Unit 1: Principles and Concept of Quantitative Analytical Chemistry

UNIT 1: PRINCIPLES AND CONCEPT OF QUANTITATIVE
ANALYTICAL CHEMISTRY
Topic Outline:
 Nature of analytical chemistry
 Role of analytical chemistry
 Quantitative analysis
 Steps in quantitative analysis
Learning Objectives:
At the end of the lesson, the student’s should be able to:
 Understand the nature of analytical chemistry and its importance in various
fields of study.
 Describe and identify different methods of chemical analysis.
 Describe and apply the steps in a typical quantitative analysis.
________________________________________________________________________________________________
OVERVIEW
Analytical Chemistry is“ defined as a self-reliant chemical sub-discipline
which develops and delivers appropriate methods and tools to gain information on
the composition and structure of matter, especially concerning type, number,
energetic state and geometrical arrangements of atoms and molecules in general or
within any given sample volume.” (K. Cammann: “Analytical Chemistry-today’s
definition and interpretation”, Fresenius J Analytical Chemistry 343, 810-11 (1992))
ANALYTICAL CHEMISTRY DEFINED AS:
 Branch of Chemistry that deals with the analysis, identification, separation
and composition of matter
 Involves methods used to identify the substances that are present in a
sample (qualitative analysis) and the exact amount of the identified
substances (quantitative analysis)
Major Areas of Analytical Chemistry
 Qualitative Analysis - reveals chemical identity of elements and compounds
in a sample.
 Quantitative Analysis – determines the relative amounts of each substance in
a sample.
 Structural Analysis – determines the spatial arrangement of atoms in a
compounds.
THE ROLE OF ANALYTICAL CHEMISTRY
Analytical chemists use science and technology to solve practical problems.
Analytical chemistry is applied in all areas of science, industry, and medicine
as follows:
 Quality Control- Monitoring of raw materials, intermediates, and finished
products to ensure satisfactory quality and consistency.
 Monitoring and Control of Pollutants- Monitoring of pollutants and other
environmental hazards (heavy metals, halogenated organic compounds,
vehicle emissions, etc.)
 Clinical and biological studies – Medical diagnostics (e.g. Blood tests,
urinalysis) , Nutrition (e.g. Caloric value, vitamin and mineral content of food
products), Pharmacology (e.g. activity, efficacy/potency) and Toxicology
(lethal dosage (LD50)
 Geologic Assays- Ores (mining) and geological dating
 Forensics- Narcotics (identification of abused substances), ballistics
(determination of gun powder residue) and Trace analysis (blood, semen,
saliva, fabrics, etc.)
 Fundamental and Applied Research- drug discovery, development of new
analytical methods and instrumentation, chemical and biochemical sensors.
Figure 1.1. The

relationship between
analytical chemistry and
other fields of study.
Adapted from
Fundamentals of
analytical chemistry (9th
ed.) (page 3), by D. A.
Skoog et al., 2014,
Brooks/Cole.
LANGUAGE OF ANALYTICAL CHEMISTRY
 Analysis - A process that provides chemical or physical information about the
constituents in the sample or the sample itself.
 Determination - An analysis of a sample to find the identity, concentration, or
properties of the analyte.
 Measurement - An experimental determination of an analyte’s chemical or
physical properties.
 Analyte - The constituents of interest in a sample.
 Matrix - All other constituents in a sample except for the analytes.
 Signal - An experimental measurement that is proportional to the amount of
analyte
 Technique - A chemical or physical principle that can be used to analyze a
sample.
 Method - A means for analyzing a sample for a specific analyte in a specific
matrix.
 Procedure - Written directions outlining how to analyze a sample.
 Protocol - A set of stringent written guidelines detailing the procedure that
must be followed if the agency specifying the protocol is to accept the results of
the analysis.
CLASSIFICATION OF ANALYTICAL METHODS
According to Method:
Classical methods
 Gravimetric methods: determine the mass of analyte or some compound
chemically related to it.
 Volumetric methods use the volume of a solution containing sufficient
reagent to react with the analyte.
Instrumental methods
 Spectroscopic methods based on interaction of electromagnetic radiation
with analyte atoms and molecules, or on the production of radiation by
analytes.
 Electroanalytical methods involves measurement of the electrical properties
of the analyte such as current, potential or quantity of charge
 Chromatographic methods
According to the Extent of Analysis
 Complete or exact analysis – The amount of each constituents of the sample
is determined.
 Ultimate analysis- The amount of each element in a given sample is
determined.
 Proximate analysis –The amount of a certain selected constituent or groups
of constituents is/are determined.
According to Sample Size
Table 1. Classification of analysis based on sample size
Analysis Mass of Sample Volume of Sample
Macro analysis >100mg >100µL

Semi micro analysis 10-100mg 50-100 µL
Micro analysis 1-10mg <50µL

Ultra micro analysis <1mg --------
According to Amount of the Desired Constituents

Table 2. Classification of constituents in a sample
Major Constituents >1% of the sample
Minor Constituents 0.01-1% of the sample
Trace Constituents 0.001-0.01% of the
sample
Ultratrace <0.001% of the sample
Constituents
Typical Quantitative Analysis

Choosing a Method: The choice is sometimes difficult and requires experience as
well as intuition. - level of accuracy :investment on time and money - Number of
samples analyzed and number of components in the sample, availability of
equipment and trained personnel and the time of analysis
Acquiring the Sample: - an analysis must be performed on a sample that has the
same composition as the bulk of material from which it was taken. When the bulk is
large and heterogeneous, great effort is required to get a representative sample.
The collection of specimens from biological sources represents a second type of
sampling problem. Three steps are generally followed in obtaining samples:
obtaining a gross sample, obtaining a laboratory sample and obtaining an analysis
sample. A gross sample is obtained from a bulk sample and obtained in such a
manner that it is considered a representative of the bulk sample. A laboratory
sample is a fraction of the gross sample weighing several grams wherein further
reduction to few milligrams results into an analysis sample.
Processing the Sample:
Preparing a Laboratory Sample: grounding, mixing, storing. Defining Replicate
Samples: Replicate samples, or replicates, 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. Preparing Solutions: Physical and Chemical Changes.
Converting the sample into a soluble form: acid-base addition, ignition, high
temperature fusion. Converting the sample into a form suitable for the
measurement step. Mn → MnO4 colored solution
Eliminating Interferences: An interference or interferent is a species that causes
an error in an analysis by enhancing or attenuating (making smaller) the quantity
being measured. The matrix, or sample matrix, is the collection of all of the
components in the sample containing an analyte.
Calibrating and Measuring Concentration: Ideally, the measurement of the
property is directly proportional to the concentration, that is, cA= kX where k is a
proportionality constant. The process of determining k is called a calibration.
Calculation of results and reporting of data
Results of analysis can be expressed depending on the nature of analyte
a. Solid Samples. Calculations on solid samples are based on mass. The most
common way of expressing results in a macro determination is by % mass or %
weight
Table 3. Concentrations of analyte in solid samples in trace concentrations
b. Liquid Samples. Similarly, concentrations of solid or liquid analytes in liquid

samples obtained from a macro analysis is usually expressed as % weight by
volume or % volume by volume defined as follows:
Table 4. Concentrations of analyte in liquid samples in trace concentrations (wt/vol

and vol/vol)
Figure 1.2. Flow diagram showing the steps in a quantitative analysis. Adapted
from Fundamentals of analytical chemistry (9th ed.) (page 5), by D. A. Skoog et al.,
2014, Brooks/Cole.
UNIT EXERCISE
Based on the discussion, illustrate using a flow diagram how chemical

analysis is used in the identification and determination of quantities of mercury in
the fish samples.
REFERENCES
Harris, DC (2010). Quantitative chemical analysis (8th ed.). New York, NY: W.H.
Freeman & Co
Skoog DA, West DM, Holler FJ, Crouch SR (2014). Fundamentals of analytical
chemistry (9th ed.). Belmont, CA: Brooks/Cole

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UNIT 1: PRINCIPLES AND CONCEPT OF QUANTITATIVE

Figure 1.1. The

Macro analysis >100mg >100µL

Micro analysis 1-10mg <50µL

According to Amount of the Desired Constituents

Typical Quantitative Analysis

b. Liquid Samples. Similarly, concentrations of solid or liquid analytes in liquid

Table 4. Concentrations of analyte in liquid samples in trace concentrations (wt/vol

Based on the discussion, illustrate using a flow diagram how chemical

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