Fluorometric Determination of Tryptophan in Human Serum Using Phenyiglyoxal

Abstract

A simple fluorometric method is described for the determination of the total (free+albumin-bound) and free tryptophan in human serum. After eproteinization of the serum (perchloric acid precipitation for total tryptophan; ultrafiltration for free tryptophan), the samples are treated with phenylglyoxal in dilute perchloric acid to develop fluorescence. The method is sensitive and fairly selective for tryptophan in serum; the limit of detection is 0.84nmol ml^-1 in serum, thus giving a fluorescence intensity that is twice that of the blank.