Optimisation of liquid scintillation counting conditions for rapid tritiumdetermination in aqueous samples

Several studies were carried out to optimise rapid tritium analysis in fres h waters by ultra-low background liquid scintillation. These included the o ptimisation of (1) sample/scintillant ratio, (2) pulse shape analysis, and (3) pulse-amplitude comparator, and studies concerning (1) the combination scintillant/vial and (2) the effect of chemiluminescence. The proposed meth od involves the mixing of 8 mi sample with 12 mi scintillation cocktail Ult ima Gold AB in Zinsser low diffusion vials. These are stored during one day before counting in order to reduce chemiluminescence. The minimum detectab le activity achieved was 2.2 Bq . l(-1) for a total counting time of 360 mi nutes. In order to test the method, tritium was determined in Ebro river sa mples.