Benzidine Test

The benzidine test or benzidine Gregersenne reaction is a method for determining methionine (an amino acid from a protein molecule), based on a qualitative (cuvette) or quantitative (measured flow rate) change in the color of a solution under the influence of amidine azo dye derivatives (simple benzidine). One of the methods used in the laboratory to determine the methionine content in food, milk, and blood. The method was first proposed by Langer and Gregersen in 1927.