Selective determination of polonium by photon electron rejecting alpha liquid scintillation (PERALS (R) System)

We developed a fast analysis method for the determination of polonium by al pha liquid scintillation with beta-gamma rejection in environmental samples . The liquid-liquid extraction with several extractants like HDEHP, TNOA, T OPO or NDA was applied. Among them, the use of the trioctylamine (TNOA) all ows the separation of polonium from uranium, plutonium and thorium in a mix ture containing 3 M H2SO4 and sodium chloride (2 x 10(-2) to 1 M). The dist ribution ratio of polonium is over 10(4), whereas it is only equal to about 10(-1) for U, 3 x 10(-2) for Th, and 3 x 10(-3) for Pu. This separation pr ocess was applied with success to large volume of aqueous solution (250 ml) . The detection limit is below 1 mBq l(-1) for 200 ml of solution and for a counting time equal to 1000 min. We also successfully applied this procedu re for the polonium activity measurement in various colorless aqueous solut ions. Several difficulties were encountered by using this method to organic matte r such as fish or shellfish. A yellow coloration occurs which does not allo w a measurement. Moreover, the volatility of polonium compounds unables the use of conventional dissolution methods for organic matter. These problems are also discussed in this paper. (C) 2000 Elsevier Science B.V. All right s reserved.