EGU21-132, updated on 03 Mar 2021
https://doi.org/10.5194/egusphere-egu21-132
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Cryogen-free fully automated preconcentration unit to enable Δ13CH3D and Δ12CH2D2 analysis

Ivan Prokhorov and Joachim Mohn
Ivan Prokhorov and Joachim Mohn
  • Laboratory for Air Pollution and Environmental Technology, Swiss Federal Laboratories for Materials Science and Technology - Empa, Dübendorf, Switzerland (ivan.prokhorov@empa.ch)

Clumped isotope analysis is a powerful tool to constrain methane's origin in various geological, biogeochemical, and environmental settings. The extremely low abundance of 12CH2D2 and 13CH3D isotopologues poses a challenge for the existing analytical systems. Mole fraction enhancement and cleaning of the environmental samples are necessary to fully exploit the potential of modern analyzers, requiring 50 to 1000 μmol of pure CH4. To enable high-precision Δ12CH2D2 and Δ13CH3D analysis with dual-QCL (8.6 μm and 9.3 μm) absorption spectroscopy in a multipass cell (400 m), we have developed a new automated cryogen-free unit for methane Cleaning and Extraction – CleanEx.

The unit can process up to 18 liters of sample air at a high flow rate of 900 ml min−1. Methane (TBP = −161 °C) is separated from major air components on a high capacity trap filled with HayeSep D (Trap 1, −176 °C). Sequential desorption and transfer to a second trap (Trap 2, −181°C) ensure complete O2 and Ar removal. Substances with a higher boiling point, i.e., CO2, N2O, H2O, CnHm, remain on Trap 1 to be removed at a later conditioning phase. CleanEx demonstrates equal performance for gas mixtures with initial methane mole fraction ranging from 2 ppm up to 2%. In contrast to the previously developed single trap TREX system (Eyer et al., 2016), atmospheric O2 and Ar are effectively separated by cryo-focusing of CH4 on the second trap. Ongoing work is focused on the separation of atmospheric gases with boiling points close to methane, e.g., Kr (TBP = −153 °C).

We present the instrument design, performance, and details of its operation. Fractionation effects, methane recovery efficiency, and implications for high-precision δ13C-CH4, δD-CH4, Δ13CH3D, and Δ12CH2D2 analyses are being discussed.

Acknowledgments. This work was supported by the Swiss National Science Foundation (SNSF) under R'Equip project QCL4CLUMPS (no. 206021_183294) and the project STELLAR (grant no. 19ENV05; Stable isotope metrology to enable climate action and regulation) which has received funding from the EMPIR programme co-financed  by  the  Participating  States  and  from  the  European  Union's  Horizon  2020  research  and innovation programme.

 

References

Eyer, S., Tuzson, B., Popa, M. E., van der Veen, C., Röckmann, T., Rothe, M., Brand, W. A., Fisher, R., Lowry, D., Nisbet, E. G., Brennwald, M. S., Harris, E., Zellweger, C., Emmenegger, L., Fischer, H., and Mohn, J.: Real-time analysis of δ13C- and δD-CH4 in ambient air with laser spectroscopy: method development and first intercomparison results, Atmos. Meas. Tech., 9, 263–280, https://doi.org/10.5194/amt-9-263-2016, 2016.

 

 

How to cite: Prokhorov, I. and Mohn, J.: Cryogen-free fully automated preconcentration unit to enable Δ13CH3D and Δ12CH2D2 analysis, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-132, https://doi.org/10.5194/egusphere-egu21-132, 2020.

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