Ion exchange separation of strontium and rubidium on Dowex 50W-X8, using the complexation properties of EDTA and DCTA

• Published in: Analytical and bioanalytical chemistry Vol. 392; no. 1-2; pp. 287 - 296
• Main Authors: Vorster, C, van der Walt, T. N, Coetzee, P. P
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Berlin/Heidelberg : Springer-Verlag 01.09.2008; Springer-Verlag
• Subjects: Analytical Chemistry; Biochemistry; Characterization and Evaluation of Materials; Chemistry; Chemistry and Materials Science; DCTA; EDTA; Food Science; Ion exchange separation; Laboratory Medicine; Monitoring/Environmental Analysis; Original Paper; Rb separation; Sr separation; Ion exchange separation; DCTA; EDTA; Rb separation; Sr separation
• ISSN: 1618-2642; 1618-2650
• DOI: 10.1007/s00216-008-2260-0

A chromatographic method for separation of strontium from rubidium, using the unique alkaline-earth metal complexation ability of the carboxylic acids EDTA and DCTA is proposed. The method was developed in order to improve the effectiveness of ⁸⁷Sr/⁸⁶Sr isotope studies with ICP-QMS. Due to the isobaric overlap of ⁸⁷Rb with ⁸⁷Sr, strontium needs to be separated from rubidium prior to sample analysis with ICP-QMS. The method involves the retention of strontium, calcium, magnesium, and rubidium on Dowex 50W-X8 resin in its NH₄ ⁺ form, followed by elution of the divalent cations as metal EDTA or DCTA complexes. Because divalent cations have different EDTA and DCTA complex formation constants, it is possible to separate them under the correct conditions. Neither EDTA nor DCTA form complexes with alkali metals, thus rubidium remains retained by the column and is later eluted using HNO₃. Both EDTA and DCTA elution methods were tested with different concentrations of the elements to determine the effect of increased concentration on separation efficiency. The EDTA elution procedure was proved to be effective in separating strontium from both calcium and rubidium, while the DCTA method was found to be even more effective, because strontium is separated from all the elements involved in this study.