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dc.contributor.authorVerkouteren, R. Michael
dc.contributor.authorKlinedinst, Donna B.
dc.contributor.authorCurrie, Lloyd A.
dc.date.accessioned2021-02-11T20:44:37Z
dc.date.available2021-02-11T20:44:37Z
dc.date.issued1997-01-01
dc.identifier.citationVerkouteren, R. M., Klinedinst, D. B., & Currie, L. A. (1997). Iron-manganese system for preparation of radiocarbon AMS targets: Characterization of procedural chemical-isotopic blanks and fractionation. Radiocarbon, 39(3), 269-283.
dc.identifier.issn0033-8222
dc.identifier.doi10.1017/S003382220005325X
dc.identifier.urihttp://hdl.handle.net/10150/653636
dc.description.abstractWe report a practical system to mass-produce accelerator mass spectrometry (AMS) targets with 10-100 micrograms carbon samples. Carbon dioxide is reduced quantitatively to graphite on iron fibers via manganese metal, and the Fe-C fibers are melted into a bead suitable for AMS. Pretreatment, reduction and melting processes occur in sealed quartz tubes, allowing parallel processing for otherwise time-intensive procedures. Chemical and isotopic (13C, 14C) blanks, target yields and isotopic fractionation were investigated with respect to levels of sample size, amounts of Fe and Mn, pretreatment and reduction time, and hydrogen pressure. With 7-day pretreatments, carbon blanks exhibited a lognormal mass distribution of 1.44 micrograms (central mean) with a dispersion of 0.50 micrograms (standard deviation). Reductions of 10 micrograms carbon onto targets were complete in 3-6 h with all targets, after correction for the blank, reflecting the 13C signature of the starting material. The 100 micrograms carbon samples required at least 15 h for reduction; shorter durations resulted in isotopic fractionation as a function of chemical yield. The trend in the 13C data suggested the presence of kinetic isotope effects during the reduction. The observed CO2-graphite 13C fractionation factor was 3-4% smaller than the equilibrium value in the simple Rayleigh model. The presence of hydrogen promoted methane formation in yields up to 25%. Fe-C beaded targets were made from NIST Standard Reference Materials and compared with graphitic standards. Although the 12C ion currents from the beads were one to two orders of magnitude lower than currents from the graphite, measurements of the beaded standards were reproducible and internally consistent. Measurement reproducibility was limited mainly by Poisson counting statistics and blank variability, translating to 14C uncertainties of 5-1% for 10-100 micrograms carbon samples, respectively. A bias of 5-7% (relative) was observed between the beaded and graphitic targets, possibly due to variations in sputtering fractionation dependent on sample size, chemical form and beam geometry.
dc.language.isoen
dc.publisherDepartment of Geosciences, The University of Arizona
dc.relation.urlhttp://radiocarbon.webhost.uits.arizona.edu/
dc.rightsCopyright © by the Arizona Board of Regents on behalf of the University of Arizona. All rights reserved.
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/
dc.subjectmanganese
dc.subjectparallel processing
dc.subjectsample size
dc.subjectquantitative analysis
dc.subjectiron
dc.subjectstandardization
dc.subjectisotope fractionation
dc.subjectsize
dc.subjectstandard materials
dc.subjectgraphite
dc.subjectnative elements
dc.subjectisotope ratios
dc.subjecttechniques
dc.subjectdata processing
dc.subjectaccelerator mass spectroscopy
dc.subjectmass spectroscopy
dc.subjectspectroscopy
dc.subjectmetals
dc.subjectsample preparation
dc.subjectmethods
dc.subjectgeochronology
dc.subjectC 14
dc.subjectcarbon
dc.subjectisotopes
dc.subjectradioactive isotopes
dc.subjectC 13 C 12
dc.subjectstable isotopes
dc.subjectabsolute age
dc.subjectC 13
dc.titleIron-Manganese System for Preparation of Radiocarbon AMS Targets: Characterization of Procedural Chemical-Isotopic Blanks and Fractionation
dc.typeArticle
dc.typetext
dc.identifier.journalRadiocarbon
dc.description.noteThis material was digitized as part of a cooperative project between Radiocarbon and the University of Arizona Libraries.
dc.description.collectioninformationThe Radiocarbon archives are made available by Radiocarbon and the University of Arizona Libraries. Contact lbry-journals@email.arizona.edu for further information.
dc.eprint.versionFinal published version
dc.description.admin-noteMigrated from OJS platform February 2021
dc.source.volume39
dc.source.issue3
dc.source.beginpage269
dc.source.endpage283
refterms.dateFOA2021-02-11T20:44:37Z


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