Precise analysis of antimony isotopic composition in geochemical materials by MC-ICP-MS

Abstract

Antimony (Sb) isotopes have been shown to be promising tracers for studying Sb cycling in the environment and its impact on ecosystem and human health. Yet precise measurements of Sb isotopic composition have been challenged by low Sb concentrations and high matrix effect and by the lack of a common reference material (zero-delta). Here we report an improved analytical scheme that is capable of high-precision measurement of Sb isotopes in environmental and geochemical samples. The method employs a two-column ion exchange set-up to remove interfering matrix elements to allow Sb isotopic measurements with low Sb (< 0.15 μg/g) and high matrix content. The instrument mass bias is corrected by combining the sample-standard bracketing method with internal normalization of cadmium. To allow for interlaboratory comparisons, a standard reference material certified for the total Sb concentration, NIST SRM 3102a, is recommended as the reference standard (“zero-delta”) for Sb isotope measurements. The improved method is applied for high-precision and high-accuracy Sb isotope composition measurements in environmental and geochemical reference samples with a minimum Sb required per analysis as low as 3.0 ng. By expressing our data and previously reported literature data against the same reference standard (NIST SRM 3102a), we provide an update on isotopic compositions of various types of environmental, geological and anthropogenic materials. The improved analytical method and database aid further studies on the mechanisms of Sb isotope fractionation and its application as a tracer for the study of the sources, processes and fate of Sb in the environment.