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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5708_Библиотеки_им_академика_М_И_Перельмана.pdf
Chapter
5
Chapter
Qualitative Analysis of
Inorganic and Organic
Drugs
To have therapeutic effectiveness, a drug must be pure. Identification tests are
performed to determine the quality of a drug for its safe use. These tests for
inorganic and organic drugs are based, generally, on physical evaluation and
chemical reactions of an anion or a cation present in a molecule.
Identification tests of some inorganic and organic drugs feasible in the
laboratory are presented in this chapter.
Experiment 1 To perform identification tests with a given sample of
ammonium chloride
NH
4
Cl
Molecular weight: 53.49
Pharmaceutical use: Expectorant, diuretic and systemic acidifier
Procedure
Physical test
1. Odourless
2. Colourless crystals or white crystalline powder
3. Saline taste
4. Freely soluble in water
5. Sparingly soluble in ethanol
148
Practical Pharmaceutical Analytical Chemistry
Chemical test
S. no. Experiment Observation Inference
1. Heat a small quantity of ammonium
chloride with sodium hydroxide
solution.
Place moist red litmus paper over the
mouth of test tube.
Evolution of gas having
characteristic odour of
ammonia.
Turns red litmus blue.
Indicates the
presence of
ammonium ion.
2. Add 1 mL 10% w/v sodium cobalti-
nitrite to ammonium chloride solution
Yellow precipitate is
formed.
Indicates the
presence of
ammonium ion.
3. Acidify ammonium chloride solution
with nitric acid, further add silver nitrate
solution.
Add ammonia solution.
A curdy white precipitate is
formed.
Precipitate dissolves.
Indicates the
presence of chloride
ion.
Reaction involved
S. No. 1
NH Cl NaOH NH
Ammonium
chloride
Sum
hydroxide
Ammonia
43
+⎯→⎯⎯⎯ ↑ +
odi
NNaCl H O
Sodium
chloride
Water
+
2
S. No. 2
3
432
6
NH Cl Na Co NO
Ammonium
chloride
Sodium
cobaltinitri
+
()
⎡
⎣
⎢
⎤
⎦
⎥
tte
Ammonium
cobaltinitrite
pr
NH Co NO⎯→⎯⎯⎯
()()
⎡
⎣
⎢
⎤
⎦
⎥
4
3
2
6
yellow eecipitate
Sodium
chloride
NaCl
()
+ 3
S. No. 3
NH Cl AgNO AgCl
Ammonia
chloride
Silver
nitrate
Silver
chl
43
+⎯→⎯⎯⎯ ↓
ooride
Ammonium
nitrate
Silver
chloride
Ammonia
NH NO
AgCl NH
+
+
43
3
2 ⎯⎯→⎯⎯⎯
()
⎡
⎣
⎢
⎤
⎦
⎥
+
Ag NH Cl
A complex
3
2
-
Result The given sample was identified as ammonium chloride.
149
Qualitative Analysis of Inorganic and Organic Drugs
Experiment 2 To perform identification tests with a given sample of
ascorbic acid
O
O
HOH
2
C
OH
OH
HO
Molecular weight: 176
Pharmaceutical use: Vitamin (antiscorbutic)
Procedure
Physical test
1. Colourless crystal or white to very pale yellow crystalline powder
2. Odourless
3. Darkens on exposure to air
4. Freely soluble in water; sparingly soluble in ethanol; insoluble in
chloroform, ether, and benzene
5. Acidic taste
S. no. Experiment Observation Inference
1. Put a drop of ascorbic acid solution over a
blue litmus paper.
Turns red.
2. Add 2 mL 2% w/v solution of ascorbic acid
to 2,6-dichlorophenolindophenol.
The blue coloured solution
gets decolourized.
3. To 1 mL; 2% w/v solution of ascorbic
acid add 5 mL water, 1 drop 5% w/v
sodium nitroprusside, and 2 mL dilute
sodium hydroxide solution. Add 0.6 mL of
hydrochloric acid drop wise and stir.
Yellow colour turns blue.
4. To 2 mL; 2% w/v solution of ascorbic acid
add 2 mL water, 0.1 g sodium bicarbonate,
and 20 mg of ferrous sulphate.
Further, add 5 mL; 1 M sulphuric acid.
Deep violet colour is produced.
The colour disappears.
Confirms the
presence of
ascorbic acid.
Chemical test
150
Practical Pharmaceutical Analytical Chemistry
Reaction involved
S. No. 2
[O]
Ascorbic acid
Reduced poduct
(Colourless)
2,6-Dichlorophenol-indophenol
(Blue colour)
Reduction
2e
−
2H
+
O
O
HOH
2
C
OH
OH
HO
Dehydroascorbic acid
O
O
HOH
2
C
OH
OH
HO
N
O
Cl
Cl
O
−
Na
+
2e
−
2H
+
Cl
Cl
O
N
O
−
Na
+
Result The given sample was identified as ascorbic acid.
Experiment 3 To perform identification tests with a given sample of aspirin
CC
3
C
Molecular weight: 180
Pharmaceutical use: Analgesic; antipyretic
Procedure
Physical test
1. Colourless crystals or white crystalline powder
2. Odourless or almost odourless
3. Slightly acidic in taste
4. Freely soluble in alcohol, soluble in chloroform and ether, slightly
soluble in water
Chemical test: Boil about 0.5 g of aspirin with 10 mL of sodium hydroxide
solution for 3 min, cool and add 10 mL of dilute sulphuric acid. A white, crystal-
line precipitate is produced and the odour of acetic acid is perceptible. Filter the
precipitate.
151
Qualitative Analysis of Inorganic and Organic Drugs
Reaction involved
CH
3
COONa
Sodium acetate
(Filtrate)
NaOH
OCOCH
3
COOH
Aspirin (Acetyl salicylic acid)
OH
COOH
Salicylic acid
(Precipitate)
CH COONa C H OH C
Sodium acetate
Filtrate
Ethanol
HSO
325
24
()
+⎯→⎯⎯⎯⎯ HH COOC H
Ethyl acetate
Fruity odour
325
()
Result The given sample was identified as aspirin.
Experiment 4 To perform identification tests with a given sample of barium
sulphate
BaSO
4
Molecular weight: 233.39
Pharmaceutical use: Diagnostic aid (radiopaque medium for gastrointestinal
tract)
Procedure
Physical test
1. Fine, heavy, white powder
2. Free from gritty particles
3. Odourless
4. Practically insoluble in water, organic solvents and dilute solution of
acids and alkalis
5. Tasteless
S. no. Experiment Observation Inference
1. Precipitate: Dissolve the precipitate in
about 2 mL of water and add ferric
chloride test solution.
A deep violet colour is
produced.
2. Filtrate: To the filtrate add 3 mL of
ethanol and 3 mL of sulphuric acid and
warm it.
A fruity odour is
perceptible.
Indicates the
formation of an
ester.
Chemical test
152
Practical Pharmaceutical Analytical Chemistry
Chemical test
Boil barium sulphate (0.2 gm) with 50% solution of sodium
carbonate (5 mL) for 5 min. The salt is insoluble. It is converted into less soluble
salt by fusion with anhydrous sodium or potassium carbonate. Treat the resulting
mass with hot water and filter. Perform the test for sulphate in filtrate and for
barium in the residue.
Reaction involved
BaSO Na CO BaCO
Barium
sulphate
Sodium
carbonate
Barium
c
423 3
+⎯→⎯⎯⎯
aarbonate
Residue
Sodium
sulphate
Filtrate
Na SO
() ()
+
24
S. No. 1
BaCO HCl BaC
Barium carbonate
residue
Hydrochloric acid
3
2
()
+⎯→⎯⎯⎯ ll H C O
Barium chloride
Hydrogen
Carbonic acid
223
+
BaCl H SO BaSO
Barium chloride
Sulphuric acid
Barium chl
224 4
+⎯→⎯⎯⎯ ↓
ooride
White precipitate
Hydrochloric
acid
HCl
()
+ 2
S. no. Experiment Observation Inference
1. Residue: Dissolve a portion of residue
in hydrochloric acid and perform flame
test.
Wash the above residue with successive
small quantities of water. To the residue
add dilute hydrochloric acid (5 mL),
filter and to the filtrate, add dilute
sulphuric acid (0.3 mL).
Further add dilute sodium hydroxide
solution.
Yellowish green colour is
produced.
A white precipitate is
formed.
Precipitate is insoluble
in it.
Indicates the formation
of barium sulphate.
2. Filtrate: Add barium chloride solution.
Add lead acetate solution (1 mL) to the
filtrate (1 mL).
To the mixture further add ammonium
acetate solution and sodium hydroxide
solution.
A white precipitate is
formed.
A white precipitate is
formed.
The precipitate formed is
insoluble.
Indicates the formation
of barium sulphate.
Indicates the formation
of lead sulphate.
Due to the
formation of sodium
hydroxyplumbate (II).
Chemical test
153
Qualitative Analysis of Inorganic and Organic Drugs
S. No. 2
Na SO BaCl BaS
Sodium sulphate
Filtrate
Barium chloride
24 2
()
+⎯→⎯⎯⎯ OONaCl
Na
Barium sulphate
White precipitate
Sodium chloride
4
2↓+
()
224 3
2
SO CH COO Pb P
Sodium sulphate
Filtrate
Lead acetate
()
+
()
⎯→⎯⎯⎯ bbSO CH COONa
Lead sulphate
White precipitate
Sodium acetat
43
2↓+
()
ee
Result The given sample was identified as barium sulphate.
Experiment 5 To perform identification tests with a given sample of
boric acid
H
3
BO
3
Molecular weight: 61.83
Pharmaceutical use: Local anti-infective
Procedure
Physical test
1. White, colourless powder or colourless shiny plates unctuous to the
touch or white crystals
2. Odourless
3. Taste slightly acidic and bitter that give sweetish taste after sometime
4. Soluble in water and in ethanol; freely soluble in boiling water,
boiling ethanol, and in glycerine
S. no. Experiment Observation Inference
1. Dissolve 0.1 g of boric acid by gently
warming with 5 mL of ethanol or
methanol to which a few drops of
sulphuric acid have been added.
Ignite the solution.
The flame has a green
border.
Indicates the formation of
ethyl or methyl borate.
2. Dissolve 3 g of boric acid in 90 mL
of boiling distilled water, cool, and
check the acidity of solution with
blue litmus paper.
The litmus paper turns
red.
Indicates the presence of
boric acid (a weak acid).
Chemical test
154
Practical Pharmaceutical Analytical Chemistry
Reaction involved
HBO CHOH B OCH
Boric acid Methyl alcohol
Methyl borat
33 3 3
3
3+⎯→⎯⎯⎯
()
ee
Water
HO+ 3
2
Result The given sample was identified as boric acid.
Experiment 6 To perform identification tests with a given sample of calcium
gluconate
C
C
C
2
Ca
_
2
C
C
C
Molecular weight: 448.40
Pharmaceutical use: Calcium replenisher
Procedure
Physical test
1. White, crystalline powder or granules
2. Odourless
3. Almost tasteless
4. Sparingly soluble in water but freely soluble in boiling water;
insoluble in ethanol
Chemical test: Calcium gluconate gives reactions for calcium ions and for
D-gluconic acid.
Prepare 3% w/v solution of calcium gluconate.
155
Qualitative Analysis of Inorganic and Organic Drugs
Chemical test
S. no. Experiment Observation Inference
1. Calcium ion
Add 0.5 mL of potassium ferrocyanide
and 50 mg of ammonium chloride to
5 mL of calcium gluconate solution in
acetic acid.
Add ammonium oxalate solution to
the solution of sample in hydrochloric
acid.
Further add ammonium chloride.
Add 5 mL of ammonium carbonate
solution to a neutral solution of
calcium gluconate.
A white crystalline
precipitate is formed.
A white precipitate is
formed.
The precipitate gets
solubilized
A white precipitate is
formed.
Indicates the formation
of ammonium calcium
ferrocyanide, a mixed
salt.
Formation of calcium
oxalate.
Formation of calcium
carbonate.
2.
D-gluconic acid
To 1 mL of solution add 1 drop of
ferric chloride test solution.
To 1 mL of solution, add 1 mL
glacial acetic acid and 1.5 mL phenyl
hydrazine and heat the mixture on
water bath for 30 min.
Yellow colour is produced.
White crystal is obtained.
Indicates the formation
of gluconic acid phenyl
hydrazide.
Reaction involved
S. No. 1
With potassium ferrocyanide
Ca Fe CN K
Calcium ion
Ferrocyanide
Potassium ion
2
6
4
2
++
+
()
⎡
⎣
⎢
⎤
⎦
⎥
+
-
CCH COOH
Acetic acid
White crystall
CaK Fe CN
3
2
6
4
⎯→⎯⎯⎯⎯⎯⎯
()
⎡
⎣
⎢
⎤
⎦
⎥
-
iine precipitate
With ammonium oxalate
NH C O NH C O
Ammonium oxalate
Ammonium ion
4
2
24 4 24
2
()
+
+
22
24
22
24
-
Oxalate ion
Oxalate ion
Calcium ion
Cal
C O Ca CaC O
++
+⎯→⎯⎯⎯
ccium oxalate
White precipitate
()
156
Practical Pharmaceutical Analytical Chemistry
Calcium
oxalate
Hyd
CaC O HCl+
24
2
rrochloric
acid
Calcium
chloride
Oxalic acid
CaCl COOH⎯→⎯⎯⎯ +
()
2
2
With ammonium carbonate
Calcium
gluconate
HCl CaCl
Hydrochloric acid
Calcium chlor
+⎯→⎯⎯⎯
2
iide
Calcium
chloride
Ammonium car
Gluconic
acid
CaCl NH CO
+
+
()
24
2
3
bbonate
Ammoinum chloride Calcium
carbonate
NH Cl CaCO⎯→⎯⎯⎯ +2
43
S. no. 2
++
H
2
O
Gluconic acid
Gluconic acid phenyl hydrazide
Phenyl hydrazine
Water
OHH
HHO
OHH
OHH
CH
2
OH
COOH
OHH
HHO
OHH
OHH
CH
2
OH
OC
NHNH
2
NHNH
Result The given sample was identified as calcium gluconate.
Experiment 7 To perform identification tests with a given sample of ferrous
sulphate
FeSO
4
·7H
2
O
Molecular weight: 278.01
Pharmaceutical use: Haematinic agent
Procedure
Physical test
1. Bluish-green crystals or light green crystalline powder
2. Odourless
3. Efflorescent in air