Analytical
Chemistry:
Introduction
Analytical Chemistry
• Branch of science that deals with the
__________________________________
______of the components in a sample
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Analytical Chemistry
• Analytical chemistry is particularly
concerned with the questions of
“___________________, ___________
and _____________________?"
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Analytical Chemistry
Biology
Botany
Genetics
Microbiology
Molecular
Biology
Zoology
Chemistry
Biochemistry
Inorganic
Chemistry
Organic
Chemistry
Physical
Chemistry
Physics
Astrophysics
Astronomy
Biophysics
Engineering
Civil
Chemical
Electrical
Mechanical
Geology
Geophysics
Paleontology
Paleobiology
Analytical
Chemistry
Medicine
Clinical
Chemistry
Medicinal
Chemistry
Pharmacy
Toxicology
Environmental
Sciences
Ecology
Meteorology
Oceanography
Agriculture
Agronomy
Animal Science
Crop Science
Food Science
Horticulture
Soil Science
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Social Sciences
Archeology
Anthropology
Forensics
Materials
Science
Metallurgy
Polymers
Solid State
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Accuracy and precision
• Accuracy
pertains
to
agreement
of
an
experimental results with true value
• Precision
is the measure of reproducibility of
data within a series of results.
Accuracy and Precision
Types of Analytical Chemistry
• _________________
– is a method of analytical chemistry which
seeks to find elemental composition of
inorganic compounds and the functional
group of organic compounds.
• ________________
– in analytical chemistry, the measurements of
quantities of substances produced in
reactions rather than simply noting the nature
of the reactions
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1. Qualitative Chemistry
• What is in the sample?
Identification
Composition determination
Ascertainment of impurities
2. Quantitative chemistry
• How much is in the sample?
determination of the proportion of
components in a substance
Classification of Analysis
I. Based on ______________
II. Based on _________________
III. Based on ___________________
IV. Based on ________________
I. Based on sample size
•
•
•
•
Ultramicroanalysis
Microanalysis
Semi-microanalysis
Macroanalysis
________
___________
____________
___________
II. Based on the extent of
determination
• __________________
total amount of a class or a group of
active plant principles in a given sample.
• __________________
Amount of a specific constituent or a
single chemical species present in the
sample
III. Based on the nature of methods
A. Classical method
B. Instrumental method
C. Miscellaneous or special method
III. Based on the nature of methods
A. Classical method
– also known as _________________
method
– example : titrimetric analysis
gravimetric analysis
III. Based on the nature of methods
B. Instrumental method
– more accurate
– based on _______________________
– Examples: spectrometry
polarimetry
chromatography
III. Based on the nature of methods
C. Miscellaneous or special method
– Involves the __________________
– Examples: Acid value
Ash content
Water content
IV. Based on materials used
• Chemical = ________________
• Physical = _________________
• Biological = _________________
Types of Quantitative Analysis
A. _________________
B. _________________
C. _________________
D. _________________
Types of Quantitative Analysis
A. Volumetric Analysis
analysis involving the measurement of
volume of a solution of known
concentration required to react with
the desired constituent.
Types of Quantitative Analysis
Divisions of volumetric analysis:
I. Neutralization
II. Precipitation
III. Compleximetry
IV. Oxidation-reduction
permanganate
ceric sulfate
iodometry
iodimetry
bromine
potassium iodate
diazotization assay with nitrite
Types of Quantitative Analysis
B. Gravimetric Analysis
Analysis involving the accurate
measurement of weight of substance
being determined which may be isolated
in pure form or converted to another
substance of known composition by
making it react quantitatively with another
substance usually a precipitant.
Types of Quantitative Analysis
C. Special Methods
analysis which require a distinct type of
technique such as analysis of crude
drugs, assay of fats and fixed oils, assay of
volatile oils and assay of alkaloids.
Types of Quantitative Analysis
D. Physico-Chemical Methods
Analysis based on some specific physical
or chemical property or properties of the
substance being analyzed with the use of
instruments such as: spectrophotometer,
chromatograph units, polarographer,
polarimeter, flourometer.
Specialized Analytical Methods and
Equipment
• ___________ -determination of alcohol,
protein components, volatile component,
alkaloids
• ___________ – physical characterization
• ___________ – rotatory power
• ___________ – purity of substance
• ___________ – moisture content
Specialized Analytical Methods and
Equipment
• _____________ – moisture content
• _____________ – moisture content
• _____________ – identity and quantity of
component
• _____________ – identity and purity
• _____________ – quality and quantity of
components
• _____________ – determination of amounts
required to produce the desired, definite
effect
Qualitative Inorganic Analysis
• Detecting Cations
– According to their properties, cations are
usually classified into five groups.
– Each group has a common reagent which can
be used to separate them from the solution.
The separation must be done in the sequence
specified, otherwise, some ions of 1st group
can also react with 2nd group reagent, so that
the solution must not have any ions left from
previous groups to obtain meaningful results.
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1st analytical group of
cations
• 1st analytical group of cations consists of
ions that form ______________.
• As such, the group reagent to separate
them is _____________, usually used at a
concentration of _____. Concentrated HCl
must not be used, because it forms a
soluble complex ion ([PbCl4]2-) with Pb2+.
Consequently the Pb2+ ion would go
undetected.
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1st analytical group of
cations
• The most important cations in 1st group
are ___, _____, and _____. The chlorides
of these elements cannot be distinguished
from each other by their colour - they are
all white solid compounds.
• PbCl2 is soluble in hot water, and can
therefore be differentiated easily.
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1st analytical group of
cations
• Ammonia is used as a reagent to
distinguish between the other two. While
AgCl dissolves in ammonia (due to the
formation of the complex ion [Ag(NH3)2]+),
Hg2Cl2 gives a black precipitate consisting
of a mixture of chloro-mercuric amide and
elemental mercury. Furthermore, AgCl is
reduced to silver under light, which gives
samples a violet colour.
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1st analytical group of
cations
• PbCl2 is far more soluble than the chlorides of the other
two ions, especially in hot water.
• Therefore, HCl in concentrations which completely
precipitate Hg22+ and Ag+, may not be sufficient to do the
same to Pb2+.
• Higher concentrations of Cl- cannot be used for the
aforementioned reasons.
• Thus, a filtrate obtained after first group analysis of Pb2+
contains an appreciable concentration of this cation,
enough to give the test of the second group, viz.
formation of an insoluble sulfide.
• For this reason, Pb2+ is usually also included in the 2nd
analytical group.
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2nd analytical group of
cations
• The 2nd analytical group of cations
consists of ions that forms ____________.
• Cations in the 2nd group include: ____,
____, ____, ____, ____, _____, ____,
____, ____ and ____.
• Pb2+ is usually also included here in
addition to the first group.
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2nd analytical group of
cations
• The reagent can be any substance that gives S2ions in such solutions; most commonly used are
____________, CH3CSNH2
(_________/ATK)(at 0.3-0.6 M).
• The test with the sulfide ion must be conducted
in the presence of dilute HCl.
• Its purpose is to keep the sulfide ion
concentration at a required minimum, so as to
allow the precipitation of 2nd group cations
alone.
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2nd analytical group of
cations
• If dilute acid is not used, the early
precipitation of 4th group cations (if
present in solution) may occur, thus
leading to misleading results.
• Acids beside HCl are rarely used. Sulfuric
acid may lead to the precipitation of the
4th group cations, while nitric acid directly
reacts with the sulfide ion (reagent),
forming colloidal sulfur.
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2nd analytical group of
cations
• The precipitates of these cations are
almost indistinguishable, except for CdS
which is yellow.
• All the precipitates, except for HgS, are
soluble in dilute mineral acids. HgS is
soluble only in aqua regia, which can be
used to separate it from the rest.
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2nd analytical group of
cations
• The action of ammonia is also useful in
differentiating the cations.
• CuS dissolves in ammonia forming an
intense blue solution, while CdS dissolves
forming a colourless solution.
• The sulfides of As3+, As5+, Sb3+, Sb5+,
Sn2+, Sn4+ are soluble in yellow
ammonium sulfide, where they form
polysulfide complexes.
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3rd analytical group of
cations
• 3rd analytical group of cations includes
ions that form ___________________.
• The reagents are similar to these of the
2nd group, but separation is conducted at
pH of ______. Occasionally, a buffer
solution is used to ensure this pH.
• Cations in the 3rd group are, among
others: ____, ____, ____, ____, ____,
____, ____, and ____.
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4th analytical group of
cations
• Ions in 4th analytical group of cations form
_________________.
• The reagent usually used is (NH4)2CO3 (at
around 0.2 M), the pH should be neutral or
slightly basic.
• Caution should be taken to properly
separate all lower analytical groups
beforehand, as many of cations in previous
groups also form insoluble carbonates.
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4th analytical group of
cations
• Most important ions in the 4th group:
____, ____, and ____. After separation,
the easiest way to distinguish these ions is
by testing flame colour: barium gives a
yellow-green flame, calcium orange-red
and strontium deep red.
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5th analytical group of
cations
• Cations which are left after carefully
separating previous groups are considered
to be in the fifth analytical group.
• The most important ones are ____, ____,
____, ___ and ____.
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Qualitative Inorganic Analysis
• Detecting Anions
– Halides are precipitated by silver nitrate; they
can be further identified by color.
– Sulfates can be precipitated by barium
chloride.
– Nitrates can be reduced to ammonia.
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1st analytical group of anions
• The 1st group of anions consist of CO32-,
HCO3-, CH3COO-, S2-, SO32-, S2O32- and
NO2-.
• The group reagent for Group 1 anion is
______ or _______.
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Modern techniques
• Qualitative inorganic analysis is now used
only as a pedagogical tool.
• Modern techniques such as atomic
absorption spectroscopy and ICP-MS
(Inductively coupled plasma mass
spectrometry) are able to quickly detect
the presence and concentrations of
elements using a very small amount of
sample.
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