Analysis of kerogens and kerogen precursors by flash pyrolysis in combination with isotope‐ratio‐monitoring gas chromatography‐mass spectrometry (irm‐GC‐MS)

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Abstract
This study describes the application of isotope ratio monitoring gas chromatography‐ mass spectrometry (irm‐GC‐MS) for compound‐specific stable carbon isotopic analysis of aliphatic hydrocarbon and phenolic products from flash pyrolysis (800 °C, 20s) of natural biopolymers and sedimentary kerogens. As part of this work, we provide a detailed description of the analysis of complex samples, including approaches for peak integration, data handling and correction for derivative carbons. Several aliphatic and aromatic biopolymers are analyzed by irm‐GC‐MS in order to establish relationships between the isotopic signatures of pyrolysis products and those of their parent macromolecules. We also analyze a select group of kerogens and kerogen precursors of different ages and biopolymer compositions to evaluate the applicability of combined pyrolysis/irm‐GC‐MS to complex geochemical mixtures. Our findings suggest that, in spite of the wide degree of heterogeneity, the isotopic values of individual aliphatic and phenolic pyrolysis products determined by irm‐GC‐MS can be related to the isotopic composition of the total organic carbon in kerogens and used to trace its biological sources. This study also highlights the need for optimum chromatographic separation in order to fully realize the potential of compound specific isotope analyses.