A rapid and simple single-step method for Mg separation from carbonates for isotopic analysis by MC-ICP-MS

Abstract

A new simple and rapid method was developed for the purification of Mg from carbonate samples, especially for calcite-rich carbonates. The proposed separation protocol consists of only two types of eluents (4 mol l⁻¹ HNO₃ and deionized water) based on 2 ml of DGA resin. 4 ml of HNO₃ can effectively separate Mg from calcite-rich carbonates with a high yield within one hour. The Mg elution curve would not drift with different Mg and Ca loading onto the DGA resin. Ca/Mg ratios of the purified samples could be reduced by five orders of magnitude compared to the unpurified calcite-rich carbonate samples. The precision and accuracy of this new method have been evaluated by measurements of the synthetic solution, carbonate standard material, and ten readily available Chinese carbonate reference materials. All the Mg isotopic analytical results were, within analytical uncertainties, essentially identical with the data published previously. Therefore, the new method can be a great option for purifying Mg from carbonate samples for isotopic analysis.