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Preparation of Graphite Targets from Small Marine Samples for AMS Radiocarbon Measurements

Published online by Cambridge University Press:  18 July 2016

Laval Liong Wee Kwong ,
Pavel P Povinec  and
J A Timothy Jull
Laval Liong Wee Kwong
Affiliation:
International Atomic Energy Agency, Marine Environment Laboratory, MC 98000 Monaco.
Pavel P Povinec*
Affiliation:
International Atomic Energy Agency, Marine Environment Laboratory, MC 98000 Monaco.
J A Timothy Jull
Affiliation:
NSF Arizona AMS Facility, The University of Arizona, Tucson, Arizona 85721, USA.
*
Corresponding author. Email address: p.povinec@iaea.org.
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Abstract

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A vacuum sample processing line was set up and methods were developed for the determination of radiocarbon in small-volume seawater and biota samples. Seawater samples (500 mL per borosilicate glass bottle and poisoned with HgCl2) were acidified with 5 mL concentrated hydrochloric acid. Pure N2 was used as a carrier gas to strip CO2 from the samples for 10 min in a circulation mode. After purification through several water traps, the CO2 was isolated cryogenically. Using Na2CO3 standard solutions, recovery yields were calculated superior to 95 ± 5%. Freeze-dried marine biota samples were thoroughly mixed with Cu(II)O and combusted at 900°. The CO2 was purified by passing through Ag wool and Cu granules at 450° before reduction to graphite. Finally, graphite was synthesized using Zn dust heated to 450° in the presence of an Fe catalyst at 550°. Although this method takes about 8 hr (synthesis done overnight), the advantage is that no water vapor by-product is formed to hinder the reaction. The graphite yields, measured both by gravimetric methods and by pressure readings, were 95 ± 5%. Accelerator mass spectrometry (AMS) measurements were carried out at the NSF-Arizona AMS Facility. Results for water samples from the northwest Pacific Ocean are reported which are in agreement with data reported elsewhere.

Type
Articles
Information
Radiocarbon , Volume 46 , Issue 1: Proceedings of the 18th International Radiocarbon Conference (Part 1 of 2), Conference Editors: Nancy Beavan Athfield, Rodger J Sparks , 2004 , pp. 133 - 139
Copyright
Copyright © 2004 by the Arizona Board of Regents on behalf of the University of Arizona 

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