Combining thermal hydrolysis and methylation-gas chromatography/mass spectrometry with X-ray photoelectron spectroscopy to characterise complex organic assemblages in geological material

Graham Purvis; Naoko Sano; Cees van der Land; Anders Barlow; Elisa Lopez-Capel; Peter Cumpson; James Hood; Jake Sheriff; Neil Gray

doi:10.1016/j.mex.2019.10.034

Combining thermal hydrolysis and methylation-gas chromatography/mass spectrometry with X-ray photoelectron spectroscopy to characterise complex organic assemblages in geological material

MethodsX. 2019 Nov 2:6:2646-2655. doi: 10.1016/j.mex.2019.10.034. eCollection 2019.

Authors

Graham Purvis¹, Naoko Sano², Cees van der Land¹, Anders Barlow³, Elisa Lopez-Capel¹, Peter Cumpson⁴, James Hood⁵, Jake Sheriff⁵, Neil Gray¹

Affiliations

¹ Earth, Ocean & Planetary Science Research, School of Natural and Environmental Sciences, Newcastle University, Newcastle upon Tyne, UK.
² Ionoptika Ltd., Eastleigh, Hampshire, UK.
³ Materials Characterisation and Fabrication Platform (MCFP), Department of Chemical Engineering, The University of Melbourne, Melbourne, Victoria, Australia.
⁴ Mark Wainwright Analytical Centre, University of New South Wales, Sydney, New South Wales, Australia.
⁵ National ESCA and XPS Users' Service (NEXUS), Newcastle University, Newcastle upon Tyne, UK.

Abstract

What follows is a method applicable generically to the analysis of low levels of organic matter that is embedded in either loose fine-grained or solid geological material. Initially, the range of organic compounds that could be detected in a geological sample using conventional pyrolysis chromatography/mass spectrometry was compared to the range that was detected using thermally assisted hydrolysis and methylation-gas chromatography/mass spectrometry (THM-GC/MS). This method was used to validate the synthetic components fitted to X-ray photoelectron spectroscopy (XPS) carbon spectra of the sample. Reciprocally, XPS analysis was able to identify the constituent carbon-carbon, carbon-oxygen and carbon-nitrogen bonds of the functional groups in the compounds identified by THM-GC/MS. The two independently derived outputs from the THM-GC/MS and the XPS techniques mutually validated the identification of organic compounds in our geological samples. We describe in detail the improvements to: •The preparation of geological samples for analysis by XPS.•Measurements of organic material in geological samples using GC/MS.•The use of THM-GC/MS and XPS data used together to characterise low levels of organic material in geological samples.

Keywords: Analysis; Combining thermal hydrolysis and methylation-gas chromatography/mass spectrometry with X-ray photoelectron spectroscopy; GC/MS; Geological material; Organic geochemistry; Pyrolysis; THM; TMAH; XPS.