Kaiser Test (Ninhydrin Test)

The Kaiser Test is a very sensitive test for primary amines. It is commonly utilized in solid phase peptide synthesis to determine if coupling reactions are complete. Ninhydrin reacts with the deprotected Nterminal amine group of the peptide-resin to produce an intense blue color. The Kaiser test is not reliable for detecting secondary amines. Thus, if the N-terminal amino acid is proline, pipecolic acid, or tetrahydroisoquinoline-3-carboxylic acid, another test such as the Isatin Test or the Chloranil Test is used.