engleski

Measurement of Low 14C Activities in Liquid Scintillation Counter in the Zagreb Radiocarbon Laboratory

Two methods of chemical preparation of 14C samples are implemented in the Zagreb Radiocarbon Laboratory for measurement by a new liquid scintillation counter (LSC), Quantulus 1220TM: a CO2 absorption method (LSC-A) and a benzene synthesis method (LSC-B). For samples prepared by both methods the optimal counting windows for measurement in LSC were determined. The total efficiency of LSC-A method is 65% and that of LSC-B 83%, while the corresponding 14C dating limits are 31, 800 yr and 52, 160 yr. 14C activities measured by LSC-A and LSC-B methods were compared with those measured by the gas proportional counter (GPC) method (efficiency 75%, 14C dating limit 37, 500 yr). The results obtained by the LSC-A method have larger errors than those measured by the GPC method, but the method is quick, cheep and simple, and requires less carbon than the GPC method. It is suitable for 14C measurements of geological, hydrological and environmental samples. The results obtained by the LSC-B method give smaller errors and larger 14C dating range. Therefore, the LSC-B method is more suitable for 14C dating of archaeological samples.

14C dating; preparation; CO2 absorption; benzene synthesis

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