VPB 112: General Veterinary Biochemistry (1+1)

NINHYDRIN TEST

This test is for the identification of α – amino acids, proteins and peptides.

Principle

• Ninhydrin, an oxidsing agent causes oxidative decarboxylation of α-amino acids.
• It removes CO₂ and NH₃ and the product is one carbon lesser than the parent amino acid.
• The reduced ninhydrin (hydrindantin) reacts with released NH₃ and one more molecule of
• Ninhydrin to produce a blue colored complex known as “Ruhemann’s purple”.

Procedure

• To 1 mL of test solution add 2-5 drops of Ninhydrin solution, mix well and heat it.
• Observe the development of pink or purple or violet blue color.
• Imino acids (proline and hydoxy proline) give a yellow colored complex.
• This test also answers for proteins / peptides as they contain α-amino acids.