Carbon, Hydrogen and Chlorine Stable Isotope Fingerprinting for Forensic Investigations of Hexachlorocyclohexanes

Abstract

Multielemental stable isotope analysis of persistent organic pollutants (POPs) has the potential to characterize sources, sinks, and degradation processes in the environment. To verify the applicability of this approach for source identification of hexachlorocyclohexane (HCHs), we provide a data set of carbon, hydrogen, and chlorine stable isotope ratios (δC, δH, δCl) of its main stereoisomers (α-, β-, δ- and γ-HCHs) from a sample collection based on worldwide manufacturing. This sample collection comprises production stocks, agricultural and pharmaceutical products, chemical waste dumps, and analytical-grade material, covering the production time period from the late 1960s until now. Stable isotope ratios of HCHs cover the ranges from -233‰ to +1‰, from -35.9‰ to -22.7‰, and from -6.69‰ to +0.54‰ for δH, δC, and δCl values, respectively. Four groups of samples with distinct multielemental stable isotope fingerprints were differentiated, most probably as a result of purification and isolation processes. No clear temporal trend in the isotope compositions of HCHs was found at the global scale. The multielemental stable isotope fingerprints facilitate the source identification of HCHs at the regional scale and can be used to assess transformation processes. The data set and methodology reported herein provide basic information for the assessment of environmental field sites contaminated with HCHs.

Requirements for Chromium Reactors for Use in the Determination of H Isotopes in Compound-Specific Stable Isotope Analysis of Chlorinated Compounds

“…Furthermore, including hydrogen CSIA as one of multiple elements analyzed for a given contaminant can provide two-or three-dimensional isotope plots useful for characterizing degradation processes and source characterization. [2][3][4]8,11,13 Hydrogen isotope ratios of nonhalogenated compounds using CSIA are typically analyzed using a gas chromatograph (GC) coupled to a high temperature conversion (HTC) oven at 1400−1500 °C, followed by the measurement of the produced hydrogen gas by isotope-ratio mass spectrometry (IRMS). 14 However, for halogenated compounds, this method can induce isotope fractionation artifacts due to incomplete conversion of the compound to H 2 and simultaneous formation of byproducts, e.g., HCl.…”

Compound-Specific Chlorine Isotope Analysis of the Herbicides Atrazine, Acetochlor, and Metolachlor

“…12 These techniques have been used for measuring 37 Cl signatures of commercial and pure samples of pesticides, but they are not suitable for online coupling to a chromatograph. [13][14][15][16][17][18][19] Chlorine isotope ratios can also be measured by gas chromatography (GC)-continuous flow (CF)-IRMS, although this method is costly since specialized IRMS instruments with a modified layout of ion detectors are required. 12 Furthermore, GC-CF-IRMS is restricted to analysis of certain compounds and molecular fragments by the fixed Faraday detector arrangement and modest mass range, which limits its applicability to pesticides.…”

“…Offline methodssuch as dual-inlet isotope ratio mass spectrometry (DI-IRMS) after conversion to CH 3 Cl, fast atom bombardment IRMS (FAB-IRMS) after conversion to AgCl and thermal ionization mass spectrometry (TIMS) after conversion to CsClrequire time-intensive preparation procedures with multiple steps and relatively large sample amounts . These techniques have been used for measuring 37 Cl signatures of commercial and pure samples of pesticides, but they are not suitable for online coupling to a chromatograph. − Chlorine isotope ratios can also be measured by gas chromatography (GC)–continuous flow (CF)-IRMS, although this method is costly since specialized IRMS instruments with a modified layout of ion detectors are required . Furthermore, GC–CF-IRMS is restricted to analysis of certain compounds and molecular fragments by the fixed Faraday detector arrangement and modest mass range, which limits its applicability to pesticides.…”

Molecularly Imprinted Polymers for Compound-Specific Isotope Analysis of Polar Organic Micropollutants in Aquatic Environments

“…The analysis of stable isotope ratios in organic soil and water contaminants has become a widely used approach to identify the sources of pollution and to identify (bio)­degradation pathways. − Whereas constant ratios of 13 C/ 12 C, 2 H/ 1 H, 15 N/ 14 N, and of other elements in a compound enable one to infer precursor materials, synthesis routes, and formation pathways of pollutants, − changes of isotope ratios lead to stable isotope fractionation patterns that reveal the (bio)­chemical reaction by which a pollutant is degraded. − However, because of the poor sensitivity of gas and liquid chromatography used in combination with isotope-ratio mass spectrometry, − the applications of compound-specific isotope analysis (CSIA) have largely focused on so-called legacy contaminants such as halogenated solvents, nitroaromatic explosives, and fuel constituents − Those compounds are often found in the high μg/L to mg/L concentration range and can be extracted from the environmental matrices in straightforward procedures, for example, through transfer of the analytes into the gas phase and enrichment onto solid sorbents. − Unfortunately, such procedures are not necessarily applicable for CSIA of polar organic micropollutants of current interest, such as pesticides, pharmaceuticals, consumer chemicals, and personal care products. Their sub-μg/L concentrations in natural and treated waters require the processing of large sample volumes greater than 5 L by solid-phase extractions (SPE, e.g., ref ) to obtain the necessary analyte mass for isotope-ratio mass spectrometry.…”