ANACHEM

1. CHEM 400
Introduction to Analytical Chemistry
By
Skoog, West, Holler, Crouch

2. The Role of Analytical Chemistry
• Analytical chemistry plays a vital role in the
development of science.
• Plays a vital role in many research areas in
chemistry, biochemistry, biology, geology,
physics and the other sciences.
• All branches of chemistry draw on the ideas and
techniques of analytical chemistry.
• The interdisciplinary nature of chemical analysis
makes it a vital tool in medical, industrial,
government and academic laboratories.

3. Chemistry as the Central Science

4. The Role of Analytical Chemistry
-Friedrich Wilhelm Ostwald
“Analytical Chemistry, or the art of
recognizing different substances and
determining their constituents, takes a
prominent position among the
applications of science, since the
questions which it enables us to answer
arise wherever chemical processes are
employed for scientific or chemical
purposes.”
http://www.pace.edu/dyson/academics/chemistryplv/

5. The Nature of Analytical Chemistry
 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).

6. Analytical Methods
• Classical Methods: Wet chemical methods such as
precipitation, extraction, distillation, boiling or melting
points, gravimetric and titrimetric measurements.
• Instrumental Methods: Analytical measurements
(conductivity, electrode potential, light absorption or
emission, mass-to-charge ratio, fluorescence etc.) are
made using instrumentation.

7. Classifying Quantitative Analytical Methods
• Gravimetric Methods: Determine the mass of the analyte or
some compound chemically related to it.
• Volumetric Methods: The volume of a solution containing
sufficient reagent to react completely with the analyte is
measured.
• Spectroscopic Methods: Based on measurement of the
interaction between electromagnetic radiation and analyte
atoms or molecules.
• Chromatographic Methods: Separation techniques and
quantitation is based on calibration curve.
• Electroanalytical Methods: Involve the measurement of
electrical properties such as voltage, current, resistance and
quantity of electrical charge.

8. Steps in a quantitative analysis

9. Stepping Through a Typical
Quantitative Analysis
1) Picking a Method: The first step is the selection of a
method. Factors need to be considered in the selection
process are:
1. Accuracy required
2. Cost of analysis (total investment)
3. Number of sample to be analyzed
4. Time required for analysis
5. Skill required
6. Complexity of the sample
7. Number of components in the sample

10. Stepping Through a Typical Quantitative Analysis
2) Acquiring the Sample: Sampling is the process of
collecting a small mass of a material whose composition
accurately represents the bulk of the material from which it
was taken. To produce meaningful information, an analysis
must be performed on a representative sample. For large
heterogeneous sample, great effort is required to get a
representative sample. Sometime proper sampling is the
most difficult step in an analysis and the source of greatest
error. The final result of an analysis will never be any more
reliable than the reliability of the sampling step.

11. Stepping Through a Typical Quantitative Analysis
3) Processing the sample: The third step in an analysis is to
process the sample. Sometimes no sample processing is
required prior to the measurement step such as pH of
water sample can be measured directly. Under most
circumstances, sample need to be processed in a variety of
different ways.
i. Preparing a Laboratory Sample – hydrate or dehydrate
ii. Defining Replicate Samples – improves the reliability
iii. Preparing Solutions: Physical and Chemical Changes

12. Stepping Through a Typical Quantitative Analysis
4) Eliminating Interferences: Need to eliminate substances
from the sample that may interfere with the measurement
step. Few chemical or physical properties of importance in
chemical analysis are unique to a single chemical species.
Species other than the analyte that affect the final
measurement are called interferences. An interference
causes an error in an analysis by enhancing or attenuating
the quantity being measured. A scheme must be devised to
isolate the analytes from interferences before the final
measurement is made.

13. Stepping Through a Typical Quantitative Analysis
5) Calibration and Measurement: An analytical
results depend on a final measurement of a physical or
chemical property (X). Ideally, the measurement of
the property is directly proportional to the
concentration (CA).
CA = kX
where, k is a proportionality constant. The process of
determining k is an important step in most analyses.
This step is called a calibration.

14. Stepping Through a Typical Quantitative Analysis
6) Calculating Results: Analyte concentrations from
experimental data need to be calculated. These
computation are based on the raw experimental data
collected in the measurement steps, the characteristics of
the measurement instruments and the stoichiometry of the
analytical reaction.
7) Evaluating Results by Estimating Their Reliability:
Analytical results are incomplete without an estimate of
their reliability. Some measure of the uncertainties
associated with computed results need to be provided.

15. FEED BACK CONTROL
SYSTEM