210 Po (t 1/2 =138.38 d) occurs naturally via 210 Pb (t 1/2 =22.3 y) and 210 Bi (t 1/2 =5.15 d) in the 238 U decay chain. The contribution of 210 Pb, 210 Bi and 210 Po to the internal radiation dose to human has been estimated to be around 8%.1 Various analytical methods have been applied to the separation and determination of 210 Po. 2,3 Recently, a crown ether loaded extraction chromatographic resin (EiChroM Sr.Spec™) was applied to the selective separation of Pb and Po in several samples. Vajda et al. determined the distribution coefficients of Bi, Pb and Po on Sr.Spec™ in 0.5 -8 M HCl, and developed a large-column method for the separation of 210 Pb and 210 Po in standard samples. 4 The resin was applied to the separation of Pb ( 210 Pb) for measurements by thermal ionization mass spectrometry 5 , graphite furnace atomic absorption spectrometry 6 and liquid scintillation counting. 7 However, the distribution coefficients for Fe and Cu on the resin in a HNO 3 and HCl solution are not available in the literature.In this study, the weight distribution coefficients of Fe, Cu, Pb, Bi and Po on the resin in HCl and HNO 3 solutions were determined using a batch equilibrium method, after which the elution behavior of Po and several elements from the resin column was examined. Subsequently, the coprecipitation behavior of Pb and Po on CuS was examined. The plating condition was investigated for counting samples in the alpha ray spectrometry of Po. Moreover, the loss of Po in ashing samples was examined because of its volatility. From a series of investigations, it was found that Pb and Po were effectively isolated from interference elements using a Sr.Spec™ resin short column (2 ml).Finally, a combination of coprecipitation and Sr.Spec™ resin separation was developed for the determination of 210 Pb and 210 Po in several standard materials (sediments, soils) and biological samples (shellfish, seaweed) by alpha ray spectrometry.
Experimental
Alpha ray measurementsAn EG &G ORTEC Model 576A alpha ray spectrometer with a Canberra [passivated ion-implanted planar silicon (PIPS) detector having 450 mm 2 of an active area] was used for alpha ray measurements. The counting efficiencies, determined by measuring JRIA (Japan Radioisotope Association) standard uranium sources, were typically 20 -30% with this arrangement. The energy resolutions, determined with LMRI (Laboratoire de Métrologie des Rayonnements Ionisants, France) standard 243 Am sources, were typically 20 -40 keV full width at the half-maximum peak height (FWHM) at 5.47 MeV.
TracerThe 208 Po tracer solution supplied by AEA Technology, UK was diluted to activity concentration of approximately 60 mBq/ml in 1 M HCl, and stored in a Teflon bottle.
ReagentsAll of the reagents used were of analytical grade. Water was purified with an ORGANO PURIC Model-S Po were 0.6 mBq/sample at a counting time of 70000 s.
