SIMPLIFIED PROCEDURE FOR THE DETERMINATION OF TRYPTOPHAN OF FOODS AND FEEDSTUFFS FROM BARYTIC HYDROLYSIS

A procedure simplifying the treatment of barytic hydrolysate prior to chromatographic analysis of tryptophan was tested on eight samples of foods and feedstuffs. It involves the addition of 5-methyl-tryptophan as internal standard to the mixture subjected to hydrolysis, the dilution of a very small volume (3-mu-L) of liquid phase of cold (0-degrees-C) hydrolysate with 1 mL of pH 4.5 buffer, and the chromatography of aliquots after dilution. Tryptophan was evaluated from 5-methyltryptophan. The simplified procedure compared with the conventional one, using the remainder of hydrolysate and requiring acidification, quantitative transfer, and clarification, gave identical results irrespective of samples. It is convenient and precise and leads to routine determination of tryptophan of a large number of samples.