Qualitative Tests For Amino Acids

Question 1

Ninhydrin reagent

Answer 1

Analyte: alpha amino acid
Color: violet complex (Ruhemann’s Purple); yellow coloration for Proline

Question 2

Schiff’s Reagent

Answer 2

Analyte: lysine
Color: pink-violet

Question 3

Sakaguchi

Answer 3

Analyte: arginine (guanidine group)
Color: red-orange

Question 4

Xanthoproteic

Answer 4

Analyte: aromaticity (W, Y, F)
Color: yellow-orange

Question 5

Millon-Nasse

Answer 5

Analyte: tyrosine (phenolic group)
Color: old rose; pink; red

Question 6

Hopkins-Cole

Answer 6

Analyte: tryptophan (indole group)
Color: violet complex

Question 7

Bromine water

Answer 7

Analyte: tryptophan
Color: pinkish lavender or violet alcohol layer

Question 8

Fohl’s test/ Lead acetate

Answer 8

Analyte: cysteine
Color: black

Question 9

Nitroprusside test

Answer 9

Analyte: cysteine
Color: red complex

Question 10

Biuret test

Answer 10

Analyte: peptide linkages
Color: blue violet

Question 11

Pauly-Diazo reaction

Answer 11

Analyte: tyrosine; histidine
Color: red/purple