Method for Detection of Cs and Sr Isotopes Avoiding Interferences of Ba and Rb in Radioactive Samples using Ion Chromatography Coupled with ICP-MS

A simple and fast on-line chromatographic procedure has been developed for separation of ¹³⁴Cs, ¹³⁵Cs, ¹³⁷Cs and ⁸⁷Sr ions from interfering isotopes of ¹³⁴Ba, ¹³⁵Ba, ¹³⁷Ba and ⁸⁷Rb. This analytical method offers the possibility to measure the chromatograms of Rb, Cs, Sr and Ba isotopes using ICP-MS technique in isocratic conditions in one run. For the separation, the oxalic acid neutralized with ammonia could be used as the main component of the mobile phase. For specialized ion chromatography (IC) column IonPac CS5A and standard HPLC column Zorbax SCX300, an optimal concentration of oxalic acid has been fixed at 0.1 mol/L and eluent pH range has been fixed at 4.5-5.5. Under these conditions, the retention time of all four elements did not exceed 15 minutes. Our observations demonstrate that the sample injection volume can be increased up to 1 mL. The application of the method for the determination of ¹³⁴Cs, ¹³⁵Cs, ¹³⁷Cs and some isotopes of Rb, Sr and Ba in sample from spent nuclear fuel storage has been demonstrated. Activity of ¹³⁴Cs and ¹³⁷Cs calculated from ICP-MS data is comparable to the gamma spectroscopy data.