The given blank can be filled with ninhydrin.
It refers to a synthetic crystalline component, which produces deeply colored products with primary amines and is utilized in analytical tests for amino acids. It is a chemical that is generally utilized to determine primary or secondary amines.
In the ninhydrin test, the amines react with ninhydrin to produce a colored component. It can be used quantitatively (for peptide sequencing) or qualitatively (for chromatographic visualization). The alpha-amino acids usually give a blue-purple product.