Evaporation-free tandem-column separation for Sr from geological samples with high Rb/Sr ratios

A novel tandem column method was devised for effective purification of Sr from geological samples characterized by relatively high Rb/Sr ratios, employing a strategic sequence of columns of AG50-X12 cation resin, Chelex-100 chelating resin and AG50-X8 cation resin. The process initiates with the AG50-X12 column to remove most of the matrix elements, followed by the Chelex-100 column to remove the residual Rb under alkaline conditions despite its inability to adsorb alkali metals such as Na, K, and Rb. The Sr fraction was eluted directly into the Chelex-100 column from the AG50-X12 column by a NH3-NH4Cl solution. The final purification through the AG50-X8 column to eliminate residual NH4Cl ensures the effective removal of matrix elements (such as K, Na, Li, Ti, Al, Fe, Mg, Mn and Ca) and Rb. The Chelex-100 resin acts comparatively to a similar Sr-specific resin for Rb and Sr. This method proved its efficacy and precision by aligning the Sr isotopic ratios from a range of reference materials, (JR-1, JR-2, JB-2, BCR-2, BHVO-2, W-2, GSP-2, CRPG Mica-Mg, CRPG Mica-Fe and NIST SRM 987) with their published values, demonstrating its reliability for Sr isotope analysis in complex geological matrices. [Display omitted] •Sr is isolated from Rb rich samples and the interference of Rb is completely eliminated.•The tedious evaporation and medium conversion steps between multi-columns are avoided.•The interference of Yb and Er on Sr is eliminated.•Lower cost than Sr-spec resin•Elution of AG50–12 and chelex-100 with NH3-NH4Cl buffer solution