| Pressure baseline correction and high-precision CO(2) clumped-isotope (∆(47) ) measurements in bellows and micro-volume modes. | |
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MedLine Citation:
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PMID: 23136015 Owner: NLM Status: In-Data-Review |
Abstract/OtherAbstract:
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RATIONALE: CO(2) 'clumped-isotope' measurements (tracking enrichment of (16) O(13) C(18) O, reported as ∆(47) values, on CO(2) derived from carbonate minerals or the atmosphere) are becoming central to a wide range of geochemical investigations. We present a novel approach to address problems with instrument stability, external precision, and the analysis of small samples that have hampered the advancement of Δ(47) measurements. METHODS: We measured Δ(47) values on CO(2) gases introduced via dual inlet to an isotope ratio mass spectrometer. We developed a method for determining the 'pressure baseline' and integrating a correction to ion beam intensity measurements during analysis. We then tested this approach for both bellows and micro-volume modes of sample introduction. Heated gas and equilibrated gas lines (Δ(47) vs. δ(47) ) established the effectiveness of this correction. RESULTS: We have determined that drift in instrument calibration that compromises Δ(47) measurements results from a shift in the baseline signal on sensitive collectors (m/z 47, 48, and 49) that occurs when gas is admitted to the ion source. Applying a 'pressure baseline' (PBL) correction significantly stabilizes ∆(47) measurements and reduces the dependence of ∆(47) values on δ(47) values by up to an order of magnitude. CONCLUSIONS: PBL-corrected heated gas and equilibrated gas calibrations in bellows and micro-volume modes are nearly identical and stable through time. Introduction of the PBL correction, a revision to the absolute reference frame approach to determining Δ(47) values, dramatically improves the external precision of Δ(47) measurements to near instrumental analytical uncertainty (6-8 ppm (1σ) in bellows mode; 10-12 ppm in micro-volume mode). Copyright © 2012 John Wiley & Sons, Ltd. |
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Authors:
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Bo He; Gerard A Olack; Albert S Colman |
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Publication Detail:
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Type: Journal Article |
Journal Detail:
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Title: Rapid communications in mass spectrometry : RCM Volume: 26 ISSN: 1097-0231 ISO Abbreviation: Rapid Commun. Mass Spectrom. Publication Date: 2012 Dec |
Date Detail:
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Created Date: 2012-11-08 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 8802365 Medline TA: Rapid Commun Mass Spectrom Country: England |
Other Details:
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Languages: eng Pagination: 2837-53 Citation Subset: IM |
Copyright Information:
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Copyright © 2012 John Wiley & Sons, Ltd. |
Affiliation:
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The Department of The Geophysical Sciences, The University of Chicago, 5734 S. Ellis Ave., Chicago, IL, 60637, USA. |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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