This study presents high-precision analyses of calcium (Ca) isotope ratios using a collision-cell multi-collector inductively coupled plasma mass spectrometer (CC-MC-ICP-MS, Nu Sapphire). This instrument allows Ca isotope measurement in the low resolution mode, requiring much less sample compared with TIMS and conventional MC-ICP-MS, and has additional measurement capability of both radiogenic (ε⁴⁰Ca) and stable isotope ratios (δ^44/40Ca and δ^44/42Ca). The effects of several factors on the precision and accuracy of Ca isotopic data were evaluated, including the total Ca concentration, Ca intensity mismatch between the sample and standard, HNO₃ molarity mismatch between the sample and standard, and the presence of matrix elements. High precision was obtained on 100 ng g⁻¹ Ca samples (i.e., for 6 replicates ∼600 ng of Ca). Accurate measurements require the following conditions: (1) Ca intensities matched within 3% between the sample and standard, (2) low contents of Sr, Mg and Cr (Sr/Ca, Mg/Ca and Cr/Ca ratios need to be lower than 0.01%, and K/Ca, Al/Ca, Ti/Ca and Cr/Ca ratios <1%). Eleven standard reference materials analyzed using the established method yield highly consistent Ca isotope results with literature values. The long-term external precisions are higher than 0.07‰ (2 SD) for δ^44/40Ca and higher than 0.05‰ (2 SD) for δ^44/42Ca. The slope of the fractionation line between δ^44/40Ca and δ^44/42Ca is 1.9616 ± 0.0794, within the error of the slope value from the exponential law.

Here we present an analytical method for Fe isotopic measurements in low resolution mode, using a Nu Sapphire collision cell-equipped multi-collector inductively coupled plasma mass spectrometer by standard-sample bracketing. High Fe sensitivity was obtained through reducing Ar based interference by over 9 orders of magnitude whilst other analytes remained unaffected. The effects of Fe concentration, Fe beam intensity and HNO₃ molarity mismatch between the standard and sample and the presence of matrix elements have been evaluated. The long-term analyses of JMC Fe and BCR-2 indicate that the obtained isotopic ratios are highly reproducible, with precisions of better than ±0.03‰ for δ⁵⁶Fe (2SD). Such accurate and precise data could be acquired via 3 to 6 repeat measurements consuming 50–100 ng Fe, which has improved by a factor 40 compared to those previously reported on other instruments. Accurate measurements were achieved by closely matching Fe intensities between the sample and standard (a 5% mismatch would create a 0.02‰ offset in the ⁵⁶Fe/⁵⁴Fe ratio). On the other hand, the ratio of the concentration between the matrix elements and Fe, such as C_Na/C_Fe, C_Mg/C_Fe, C_Ca/C_Fe, C_Ti/C_Fe and C_Ni/C_Fe, should be kept under 0.1, C_K/C_Fe under 0.3, C_Al/C_Fe and C_Cu/C_Fe under 1, and C_Co/C_Fe and C_Zn/C_Fe under 2 to avoid any matrix effect. In addition, high precision Fe isotopic data were obtained on twenty-one geological reference materials and were highly consistent with the literature values. Furthermore, we obtained δ⁵⁶Fe of standard chalcopyrite (XTC) for the first time: 0.127 ± 0.027‰ (2SD, n = 3).

With single-column chemical purification, highly accurate δ ⁷ Li values for eight international reference materials are presented together with seventeen Chinese geological reference materials from NRCG using the Nu Sapphire.

Effect of K concentration mismatch up to 30% on δ⁴¹K value from RF Ref. of 1.05 V.

Here we present an analytical method for Cu isotopic measurement using standard-sample bracketing on a Nu Sapphire multi-collector inductively coupled plasma mass spectrometer. The effects of Cu concentration and HNO₃ molarity mismatch between the standard and the sample, as well as the presence of matrix elements have been evaluated. Intermediate precision of better than ±0.030‰ for δ⁶⁵Cu (2SD) was routinely obtained on NIST SRM 3114 and NWU-Cu-A. Accurate measurements were achieved when C_Na/C_Cu < 0.5, C_Ti/C_Cu, C_Fe/C_Cu and C_Co/C_Cu < 1, C_Ni/C_Cu < 3 and C_Zn/C_Cu < 10. High-precision Cu isotopic data were determined for nineteen geological reference materials, including igneous rocks, sedimentary rocks, metamorphic rocks and chalcopyrite, with an overall range of ∼0.44‰ (−0.056‰ to 0.384‰), nearly 15 times the current analytical precision. The Cu isotopic data of these reference materials can be used for future interlaboratory comparisons.