Experimental Procedure:
S. No.
1.
Test
Observation
Inference
blue color formed
Amino acid present
Ninhydrin test: To 1ml solution
of unknown material add 5
drops
of
0.2%
ninhydrin
solution in acetone. Boil over a
water bath for 2 min. Allow to
cool
2.
Xanthoproteic test: To 2ml of
solution in a boiling test tube,
add an equal volume of conc.
Amino acid present
HNO3. Heat over a flame for 2
min and observe the color. Now
Yellow color formed
COOL THOROUGHLY under
(tyrosine,
tryptophan and
glutamic acid)
the tap and CAUTIOSLY run in
sufficient 40% NaOH to make
the solution strongly alkaline.
3.
Hopkins-Cole Test: To a few ml
of glacial acetic acid containing
glyoxylic acid, add 1-2 drops of
the amino acid solution. Pour 1-
purple color at the
2ml concentrated H2SO4 down
interface
the side of the sloping test tube
Amino acid present
(tyrosine, glycine and
tryptophan)
to form a layer underneath the
acetic acid.
4.
Millon’s test: To 2ml of amino
acid solution in a test tube, add
1-2 drops of Millon’s reagent.
A brick red color is a
positive reaction.
Amino acid present
(tyrosine,
phenylalanine,
glycine)
Warm the tube in a boiling bath
5.
Pauly’s test: Into clean test tube,
dispense 1mL of 1% sulphanilic
acid and 2 drops of 5% sodium
Yellow product
nitrite. Mix for 1 min. Add
formed
Amino acid present
about 0.5mL of amino acid
solution.
6.
Ehrlich test: To 0.5ml of the
A colored complex
Amino acid present
amino acid solution, add 2ml
formed
(glycine and
tryptophan)
Ehrlich reagent
7.
Nitroprusside test: Add 2ml of
the amino acid solution into test
tubes. Add 0.5ml fresh sodium
nitroprusside
solution
Red color formed
and
Amino acid present
(cystine, cysteine and
methionine)
shake thoroughly. Add 0.5ml
ammonium hydroxide
8.
Lead acetate test: Everything
needed to carry out this test will
be in the hood and should not
remove anything from the hood.
A toxic, stinky gas will be made
(in small, but immensely smelly
quantities) and you don’t want
brownish-black
to smell it. Dispense about
precipitate
0.5mL
of
the
amino
acid
solution only into a clean test
tube (found in the hood, where
you will leave it when you are
done). Add 0.5mL of 20% NaOH
and insert the test tube in a
Amino acid present
boiling water bath for 1 min.
Add 2 drops of lead (II) acetate
solution.
9.
Sakaguchi test: 1ml NaOH and
3ml of the arginine solution is
mixed
and
naphthol
2
is
drops
added.
of
αMix
Red color formed
Amino acid present
(Arginine)
thoroughly and add 4-5 drops
Bromine solution
Results: The amino acids were found to be present in given sample on
the basis of above chemical tests.