Introduction to Analytical Chemistry
• Analytical Chemistry is the branch of chemistry that
deals with the separation, identification, and
quantification of chemical composition of substances
( or chemical components of a sample).
• Employs chemical principles and analytical methods
to separate, identify and quantify the chemical
components of samples.
Analytical Chemistry
•is concerned with the questions of "what
chemicals are present, what are their
characteristics and in what quantities are
they present in any substance/material?“
• The process of determination or
identification is called chemical
analysis.
Classification of Chemical Analysis
•Qualitative analysis
• determination of chemical identity of species in the
sample.
e.g. identity the elements, ions and compound in
the sample.
•Quantitative analysis
•determination of the amount of species or analytes,
in numerical terms (determining the quantity of the
analyte present)
•Analyte = species of interest to be determined
Analytical Chemistry is classified into two general areas of
chemical analysis
Focus in this course is quantitative methods of analysis
Separation of components/chemical species is often
performed prior to analysis (by physical or chemical
‘conditioning’)
Structural analysis – involves determining spatial
arrangement of atoms in a molecule or crystalline
compound or confirmation of the presence or position of
certain organic functional groups (Qualitative)
Roles of Analytical Chemistry in
Sciences & Our Everyday Life
• Manufacturing products for quality assurance (QA)
• Clinical analysis
•Forensic science
• Food science
•Agriculture
• Metallurgical
•Pharmaceutical chemistry
• Environmental analysis, etc…
Specific examples of analysis
• Analysis of metal ores to determine the percentage
of metal that can be obtained from the ore.
• Analysis to determine alcohol content of beer.
• Determine concentration of heavy metals in mining
effluents/wastewaters.
• Analysis of blood for malaria parasites.
• Analysis of air to determine amounts of pollutants in
air. (toxic gases – carbon monoxide)
1. Classification of Quantitative Methods
of Analysis
• 1. Gravimetric: mass of pure analyte or a
stoichiometric compound containing it.
• 2. Volumetric: volume is measured or used to
determine amount of analyte via concentration.
• 3. Spectral/Spectroscopic: interaction of
electromagnetic radiation (EM) and matter.
Measures the intensity of EM emitted or absorbed
by the analyte. Employs instruments such Atomic
Absorption Spectroscopy (AAS).
4. Electrochemical methods
electrical properties of the analyte in solutions is
measured such as potential, current, resistance and
charge
5. Separation methods
Chromatography - separation of individual
analytes due to their interactions with two
different phases based on their physio-chemical
properties.
Electrophoresis - separation technique that is based
on the mobility of analytes (ions) in an electric field.
Biological samples such as protein mixtures or DNA
are analysed.
Extractions – use two immiscible phase
to separate a solute from one phase into the other.
• 6. Chemometrics: The statistical treatment of data.
Advanced Methods
Quantitative analysis
Steps in a Typical Quantitative Analysis
• 1) Define the problem: What is the problem – what needs to
be found? Qualitative and/or quantitative). What will the
information be used for? Who will use it?
• (2) Select a method to be used: method must produce
accurate and reliable results, sensitive, in time and cost
effective . This is determined by the type of sample (e.g., blood
samples).
• 3) Sampling & Samples: sample type, sample size, obtain “a
representative sample” which represents average results.
Sample selection ( knowledge of source & history).
• Random sampling is the common method employed.
• 4) Sample preparation: convert the sample to a form suitable
for the method of analysis.
• a) Drying solid sample to ensure accurate weight
b) Sample dissolution or digestion
• c) Elimination of interferences or masking
d) Conversion of analyte to a single or measurable
form.
• 5) Replicate samples – splits of same sample to reduce errors
• 6) Calibration and measurement.
• 7) Calculation and data interpretation.
• 8) Evaluate results, estimate their reliability (statistical
analysis) and reporting.
Sample dissolution or digestion
• Solvents used in dissolution or digestion of laboratory sample prior to
analysis are:
• Water – used to dissolve samples consisting entirely of soluble salts. Mild
heating is used for salts that dissolve slowly at room temperature.
• Acids – used primarily to dissolve portions of samples which do not
dissolve in water. Addition of strong acids such as HCl & H2
SO4 will make
the sample soluble. For stubborn samples, oxidizing agents such as
concentrated H2
SO4
, HNO3
acids and aqua regia are used.
• Organic solvents – used to dissolve samples that contain organic
compounds which do not dissolve in water.
• Fusion: Samples that fail to dissolve in the aqueous or organic solvent
must be fused – dissolve in a molten solvent called a flux, that has acidic,
basic, or oxidizing properties.
2. Qualitative Analysis
• A qualitative analysis determines the presence or
absence of a particular analyte, but not the mass or
concentration. That is, it is not related to quantity.
• 1. Chemical Test
• 2. Flame Test
• 3. Blood Test
• 4. Covid-19 Test
• There are numerous
qualitative chemical tests,
examples include
– Acid test for
carbonates in soil.
– Flame test for metals
in ore.
– Kastle-Meyer test for
the presence of
hemoglobin in blood.
– Blood test for
presence of HIV &
AIDS virus
Kastle-Meyer test blood.
Phenolphthalein indicator is used to
detect the presence of hemoglobin
which turn pink.
Flame color test
is due to
emission of light
of a particular
wavelength by
each element.
Precision, Accuracy, and Error
Tutorial Questions
• Q1. What is analytical chemistry?
• Q2. Distinguish between qualitative analysis and quantitative
analysis. Give examples of each analysis.
• Q3. Outline the steps commonly employed in an analytical
procedure. Briefly describe each step.
• Q4. Distinguish between analyse, determine, sample matrix,
and analyte.
• Q5. Define accuracy and give an example.
• Q6. Define precision and give an example.
• Q7. What is percentage error and give an example.
• Q8. Differentiate between a random error and systematic
error
• Q1. Analytical Chemistry is the branch of chemistry that deals with the separation, identification, and quantification of the chemical composition of substances or chemical components of a sample.
• Q2. Qualitative analysis determines the presence or absence of a particular analyte without measuring its quantity, while quantitative analysis determines the amount of analyte present in a sample. Examples of qualitative analysis include chemical tests, flame tests, blood tests, and Covid-19 tests.
• Q3. The steps commonly employed in an analytical procedure include defining the problem, selecting a method, sampling and preparing samples, replicating samples, calibration and measurement, calculation and data interpretation, and evaluating and reporting results.
• Q4. Analyte refers to the species of interest to be determined, determine is the process of identification, sample matrix is the environment in which the sample exists, and analyte is the substance to be analyzed.
• Q5. Accuracy is the closeness of a measured value to the true value. For example, if a scale measures 100 grams for an object that actually weighs 105 grams, the scale has an accuracy error of 5 grams.
• Q6. Precision is the degree of agreement among multiple measurements of the same quantity. An example would be if a scale consistently measures an object as 100 grams in multiple trials, it has high precision.
• Q7. Percentage error is the difference between the measured value and the actual value, expressed as a percentage of the actual value. For example, if a measurement is 95% accurate, the percentage error is 5%.
• Q8. Random errors are unpredictable fluctuations in measurements, while systematic errors are consistent inaccuracies caused by flawed equipment or procedures. An example of a random error is a fluctuation in temperature affecting a reaction, while a systematic error could be a misaligned instrument consistently measuring values too high.