Calibration bias of experimentally determined chlorine isotope enrichment factors: the need for a two-point calibration in compound-specific chlorine isotope analysis
The recent development of compound-specific online chlorine isotope analysis (37Cl-CSIA) methods has fostered dual chlorine–carbon isotope studies to gain better insights into sources and environmental transformation reactions of chlorinated ethenes. One-point and two-point calibration schemes are currently used to convert raw data to the international δ37ClSMOC scale, but a critical evaluation of best practices to arrive at reliable δ37ClSMOC signatures and enrichment factors was missing and is presented here.