Application of α/β discrimination in liquid scintillation counting for the purity control of 99mTc medical solutions

Tc-99m is a widely used nuclide in nuclear medicine for diagnosis. Tc-99m solutions are eluted from Mo-99/Tc-99m generators as sodium chloride solutions. As the Mo-99 source is a fission product extracted from the reprocessing of nuclear fuel, one might expect the presence of radioactive impurities. One point of special concern described in the 1997 European Pharmacopoeia (1996) is the possible contamination in alpha-impurities (U, Pu, Am, Cm, ...) which must be very low. In order to check this impurity concentration, we used liquid scintillation counting (LSC) with alpha/beta discrimination and a commercial extractive scintillator, Alphaex(R). We first made measurements using synthetic mixtures of alpha and beta-emitters and then using the real effluent. This paper describes the measurement procedure used with the optimum chemical conditions for a correct extraction of the alpha-emitting nuclides. The sensitivity of the method is also described from the measurements made using the real effluent with an addition of a quantitative amount of alpha particle contamination. (C) 2000 Published by Elsevier Science Ltd. All rights reserved.