High-precision optical measurements of ¹³C/¹²C isotope ratios in organic compounds at natural abundance

A continuous-flow cavity ring-down spectroscopy (CRDS) system integrating a chromatographic separation technique, a catalytic combustor, and an isotopic ¹³C/¹²C optical analyzer is described for the isotopic analysis of a mixture of organic compounds. A demonstration of its potential is made for the...

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Bibliographic Details
Published in:Proceedings of the National Academy of Sciences - PNAS 2009-07, Vol.106 (27), p.10928-10932
Main Authors: Zare, Richard N, Kuramoto, Douglas S, Haase, Christa, Tan, Sze M, Crosson, Eric R, Saad, Nabil M.R
Format: Article
Language:English
Subjects:
Carbon dioxide
Combustion
Combustion chambers
Isotope ratios
Isotopes
Mass spectroscopy
Methane
Oxygen
Physical Sciences
Propane
Spectroscopy
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Summary:A continuous-flow cavity ring-down spectroscopy (CRDS) system integrating a chromatographic separation technique, a catalytic combustor, and an isotopic ¹³C/¹²C optical analyzer is described for the isotopic analysis of a mixture of organic compounds. A demonstration of its potential is made for the geochemically important class of short-chain hydrocarbons. The system proved to be linear over a 3-fold injection volume dynamic range with an average precision of 0.95[per thousand] and 0.67[per thousand] for ethane and propane, respectively. The calibrated accuracy for methane, ethane, and propane is within 3[per thousand] of the values determined using isotope ratio mass spectrometry (IRMS), which is the current method of choice for compound-specific isotope analysis. With anticipated improvements, the low-cost, portable, and easy-to-use CRDS-based instrumental setup is poised to evolve into a credible challenge to the high-cost and complex IRMS-based technique.
ISSN:0027-8424
1091-6490
DOI:10.1073/pnas.0904230106