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摘要
alpha-Hexachlorocyclohexane (alpha-HCH) is the only chiral isomer of the eight 1,2,3,4,5,6-HCHs and we have developed an enantiomer-specific stable carbon isotope analysis (ESIA) method for the evaluation of its fate in the environment. The carbon isotope ratios of the alpha-HCH enantiomers were determined for a commercially available alpha-HCH sample using a gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS) system equipped with a chiral column. The GC-C-IRMS measurements revealed delta-values of -32.5 +/- 0.8 parts per thousand and -32.3 +/- 0.5 parts per thousand for (-) alpha-HCH and (+) alpha-HCH, respectively. The isotope ratio of bulk alpha-HCH was estimated to be -32.4 +/- 0.6 parts per thousand which was in accordance with the delta-values obtained by GC-C-IRMS (-32.7 +/- 0.2 parts per thousand) and elemental analyzer-isotope ratio mass spectrometry (EA-IRMS) of the bulk alpha-HCH (-32.1 +/- 0.1 parts per thousand). The similarity of the isotope ratio measurements of bulk alpha-HCH by EA-IRMS and GC-C-IRMS indicates the accuracy of the chiral GC-C-IRMS method. The linearity of the alpha-HCH ESIA method shows that carbon isotope ratios can be obtained for a signal size above 100mV. The ESIA measurements exhibited standard deviations (2 sigma) that were mostly < +/- 0.5 parts per thousand. In order to test the chiral GC-C-IRMS method, the isotope compositions of individual enantiomers in biodegradation experiments of alpha-HCH with Clostridium pasteurianum and samples from a contaminated field site were determined. The isotopic compositions of the alpha-HCH enantiomers show a range of enantiomeric and isotope patterns, suggesting that enantiomeric and isotope fractionation can serve as an indicator for biodegradation and source characterization of alpha-HCH in the environment.
- 出版日期2011-5-30
