Accurate Measurement of Mg Isotopes in Twenty-four Reference Materials by MC-ICP-MS with A Highly Efficient Optimized Method

The purification of Mg requires the separation of Mg from matrix elements, which is the prerequisite for the accurate determination of Mg isotopic compositions. With the rapid development of instrumental technology, the purification process has played an important role in affecting the efficiency of isotopic measurement. This study reported a highly efficient optimized method based on the combination of precipitation process and chromatographic procedure to finish purification process within nine hours, which improved the purification efficiency. The precipitation procedure is used to remove K and optimized 2N HNO3 is proposed for collecting Mg fraction, which shortens the time in chromatographic process. With the popularization of Mg isotope analytical method and the wide application of Mg isotope in the geosciences, the existing reference materials with confirmed delta Mg-26 values are being consumed more, and there is a situation of short supply. After the verification of eleven different types of reference materials with confirmed Mg isotopic compositions using established purification process, the delta Mg-26 values of thirteen reference materials were firstly reported for broadening the selection of reference materials. In addition, the Mg concentration mismatch effect and acid molarity mismatch effect were further evaluated using Neptune Plus MC-ICP-MS in wet plasma mode. The long-term instrumental stability was assessed by repeated analysis of the in-house standard GSB-Mg, which yielded delta Mg-26 and delta Mg-26 of 0.00 +/- 0.02% (2 SD, n = 106) and 0. 00 +/- 0.04% (2 SD, n = 106), respectively.