A gas chromatographic-mass spectrometric assay for nine hydroxyphenolic acids in uremic serum.

A mass fragmentographic method for the determination of m-hydroxybenzoic acid, p-hydroxybenzoic acid, o-hydroxyphenylacetic acid, m-hydroxyphenylacetic acid, p-hydroxyphenylacetic acid, vanillic acid, p-hydroxymandelic acid, homovanillic acid and vanilmandelic acid in uremic serum is described. The hydroxyphenolic acids were extracted from one ml of serum ultrafiltrate. After trimethylsilylation, the extract was analyzed by a gas chromatograph-mass spectrometer. Concentrations of nine hydroxyphenolic acids are higher in uremic serum. In particular, p-hydroxybenzoic acid and p-hydroxyphenylacetic acid are markedly increased in uremic serum. The influence of hemodialysis on the hydroxyphenolic acids was studied by quantitating the acids before and after hemodialysis.