Classical versus multivariate calibration for a beta emitter (14C) activity determination by liquid scintillation counting

Liquid Scintillation (LS) is a radiochemistry technique mainly used to quantify beta emitters. It is time consuming when low activity samples are determined. Using 14C as an example, classical procedures of counting efficiency and activity determination are compared with Multivariate Calibration (MVC, PLS), for a series of solutions of different activities and compositions. The predicted activities have precisions in accordance with the theoretical uncertainties, accuracies for a single determination of 0.1 dpm and detection limits of 0.1 dpm in both approaches. The MVC approach does not need background information and therefore total counting time is reduced. Moreover, in this approach, the factors found can be clearly attributed to physical causes: 14C content, quenching and lack of spectra reproducibility.