Selective determination of polonium by photon electron rejecting alpha liquid scintillation (PERALS® System) Original Research Article

We developed a fast analysis method for the determination of polonium by alpha liquid scintillation with β–γ rejection in environmental samples. The liquid–liquid extraction with several extractants like HDEHP, TNOA, TOPO or NDA was applied. Among them, the use of the trioctylamine (TNOA) allows the separation of polonium from uranium, plutonium and thorium in a mixture containing 3 M H2SO4 and sodium chloride (2×10−2 to 1 M). The distribution ratio of polonium is over 104, whereas it is only equal to about 10−1 for U, 3×10−2 for Th, and 3×10−3 for Pu. This separation process 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 procedure for the polonium activity measurement in various colorless aqueous solutions. Several difficulties were encountered by using this method to organic matter such as fish or shellfish. A yellow coloration occurs which does not allow 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.