Low-level assay of 3H and 14C MDA limits with conventional liquid scintillation counters using the ‘LOLES’ procedure

This paper presents the results obtained with a conventional liquid scintillation counter using the procedure LOLES, developed to compensate the intrinsic and cosmic background variations. Low-level 3H and 14C samples of decreasing activity, down to the minimum detectable activity limits, have been assayed and their values compared to those obtained with conventional methods. The procedure enabled us to decrease the practical detection limits of a high background (90 cpm for 20 ml) general purpose counter down to 2.2 Bq L−1 for 3H and 2.9 Bq L−1 for 14C.