Liquid chromatographic determination of available lysine in soybean and fish meal

A method for the determination of available lysine on the basis of the reactivity of the epsilon-amino group with fluorodinitrobenzene (FDNB) has been optimized. Hydrolysis is performed in closed vessels in an autoclave. Conditions for different meals were established by using a modified sequential simplex method. Hydrolysis for 4 h was sufficient for the meals studied--soybean and fish. The use of liquid chromatography to determine available lysine was studied, and optimum conditions were established for separation and quantitation of epsilon-DNB-lysine. The proposed method is faster, more accurate, and more precise than commonly used methods.