Comparative study of different methods for the activity quantification of (3)H and (14)C radionuclides in dual labeled samples using liquid scintillation analyzer.

Different methods such as full spectrum DPM (FSDPM), dual isotope estimation and inclusion methods were studied for the activity quantification of (3)H and (14)C in dual beta labeled samples using liquid scintillation analyzer. A standardized Packard tritiated water was used as tritium source and (14)C activity was standardized by CIEMAT/NIST method and compared with the results obtained by the above three methods. Minimum detectable activity was 2100dpm/l for (3)H and 1200dpm/l for (14)C with a counting time of 300min. The accuracy of the results obtained was found to be within +/-10% for (3)H: (14)C activity ratios 1:1, 1:2, 2:1, 6:1, 9:1, 13:1 and 18:1.