Simultaneous quantitation of 4-hydroxy-3-methoxymandelic (vanilmandelic) and 4-hydroxy-3-methoxyphenylacetic (homovanillic) acids in human urine.

We describe a simultaneous analysis for vanilmandelic and homovanillic acids in urine. An aliquot of a final extract, containing phenylpropriopionic acid as external standard, is dried, an internal standard (resorcinol) is added, and the mixture is silylated and chromatographed. The two compounds are identified from their characteristic retention times and from their elution behhavior in relation to four different marker compounds (the external and internal standards and two other naturally occurring compounds, p-hydroxyphenylacetic and hippuric acids) and are quantitated from their relative response factors. Within-run precision (CV) varied from 2 to 14% for vanilmandelic acid and 1 to 18% for homovanillic acid. The ratio of the amount of phenylpropionic acid extracted to the amount of added resorcinol found is a useful quality-control index. Values for vanilmandelic acid obtained by this method and by the technique of Pisano et al. [Clin. Chim. Acta 7, 285 (1962)] correlated well (r = 0.844).