Method for quantitative measurement of xanthurenic acid in urine.

A method is reported for determining urinary xanthenuric acid (XA), a meta. bolite of tryptophan. XA is extracted from urine with isobutanol (2.methyl. 1.propanol), transferred to ammonium hydroxide, and separated from other urinary metabolites on thin.Iayer cellulose plates with use of 0.2 acetate buffer, mol/liter, pH 5.4. The XA is measured spectrophotometrically after diazotization with 2-chloro-4.nitroaniline. The method, which is specific for XA, can be used to measure amounts as low as 0.4 aug/mI of urine. It has a range from 0 to 24 g/ml, and results within this range are reproducible within approximately ±5%. Data obtained by this procedure are compa. rable to results reported for other methods.