Introduction to
Analytical chemistry
Rosemarie Ann Cuevas, R.Ch., M.Sc.
Instructor
ILO’s
1. Define analytical chemistry
2. Explain the importance of quantitative analysis
3. Explain different methods of Quantitative
analysis
4. Give examples of different analysis in industrial
setting.
2
Topics
1. Definition of analytical chemistry (Quali and
Quanti)
2. Importance of quantitative analysis
3. Methods of Quantitative analysis (Gravimetric
and volumetric)
4. Instrumental analysis
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What is Analytical
Chemistry?
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Analytical Chemistry is…
A measurement science consisting of a
set of powerful ideas and methods that
are useful in all fields of science and
medicine.
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Qualitative VS Quantitative
analysis analysis
reveals the identity Indicates the amount
of the elements and of each substance in
a sample.
compounds in a
sample.
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The Role of Analytical Chemistry
applied throughout industry, medicine, and
all the sciences.
Quantitative analytical measurements also
play a vital role in chemistry, biochemistry,
biology, geology, physics, and the other
sciences.
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The relationship
between analytica
chemistry, other
branches of
chemistry, and the
other sciences.
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Classification of Analytical Methods
1. According to extent of analysis
2. Based on sample size
3. Based on amount of analyte
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Classification of Analytical Methods
According to the Extent of Analysis
1. Complete or exact analysis
◦ The amount of each constituent of the sample is determined.
2. Ultimate analysis
◦ The amount of each element in a given sample is determined (more
comprehensive: elemental composition)
3. Proximate analysis
◦ The amount of a certain selected constituent or groups of constituents
is/are determined (moisture, calorific value, volatile matter, ash,
protein, sugar, fat) 1-11
Types of Analysis based on Sample Size
Type Mass of Sample Volume of
Sample
Macroanalysis >100 mg > 100 uL
Semimicro 10 - 100 mg 50 – 100 uL
Micro 1 – 10 mg < 50 uL
Ultramicro < 1 mg
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Types of Analysis based on Amount of Analyte
Type of Constituent Analyte Level
Major >1%
Minor 0.01 % (or 100 ppm) to 1%
Trace 1 ppb to 100 ppm
Ultratrace < 1 ppb
% Analyte = (amount analyte/amount sample) x 100 1-13
Quantitative analysis
Determination of
Research the amount of a
Process Trouble valuable
control shooting component
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Classifying Quantitative Analytical Methods
Quantitative methods may be classified into two:
1. Classical Methods measures the mass or the volume of
sample to be analyzed.
2. Instrumental Methods involve the measurement of
some quantity/property that is proportional to the amount of
analyte in the sample
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Types of Classical Methods
1. Gravimetric methods determine the mass of the
analyte or some compound chemically related to it.
(moisture, amount of ppt)
2. Volumetric method determines the volume of a
solution containing sufficient reagent to react
completely with the analyte. (titration)
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Types of Instrumental Methods
Electroanalytical Methods - measurement of electrical
properties
Spectroscopic Methods - measurement of the
interaction between electromagnetic radiation and
analyte atoms or molecules or on the production of
such radiation by analytes.
Chromatographic Methods- involves the separation and
identification of components of a mixture
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Other Analytical Methods
mass-to-charge ratio sample thermal
conductivity
rate of radioactive decay optical activity
heat of reaction refractive index.
rate of reaction
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The Analytical Process
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Some Terms
Analyte
-The desired constituent/s in the sample
-The object of the analysis
Matrix
-Part of the sample where the analyte is contained
Interferents / Interferences
-Part of the sample that interferes with the
analytical method in the analysis of the analyte
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The Analytical Process
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Picking a Method
What is the level of accuracy required?
What is the number of samples to be analyzed?
The complexity of the sample and the number of
components in the sample always influence the
choice of method to some degree.
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The Analytical Process
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Acquiring the Sample
Sampling involves obtaining a small mass
of a material whose composition
accurately represents the bulk of the
material being sampled.
Sampling is frequently the most difficult
step in an analysis and the source of
greatest error.
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Acquiring the Sample
A material is heterogeneous if its
constituent parts can be distinguished
visually or with the aid of a
microscope.
An assay is the process of determining
how much of a given sample is the
material indicated by its name.
We analyze samples and we determine
substances. 1-26
The Analytical Process
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Processing the Sample
Preparing a Laboratory Sample
–A solid sample is ground, mixed to ensure
homogeneity, and stored for various lengths of
time before analysis begins.
–Because any loss or gain of water changes the
chemical composition of solids, it is a good idea
to dry samples just before starting an analysis.
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Processing the Sample
Preparing a Laboratory Sample (Cont.)
Liquid samples are subject to solvent evaporation
-If the analyte is a gas dissolved in a liquid, analyte must be
kept inside a second sealed container to prevent
contamination by atmospheric gases.
-Extraordinary measures, including sample manipulation
and measurement in an inert atmosphere, may be required
to preserve the integrity of the sample.
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Processing the Sample
Replicate samples are portions of a material
of approximately the same size that are carried
through an analytical procedure at the same
time and in the same way.
Replication improves the
quality of the results and
provides a measure of their
reliability.
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Processing the Sample
Preparing Solutions: Physical and Chemical Changes
–Ideally, the solvent should dissolve the entire sample, including the
analyte, rapidly and completely.
–The sample may require heating with aqueous solutions of strong acids,
strong bases, oxidizing agents, reducing agents, or some combination of
such reagents.
–It may be necessary to ignite the sample in air or oxygen or perform a
high-temperature fusion of the sample in the presence of various fluxes.
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Processing the Sample
Blank samples- samples that do not contain the analyte.
Types of Blank
1. Method Blank- A blank that has been subjected to all the sample
preparation procedures
2. Reagent Blank- was not subjected to sample preparation
procedures
3. Field Blank- A method blank that has been exposed to the site of
sampling 1-32
The Analytical Process
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Eliminating Interferences
Species other than the analyte that affect the final
measurement are called interferences, or interferents.
An interference is a species that causes an error in an
analysis by enhancing or attenuating (making smaller)
the quantity being measured.
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Eliminating Interferences
Techniques or reactions that work for only one analyte are said
to be specific. Techniques or reactions that apply for only a few
analytes are selective.
The matrix, or sample matrix, is all of the components in the
sample containing an analyte.
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The Analytical Process
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Remaining Steps of A Typical
Quantitative Analysis
Calibration and Measurement
Ideally, the measurement of the property, X is directly
proportional to the concentration.
X = k Canalyte
where k is a proportionality constant
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The Analytical Process
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Remaining Steps of A Typical
Quantitative Analysis
Calculating Results
Computing analyte concentrations are based on the raw
experimental data collected in the measurement step, the
characteristics of the measurement instruments, and the
stoichiometry of the analytical reaction.
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The Analytical Process
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Remain Steps of A Typical
Quantitative Analysis
Evaluating Results by Estimating Their Reliability
Analytical results are incomplete without an estimate
of their reliability.
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Assessment
1. Identify the type of analysis (based on extent) and analyte being referred to in the
following:
a) A 500-mg tablet was found to contain 30 mg of the active ingredient.
b) 20 mg of a toxic substance was found to be present in a 1-g of milk tea powder
c) A 5-g baking flour mixture containing 10 mg of potassium bromate
2. State the difference between:
a. classical and instrumental methods.
b. Major and minor constituent
c. Gravimetry and Volumetric methods 1-42
Assessment
3. Identify the word being defined:
a. a type of blank exposed to the site of sampling
b. a type of analysis using 80 mg sample
c. a type of analysis based on interaction of matter and light
d. a type of analyte comprising 0.05% of the sample
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THE END
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