13CH4/12CH4 sensing using Raman spectroscopy

Dmitry V Petrov; Aleksandr S Tanichev

doi:10.1016/j.saa.2024.124253

¹³CH₄/¹²CH₄ sensing using Raman spectroscopy

Spectrochim Acta A Mol Biomol Spectrosc. 2024 Apr 4:315:124253. doi: 10.1016/j.saa.2024.124253. Online ahead of print.

Authors

Dmitry V Petrov¹, Aleksandr S Tanichev²

Affiliations

¹ Institute of Monitoring of Climatic and Ecological Systems, 634055 Tomsk, Russia; Tomsk State University, 634050 Tomsk, Russia. Electronic address: dpetrov@imces.ru.
² Institute of Monitoring of Climatic and Ecological Systems, 634055 Tomsk, Russia.

PMID: 38603959
DOI: 10.1016/j.saa.2024.124253

Abstract

The paper presents a technique for measuring the concentration of ¹³CH₄ in natural methane using Raman spectroscopy. The peak positions and the relative scattering cross-sections of the Q-branches for the most intense vibrational bands of ¹³CH₄ are determined. Features of the ¹³CH₄/¹²CH₄ ratio measurement methods using Q-branches of the ν₁ and ν₃ bands were considered. It was shown that the ¹³CH₄/¹²CH₄ ratio can be determined by simulation of the ν₃ bands of these molecules without the use of experimental spectra. In our experiments the measurement error of δ¹³C value was 10 ‰ using the 100-s exposure spectrum at a gas pressure close to 1 atm recorded on the developed Raman spectrometer. In addition, the Raman spectra of alkanes (up to n-hexane) in the range of 2850-3050 cm^-1 at a resolution of 0.4 cm^-1 are presented, and their integrated intensities in the ranges of the characteristic bands of ¹³CH₄ and ¹²CH₄ are provided. The data obtained make it possible to expand the capabilities of Raman gas analyzers in the mud gas logging industry.

Keywords: (13)C/(12)C; Alkanes; Gas analysis; Isotopic composition; Methane; Raman spectroscopy.