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There has been a growing interest in using cadmium (Cd) isotopes to trace the source of Cd contamination and Cd cycling in the Earth surface. Yet it remains technically challenging to precisely and efficiently determine the Cd isotopic compositions of samples with extremely low Cd concentrations due to the imperfect separation of Cd from the matrix and the interference caused by resin-derived organics when TRU Spec resin was used. In this study, we present a two-stage column chromatography system (AG-MP-1M resin + UTEVA resin) for Cd purification. Here, a Prefilter resin combined with UTEVA resin effectively purifies Cd from Sn after the separation of Cd by AG-MP-1M column while keeping the phosphorous organic compounds to an acceptable level. In contrast to TRU Spec resin, which is prone to leaking through the Prefilter resin, we find that UTEVA resin is effectively retained by the Prefilter resin, thus avoiding the P-related anomalous shifts in the Cd isotope measurement (P/Cd < 1). UTEVA resin also exhibits a comparable capacity for purifying Cd from Sn and Mo when compared to TRU Spec resin. The recovery of the two-stage column system is generally higher than 99% and the procedural blank accounting for sample digestion and chemical purification is lower than 20 pg. The Cd isotopic compositions of several reference materials are determined using double spike MC-ICP-MS, with a 111Cd–113Cd double spike pair optimized for the 111Cd, 112Cd, 113Cd, and 114Cd inversion. The δ114/110Cd values of these reference materials relative to NIST SRM 3108 agree within analytical uncertainty with previous studies. The long-term external precision of δ114/110Cd determined based on replicated measurements of BCR-2 is 0.04‰ (n = 10, 2 SD) for a minimum sample size of 10 ng. Our study thus provides an efficient two-stage column system for determining the Cd isotopic compositions of geological samples with relatively low Cd concentrations. [ABSTRACT FROM AUTHOR]

Boron (B) is one of the most powerful tracers of fluid-mediated processes. However, challenges still exist for B analysis of silicate materials with the main difficulty in sample dissolution. Cai et al. (2021) reported a novel alkaline fusion method for boron isotope analysis using solid sodium peroxide and glassy carbon crucibles. Here we report a modified and improved version of this method using hydrated sodium peroxide and silver crucibles, which permits a lower flux-to-sample mass ratio (FSMR) (3 : 1), relatively low fusion temperature of 710 °C, and the use of cheaper silver crucibles. This modified method achieves complete sample dissolution while being safer and more efficient as it removes the need for grinding fresh sodium peroxide solid into powder. The B blank of the hydrated sodium peroxide solution can be determined more accurately and further reduced through chromatography. In addition to the improvements in the alkaline fusion procedure, we also propose a new procedure to dissolve the fusion cake, which greatly reduces reagent usage and minimizes the procedural blank as a result. Using these improved techniques, we analyzed B concentrations and B isotope compositions of eight silicate international standards. The results are consistent with published data within analytical uncertainties. Combined with the one-step chromatography using the Amberlite® IRA-743 B-specific resin to purify B and the Neptune plus® MC-ICP-MS for isotopic analysis, this method generates a batch of B concentration and isotope data within 48 hours with minimal need to handle hazardous chemicals. This safe and efficient method will greatly speed up research using B isotopes on silicate materials. [ABSTRACT FROM AUTHOR]