Publications

Studies on the Preparation of Small 14C Samples with an RGA and 13C-Enriched Material

Author(s)

Jakob Liebl, Roswitha Avalos Ortiz, Robin Golser, Florian Handle, Walter Kutschera, Peter Steier, Eva Maria Wild

Abstract

The minimum size of radiocarbon samples for which reliable results can be obtained in an accelerator mass

spectrometry (AMS) measurement is in many cases limited by carbon contamination introduced during sample preparation

(i.e. all physical and chemical steps to which samples were subjected, starting from sampling). Efforts to reduce the sample

size limit down to a few ƒÝg carbon require comprehensive systematic investigations to assess the amount of contamination

and the process yields. We are introducing additional methods to speed up this process and to obtain more reliable results. A

residual gas analyzer (RGA) is used to study combustion and graphitization reactions. We could optimize the reaction process

at small CO2 pressures and identify detrimental side reactions. Knowing the composition of the residual gas in a graphitization

process allows a reliable judgment on the completeness of the reaction. Further, we use isotopically enriched 13C („d98% 13C)

as a test material to determine contamination levels. This offers significant advantages: 1) The measurement of 12C/13C in CO2

is possible on-line with the RGA, which significantly reduces turnaround times compared to AMS measurements; 2) Both the

reaction yield and the amount of contamination can be determined from a single test sample.

The first applications of isotopically enriched 13C and the RGA have revealed that our prototype setup has room for improvements

via better hardware; however, significant improvements of our sample processing procedures were achieved, eventually

arriving at an overall contamination level of 0.12 to 0.15 ƒÝg C during sample preparation (i.e. freeze-drying, combustion,

and graphitization) of ƒÝg-sized samples in aqueous solution, with above 50% yield

Organisation(s)

Isotope Physics

Journal

Radiocarbon

Volume

Pages

1394-1404

No. of pages

ISSN

0033-8222

Publication date

2010

Peer reviewed

Yes

Austrian Fields of Science 2012

103005 Atomic physics

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