title: Colorimetric determination of urinary xanthurenic acid using an oxidative coupling reaction with N,N-diethyl-p-phenylenediamine.
abstract: A simple enzymatic method for the spectrophotometric determination of xanthurenic acid (XA) in urine is described. The method is based on the formation of a pigment derived from an oxidative coupling reaction with XA and N,N-diethyl-p-phenylenediamine (DE-PPD) in the presence of hydrogen peroxide and horseradish peroxidase. The color of the reaction mixture was developed with a peak absorbance at 750 nm. The recoveries against XA added to urine ranged from 91.0 to 96.5%. With this method, XA can be determined within 5 min, without a time-consuming sample preparation. The detection range of this method was between 5 and 150 microM, with a coefficient of variation of 2.7% or less. The correlation between this and the fluorometric method was  good.
authors.affiliation: Faculty of Pharmaceutical Sciences, Nagoya City University, Japan.
authors.forename: E
authors.initials: E
authors.lastname: Ohtsuki
authors.forename: M
authors.initials: M
authors.lastname: Suzuki
authors.forename: M
authors.initials: M
authors.lastname: Takayanagi
authors.forename: T
authors.initials: T
authors.lastname: Yashiro
mesh_terms: D002138:Calibration; D003124:Colorimetry; D006735:Horseradish Peroxidase / Q000737:chemistry; D006861:Hydrogen Peroxide / Q000737:chemistry; D010084:Oxidation-Reduction; D010655:Phenylenediamines; D012680:Sensitivity and Specificity; D013056:Spectrophotometry, Ultraviolet; D014977:Xanthurenates / Q000652:urine*
chemical_list: D010655:Phenylenediamines; D014977:Xanthurenates; C028330:xanthurenic acid; C013935:N,N-diethyl 4-phenylenediamine; D006861:Hydrogen Peroxide; D006735:Horseradish Peroxidase