226Ra determination in Japanese river waters by sector field ICP-MS

We describe chemical separation procedure for the determination of 226Ra in natural water samples with sector field ICP-MS (SF-ICP-MS). The proposed procedure is based on the combination of ion exchange and extraction chromatographic resins for preconcentration and separation of Ra from aqueous samples. The Diphonix ion exchange resin has been used for alkali earth cations extraction from natural water samples, followed by the separation of Ra and Ba from Mg, Ca and majority of Sr on the Muromac cation exchanger. Quantitative elution of Ba(Ra) from the resin is achieved using 6.8M HNO3. Final separation of Ra from Ba and the impurity of Sr is performed by the selective retention of Ba and Sr on the Sr-Spec extraction chromatographic resin. Overall chemical recovery for Ra was estimated to be >95%, and pre-concentration factor of 200 was achieved by the developed procedure. It has been shown that sensitivity of SF-ICP-MS is sufficient for 226Ra determination in natural waters after the selective extraction of the analyte. The method has been applied for 226Ra analysis of in river waters collected allover Japan.