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Isotope-ratio-monitoring gas chromatography-mass spectrometry: methods for isotopic calibrationIn trial analyses of a series of n-alkanes, precise determinations of 13C contents were based on isotopic standards introduced by five different techniques and results were compared. Specifically, organic-compound standards were coinjected with the analytes and carried through chromatography and combustion with them; or CO2 was supplied from a conventional inlet and mixed with the analyte in the ion source, or CO2 was supplied from an auxiliary mixing volume and transmitted to the source without interruption of the analyte stream. Additionally, two techniques were investigated in which the analyte stream was diverted and CO2 standards were placed on a near-zero background. All methods provided accurate results. Where applicable, methods not involving interruption of the analyte stream provided the highest performance (sigma = 0.00006 at.% 13C or 0.06% for 250 pmol C as CO2 reaching the ion source), but great care was required. Techniques involving diversion of the analyte stream were immune to interference from coeluting sample components and still provided high precision (0.0001 < or = sigma < or = 0.0002 at.% or 0.1 < or = sigma < or = 0.2%).
Document ID
20040089711
Acquisition Source
Headquarters
Document Type
Reprint (Version printed in journal)
Authors
Merritt, D. A.
(Indiana University Bloomington 47405, United States)
Brand, W. A.
Hayes, J. M.
Date Acquired
August 21, 2013
Publication Date
January 1, 1994
Publication Information
Publication: Organic geochemistry
Volume: 21
Issue: 7-Jun
ISSN: 0146-6380
Subject Category
Exobiology
Funding Number(s)
CONTRACT_GRANT: NAGW-1940
Distribution Limits
Public
Copyright
Other
Keywords
NASA Discipline Exobiology
Non-NASA Center

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