Measurement on high-precision boron isotope of silicate materials by a single column purification method and MC-ICP-MS

Abstract

A method with simplified chemical treatment has developed to determine high-precision δ¹¹B in silicate rocks by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) using sample-standard-bracketing (SSB) mode. Boron in silicate rocks was extracted by digesting with HF, and purified by a single ion-exchange chromatographic step through a column filled with AG MP anion resin. Only one dryness process was involved in the entire chemical treatment procedure. This simplified procedure diminishes the risk of boron contamination and losses during chemical treatment. An introduction system with a PFA spray chamber and a sapphire injector was adopted to decrease boron memory during the measurement on MC-ICP-MS, which provides high-precision δ¹¹B results. The internal precision for δ¹¹B was better than ±0.05‰ (2σ standard error), and the external precision for δ¹¹B was better than ±0.30‰ (2σ standard error) estimated by the long-term results of SRM 951. The δ¹¹B of a series of international rock standard references were measured by this method. Some of the samples have δ¹¹B reference values, and our results agree well with them within analytical errors. This indicates that our method is feasible for high-precision δ¹¹B measurement in various silicate rocks, and our results may provide δ¹¹B reference values for these rock standards.