title: Measurement by gas chromatography of urinary hippuric acid and methylhippuric acid as indices of toluene and xylene exposure.
abstract: A gas chromatographic method was applied to the determination of the urinary glycine conjugates, hippuric, o-, m- and p-methylhippuric acids. These were extracted with ethyl acetate from urine after acidification with hydrochloric acid. The internal standard solution (heptadecanoic acid methanol solution) was added before extraction and a diazomethane-ether-ethanol solution was subsequently added to the dried extracts. The methylated residues were dissolved in methanol and injected into a gas chromatograph as described by Buchet and Lauwerys (1973). By the combined use of gas chromatography and mass spectrometry the methyl esters of hippuric acid and m-methylhippuric acid were identified in the urine of a volunteer who had been exposed to toluene and m-xylene vapours. When the urine specimen contained salicyluric acid (a urinary metabolite of salicylic acid) two sharp peaks were observed. The faster peak coincided with m- or p-methylhippuric acid. The upper limit of urinary hippuric acid concentration in healthy subjects with no occupational exposure was calculated by this method to be 1.026 microgram/ml (fiducial limit 5%) after correction to 1.024 for variation in urinary density.
mesh_terms: D000328:Adult; D002849:Chromatography, Gas / Q000379:methods; D004781:Environmental Exposure; D005260:Female; D006626:Hippurates / Q000652:urine*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012459:Salicylates / Q000652:urine; D014050:Toluene / Q000378:metabolism*; D014992:Xylenes / Q000378:metabolism*
chemical_list: D006626:Hippurates; D012459:Salicylates; D014992:Xylenes; D014050:Toluene