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Analysis of the site-specific carbon isotope composition of propane by gas source isotope ratio mass spectrometer

Piasecki, Alison and Sessions, Alex and Lawson, Michael and Ferreira, A. A. and Santos Neto, E. V. and Eiler, John M. (2016) Analysis of the site-specific carbon isotope composition of propane by gas source isotope ratio mass spectrometer. Geochimica et Cosmochimica Acta, 188 . pp. 58-72. ISSN 0016-7037. doi:10.1016/j.gca.2016.04.048.

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Site-specific isotope ratio measurements potentially provide valuable information about the formation and degradation of complex molecules—information that is lost in conventional bulk isotopic measurements. Here we discuss the background and possible applications of such measurements, and present a technique for studying the site-specific carbon isotope composition of propane at natural abundance based on mass spectrometric analysis of the intact propane molecule and its fragment ions. We demonstrate the feasibility of this approach through measurements of mixtures of natural propane and propane synthesized with site-specific^(13)C enrichment, and we document the limits of precision of our technique. We show that mass balance calculations of the bulk δ^(13)C of propane based on our site-specific measurements is generally consistent with independent constraints on bulk δ^(13)C. We further demonstrate the accuracy of the technique, and illustrate one of its simpler applications by documenting the site-specific carbon isotope signature associated with gas phase diffusion of propane, confirming that our measurements conform to the predictions of the kinetic theory of gases. This method can be applied to propane samples of moderate size (tens of micromoles) isolated from natural gases. Thus, it provides a means of studying the site-specific stable isotope systematics of propane at natural isotope abundances on sample sizes that are readily recovered from many natural environments. This method may also serve as a model for future techniques that apply high-resolution mass spectrometry to study the site-specific isotopic distributions of larger organic molecules, with potential applications to biosynthesis, forensics and other geochemical subjects.

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Sessions, Alex0000-0001-6120-2763
Additional Information:© 2016 Elsevier Ltd. Received 4 September 2015; accepted in revised form 29 April 2016; Available online 26 May 2016. This work was funded by an NSF-EAR instruments and facilities grant. Additional funding was supplied by Exxon Mobil and Petrobras. I would also like to thank the reviewers including Prof. Shuhei Ono for their helpful comments to make the manuscript more clear and precise.
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Subject Keywords:Stable isotopes; Site-specific isotopes; Natural gas; Mass spectrometry
Record Number:CaltechAUTHORS:20160610-151828176
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Official Citation:Alison Piasecki, Alex Sessions, Michael Lawson, A.A. Ferreira, E.V. Santos Neto, John M. Eiler, Analysis of the site-specific carbon isotope composition of propane by gas source isotope ratio mass spectrometer, Geochimica et Cosmochimica Acta, Volume 188, 1 September 2016, Pages 58-72, ISSN 0016-7037, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:67851
Deposited By: Tony Diaz
Deposited On:10 Jun 2016 22:25
Last Modified:11 Nov 2021 03:55

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