Technical note: Rapid method for determination of amino acids in milk.

A rapid method for measurement of amino acids in milk was developed and validated. The method included a first step of milk protein hydrolysis, followed by the derivatization and separation of amino acids by HPLC. Six combinations of hydrolysis agent and temperature-time conditions were compared with a reference method; derivatization procedures as well as HPLC separation were improved. Hydrolysis of milk samples with 6 N HCl at 160 degrees C for 60 min resulted in no significantly differences compared with the reference method but allowed the analysis of a greater number of milk samples in a short time. In addition, this method was characterized by high precision, low repeatability uncertainty, and high accuracy for all amino acids evaluated; the recovery mean value of the single amino acids was 98.38%. The proposed method is, therefore, accurate, simple, rapid, and suitable for large numbers of milk samples.