What is it? Ninhydrin is a chemical used to detect ammonia or primary and secondary amines. When reacting with these free amines, a deep blue or purple color known as Ruhemann's purple is produced Uses Ninhydrin can be used in analysis of solution that contain amino acids or ammonium ions. Most of the amino acids (except proline) are hydrolyzed and react with ninhydrin, producing a deep purple color known as Ruhemann's purple. In protein analysis thin layer chromatography (TLC) and ninhydrin are combined to separate and detect the protein's amino acids. A solution suspected of containing the ammonium ion, can be tested by dotting it onto a solid support (silica gel) and treated with ninhydrin, a purple color can confirm the existence of ammonium ions in the solution. A ninhydrin solution is commonly used by forensic investigators in the analysis of latent fingerprints, on porous surfaces such as paper. Properties It is a white solid which is soluble in e