A new double spike method for the determination of mass-dependent Te isotope compositions of meteorites and terrestrial materials by MC-ICP-MS

Abstract

This study presents a new method for the determination of mass-dependent Te isotope compositions. The process encompasses a new column chromatographic procedure which separates Te from chondritic and iron meteorites and diverse terrestrial rocks with high yield and purity, combined with a robust ¹²⁵Te–¹²⁸Te double spike and optimised multi collector ICP-MS protocols. This allows for precise (2SD = 0.07‰) determination of the mass-dependent ¹³⁰Te/¹²⁵Te isotope ratio using analyte solutions containing as little as 6 ng of natural Te. The efficacy of the method is demonstrated by repeat analyses of terrestrial rock reference materials and meteorites, which show overall good agreement with previous work. In addition, an inter-laboratory cross-calibration of three different Te standard solutions was performed. This inter-laboratory cross-calibration is highly advantageous, as a well-calibrated isotope reference material is not yet available for Te. Isotope mass balance and mixing equations performed in this study show that hypothetical mass-independent Te isotope effects of reasonable magnitude are unlikely to have a significant impact on the measured mass-dependent Te isotope compositions at the current level of analytical precision. Finally, this study presents the first precise mass-dependent Te isotope composition obtained for an iron meteorite, Canyon Diablo, and komatiite reference material KAL-1 using the double spike technique.