Folin's reagent

Folin's reagent is 1,2-naphthoquinone-4-sulfonate and is a chemical reagent used to measure levels of amines and amino acids. The reagent produces a bright red color in alkaline solutions and is also fluorescent.

This should not be confused with Folin-Ciocalteu reagent, which is a mixture of sodium tungstate and sodium molybdate that is used to detect phenolic compounds.