Compound-specific chlorine isotope analysis of polychlorinated biphenyls isolated from Aroclor and Clophen technical mixtures

Compound-specific chlorine isotope analysis (CSIA–Cl) is promising as a novel and powerful method for monitoring in situ degradation of organochlorines in the environment and for source fingerprinting purposes. In order to apply CSIA–Cl in field studies of polychlorinated biphenyls (PCBs), the chlorine isotopic composition (δ37Cl) of individual PCB congeners in source materials must be known. In the present study, we determined δ37Cl of 18 congeners isolated from three widely produced technical mixtures. All congeners provided δ37Cl ranging between −1.9‰ and −3.5‰. Although the comparable products Aroclor 1242 (−2.0‰ to −2.5‰) and Clophen A30 (−1.9‰ to −3.0‰) were synthesized by different industries, they provided similar δ37Cl for the same type of congeners. On the contrary, the more chlorinated congeners present in Aroclor 1254 (−2.1 to −3.5‰) were more 37Cl depleted compared to Aroclor 1242 manufactured by the same company. Overall, δ37Cl of PCB congeners decreased by −0.26 ‰ for each additional chlorine atom.