Large-Volume Liquid Scintillation Counting of Carbon-14

Abstract

Efforts have been undertaken to further improve the relatively simple technique of low-level liquid scintillation counting of 14 C. Two different approaches have been made. By synthesizing more benzene for 14 C measurement than usual (with up to 19.5g of carbon) an experimental detection limit of about 0.1 percent modern has been achieved (97.5% confidence level, 1000 min). Absorption of CO 2 with up to 5.3g of carbon in 160ml of an absorbent-scintillation solution and counting in a special measuring chamber resulted in an experimental detection limit of about 1 percent modern, with the sample preparation taking only 1 hour. The detection limits achieved by the two techniques correspond to 14 C ages of about 55,000 and 35,000 years BP, respectively.