Altmetric

Reducing contamination parameters for clumped isotope analysis: The effect of lowering Porapak (TM) Q trap temperature to below-50 degrees C

File Description SizeFormat 
DaviesAndJohn_2017.docxAccepted version3.16 MBMicrosoft WordView/Open
Title: Reducing contamination parameters for clumped isotope analysis: The effect of lowering Porapak (TM) Q trap temperature to below-50 degrees C
Authors: Davies, AJ
John, CM
Item Type: Journal Article
Abstract: Rationale Carbonate clumped isotope thermometry examines the thermodynamic preference of 13C–18O bonds to form within the carbonate crystal lattice. The 13C18O16O isotopologue in analyte CO2 has a natural abundance of 44.4 ppm necessitating stringent purification procedures to remove contaminant molecules that may produce significant isobaric effects within range of the mass 47 isotopologue. Strict purifications of analyte CO2 are thus required as well as reliable contamination indicators. Methods CO2 purification was carried out by vacuum cryogenic purification through a static trap packed with Porapak™ Q (PPQ). The correlation between mass excesses on m/z 47, 48 and 49 in CO2 produced by acid digestion of 12 natural samples was measured by isotope ratio mass spectrometry (IRMS). CO2 from two contaminated carbonate samples was then purified at PPQ trap temperatures between –25 and –65°C and measured by IRMS to determine changes in mass excesses on m/z 47, 48 and 49. Finally carbonate standards, Carrara marble (CM) and ETH3, were purified at PPQ trap temperatures of –35 and –60°C to identify isotopic fractionation associated with lowering trap temperature. Results The correlation between mass excesses on m/z 47, 48 and 49 is determined to be sample dependent. Lowering the PPQ trap temperature to –60°C has a 78% success rate in decreasing Δ48offset, a measure of sample contamination, to within an acceptable range (<1.5 ‰). Lowering the PPQ temperature in purification of CM and ETH3 is associated with decreases in the δ13C and δ18O values as a result of isotopic fractionation. We demonstrate that we can correct for fractionation at a trap temperature of –60°C. Conclusions Lowering the temperature of the Porapak Q trap to –60°C results in improved sample cleaning. It is possible to correct for fractionation in δ13C and δ18O values at lower PPQ trap temperatures using identically prepared standards. This result has important connotations for laboratories using similar sample preparation methods.
Issue Date: 10-Jul-2017
Date of Acceptance: 6-May-2017
URI: http://hdl.handle.net/10044/1/51579
DOI: https://dx.doi.org/10.1002/rcm.7902
ISSN: 0951-4198
Publisher: WILEY
Start Page: 1313
End Page: 1323
Journal / Book Title: RAPID COMMUNICATIONS IN MASS SPECTROMETRY
Volume: 31
Issue: 16
Copyright Statement: © 2017 John Wiley & Sons, Ltd. This is the accepted version of the following article: Davies AJ, John CM. Reducing contamination parameters for clumped isotope analysis: The effect of lowering Porapak™ Q trap temperature to below –50°C. Rapid Commun Mass Spectrom. 2017;31:1313–1323, which has been published in final form at https://dx.doi.org/10.1002/rcm.7902
Keywords: Science & Technology
Life Sciences & Biomedicine
Physical Sciences
Technology
Biochemical Research Methods
Chemistry, Analytical
Spectroscopy
Biochemistry & Molecular Biology
Chemistry
MULTIPLY-SUBSTITUTED ISOTOPOLOGUES
SMALL CARBONATE SAMPLES
MASS-SPECTROMETRY
C-13-O-18 BONDS
CO2
EQUILIBRIUM
THERMOMETRY
MINERALS
GASES
03 Chemical Sciences
04 Earth Sciences
06 Biological Sciences
Analytical Chemistry
Publication Status: Published
Appears in Collections:Faculty of Engineering
Earth Science and Engineering



Items in DSpace are protected by copyright, with all rights reserved, unless otherwise indicated.

Creative Commons