Document Detail

Pressure baseline correction and high-precision CO(2) clumped-isotope (∆(47) ) measurements in bellows and micro-volume modes.
MedLine Citation:
PMID:  23136015     Owner:  NLM     Status:  In-Data-Review    
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.
Bo He; Gerard A Olack; Albert S Colman
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Rapid communications in mass spectrometry : RCM     Volume:  26     ISSN:  1097-0231     ISO Abbreviation:  Rapid Commun. Mass Spectrom.     Publication Date:  2012 Dec 
Date Detail:
Created Date:  2012-11-08     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8802365     Medline TA:  Rapid Commun Mass Spectrom     Country:  England    
Other Details:
Languages:  eng     Pagination:  2837-53     Citation Subset:  IM    
Copyright Information:
Copyright © 2012 John Wiley & Sons, Ltd.
The Department of The Geophysical Sciences, The University of Chicago, 5734 S. Ellis Ave., Chicago, IL, 60637, USA.
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