A Note on Colorimetric Determination of _L-Tryptophan

Abstract

On the experiments in view of the coloring mechanism of _L-tryptophan determination using p-dimethyl aminobonzaladhyde we found that the color development was accelerated by sunlight and on the contrary inhibited by leducing function of iron, if it is contained in the hydrochloric acid or the sample used.
Making these precautions we believe that the STEER and SEVAG's colorimetric method for tryptophan determination is superior to the others in rapid and microanalytical measurement.
The standard curves for this procedure were made and it was possible to determue as little as 30 γ per ml tryptophan. The results obtained with various materials are given as examples: casein (Merck, ) 1.20%; serum albumin (Kahlbaum) 1.35%; egg albumin (Takeda) 1.20%.