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Target preparation for continuous flow accelerator mass spectrometry.

Robert J Schneider, J M Hayes, Reden F von, Ann P McNichol, T I Eglinton, J C Wills

Abstract


For very small samples, it is difficult to prepare graphitic targets that will yield a useful and steady sputtered ion beam. Working with materials separated by preparative capillary gas chromatography, we have succeeded with amounts as small as 20 mu g C. This seems to be a practical limit, as it involves 1) multiple chromatographic runs with trapping of effluent fractions, 2) recovery and combustion of the fractions, 3) graphitization and 4) compression of the resultant graphite/ cobalt matrix into a good sputter target. Through such slow and intricate work, radiocarbon ages of lignin derivatives and hydrocarbons from coastal sediments have been determined. If this could be accomplished as an "online" measurement by flowing the analytes directly into a microwave gas ion source, with a carrier gas, then the number of processing steps could be minimized. Such a system would be useful not just for chromatographic effluents, but for any gaseous material, such as CO (sub 2) produced from carbonates. We describe tests using such an ion source.

Keywords


compression;microwave spectroscopy;gas chromatography;lignin;petroleum;volume;combustion;ions;gaseous phase;graphitization;graphite;native elements;accelerator mass spectroscopy;mass spectroscopy;spectroscopy;organic compounds;sample preparation;methods;C 14;carbon;isotopes;radioactive isotopes;carbon dioxide;absolute age;carbonates

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