Sequential-injection spectrophotometric determination of amino acids using 2,4,6-trinitrobenzenesulphonic acid Original Research Article

A sequential-injection system for the determination of nutritionally available amino acids has been developed. The method is based on the reaction of the free ε-amino acid group with 2,4,6-trinitrobenzenesulphonic acid (TNBS) to form a yellow-coloured product which is measured spectrophotometrically at 350 nm. The proposed fully computerised system is able to analyze 15 amino acid samples per hour with a relative standard deviation of <2.3%. The calibration graph is linear between 0 and 1×10−2 mol l−1.