Optimization of the radiochemical procedure of Po-210 determination in small amounts of sediment samples

摘要

The radioactivity of alpha emitter radioisotope Po-210 can be used to determine the amount of Pb-210 radionuclide. This radioisotope is commonly used in the dating of marine as well as freshwater lake sediments. In this type of research, the collected samples are small, often 1.5-3 g (wet sediments), especially if we work with sediments taken from mountain lakes. This work presents the problems found with Po-210 determinations in a sample weighting 0.1 or 0.2 g. The analysis is based on the decomposition of samples, the concentration of the analyte, preparing source via spontaneous deposition on a silver discs, and alpha measurements of this source. The aim of this work was to optimize every stage of the procedure. The main assumption of the research was to minimize the weight of samples, the amounts of reagents taken for radiochemical determinations, and to eliminate hydrofluoric acid during the analytical process. The study focused on the optimization of the decomposition of sediments (microwave digestion with concentrated HCl and HNO3 acids), the adsorption of polonium on the container wall in time, and the deposition conditions. The results show that there is a possibility to determine Po-210 in small amounts (0.1-0.2 g) of sediments without using hydrofluoric acid with the yield of radiochemical procedure above 90%. The procedure was checked by reference material, and good accuracy and precision were achieved.