Optimization of 210Pb determination via spontaneous deposition of 210Po on a silver disk

The accuracy of 210Pb determination via spontaneous deposition of 210Po on a silver disk and alpha spectrometric measurement was examined. The study focused on the storage conditions of the polonium-containing solutions, the tracer used in polonium analysis and the effect of storage time and acid concentration on 210Po deposition. The intermediate precision and repeatability associated with the improved 210Pb analysis of fresh groundwater samples was 5 and 14%, respectively. These improved values were achieved by using glass bottles as storage containers for the solution remaining from the first 210Po deposition, by rinsing the sample container with concentrated hydrochloric acid after storage and by using different isotopes of polonium as the yield determinant tracer in the first and the second deposition. Less polonium adsorption onto the storage container walls occurred with HCl than with HNO3. The overall uncertainty in 210Pb analysis was (11 ± 7)% at the 95% confidence level. The minimum detectable activity concentration was 0.1 mBq l−1 calculated from blank samples and 0.05 mBq l−1 using the background counts of the alpha spectrometer.