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Calibration bias of experimentally determined chlorine isotope enrichment factors: the need for a two‐point calibration in compound‐specific chlorine isotope analysis
Author(s) -
Ebert Karin A.,
Laskov Christine,
Elsner Martin,
Haderlein Stefan B.
Publication year - 2016
Publication title -
rapid communications in mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.528
H-Index - 136
eISSN - 1097-0231
pISSN - 0951-4198
DOI - 10.1002/rcm.7752
Subject(s) - chemistry , chlorine , calibration , isotopes of chlorine , isotope , environmental chemistry , aqueous solution , isotope analysis , calibration curve , trichloroethylene , analytical chemistry (journal) , detection limit , chromatography , organic chemistry , ecology , statistics , physics , mathematics , quantum mechanics , biology
Rationale The recent development of compound‐specific online chlorine isotope analysis ( 37 Cl‐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 δ 37 Cl SMOC scale, but a critical evaluation of best practices to arrive at reliable δ 37 Cl SMOC signatures and enrichment factors was missing and is presented here. Methods Aqueous solutions of neat perchloroethylene and trichloroethylene (TCE) and aqueous samples from a TCE biodegradation experiment with pure cultures of Desulfitobacterium hafniense Y51 were analysed for their chlorine isotope ratios using GC/qMS and GC/IRMS. The δ 37 Cl SMOC values were obtained using one‐point and two‐point calibration schemes. Chlorine isotope enrichment factors, ε Cl , were calculated using both approaches and the corresponding bias of δ 37 Cl SMOC values introduced by the different types of calibration was determined. Results Different calibration methods resulted in significant differences (up to 30%) in both δ 37 Cl signatures and ε Cl values. Conclusions Our results demonstrate that a two‐point calibration together with comprehensive information on reference materials is indispensable and should become standard practice for reliable 37 Cl‐CSIA of organic compounds. Copyright © 2016 John Wiley & Sons, Ltd.