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A Study on Trapping CO2 Using Molecular Sieve for 14C AMS Sample Preparation

Published online by Cambridge University Press:  09 February 2016

Kyumin Choe*
Affiliation:
National Center for Inter-University Research Facilities, Seoul National University, Seoul 151-742, Korea Department of Nuclear Engineering, Seoul National University, Seoul 151-744, Korea
Sujin Song
Affiliation:
National Center for Inter-University Research Facilities, Seoul National University, Seoul 151-742, Korea
Jang Hoon Lee
Affiliation:
National Center for Inter-University Research Facilities, Seoul National University, Seoul 151-742, Korea
Young Mi Song
Affiliation:
National Center for Inter-University Research Facilities, Seoul National University, Seoul 151-742, Korea
Jin Kang
Affiliation:
National Center for Inter-University Research Facilities, Seoul National University, Seoul 151-742, Korea
Myoung-ho Yun
Affiliation:
National Center for Inter-University Research Facilities, Seoul National University, Seoul 151-742, Korea
Jong Chan Kim
Affiliation:
Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea
*
Corresponding author. Email: kyuminchoe@snu.ac.kr.

Abstract

At the Seoul National University accelerator mass spectrometry (AMS) laboratory, we are planning to develop an automated sample preparation system for higher throughput of radiocarbon dating. This system will consist of several sections, including a combustion line, CO2 trap, graphitization system, and so on. We usually collect CO2 by cryogenic trapping. However, since handling liquid nitrogen is expected to be rather difficult, we are interested in replacing the cryogenic method with the molecular sieve method for the collection of CO2. In this study, we compare the performance of the cryogenic trapping method and molecular sieve method. Zeolite 13X is used as a molecular sieve, and as test samples we use the oxalic acid standard (NIST SRM 4990C), high-purity graphite powder, and archaeological charcoals. The pMC values and the radiocarbon ages (BP) obtained from samples prepared by the above 2 methods are very similar. We especially focused on the memory effect of the molecular sieve, meaning the CO2 contamination from a previous sample, which can cause errors in age determination. To reduce this effect, we flowed He gas through a zeolite container for several minutes at a high temperature before the CO2 was introduced. By the adding this step, we have obtained more reliable results.

Type
Articles
Copyright
Copyright © 2013 by the Arizona Board of Regents on behalf of the University of Arizona 

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