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Isotope-ratio detection for gas chromatography

Sessions, Alex L. (2006) Isotope-ratio detection for gas chromatography. Journal of Separation Science, 29 (12). pp. 1946-1961. ISSN 1615-9306. doi:10.1002/jssc.200600002.

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Instrumentation and methods exist for highly precise analyses of the stable-isotopic composition of organic compounds separated by GC. The general approach combines a conventional GC, a chemical reaction interface, and a specialized isotope-ratio mass spectrometer (IRMS). Most existing GC hardware and methods are amenable to isotope-ratio detection. The interface continuously and quantitatively converts all organic matter, including column bleed, to a common molecular form for isotopic measurement. C and N are analyzed as CO_2 and N_2, respectively, derived from combustion of analytes. H and O are analyzed as H_2 and CO produced by pyrolysis/reduction. IRMS instruments are optimized to provide intense, highly stable ion beams, with extremely high precision realized via a system of differential measurements in which ion currents for all major isotopologs are simultaneously monitored. Calibration to an internationally recognized scale is achieved through comparison of closely spaced sample and standard peaks. Such systems are capable of measuring ^(13)C/^(12)C ratios with a precision approaching 0.1‰ (for values reported in the standard delta notation), four orders of magnitude better than that typically achieved by conventional “organic” mass spectrometers. Detection limits to achieve this level of precision are typically <1 nmol C (roughly 10 ng of a typical hydrocarbon) injected on-column. Achievable precision and detection limits are correspondingly higher for N, O, and H, in that order.

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Sessions, Alex L.0000-0001-6120-2763
Additional Information:© 2006 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. Received: January 3, 2006; revised: June 13, 2006; accepted: June 14, 2006. The author is particularly indebted to C. Douthitt for answering many questions about the historical development of GC-IRMS methods, for numerous references, and for a thorough review of the manuscript. The kind help of W. Brand and J. Hayes is further acknowledged. ALS is supported by NSF EAR-0311824.
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Subject Keywords:Combustion interface; Compound-specific isotope analysis; GC-isotope-ratio mass spectrometry; Isotope-ratio-monitoring; Pyrolysis interface
Issue or Number:12
Record Number:CaltechAUTHORS:20130604-110627696
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Official Citation:Sessions, A. L. (2006), Isotope-ratio detection for gas chromatography. J. Sep. Science, 29: 1946–1961. doi: 10.1002/jssc.200600002
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:38781
Deposited By: Tony Diaz
Deposited On:05 Jun 2013 17:43
Last Modified:09 Nov 2021 23:39

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