title: Simultaneous analysis of the di(2-ethylhexyl)phthalate metabolites 2-ethylhexanoic acid, 2-ethyl-3-hydroxyhexanoic acid and 2-ethyl-3-oxohexanoic acid in urine by gas chromatography-mass spectrometry.
abstract: A gas chromatographic-mass spectrometric method was developed for the quantitative analysis of the three Di(2-ethylhexyl)phthalate (DEHP) metabolites, 2-ethylhexanoic acid, 2-ethyl-3-hydroxyhexanoic acid and 2-ethyl-3-oxohexanoic acid in urine. After oximation with O-(2,3,4,5,6-pentafluorobenzyl)-hydroxylamine hydrochloride and sample clean-up with Chromosorb P filled glass tubes, all three organic acids were converted to their tert.-butyldimethylsilyl derivatives. Quantitation was done with trans-cinnamic acid as internal standard and GC-MS analysis in the selected ion monitoring mode (SIM). Calibration curves for all three acids in the range from 20 to 1,000 microg/l showed correlation coefficients from 0.9972 to 0.9986. The relative standard deviation (RSD) values determined in the observed concentration range were between 1.3 and 8.9% for all three acids. Here we report for the first time the identification of 2-ethyl-3-hydroxyhexanoic acid and 2-ethyl-3-oxohexanoic acid in human urine next to the known DEHP metabolite 2-ethylhexanoic acid. In 28 urine samples from healthy persons we found all three acids with mean concentrations of 56.1 +/- 13.5 microg/l for 2-ethylhexanoic acid, 104.8 +/- 80.6 microg/l for 2-ethyl-3-hydroxyhexanoic acid and 482.2 +/- 389.5 microg/l for 2-ethyl-3-oxohexanoic acid.
authors.affiliation: Medizinische Universitätsklinik Abt. IV, Zentrallabor, Tübingen, Germany. hgwahl@klinikum-fulda.de
authors.forename: H G
authors.initials: HG
authors.lastname: Wahl
authors.forename: Q
authors.initials: Q
authors.lastname: Hong
authors.forename: D
authors.initials: D
authors.lastname: Stübe
authors.forename: M E
authors.initials: ME
authors.lastname: Maier
authors.forename: H U
authors.initials: HU
authors.lastname: Häring
authors.forename: H M
authors.initials: HM
authors.lastname: Liebich
mesh_terms: D002208:Caproates / Q000652:urine*; D004051:Diethylhexyl Phthalate / Q000378:metabolism*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D006801:Humans
chemical_list: C439932:2-ethyl-3-hydroxyhexanoic acid; C439933:2-ethyl-3-oxohexanoic acid; D002208:Caproates; C040668:2-ethylhexanoic acid; D004051:Diethylhexyl Phthalate