Document Detail

Analytical challenges in the quantitative determination of (2) H/(1) H ratios of methyl iodide.
MedLine Citation:
PMID:  23280974     Owner:  NLM     Status:  In-Data-Review    
RATIONALE: A published method to determine the hydrogen isotope ((2) H/(1) H) ratios of methoxyl groups, cleaved from lignin by hydroiodic acid (HI), calls for the analysis of methyl iodide (CH(3) I). However, analysis of halogenated compounds by gas chromatography/pyrolysis/isotope ratio mass spectrometry (GC/P/IRMS) yields incomplete conversion into H(2) and unwanted HX products post-pyrolysis.
METHODS: We tested analytical capabilities when measuring a pure CH(3) I standard using a GC Isolink pyrolysis furnace at 1420 °C and a DELTA V(Plus) ™ isotope ratio mass spectrometer, both by Thermo Scientific. We added and tested the efficacy of either a secondary reduction furnace containing heated metals or a cold trap to eliminate unwanted HI prior to IRMS analysis for (2) H/(1) H determinations.
RESULTS: While 94% of the hydrogen in CH(3) I is converted into H(2) in GC/P/IRMS, 6% yields HI. The use of either a secondary reduction furnace or cold trap can eliminate HI. However, secondary reduction is untenable given changes in reduction/transmission efficiency and (2) H/(1) H drift. A cold trap provides a pragmatic solution: the δ(2) H values of -97 ‰ were measured from injections of 23-57 µg of CH(3) I to a precision of 4.5 ‰ (n = 26), within the error of the offline measurements.
CONCLUSIONS: We have refined an earlier method to measure the δ(2) H values of CH(3) I by GC/P/IRMS by adding a cold trap to remove HI. This approach should facilitate future experimentation with the measurement of CH(3) I liberated from natural samples for potentially diverse applications including forensic sourcing of wood and tree-wood-based reconstructions of source water. Copyright © 2012 John Wiley & Sons, Ltd.
Sarah J Feakins; Miguel Rincon; Paulina Pinedo
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Rapid communications in mass spectrometry : RCM     Volume:  27     ISSN:  1097-0231     ISO Abbreviation:  Rapid Commun. Mass Spectrom.     Publication Date:  2013 Feb 
Date Detail:
Created Date:  2013-01-02     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8802365     Medline TA:  Rapid Commun Mass Spectrom     Country:  England    
Other Details:
Languages:  eng     Pagination:  430-6     Citation Subset:  IM    
Copyright Information:
Copyright © 2012 John Wiley & Sons, Ltd.
University of Southern California, Department of Earth Sciences, Los Angeles, CA, 90089-0740, USA.
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