title: Development of an enantiomer-specific stable carbon isotope analysis (ESIA) method for assessing the fate of α-hexachlorocyclo-hexane in the environment.
abstract: α-Hexachlorocyclohexane (α-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 α-HCH enantiomers were determined for a commercially available α-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 δ-values of -32.5 ± 0.8‰ and -32.3 ± 0.5‰ for (-) α-HCH and (+) α-HCH, respectively. The isotope ratio of bulk α-HCH was estimated to be -32.4 ± 0.6‰ which was in accordance with the δ-values obtained by GC-C-IRMS (-32.7 ± 0.2‰) and elemental analyzer-isotope ratio mass spectrometry (EA-IRMS) of the bulk α-HCH (-32.1 ± 0.1‰). The similarity of the isotope ratio measurements of bulk α-HCH by EA-IRMS and GC-C-IRMS indicates the accuracy of the chiral GC-C-IRMS method. The linearity of the α-HCH ESIA method shows that carbon isotope ratios can be obtained for a signal size above 100 mV. The ESIA measurements exhibited standard deviations (2σ) that were mostly < ± 0.5‰. In order to test the chiral GC-C-IRMS method, the isotope compositions of individual enantiomers in biodegradation experiments of α-HCH with Clostridium pasteurianum and samples from a contaminated field site were determined. The isotopic compositions of the α-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 α-HCH in the environment.
authors.affiliation: Department of Isotope Biogeochemistry, Helmholtz Centre for Environmental Research - UFZ, Permoserstrasse 15, 04318 Leipzig, Germany.
authors.forename: Silviu-Laurentiu
authors.initials: SL
authors.lastname: Badea
authors.forename: Carsten
authors.initials: C
authors.lastname: Vogt
authors.forename: Matthias
authors.initials: M
authors.lastname: Gehre
authors.forename: Anko
authors.initials: A
authors.lastname: Fischer
authors.forename: Andrei-Florin
authors.initials: AF
authors.lastname: Danet
authors.forename: Hans-Hermann
authors.initials: HH
authors.lastname: Richnow
mesh_terms: D001673:Biodegradation, Environmental; D002247:Carbon Isotopes / Q000737:chemistry*; D003013:Clostridium / Q000378:metabolism; D004785:Environmental Pollutants / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D001556:Hexachlorocyclohexane / Q000032:analysis* / Q000737:chemistry / Q000378:metabolism; D012044:Regression Analysis; D015203:Reproducibility of Results; D013237:Stereoisomerism
chemical_list: D002247:Carbon Isotopes; D004785:Environmental Pollutants; C040534:alpha-hexachlorocyclohexane; D001556:Hexachlorocyclohexane