ENGI 9628 – ENVIRONMENTAL LABORATORY

Environmental
Instrumental Analysis
Dr. Noori Saady
Environmental Instrumental Analysis

1. Introduction and principles

2. Calibration of instrumental methods
3. UV spectroscopy
4. Atomic absorption spectroscopy
5. Inductively coupled plasma optical emission
spectroscopy
6. Gas chromatography
7. High performance liquid chromatography
 Introduction

Analytical Chemistry deals with methods for

determining the chemical composition of samples.

 Qualitative Analysis: (identification) provides

information about the identity of species or
functional groups in the sample (an analyte can
be identified).
 Quantitative Analysis: provides numerical
information of analyte (quantitate the exact
amount or concentration).
 Introduction

 Rely of the stoichiometry of Use chemical and physical

a chemical reaction so that properties to detect and quantify
the measurement of the the target compound or element by
volume or mass of the  imposing external physical
reactants allow the direct effect/force such as
calculation of the quantity electromagnetic radiation,
of the analyte. heating, electrical voltage, etc. on
 Examples: precipitation, the sample.
extraction, distillation,  Measuring the Induced changes
boiling or melting points, (response) in the properties of the
gravimetric and titrimetric sample.
 Examples: UV-spectroscopy, GC,
measurements.
HPLC, ICP-MS
Advantages and disadvantages of instrumental
methods
Advantages Disadvantages
Low limit of detection (LOD) standards and standard
solutions, plotting of
calibration charts
Rapid Complexity of used
equipment
Automation and Expensive Devices
computerization
Analysis is possible on High cost of standard
distance substances
High selectivity Sample preparation
Simultaneous detection
capabilities
Principles of Instrumental Techniques
 Principles of Instrumental Techniques

1. Imposing external physical effect/force

such as electromagnetic radiation, heating, electrical
voltage, etc. on the sample.

2. Measuring the Induced changes (response) in the

properties of the sample, detected by measuring an
electrical, mechanical, thermal or optical (physical)
signal.
 Principles of Instrumental Techniques
Instrumental methods have several categories based on the
used properties:
1. Optical
2. Chromatographic: ability of different substances to
selective sorption.
3. Electrochemical: electrochemical properties of
substances.
4. Radiometric: radioactive properties of substances.
5. Thermal: heat effects of substances.
6. Mass spectrometric: studying of the ionized fragments of
substances.
7. Kinetic: dependence of speed of reaction
Example

Block diagram of a fluorometer

 Components of Instrumental Techniques
 Analyte: the target species that can be recognized and
measured.
 Instruments: communicate between analyte and analyst.
Components of an instruments:
 Energy Source: stimulates measurable response from
analyte
 Sensor: capable of monitoring specific chemical
characteristics nonstop
 Transducer: converts information in nonelectrical domain
to electrical domain and reverse
 Detector: indicates a change in one variable in its
environment (pressure, temperature, particles) can be
mechanical, electrical or chemical
 Signal Instrumental Methods
Emission of radiation Emission spectroscopy (X-ray, UV, visible,
electron, Auger); fluorescence,
phosphorescence, and luminescence
(X-ray, UV, and visible)

Absorption of radiation Spectrophotometry and photometry (X-ray, UV, visible, IR);

photoacoustic spectroscopy; nuclear magnetic resonance
and electron spin resonance spectroscopy

Scattering of radiation Turbidimetry; nephelometry; Raman spectroscopy

Refraction of radiation Refractometry; interferometry
Diffraction of radiation X-Ray and electron diffraction methods
Rotation of radiation Polarimetry; optical rotary dispersion; circular dichroism
Electrical potential Potentiometry; chronopotentiometry
Electrical charge Coulometry
Electrical current Polarography; amperometry
Electrical resistance Conductometry
Mass-to-charge ratio Mass spectrometry
Rate of reaction Kinetic methods
Thermal properties Thermal conductivity and enthalpy
Radioactivity Activation and isotope dilution methods
 Selection of an Analytical Method
It depends on

1. Accuracy, Precision, Sensitivity, Selectivity

2. Available sample volume or quantity
3. Concentration range of the analyte (Dynamic range)
4. Interference in sample
5. Physical and chemical properties of the sample matrix
6. Number of samples to be analyzed
7. Speed, ease, skill and cost
8. Bias
9. Detection limit
Calibration of Instrumental Methods
External standard method
Internal standard method
Standard addition method
(spiking method)

Statistical Terms
Accuracy
Mean
Precision (relative or systematic error)
Standard deviation
Variance
Relative standard deviation
Sensitivity
Detection limit
 Calibration of Instrumental Methods

Figure 4. Standard Addition Method

Table 2. Internal Standard signals and ratio for Chloroform

5
STANDARDS 4.5
4
Ret. y = 0.0028x + 0.1244
3.5
Time 6.58 14.01 17.44 R² = 0.9946
3

Ratio
Conc. CHCl3 IS SS 2.5
area ratio area ratio area ratio 2
1.5
0 3622.818 0.000 47990 0.443 365145 7.609 1
20 16308.4 0.156 104621.8 0.827 298377.2 2.852 0.5
50 23181.54 0.208 111625.7 1.000 266700.3 2.389 0
0 500 1000 1500 2000
100 340507.3 0.459 121144.1 1.000 278714.6 2.301 Conc. (ppb)
200 86628.96 0.709 122101.4 1.000 318410 2.608
500 191282 1.766 108342.9 1.000 264480.8 2.441 Figure 5. Internal Standard
1500 545865.9 4.314 126528.3 1.000 278326.4 2.200 Method for CHCl3
LOQ = limit of quantitation
= the concentration at
which the calibration
curve departs from
linearity (limit of linearity,
or LOL).
 UV Spectroscopy
Spectral Distribution of Radiant Energy

Figure. Electromagnetic Spectrum

Figure. Schematic of UV spectrophotometer

 UV Spectroscopy
Conventional Spectrophotometer

Absorbance and
Complementary
Colors
 UV Spectroscopy
Instrument Components
 Light Sources  Dispersion Devices
Hydrogen Gas Lamp Non-linear dispersion
Mercury Lamp  Temperature sensitive
 Detector Linear Dispersion
 Cells  Different orders
 Quartz (crystalline silica)

Wave Number (cycles/cm)

X-Ray UV Visible IR Microwave

200nm 400nm 800nm

WAVELENGTH(nm)
UV spectroscopy
 UV spectroscopy
Transmittance and Path Length: Beer’s Law

T  I / I 0  e ConstConcentration

Concentration
Source URL: http://www.asdlib.org/onlineArticles/ecourseware/Analytical%20Chemistry%202.0/Text_Files.html
Atomic Absorption Spectroscopy
Atomic Absorption Spectroscopy is a quantitative method of
analysis that is applicable to many metals and a few other
elements; it is not suitable for non-metallic elements.
Sample
Atomic absorption can
Compartment
be used for the
analysis of > 60
elements at ≤ μg/L.

Detector
Light
Source
Atomic Absorption Spectroscopy
 Light Source (Hollow cathode lamp) filled with the element to
be measured
 Nebulizer (Flame) for atomizing the sample, air- acetylene
temp. > 2700ºC
 Monochromator for generating spectrum
 Photomultiplier Detector
 Output Device

Figure. Atomic absorption components

Atomic Absorption Spectroscopy

Advantages & Disadvantages

 High sensitivity: [10-10g (flame), 10-14g (non-flame)]
 Good accuracy: (Relative error 0.1 ~ 0.5 %)
 High selectivity
 High throughout put: 250–350 determinations per hour.

It requires
 A resonance line source is required for each element to be
determined
 Sample preparation
Atomic Absorption Spectroscopy
The Instrument Components
1. A flame

2. Lamps to produce the correct

wavelength of light (hollow
cathode lamp)

3. A detector

4. A system to aspirate (atomize)

solutions into the flame;
nebulizer

5. A computer to control the

experiment
Atomic Absorption Spectroscopy
Colors Produced by Different Ions

 Different flame colors are produced for different

ions.
 Intensity of the color α concentration.

Calcium Copper Potassium Manganese Cobalt

Atomic Absorption Spectroscopy
 Sample preparation
 The sample should be in solution.
 Solid samples must be dissolved in a suitable
solvent.
 Dilute solutions can be concentrated by liquid-
liquid extraction.
 Minimizing spectral interference
 Minimizing chemical interferences
 Standardizing the method
 Inductively Coupled Plasma Mass spectroscopy
(ICP-MS)

ICP-MS Principles
ICP converts elements to ions (excited) which can be
separated and detected by Mass Spectroscopy (MS).
• Determine several elements (metallic and some non-
metallic) simultaneously
• Speed, sensitivity and precision
 Monochromator: generate the spectrum
 Detector
 Plasma is an ionized gas with positive ions, free atoms and
electrons resulting in electrically neutral gas with high
conductivity for electricity at very high temperature >6000ºC
28
(ICP-MS): Instrument

Figure. Schematic of Inductively Coupled

Plasma Mass Spectroscopy
(ICP-MS): Instrument
 ICP-MS Instrumentation

 Heating of an electrically
conducting object by Plasma
electromagnetic induction
 induction heat  ionized plasma Magnetic
force
 Analytical plasma is derived from
the magnetic field.
 Argon or helium are used to RF Coil
Cooling
produce plasmas gas

 ICP operates between 1 to 5

kilowatt Quartz
tube
 ICP torch is cooled by water
flowing in a coil Ar Sample &
Carrier gas
from Nebulizer
31
Figure. Schematic of ICP-Torch
 ICP-MS Instrumentation- Mass Spectroscopy

 Mass Spectroscopy: sorts ions based on their mass to

charge ratio

 no more than 0.2% total dissolved solids (TDS) in sample

 Preferred for positive ions, 𝑀+ or 𝑀2+

 not suitable for elements which form negative ions, such

as Cl, I, F, etc.

32
 ICP-MS Instrumentation- Mass Spectroscopy

 Quadrupole Mass filter

 Separate ions by their mass-to-charge ratio.
 4 rods (approximately 1 cm in diameter and 15-20 cm long)
 Ions of a single mass-to charge ratio (m/e) can pass through the
rods (electrostatic filter) to the detector at a given instant in time
 There is a specific setting for each mass to charge
 Can separate 2400 atomic mass unit per second

Figure 18. Schematic of Quadrupole Mass filter

 Detector
 translate the number of ions striking the detector into an
electrical signal 33
 ICP-MS Instrumentation- Cons and pros
Advantages and Disadvantages

 Detectors are consumable and should be replaced ($1500-

$2500)

 They have interferences for some specific ions and isotopes

based on the precision

Application
 Elemental analysis, forensic, bone and teeth, toxicology

34
 Chromatography
Principle
• A site in which a
moving phase
(mobile phase) and
a non-moving phase
(stationary phase)
make contact via an
interface that is set
up.

The affinity with the mobile phase

and stationary phase varies with
the solute.  Separation occurs
due to differences in the speed of
motion.
Chromatography
Types of Chromatography
The Chromatogram

Retention time

Peak Peak
area
height
The Chromatogram
 Liquid Chromatography
In liquid chromatography:

 The liquid mobile phase is called the “eluent”.

 The stationary phase is usually a solid or a liquid.
 Any substance that can be stably dissolved in the mobile
phase can be analyzed.
 Differences in the interactions between the solutes and
stationary and mobile phases enable separation.
 Gas Chromatography
Gas chromatography (GC) can separate volatile organic
compounds. However, GC is not suitable if the compound
has limited stability at the elevated temperatures used during
GC.
 GC instrument
1. Carrier gas: type, flow and pressure
2. Injector: temperature and split ratio
3. Column: type, dimensions, and packing
4. Detector: type

Rouessac and Rouessac 2007

 GC instrument
GC column

Rouessac and Rouessac 2

 GC instrument
GC Detectors
A large number of sensitive and selective detectors that can
be used in GC.

Detector Temp Remarks

Range (0C)
Thermal conductivity (TCD) 450 Non-destructive,
temperature and flow
rate sensitive
Flame ionization (FID) 400 Destructive, excellent
stability
Electron capture (ECD) 350 Non-destructive, quickly
contaminated,
temperature sensitive
Nitrogen-phosphor sensitive 400 See FID
(NPD)
Flame photometric (FPD)
Photo ionization (PID)
 High Performance Liquid Chromatography
(HPLC)
A chromatographic technique with its mobile phase is a liquid
HPLC instrument
HPLC: Instrument Components

Injector
1. Solvent Reservoirs
2. Pump
Mixer
3. Sample Injector
4. Column(s)
Pump 5. Detector
s
6. Data System
Column

Detector

Solvents Waste
 TYPES OF HPLC TECHNIQUES
Based on modes of chromatography
1. Normal phase mode
2. Reverse phase mode

Based on principle of separation

1. Adsorption chromatography
2. Ion exchange chromatography
3. Ion pair chromatography
4.Size exclusion(or)Gel permeation chromatography
5. Affinity chromatography
6. Chiral phase chromatography
 TYPES OF HPLC TECHNIQUES
Based on elution technique
1. Isocratic separation
2. Gradient separation

Based on the scale of operation

1. Analytical HPLC
2. Preparative HPLC

Based on the type of analysis

1. Qualitative analysis
2. Quantitative analysis
 Performance Liquid Chromatography

Different
combinations of
stationary phase and
mobile phase make
Many types of liquid
chromatography Molecular mass

Each type may be

further characterized
based on its overall
efficiency or
performance
Advantages of LC compared to GC:

 LC can be applied to the separation of any compound that is

soluble in a liquid phase.

 LC more useful in the separation of biological compounds,

synthetic or natural polymers, and inorganic compounds

 Liquid mobile phase allows LC to be used at lower

temperatures (Room temperature) than required by GC

 Not limited by sample volatility or thermal stability

 Ease of sample recovery

 HPLC

Advantages
– fast analysis time
– ease of automation
– good limits of detection
– preferred choice for analytical applications
– popular for purification work

Disadvantages
– greater expense
– lower sample capacities
 Types of HPLC Detectors

1. Refractive index detectors

2. U.V detectors
3. Fluorescence detectors
4. Electro chemical detectors
5. Evaporative light scattering detectors
6. IR detectors
7. Photo diode array detector
8. Mass spectrometer
 HPLC Applications
Environmental Chemical
Inorganic ions, Hazardous organic polystyrenes
substances, etc. dyes
polyaromatic hydrocarbons Phthalates
Inorganic ions
herbicides Bioscience
Sugars, lipids, nucleic
Consumer Products acids, Nucleotides, amino
lipids, antioxidants, sugars acids, proteins, peptides,
Vitamins, food additives, organic steroids, amines, etc
acids, etc
Pharmaceuticals
Clinical Drugs, antibiotics
amino acids, vitamins,
homocysteine