We report a modified procedure for separating Mg and Al from meteorites and terrestrial igneous rocks for high-precision analysis of Mg isotopes with multiple collector-inductively coupled plasma-mass spectrometry. The separating procedure was carried out in a single ion-exchange column filled with AG50W-X12 resin, and Mg was eluted with 1 M HNO3, followed by Al eluted with 4M HNO3. The modified procedure efficiently eliminates most matrix elements (except for Ni, Co, and Cu) with a recovery yield of Mg > 99%. Measurements of Ni-, Co-, and Cu-bearing simulation solutions revealed no detectable matrix effects. However, test runs demonstrated significant mass-dependent fractionation during the chromatographic process; consequently, a high recovery yield of Mg (>99%) is required to limit the deviation to less than 0.05‰. Furthermore, analysis of Mg standard solution with a wide range of concentrations demonstrated negligible deviation for samples with concentrations of 0.3–2.5 μg ml−1Mg relative to Mg standard solution concentrations of 1 μg ml−1Mg. The total procedure bank is less than 2 ng. The long-term reproducibility of instrumental measurements of Mg isotopes is ±0.05‰ for δ25Mg, ±0.10‰ for δ26Mg, and ±0.06‰ for δ26Mg* (2 SD, n = 211), based on analyzing five pure Mg standard solutions. Analysis of three chondrites and seven igneous rock standards showed ranges of δ26Mg(DSM3) from 0.02‰ to 0.30‰ for the former and from 0.03‰ to 0.30‰ for the latter. This method is simple and actionable.
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