol ethyl ether 79
Diethylene glycol monoethyl ether 79
Diethyl ether 78
Diglycolic acid 90
Dihydropyran 79
(2,3-) Dihydrofuran 78,79
(,-) Dihydroxyadipic acid 90
Di-isopropylamine 98,99
Di-isobutylamine 97
206
Di-isopropanolamine 97
Di-isopropyl ketone 38,83
Di-isopropyl malonate 92
(N,N-) Dimethyl acetamide 101
Dimethyl aminomethyl phenol 99
(3-) Dimethylamino propionitrile 99
(N,N-) Dimethylaniline 97
(N,N-) Dimethyl benzylamine 98,99
(N,N-) Dimethylcyclohexylamine 97
(N,N-) Dimethylethanolamine 97
78
Dimethyl ether
(N,N-) Dimethyl formamide 100,101
Dimethylglyoxime 103
(2,4-) Dimethyl pentane 72
(2,4-) Dimethyl-3-pentanol 76
(N,N-) Dimethyl-p-toluidine 99
Dimethyl sulfoxide 108,109
Di-n-butylamine 99
(m-) Dinitrobenze 103,104
(3,5-) Dinitrobenzoic acid 89,103
Dinitrophenyl hydrazine 102
(2,4-) Dinitrotoluene 104
Dioxane 78,79
Dipentene
72
Dipentylamine 97
Diphenyl 72
Diphenyl carbinol 77
Diphenyl ether 78
Diphenylamine 97,154,155
(1,3-) Diphenyl thiourea 111
Di-sec-butylamine 97
Di-tert-butyl peroxide 107
Dithio acid 108,111
(n-) Dodecane 73
Dodecanol 76
Dried vegetable 171
Drops
175
Dyestuff 153
E:
178
Egg yolk
Electric insulating oil 146,143
Emulsifier 168
Emulsion 163,164
Enamel 156,157
Engine oil 145,146
Enzyme 180
Epoxy resin 148,149
Chapter VI: Index
Erucamide 101
Ethanol 76,77
Ethanolamine 97
Ethyl acetate 91,92
Ethylamine 97
(N-) Ethyl aniline 98
Ethyl benzene 72
(p-) Ethylbenzene sulfonyl chloride
106
Ethyl carbamate 92
Ethyl carbonate 91
Ethyl chlorocarbonate 91
Ethyl citrate 91
Ethylene 72,141
Ethylene bromide 75
Ethylene chloride 75
Ethylene glycol 76,77
Ethylene glycol dimethyl ether 78
Ethylene glycol monoethyl ether 77,79
Ethylene oxide 78
Ethylene propylene rubber 150
Ethylene thiocyanate 108
Ethyleneurea 100
Ethylene vinyl acetate 148
Ethylene vinyl acetate copolymer
148,149
Ethyl formate 91
(2-) Ethyl hexanol 77
Ethylidene bromide 75
Ethyl iodode 75
Ethyl isothiocyanate 108
Ethyl malonate 91
Ethyl mercaptan 110
(N-) Ethyl morpholine 98
Ethyl thioacetate 108
Ethyl thiocyanate 108
Ethyl vinyl ether 78
Eugenol 81
F:
Fat 176
Ferrite 114,187
Fertilizer 133
Fiber 152
Filter paper 152
Flavoring 167,168
Fluorine glass 137
Fluorine resin 149
Formaldehyde 86
Formaldehyde cyanhydrine 101,103
86
Formalin
Formamide 100,101
Formic acid 89,91
Furfural 83
G:
Gadolinium oxide 120
Gasoline 144,146
Gasoline engine oil 145,146
144,146
Gear oil
Gelatin 178,179,185
Geraniol 76
Gibberellin methyl ester 183
Glass powder 136,137
Glass wool 137
Glucose 173
Glutamic acid 90
Glutathione 183,184
Glycerine 76,77
Glycine 90
Glycolic acid 90
Glycylglycine 181
Granulated sugar 173
Grease 143,145
Grinding oil 144,146
Guaiacol 81
Guanidine nitrate 103
Gypsum 126
H:
Hair (black,blond) 185
Hair tonic 163,164
Heat treatment oil 144
Heavy oil 144,146
Helium 29
Hemin 183
Hepta-aldoxime 103
(n-) Heptane 26
Heptyl mercaptan 110
Hexadecyl bromide 75
Hexamethyl benzene 72
(n-) Hexane 73
(1-) Hexene 73
(n-) Hexylamine 97,99
Hexyl mercaptan 110
High-grade chemical fertilizer 134
207
Index
(L-) Histidine 94
Hop 179
Hydraulic oil 144,146
Hydrazine hydrate 95
Hydrazine hydrochloride 102
Hydrochloric acid 116
Hydrocyanic acid 116
Hydrofluoric acid 116
Hydrogen 129,130
Hydrogen chloride gas 116
Hydrogen peroxide 40
Hydrogen sulfide 143
Hydroquinone
80
(-) Hydroxyadipic acid 90
Hydroxylamine 40
(-) Hydroxybutyric acid 90
(-) Hydroxycaproic acid 90
(1-) Hydroxy-2-naphthoic acid 154
I:
Imidazole 97
Iminodiacetic acid 90
Indole 97
158
Ink
Insecticide 135
Iodobenzene 75
Iodoform 75
Iron (III) chloride 121
Iron (III) oxide 120
Iron ore 186,187,188
Isoamyl acetate 92
Isoamyl alcohol 76
Isoamyl mercaptan 110
Isobutyraldehyde 86
Isoctane 72,73
Isocyanate 104
Isopropanol 76
Isopropylamine 97
Isopropyl ether 78,79
Isopropyl isovalerate 92
Isopropyl mercaptan 110
J:
J-acid 154
Juice powder 178
208
K:
Kaolin 187
Kerosene 143,144,146
Kitazine (-P) 135
153
Kraft paper
L:
Lacquer
157,190
Lauryl peroxide 107
Lead acetate 93
Lead dioxide 119
Lead glass 137
Leaf 189,190
Leucine
90
Libotite 183
Licorice powder 185
Ligroin 73
Limestone 187
Linolenic acid 89
Lipid 180
Liquefied petroleum gas 138,140,141
Liquid crystal 165,166
Liquid Paraffin 144,146
Lithium acetate 94
Lithium chlorate 122
Lithium chloride 122,123
Lithium citrate 93,94
Lithium hydroxide 118
Lotion 163
LPG 138,140,141
Lubricant 143,146
M:
Machine-made paper 153
Machine oil 144,146
Magnesium acetate 93,94
Magnesium carbonate 124
Magnesium chloride 121,122
Magnesium hydroxide 119
Magnesium hypophosphate 128
Magnesium oxide 119,120
Maize 172
Maleic acid 90
Malic acid 168,169,170
Malonamide 100
Malonic acid 90
Maltitol 168
Chapter VI: Index
Maltose 173
Malt syrup5 172,173,175
Manganese benzoate 94
Manganese carbonate 124
Manganese chloride 121,122
Manganese ore 187,188
Manganese oxide 119,120
Manganese sulfate 125
(D-) Mannitol 76
Margarine 176,177
Mayonnaise 173,174
Meat extract 176,177
Medicinal wafer 185
Melamine resin 103,147,148
Mercaptan 108,143
Mercury (I) nitrate 127
Mercury (I) oxide 119
Mesitylene
72
Metaboric acid 40
Metacrylic resin 149
Metanilic acid 154
Methacrylic acid 89
Methane sulfonyl chloride 106
Methanol 76,77
Methionine
90
(2-) Methoxy-2-methyl-4-pentanone 84
(3-) Methoxypropylamine 97
Methyl acetate 91,92
Methyl acrylate 91,92
Methyl adipate 91
(2-) Methylaminopyridine 98,99
Methyl benzoate 91
(2-) Methyl-4-butanol 76
Methyl carbamate 92
Methyl carbitol 78
Methyl chloride 75,140
Methyl cyclohexane 72
Methyl cyclopentane 72
Methylene aminoacetonitrile 101
Methylene bromide 75
Methylene chloride 75
Methylene iodide 75
Methyl ethyl ketone 83,84
Methyl formate 91
Methyl glycolate 91
(3-) Methylhexane 72
Methyl iodide
75
Methyl isobutyl ketone 83,84
Methyl isothiourea 108
Methyl methacrylate 91
(N-) Methyl morpholine 99
(2-) Methyl-1,3-propanediol 76
(N-) Methyl pyrrolidine 104
2,2-Methyl pentane 72
(5-) Methyl resorcinol 81
Methyl salicylate 91
Methyl sebacate 91
(2-) Methyl tetrahydrofuran 79
(N-) Methyl thiourea1 111
Methyl valerate 91
Mica 187,188
176,177
Milk
Mineral oil 145,146
Mint 185
Miso 173
Monochloroacetic acid 89,90
Monoethanolamine 99
Morpholine
97
Muscle 185
N:
Namekat 135,136
Naphtha 146
Naphthalene 72,73
Naphthalenesulfonic acid 90
(-) Naphthol 81
(-) Naphthol 81
Naphthoquinone 106
Naphthylamine 97
(1-) Naphthyl isocyanate 103
(1-) Naphthyl isothiocyanate 108
Natural rubber 150
Nickel 114
93
Nickel acetate
Nickel hydroxide 119
120
Nickel oxide
83,94
Ninhydrin
Nitric acid 115,116
Nitrile-butadiene rubber 150
Nitrilotriacetic acid 90
(m-) Nitroaniline 104,154
Nitroethane 104
129,130
Nitrogen
Nitroglycerine 103
Nitromethane 103,104
(o-) Nitro-p-chloroaniline 104
209
Index
(p-) Nitrophenol 104,154
(1-) Nitropropane 103,104
(2-) Nitropropane 103,104
(m-) Nitro-p-toluidine 104
(N-) Nitrosodiphenylamine 103
Nucleic acid 180,181
(6-) Nylon 148,149
(6,6-) Nylon 148,149
O:
Octadecane 72
Octadecanol 76
Octane 72
Oil paper 153
Oleic acid 89
Oleylamide 101
Oxalic acid 90,91,94
Oxygen 129,130
P:
Paint 156,157
Palm oil 177
Pancreas 185
Pantechinan 183
Paper 152,153
Paper tape 153
Paraffin wax 151
Paste 160
Penicillin(1,3-) 184
Pentadiene 72
Pentaerythritol 76
(n-) Pentane 72,73
(2-) Pentene 72
Peri acid 153
Pharmaceuticals 180,182
(o-) Phenanthroline 94
Phenanthrene 72
(p-) Phenetidine 153,154
Phenol 80,81
Phenol resin 147,148,149
Phenyl acetate 91
Phenylalanine 90
Phenylhydrazine hydrochloride 103
Phenyl isocyanate 103
(3-) Phenylpropionaldehyde 88
(1-) Phenyl-2-thiourea 111
Phosphoric acid 116
Phosphate glass 137
210
Phosphomycin Ca 183,184
Photocopy paper 153
Photoresist 165,166
Photosensitive resin 158
90
Phthalic acid
Phthalic anhydride 105
97
(2-) Picoline
81
Picric acid
Pigment
155,156
Pill 185
Pine resin 189
Piperazine 94,97,99
Piperidine 97,98,99
Pitch tar 142
Plastics 147
Pollen 189
Polyacetal 149
Polybutene 145
Polybutylene terephthalate(PBT) 148,149
Polycarbonate 148,149
Polyester 148,153
Polyethylene 148,149
Polyethylene terephthalate(PET) 148,149
Polyglycerine 162
148
Polyimide
Polymethyl methacrylate 148
Polyol 149
Polyoxymethylene 148
Polypeptide
183
Polypropylene 148,149
Polystyrene 148,149
Polytetrafluoroethylene 148
Polyvinyl acetate 147
Polyvinyl alcohol 147,148,149
Polyvinyl butyral 148,149
Polyvinyl chloride 148
Potassium asparaginate 181
Potassium carbonate 124
Potassium chloride
121,122,123,133,134
Potassium dichloroisocyanurate 106
Potassium fluoride 121
Potassium glycylrhizinate 168
Potassium hydrogen tartrate 93
Potassium hydroxide 118
Potassium iodide 121
Potassium metabisulfite 126
Potassium nitrate 127
Chapter VI: Index
Potassium oxalate 93
Potassium permanganate 127
Potassium persulfate 40
Potassium sorbate 168,169,170
Potassium xanthogenate 183
Potato chip
175
Power cable rubber 150
Press board paper 152
Printed circuit board 166
Propane 72,138,140,141
(1,2-) Propane diamine 99
(1,2-) Propanediol 76
(1,3-) Propanediol 76
(i-) Propanol 77
(n-) Propanol 77
Propargyl alcohol 76
Propionaldehyde 86
Propionanilide 100
Propionic acid 89,90,91
Propionic anhydride 105
Propionyl chloride 105
Propylamine
97
(n-) Propylamine 97
(i-) Propylamine 99
Propylene
72
Propylene glycol 77
Propylene oxide 78,79,80
Prussian blue 155
Pyridine 97
(2-) Pyridyl ethanol 97
(4-) Pyridyl ethanol 97
Pyrogallol 81
Pyromellitic acid 94
Pyrrole
97,99
Pyrrolidine 97,99
Q:
Quartz 187,188
Quinalizarin
83
Quinoline
97
(p-) Quinone 106
R:
Raffinose 94
Rapeseed oil 176
Red iron oxide 120,155
Red phosphorus 114
Refrigerating machine oil
143,144,146
Resorcinol 81
(L-) Rhamnose 94
(Small) Rice cracker 175
Ricinoleic acid 90
Rinse 163,164
Rock 186,187,188
Rolling oil 144,146
Roots 189,190
Rosin
189
Rotary pump oil 144
Rubber 150
Rust preventive oil 144,146
Rutin 183
S:
Saccharin 169,170
Salad oil
177
Salicylaldehyde 88
Salicylamide 100
Salicylic acid 90,91
Sand 186,188
Sarcosine
90
Sealer 137
Sebacic acid 90
Sebaconitrile 101
Semicarbazide hydrochloride 103
Sesame oil 177
Shampoo
162
Silica
188
Silicon rubber 150
Silicon oil 143,145
Silicon oxide 120
Silicon wafer 166
Silver (I) oxide 119
Snack 175
Soap 161,163
Sodium acetate 93,94
Sodium adipicate 93
Sodium arsenite
127
Sodium aspartate 94,183
Sodium benzoate 93,168,169,170
Sodium bicarbonate 123,124
Sodium carbonate 124
Sodium chloride 121
Sodium chondroitin sulfate 168,170
Sodium citrate 93,94,168,169
Sodium glutamate 168,170
211
Index
Sodium 5'-guanylate 170
Sodium hydroxide 118
Sodium 5'-inosinate 168,169,170
Sodium formate 93
Sodium hydrosulfite 126
Sodium iodide 122,123
Sodium L-aspartate 94,183
Sodium metaarsenite 41
Sodium metabisulfite 126
Sodium metasilicate 128
Sodium naphthionate 93,94,154,155
Sodium nitrate 127,128,134
Sodium nitrite 127
Sodium peroxide 40
Sodium phthalate 93
Sodium polyphosphate 170
Sodium pyrosulfite 125
Sodium succinate 93,170
Sodium sulfate 125,126
Sodium sulfite
125,126
Sodium tartrate 93
Sodium tetraborate 127
Sodium thiosulfate 41
Sodium tripolyphosphate 128
Soil 187,188
Sorbic acid 168,169,170
Sorbit 168
(D-) Sorbitol 76
Soup 173,174
Soy bean oil 177
Soy flour 172
Soy milk
178
Soy sauce 173,174
Spice 174
Spray 141
Starch
171
Stearamide 100
Stearic acid 89,90,91,151
Stearoyl chloride 105
Stearyl alcohl 76
Strontium chloride 121,122
Styrol foam 149
Styrene
72
Styrene-butadiene rubber 150
Succinic acid 90
Succinic anhydride 105
Sugar 173,174,180
Sugar syrup 173
212
Sulfanilic acid 90
114,135,151
Sulfur
Sulfur dioxide 140
Sulfur hexafluoride 122
Sulfuric acid 115,116
Surfactant 162
Sweetener 168
Synthetic paper 153
T:
Talc 187,188
Tea
178
Tartaric acid 90
Terpinenol 76
Tetrabromoethane 75
(1,1,2,2-) Tetrachloroethane 75
(1-) Tetradecene 73
Tetrahydrofuran 78,79
Tetramethylene oxide 78
Terephthalic acid 90
Thiamine hydrochloride 168
Thinner 157
Thioacetic acid 108,111
Thiobenzamide 111
Thioglycollic acid 110
(2-) Thionaphthol 110
Thiophene 108
Thiophenol 110
Thiourea 108,110,111
Tin (II) chloride 121
Tin (IV) chloride 121
Tire rubber 150
Titanium 114
Titanium oxide 120,155,156
Toluene
72,73
Toluene 2,4-disulfonyl chloride 106
Toluenesulfonic acid 90
(o-) Toluenesulfonamide 154
(p-) Toluene sulfonyl chloride 106
Toluidine 97,99,154
Toner 158
Toothpaste 185
Transformer oil 143,144
Triacetone peroxide 107
Triazine 97
Triazole 97
Tri-n-butylamine 98,99
Trichloroacetic acid 89
Chapter VI: Index
(1,1,1-) Trichloroethane 75
(1,1,2-) Trichloroethane 75
Triethanolamine 97,99
Triethylamine 97
Trifluoroacetic acid 89
Trimethylacetic acid 89
Trimethylamine 97
(2,2,4-) Trimethyl pentane 72
Tri-isopropanolamine 97
Tri-n-propylamine 99
Tris (hydroxymethyl) aminomethane 97
Tri-sodium phosphate8 128
Tungsten
114
Turbine oil 144,146
U:
Undecanol
77
Uranyl acetate 93
Urea
100,133,134
Urea resin 147,148,149
Urethane 148,149
X:
Xylene 72,73
Xylenesulfonic acid 90
(2,6-) Xylenol 81
Y:
Yeast extract
168,170,181
Z:
Zinc acetate 93
Zinc fluoride 123
Zinc oxide 119,120,151
Zinc (Powdered metal) 114
Zinc stearate 93
Zinc sulfate 125
V:
(n-) Valeric anhydride 105
Valeryl chloride 105
90
Valine
Vanadium chloride 122
Varnish 156
Vegetable oil 176
Vinyl acetate 149
Vinyl chloride 74,75,140,149
Vinyl ether 78,79
(N-) Vinyl pyrrolidone 104
Vitamin B12 181
Vitamin B1 hydrochloride 181
Vitamin C 180,181
Vulcanization accelerator 150,151
W:
175
Wafers
Wasabi 173,174
144,146
Wax
172
Wheat
172
Wheat flour
Wool 153
213
214
Afterword
Nine years have passed since I first thought of the production of this Karl
Fischer Reagent Manual and the work was suspended for a considerable
period. Now that the project is finally complete, it feels as if a heavy load has
been lifted from my shoulders. I hope that this book will assist you with the
use of the various Karl Fischer reagent products.
At the completion of the project, I should like to acknowledge the
contribution of Mr. Shin'ichi Kuwata (formerly leader of this group) who
created the basic framework for the book, Professor Kaname Muroi who has
spent many years researching the Karl Fischer moisture measurement
method and Mr. Mitsumasa Ono (currently with Daia Instruments Co., Ltd. )
who carried out the actual Karl Fischer moisture measurements used as
examples in this book. I should like also to thank Mr. Akiyoshi Nozawa
(currently of Nippon Rensui Co., Ltd.), Ms. Hiroko Fujino, Ms. Akiyo Sekino
(retired), Ms. Yuka Nitta (nee Fujimoto, retired) and Ms. Naoko Katayama.
Thanks are due also to Mr. Kazuo Kikuchi, Director, Business Department,
Deputy General Manager Masaki Hayashi, Acting Department Manager
Takazumi Kanekiyo, Acting Department Manager Toshiyuki
Narikiyo,Mr.Toshihiko Yamashita,Mr. Takashi Kowada ,Mr.Mitsunari Morishita
and Kengo Itou of Mitsubishi Chemical Corporation's Functional Chemical
Company, and to Mr. Yasuo Koike and Kazuo Kumamoto, Directors and
Group Leader Toshio Kaneko of the Analytical Sciences Laboratory at the
Yokohama Research Center. Without their assistance this project would not
have been possible.
Hiromasa Kato (responsible for the text)
Analytical Sciences Laboratory
Yokohama Research Center
July 1999
215
216
Mitsubishi Chemical
Group
API Corporation
A subsidiary of
Mitsubishi Chemical Corporation
Head Office
2-4-9, Hiranomachi, Chuo-ku, Osaka 541-0046, JAPAN
Tokyo Office
1-5-20, Yaesu, Chuo-ku, Tokyo 103-0028, JAPAN
Telephone:+81-3-5205-0632 Facsimile: +81-3-5205-0641
E-mail: mcckf@cc.m-kagaku.co.jp
URL: http://www.mcckf.com
Agent:
217
copyright2004by
API Corporation
All rights reserved.
Edited and published by API Corporation
Printed in Japan
218
219
Printed in Japan
Rev. 3
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