Observation of “Ruhemann’s purple” is a confirmatory test for the presence of

Ninhydrin is often used to detect ∝ − amino acids and also free amino and carboxylic acid groups on proteins and peptides. When about 0.5 mL of a 0.1% solution of  nuhydrin is boiled for one or tow minutes with a few mL of dilute amino acid or protein solution, a blue color develops. Ninhydrin degrades amino acids into aldehyde, ammonia, and CO₂ through a series of reactions.

to produce an intensely blue or purple pigment, sometimes called Ruhemann’s purple