An improved method for the determination of uranium isotopes in environmental samples by alpha-spectrometry

In order to improve the selectivity of the uranium isotopes determination in environmental samples, further studies have been carried out, including (1) interference of Po-210 with uranium isotope determination, (2) distribution coefficients of polonium between 5% TOPO in toluene and aqueous hydrochloric and nitric acids, (3) decontamination factor of uranium from polonium of the recommended procedure, and (4) leaching effect comparison of two different leaching procedures in a lichen sample. Based on the new findings, a more accurate extraction chromatographic/alpha-spectroscopy method has been developed. For the method's validation, four kinds of reference materials supplied by the IAEA have been tested. It is observed that nearly all the U-238, U-234 and U-235 concentrations obtained are in good agreement with the recommended or information values, showing that the method can give reliable results. A comparison with existing uranium determination methods has also been made. It is concluded that due to involving preconcentration and chemical separation, the extraction chromatographic/alpha-spectroscopy method is a more selective, very sensitive and accurate, and low cost method.