c
Ninhdrin is often used to detect \(\alpha \) - amino acids and also free amino and carboxylic acid group on proteins and peptides. when about \(0.5\,ml\) of a \(0.1\%\) solution of ninhydin is boiled for one or two minutes with a few \(\,ml\) of dilute amino acid or protein solution, a blue colors decelops, ninhydrin degrades amino acids into aldehydes, ammonia, and \(CO_2\) through a series of reactions; the net result is ninhydrin in a partially reduced form hydrindantin;

Ninhydrin then condenses with ammonia and hydrin dantin to produce an intensely blue or puple pigment, sometimes called Ruhemann's purple: