Use of cloud point extraction to detect radionuclides in aqueous samples

The identification of nuclear activities such as weapons production, nuclear fuel reprocessing, disposal and accidental releases can be achieved through the detection of anthropogenic radionuclides such as plutonium (Pu), neptunium (Np) and technetium (Tc) in aqueous samples. However, in environmental samples their detection is often complicated by their low concentrations, the presence of other metals and the presence of complex media. Consequently, large volumes of solutions may need to be collected and pre-concentrated prior to analysis. Cloud point extraction (CPE) is an emerging technique which utilizes water as the predominant solvent along with small amounts of inexpensive, environmentally-benign surfactants, such as Triton X-114. Above a certain temperature, identified as the cloud point, a surfactant solution suddenly becomes turbid and subsequently can be separated into two phases: a bulk aqueous phase and a surfactant rich phase, which contains the analyte of interest. CPE has been used to concentrate a wide variety of analytes with high extraction efficiencies and pre-concentration factors, comparable to existing techniques. To date, CPE has not been applied to the isolation of Pu, Np and Tc, but since CPE utilizes the formation of metal-ligand complexes it should be ideally suited to separating these radionuclides. We have investigated the CPE process using Triton X-114 and various chelating ligands to detect these radionuclides in aqueous samples. Here we report on the results of these experiments and our efforts to optimize the process to allow the rapid detection of Pu, Np and Tc in aqueous environmental samples.