Identification and quantitative determination ofo- andm-hydroxymandelic acid in human urine

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Abstract
o-Hydroxymandelic acid and m-hydroxymandelic acid have been identified in human urine by gas chromatography mass spectrometry selected ion monitoring. After solvent extraction the urinary acids were converted to their O-trifluoroacetoxy methyl ester derivatives which were identified by comparison of the retention times and relative intensities of the characteristic m/z 374 and m/z 315 ions with those from authentic samples. 4,6-[2H2]-o-hydroxymandelic acid and 2,4,6-[2H3]-m-hydroxymandelic acid were synthesized for use as internal standards in the quantitative estimation of the isomeric hydroxymandelic acids excreted in urine. In ten normal adults the following results were obtained: o-hydroxymandelic acid 4–16 ng mg−1 creatinine and m-hydroxymandelic acid 11–71 ng mg−1 creatinine. Acid hydrolysis of the urine or ingestion of a diet of known composition did not affect these results, indicating that these compounds are excreted as the free acids and probably arise by metabolism of the corresponding phenylethanolamine(s).