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Nataraj A, Tuzson B, Gianella M, Prokhorov I, Li G, Ebert V, Faist J, Emmenegger L. Position-Specific Isotope Analysis of Propane by Mid-IR Laser Absorption Spectroscopy. Anal Chem 2023; 95:5354-5361. [PMID: 36913630 DOI: 10.1021/acs.analchem.2c05489] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/15/2023]
Abstract
Intramolecular or position-specific carbon isotope analysis of propane (13CH3-12CH2-12CH3 and 12CH3-13CH2-12CH3) provides unique insights into its formation mechanism and temperature history. The unambiguous detection of such carbon isotopic distributions with currently established methods is challenging due to the complexity of the technique and the tedious sample preparation. We present a direct and nondestructive analytical technique to quantify the two singly substituted, terminal (13Ct) and central (13Cc), propane isotopomers, based on quantum cascade laser absorption spectroscopy. The required spectral information on the propane isotopomers was first obtained using a high-resolution Fourier-transform infrared (FTIR) spectrometer and then used to select suitable mid-infrared regions with minimal spectral interference to obtain the optimum sensitivity and selectivity. We then measured high-resolution spectra around 1384 cm-1 of both singly substituted isotopomers by mid-IR quantum cascade laser absorption spectroscopy using a Stirling-cooled segmented circular multipass cell (SC-MPC). The spectra of the pure propane isotopomers were acquired at both 300 and 155 K and served as spectral templates to quantify samples with different levels of 13C at the central (c) and terminal (t) positions. A prerequisite for the precision using this reference template fitting method is a good match of amount fraction and pressure between the sample and templates. For samples at natural abundance, we achieved a precision of 0.33 ‰ for δ13Ct and 0.73 ‰ for δ13Cc values within 100 s integration time. This is the first demonstration of site-specific high-precision measurements of isotopically substituted non-methane hydrocarbons using laser absorption spectroscopy. The versatility of this analytical approach may open up new opportunities for the study of isotopic distribution of other organic compounds.
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Affiliation(s)
- Akshay Nataraj
- Laboratory for Air Pollution/Environmental Technology, Empa, 8600 Dübendorf, Switzerland
| | - Béla Tuzson
- Laboratory for Air Pollution/Environmental Technology, Empa, 8600 Dübendorf, Switzerland
| | - Michele Gianella
- Laboratory for Air Pollution/Environmental Technology, Empa, 8600 Dübendorf, Switzerland
| | - Ivan Prokhorov
- Laboratory for Air Pollution/Environmental Technology, Empa, 8600 Dübendorf, Switzerland
| | - Gang Li
- Physikalisch-Technische Bundesanstalt, 38116 Braunschweig, Germany
| | - Volker Ebert
- Physikalisch-Technische Bundesanstalt, 38116 Braunschweig, Germany
| | - Jérôme Faist
- Institute for Quantum Electronics, ETH Zurich, 8093 Zurich, Switzerland
| | - Lukas Emmenegger
- Laboratory for Air Pollution/Environmental Technology, Empa, 8600 Dübendorf, Switzerland
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Eiler JM, Clog M, Lawson M, Lloyd M, Piasecki A, Ponton C, Xie H. The isotopic structures of geological organic compounds. ACTA ACUST UNITED AC 2017. [DOI: 10.1144/sp468.4] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
AbstractOrganic compounds are ubiquitous in the Earth's surface, sediments and many rocks, and preserve records of geological, geochemical and biological history; they are also critical natural resources and major environmental pollutants. The naturally occurring stable isotopes of volatile elements (D, 13C, 15N, 17,18O, 33,34,36S) provide one way of studying the origin, evolution and migration of geological organic compounds. The study of bulk stable isotope compositions (i.e. averaged across all possible molecular isotopic forms) is well established and widely practised, but frequently results in non-unique interpretations. Increasingly, researchers are reading the organic isotopic record with greater depth and specificity by characterizing stable isotope ‘structures’ – the proportions of site-specific and multiply substituted isotopologues that contribute to the total rare-isotope inventory of each compound. Most of the technologies for measuring stable isotope structures of organic molecules have been only recently developed and to date have been applied only in an exploratory way. Nevertheless, recent advances have demonstrated that molecular isotopic structures provide distinctive records of biosynthetic origins, conditions and mechanisms of chemical transformation during burial, and forensic fingerprints of exceptional specificity. This paper provides a review of this young field, which is organized to follow the evolution of molecular isotopic structure from biosynthesis, through diagenesis, catagenesis and metamorphism.
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Affiliation(s)
- John M. Eiler
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125
| | - Matthieu Clog
- University of Glasgow, Glasgow G12 8QQ, Scotland, UK
| | | | - Max Lloyd
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125
| | - Alison Piasecki
- Department of Earth Science, University of Bergen, 5020 Bergen, Norway
| | - Camilo Ponton
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125
| | - Hao Xie
- Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 91125
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