Determination of tryptophan by high-performance liquid chromatography of alkaline hydrolysates with spectrophotometric detection

A procedure for quantitation of tryptophan in feedstuff is described. It consist of hydrolysis in sodium hydroxide at 100 °C for 4 h, neutralization of the resulting hydrolysate to pH 7, dilution with sodium borate buffer (pH 9), and analysis by reverse-phase high-performance liquid chromatography with spectrophotometric determination of tryptophan at 280 nm. The recovery of tryptophan from lysozyme, added to some feedstuff before hydrolysis, ranges from 98.6 to 100%. A reduction of the time of analysis has been achieved as compared to previous methods for analysis of tryptophan.