Characterization of Compound-Specific Chlorine Isotopologue Distributions of Polychlorinated Organic Compounds by GC-HRMS for Source Identification

Distributions of chlorine isotopologues are potentially a fingerprint feature of organochlorines. However, the exact distributions remain little known. This study measured compound-specific chlorine isotopologue distributions of six polychlorinated organic compounds (POCs) for source identification. Complete chlorine isotopologues of POCs were detected by gas chromatography coupled to high-resolution mass spectrometry. The measured relative abundances (A(meas)), theoretical relative abundances (A(theo)), and relative variations between A(meas) and A(theo) (Delta A) of chlorine isotopologues were determined. These Delta A values were applied to characterize differences in isotopologue distribution patterns, and the Delta A patterns directly illustrated the distribution characteristics. Perchloroethylene (PCE) and trichloroethylene (TCE) from two manufacturers were chosen as model analytes to develop and validate the analytical method, including precision, concentration dependency, and temporal drift. The Delta A values of isotopologues of the PCE and TCE chemicals were from -82.5 to 19.9% with standard deviations (SDs) of 0.3-16.9%. In addition, the Delta A values of the first three isotopologues (with 0-2 Cl-37 atoms) were from -15.5 to 19.9% with SDs of 0.3-1.6%, showing sufficient precisions. No concentration dependency and temporal drift of Delta A were observed. The method has been successfully applied to source identification for PCE and TCE in commercial chemicals and plastic materials, and four polychlorinated biphenyls in chemicals and sediments, demonstrating that the Delta A values and Delta A patterns were discernable for POCs from different sources. This study demonstrates that compound-specific chlorine isotopologue distributions of POCs are differentiable and measurable, proposing a novel approach to perform fingerprinting analysis for the distributions, which is anticipated to facilitate source identification for organochlorine pollutants.YYY

Automated summary

This study measured compound-specific chlorine isotopologue distributions of POCs using gas chromatography coupled to high-resolution mass spectrometry for source identification. The Delta A values and Delta A patterns were discernible for POCs from different sources.