Humans are continuously exposed to volatile organic compounds (VOCs) as these chemicals are ubiquitously present in most indoor and outdoor environments. In order to assess recent exposure to VOCs for population-based studies, VOCs are measured in the blood of participants. This work describes an improved method to detect 12 VOCs by head-space solid-phase microextraction gas chromatography coupled with isotope-dilution mass spectrometry in selected reaction monitoring mode (SPME-GC-MS/MS). This method was applied to the analysis of trihalomethanes, styrene, trichloroethylene, tetrachloroethylene and BTEX (benzene, toluene, ethylbenzene, m-xylene, p-xylene, o-xylene) in a population-based biomonitoring study (Canadian Health Measures Survey). The method showed good linearity (>0.990) in the range of 0.010-10μg/L and detection limits between 0.007 and 0.027μg/L, precision better than 25% and good accuracy (±25%) based on proficiency testing materials. Quality Control data among runs over a 7 month period showed %RSD between 14 and 25% at low levels (∼0.03μg/L) and between 9 and 23% at high levels (∼0.4μg/L). The method was modified to analyze samples from a pharmacokinetic study in which 5 healthy volunteers were exposed to single, binary and quaternary mixtures of CTEX (chloroform, ethylbenzene, toluene and m-xylene), thus the expected concentration in blood was 1 order of magnitude higher than those found in the general population. The method was modified by reducing the sample size (from 3g to 0.5g) and increasing the upper limit of the concentration range to 395μg/L. Good linearity was found in the range of 0.13-395μg/L for toluene and ethylbenzene and 0.20-609μg/L for m/p-xylene. Quality control data among runs over the period of the study (n=13) were found to vary between 7 and 25%.
Keywords: Biomonitoring; Blood; Exposure studies; General population; Solid-phase microextraction; Volatile organic compounds.
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