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

摘要

A gas chromatographic-mass spectrometric method was developed for the quantitative analysis of the three Di(2-ethylhexyl)phthalate (DE HP) 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 1000 #mu#g/i 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 DE HP metabolite 2-ethylhexanoic acid. In 28 urine samples from healthy persons we found all three acids with mean concentrations of 56.1+-13.5 #mu#g/I for 2-ethylhexanoic acid, 104.8 +- 80.6 #mu#g/l for 2-ethyl-3-hydroxyhexanoic acid and 482.2~ 389.5 fJ.g/I for 2-ethyl-3-oxohexanoic acid.