EGU2020-11630
https://doi.org/10.5194/egusphere-egu2020-11630
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

A novel method to quantify exchangeable hydrogen fraction in organic matter

Cristian Gudasz1, David X. Soto2,3, Tobias Sparrman4, and Jan Karlsson1
Cristian Gudasz et al.
  • 1Umeå University, Department of Ecology and Environmental Sciences, Umeå, Sweden (cristian.gudasz@umu.se)
  • 2UK Centre for Ecology and Hydrology, Lancaster, UK (dsoto@ceh.ac.uk)
  • 3KU Leuven, Leuven, Belgium (dsoto@ceh.ac.uk)
  • 4Umeå University, Department of Chemistry, Umeå, Sweden (tobias.sparrman@umu.se)

Stable isotope measurements of nonexchangeable hydrogen (δ2Hn) of bulk organic matter has emerged as a tool, with a wide range of applications in biology, biogeochemistry and forensics. However, reproducible and precise measurements of δ2Hn between laboratories and methods are still challenging. One of the largest impediments to obtain accurate isotope ratios is to use reference materials of similar exchangeable hydrogen fraction (fx) to the matrix of interest. The organic matter has typically three pools of hydrogen (H): (i) the adsorbed water, which can be minimized by extensive drying, (ii) the carbon bound H (the fraction of interest), which is non-exchangeable and cannot be removed and (iii) the non-carbon bound H, (i.e. N-, COO-, O-, and S-bound H) that cannot be removed but can be readily exchanged with the environmental moisture. Quantification of fbased on dual water vapor isotope exchange and Isotope Ratio Mass Spectrometry (IRMS) have shown large variability in fbetween studies for the same organic matter type such as keratin. High variability in fx between samples and standards can translate into a large impact on the measured isotopic values. Here we used a novel approach to independently quantify fin 21 natural organic material sources with minimal sample manipulation based on 1H-2H exchange experiments and quantified through proton based liquid-state nuclear magnetic resonance (1H-NMR) spectroscopy. The experiments were carried out at room temperature by immersing separate solid powdered samples in deuterated dimethylsulfoxide (background) and deuterium oxide (2H source) followed by the quantification of the water generated in the supernatant fraction through 1H-NMR using glucose as reference. At the same time, samples were analyzed through the most recent procedure of dual water vapor isotope equilibration method using online drying and equilibration in a UniPrep carousel. We discuss these findings and suggest that the proposed 1H-NMR method of quantifying fis an independent and novel approach that can contribute to a better understanding of H exchangeability in a wider range of organic materials, critical for accurate measurement of the δ2Hn.

How to cite: Gudasz, C., Soto, D. X., Sparrman, T., and Karlsson, J.: A novel method to quantify exchangeable hydrogen fraction in organic matter, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-11630, https://doi.org/10.5194/egusphere-egu2020-11630, 2020

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