Validation of GC-IRMS techniques for δ13C and δ2H CSIA of organophosphorus compounds and their potential for studying the mode of hydrolysis in the environment.
Compound-specific stable isotope analysis (CSIA) is among the most promising tools for studying the fate of organic pollutants in the environment. However, the feasibility of multidimensional CSIA was limited by the availability of a robust method for precise isotope analysis of heteroatom-bearing organic compounds. We developed a method for δ13C and δ2H analysis of eight organophosphorus compounds (OPs) with different chemical properties. In particular, we aimed to compare high-temperature conversion (HTC) and chromium-based HTC (Cr/HTC) units to explore the limitations of hydrogen isotope analysis of heteroatom-bearing compounds. Analysis of the amount dependency of the isotope values (linearity analysis) of OPs indicated that the formation of HCl was a significant isotope fractionation process leading to inaccurate δ2H analysis in HTC. In the case of nonchlorinated OPs, by-product formation of HCN, H2S, or PH3in HTC was observed but did not affect the dynamic range of reproducible isotope values above the limit of detection. No hydrogen-containing by-products were found in the Cr/HTC process by use of ion trap mass spectrometry analysis. The accuracy of gas chromatography - isotope ratio mass spectrometry was validated in comparison with elemental analyzer - isotope ratio mass spectrometry. Dual-isotope fractionation yielded Λ values of 0 ± 0 at pH 7, 7 ± 1 at pH 9, and 30 ± 6 at pH 12, indicating the potential of 2D CSIA to characterize the hydrolysis mechanisms of OPs. This is the first report on the combination of δ2H and δ13C isotope analysis of OPs, and this is the first study providing a systematic evaluation of HTC and Cr/HTC for hydrogen isotope analysis using OPs as target compounds. Graphical Abstract Comparison of δ2H measurement of non-chlorinated and chlorinated OPs via GC-Cr/HTC-IRMS and GC-HTC-IRMS system.
Department of Isotope Biogeochemistry, Helmholtz Centre for Environmental Research, UFZ, Permoserstrasse 15, 04318, Leipzig, Germany.
Langping
L
Wu
Department of Isotope Biogeochemistry, Helmholtz Centre for Environmental Research, UFZ, Permoserstrasse 15, 04318, Leipzig, Germany.
Steffen
S
Kümmel
Department of Isotope Biogeochemistry, Helmholtz Centre for Environmental Research, UFZ, Permoserstrasse 15, 04318, Leipzig, Germany. hans.richnow@ufz.de.
Hans H
HH
Richnow
Chromium-based high-temperature conversion; Compound-specific stable isotope analysis; Hydrogen isotope; Organophosphorus compounds; Pesticides