Effects of oxygen plasma ashing treatment on carbonate clumped isotopes
Author(s)
Adlan, Qi
Davies, Amelia J
John, Cedric M
Type
Journal Article
Abstract
Rationale:For clumped isotope analysis (Δ47), hydrocarbon and organic moleculespresent an important contaminant that cannot always be removed by CO2purification through a Porapak-Q trap. Low-temperature oxygen plasma ashing (OPA)is a quick and easy approach for treatment; however, the impact of this treatment onthe original carbonate clumped isotope values has never been fully studied.Methods:We tested the isotopic impact of OPA using three natural samples with alarge range of initialΔ47values. Crushed and sieved (125μm mesh) samples wereplaced into a Henniker Plasma HPT-100 plasma system and treated at a flow rate of46 mL/min and a power of 100 W at a vacuum of 0.2 mbar for 10, 20, 30 and60 min before clumped isotope analysis using two MAT 253 isotope ratio massspectrometers modified to measure masses 44–49.Results:OPA treatment for 30 min or more on calcite powder samples has thepotential to alter the clumped isotopic composition of the samples beyond analyticalerror. A systematic positive offset is observed in all samples. The magnitude of thisalteration translates to a temperature offset from known values ranging from 4 Cto13 C. We postulate that the observed positive offset inΔ47occurs because thebonds within lighter isotopologues are preferentially broken by plasma treatment,leading to an artificial increase in the‘clumping’value of the sample.Conclusions:We recommend that any laboratory performing OPA treatments shouldreduce the runs to 10–20 min or carry out successive runs of 10 min followed bysample stirring, as this procedure showed no alteration in the initialΔ47values. Ourresults validate the use of OPA for clumped isotope applications and will allow futureresearch to use clumped isotopes for challenging samples such as oil-stainedcarbonates, bituminous shales or host rocks with very high organic carbon content.
Date Issued
2020-05-23
Date Acceptance
2020-03-30
Citation
Rapid Communications in Mass Spectrometry, 2020, 34 (14)
ISSN
0951-4198
Publisher
Wiley
Journal / Book Title
Rapid Communications in Mass Spectrometry
Volume
34
Issue
14
Copyright Statement
© 2020 The Authors. Rapid Communications in Mass Spectrometry published by John Wiley & Sons Ltd
License URL
Identifier
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000534817600001&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
Subjects
Science & Technology
Life Sciences & Biomedicine
Physical Sciences
Technology
Biochemical Research Methods
Chemistry, Analytical
Spectroscopy
Biochemistry & Molecular Biology
Chemistry
STABLE-ISOTOPES
PHOSPHORIC-ACID
TRAP TEMPERATURE
ORGANIC-MATTER
THERMOMETRY
CALCITE
DOLOMITIZATION
FRACTIONATION
SKELETAL
RECRYSTALLIZATION
Publication Status
Published
Article Number
ARTN e8802