Study Set Content:
then couples with the amino acids
diazonium salt
The diazonium salt then couples with the amino acids (either tyrosine or histidine) by giving a (blank) to the solution in the alkaline medium.
red color
he principle of Histidine test is based upon the principle of
Bromination” reaction
n Histidine test, bromination of amino acid occurs to give a
blue colored compound in the presence of bromine in acid solution
Histidine Test Positive result
Gives blue color
Used for the detection of Histidine amino acid
Histidine test
Used for the detection of specific amino acid like Tryptophan
Hopkin's Test
Used for the detection of amino acid-containing sulfhydryl group (-SH group). Example: cysteine
Lead Sulphide test
Hopkin's Test positive result
Forms violet colour ring
Lead Sulphide Test positive result:
Forms black precipitate
is specific for the detection of tryptophan.
Hopkins-Cole Test
The principle of Hopkin’s Cole test is based upon the
“Dehydration” reaction
Hopkin’s Cole test, the amino acid reacts with the reagent
glyoxylic acid
n Hopkin’s Cole test, the amino acid reacts with the reagent glyoxylic acid in the presence of
concentrated sulfuric acid
This reaction causes the dehydration of tryptophan which forms a
purple colored ring between the junctions of two solutions.
is useful for the detection of amino acids like cysteine which contains the Sulfhydryl group
Lead Sulfide Test
The principle of Lead sulfide test is based upon the
“Precipitation” reaction
In Lead sulfide test, the
cysteine
n Lead sulfide test, the cysteine reacts with
sodium hydroxide
n Lead sulfide test, the cysteine reacts with sodium hydroxide and after boiling, it gets converted into
sodium sulfide
