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In this study, we provide a microsampling method that determines the Cu isotopic composition of copper-bearing minerals using the microdrill sampling and MC-ICP-MS measurement. Eleven different natural copper minerals were sampled with microdrill and analyzed using MC-ICP-MS after digestion for half an hour on a 140 °C hot plate without chromatography. The Cu isotope results were calibrated using the standard sample bracketing combined with NIST 994 Ga as the internal standard. Cu isotope compositions of the same sample processed with chromatography were also determined to verify the accuracy of this method. Results have shown that δ65Cu of all sample solutions with or without chromatography are overlapped and the deviations between them are less than 0.04‰, indicating this method is applicable to most natural copper-bearing minerals. All the microdrill-sampled copper minerals were directly digested without chemical purification, thus potential matrix elements, including metal cations and some anions, still existed in the solutions. The matrix effects of metal cations and anions were systematically investigated in this study. Results have shown that the δ65Cu deviations are less than 0.05‰ within the uncertainty when the concentration ratios of matrix elements Zn, Fe, Ni, Al, Sb, and Co/Cu + S were less than 2, Ti/Cu + S ≤ 0.8, and Mn/Cu + S ≤ 0.5. This method has the merits of saving time and reagents, low background, good accuracy and reliability as well as improved spatial resolution. It is easier to achieve in most isotope laboratories compared to other microsampling methods such as laser ablation method. This study represent determination of δ65Cu of Cu-bearing minerals using microdrills and MC-ICP-MS without chromatography Image 1. • A microsampling procedure of Cu isotope determination was processed using MC-ICP-MS and microdrill without chromatography. • This procedure simplifies the digestion procedure, combines the advantage of high precision of MC-ICP-MS with spatial resolution. Furthermore, there is no needs of matrix matched reference compare to LA-MC-ICP-MS. • Eleven copper bearing minerals were applied to verify the reliability and robustness of our analytical protocol, including native copper, cooper sulfides, carbonates copper chloride. [ABSTRACT FROM AUTHOR]

This study presented a chemical protocol for purification of calcium and magnesium from a single aliquot of biological and geological samples. The separation protocol was based on a two-step cation exchange chromatography using DGA resin and AG50W-X12 (200–400 mesh) resin. Calcium fraction was first collected using 0.25 mL of DGA resin, and Mg fraction was then collected using 0.5 mL of AG50W-X12 cation exchange resin. For Ca isotope analysis, the effect of acidity and concentration mismatch as well as the matrix effect were rigorously evaluated using the Neptune Plus MC-ICP-MS with a wet-plasma mode. Based on repeated measurements on BHVO-2 and NIST SRM 1400, the long-term reproducibility was evaluated at 0.08‰ (2SD) for δ44/42Ca 915a. The δ26Mg ratios of the analyzed reference materials varied from −1.22‰ to 0.03‰ with the external precision better than 0.11‰ (2SD). The robustness of the protocol has been validated by replicated analyses of biological and geological standards. Calcium and magnesium isotopic ratios of all reference materials measured in this study agreed well with previous data within uncertainties. Therefore, the proposed method can be used for simultaneous determination of Ca and Mg isotopic ratios from a single aliquot of biological and geological samples. Image 1 • Purification of calcium and magnesium from a single aliquot of biological and geological samples. • Mg isotopic ratios of GSH-1, GSV-3, NIST SRM 1400, and NISR SRM 1486 were reported for the first time. • The method reduces the amount of acid used, saves time and is more efficient. [ABSTRACT FROM AUTHOR]