High precision magnesium isotope data have been widely used in geological and astrochemical research. Previous studies used cation-exchange resins (e.g., AG50W-X8, AG50W-X12, AGMP-50) for Mg purification of routine geological samples, and these Mg purification protocols yield solutions meeting multiple-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) analytical requirements, but one problem with the reported protocols is that the elution procedure is complex and time-consuming. In addition, some manganese nodule and shale samples have high Mn/Mg mass ratios. Previous studies have used highly concentrated HCl (e.g., 9–12 mol·L?1 HCl) or acetone (95%) to separate Mg from Mn and other elements. However, a low Mn removal efficiency, alongside the toxicity of acetone, may limit the purification of Mg in high-Mn samples (Mn/Mg >16), suggesting that further improvements should be made to the protocol. Here, we developed an efficient, user-friendly, and highly robust protocol for Mg isotope purification and analysis by MC-ICP-MS. Briefly, to isolate Mg from high-Mn matrices, an initial separation from matrix elements (e.g., Mn, Cu, Zn) was performed using AGMP-1M resin (100–200 mesh) eluted with 4.5 mL of 10 mol·L?1 HCl. A subsequent purification step using AG50W-X12 resin (200–400 mesh) was applied to remove major residual matrix elements with a mixed HNO?–HF solution, and Mg was finally collected by elution with 8 mL of 2 mol·L?1 HNO?. With this method, the yield during Mg purification was ~100%, and after one column or a two-column pass, most geological samples were suitable for high-precision Mg isotope analysis. We demonstrate that our method yields accurate Mg isotope ratios with a precision of ±0.07‰ for δ2?Mg, based on analyses of seawater, basalt, granodiorite, shale, manganese nodule, and carbonate reference materials.
CORE (COnnecting REpositories)
CORE (COnnecting REpositories)