Congener-specific carbon isotopic analysis of technical PCB and PCN mixtures using two-dimensional gas chromatography - Isotope ratio mass spectrometry

Analysis of stable carbon isotope fractionation is a useful method to study the sources and fate of anthropogenic organic contaminants such as polychlorinated biphenyls (PCBs) in the environment. To evaluate the utility of carbon isotopes, determination of isotopic ratios of C-13/C-12 in source materials, for example, technical PCB preparations, is needed. In this study, we determined delta C-13 values of 31 chlorobiphenyl (CB) congeners in 18 technical PCB preparations and 15 chloronaphthalene (CN) congeners in 6 polychlorinated naphthalene preparations using two-dimensional gas chromatography-combustion furnace-isotope ratio mass spectrometry (MC-C-IRMS). Development of 2DGC-IRMS enabled improved resolution and sensitivity of compound-specific carbon isotope analysis (CSIA) of CB or CN congeners. delta C-13 values of PCB congeners ranged from -34.4 (Delors) to -22.0 parts per thousand (Sovol). Analogous PCB preparations with similar chlorine content, but different geographical origin, had different delta C-13 values. PCB preparations from Eastern European countries-Delors, Sovol, Trichlorodiphenyl, and Chlorofen-had distinct delta C-13 values. PCB mixtures showed increased C-13 depletion with increasing chlorine content. delta C-13 values for individual CB congeners varied depending on the degree of chlorination in technical mixtures. delta C-13 values of CN congeners in Halowaxes ranged from -26.3 to -21.7 parts per thousand and these values are within the ranges observed for PCBs. This study establishes the range of delta C-13 values in technical PCB and PCN preparations, which may prove to be useful in the determination of sources of these compounds in the environment. This is the first study to employ 2DGC-IRMS analysis of delta C-13 values in technical PCB and PCN preparations.