Ninhydrin is most commonly used to detect fingerprints, as the terminal amines of lysine residues in peptides and proteins sloughed off in fingerprints react with ninhydrin. It is a white solid which is soluble in ethanol and acetone at room temperature.

What is ninhydrin used on?

Ninhydrin is the most widely used chemical reagent for the detection of latent fingermarks on porous surfaces such as paper and cardboard. The compound reacts with the amino acid (eccrine) component of the fingerprint deposit to give a dark purple product known as Ruhemann's purple (Figure 4).

Why is ninhydrin test performed?

Ninhydrin test is used to detect the presence of amino acids in unknown samples. This test is also used in solid-phase peptide synthesis to monitor the protection for amino acid analysis of proteins. As the ninhydrin test is quite sensitive, it is commonly used to detect fingerprints.