Simultaneous analysis of PAH urinary mono- and dihydroxylated metabolites by GC-MS-MS following SPE and two-stage derivatization

A new gas chromatography-tandem mass spectrometry method for the determination of mono- and dihydroxylated polycyclic aromatic hydrocarbon metabolites (OH-PAHs and diol-PAHs) in urine was developed and validated. Various sample preparation procedures were compared, namely liquid-liquid extraction (LLE), dispersive solid-phase extraction (dSPE), and SPE, alone or combined. A novel two-stage derivatization approach using 2 silylation reagents was developed, and an experimental procedure design was used to optimize the programmed temperature vaporization-solvent vent injection (PTV-SV) GC parameters. The method focused on 11 target compounds resulting from four- to five-ring suspected carcinogenic PAHs. SPE was identified as an acceptable and more convenient extraction method for all tested metabolites, with extraction rates ranging from 63 to 86% and relative standard deviations lower than 20%. The two-stage derivatization approach successfully allowed first the derivatization of OH-PAHs by MTBSTFA (N-tert-butyldimethylsilyl-N-methyltrifluoroacetamide) and then diol-PAHs by BSTFA (N,O-bis(trimethylsilyl)trifluoroacetamide) in a single run. The limits of quantification were in the range of 0.01-0.02 mu g l(-1) for OH-PAHs and 0.02-0.2 mu g l(-1) for diol-PAHs. The intra- and interday precisions were lower than 10%. The method was applied to determine PAH metabolites in urine collected at the beginning and at the end of the working week from 6 workers involved in aluminum production. The mean diol-PAH levels at the end of the week were 10 to 20 times higher (0.86-2.34 mu g g(-1) creatinine) than those of OH-PAHs (0.03-0.30 mu g g(-1)). These results confirmed the usefulness of this new analytical technique for detecting and characterizing metabolic patterns of PAHs in urine and assessing carcinogenic occupational exposures.

Automated summary

A new gas chromatography-tandem mass spectrometry method was developed and validated for determining metabolites of polycyclic aromatic hydrocarbons in urine. Utilizing a two-stage derivatization approach and SPE extraction, the method successfully detected 11 target compounds with low limits of quantification and high precision. Application to workers in aluminum production confirmed the effectiveness of the method in assessing carcinogenic occupational exposures.