Precise isotope analysis of tellurium by inductively coupled plasma mass spectrometry using a double spike method

Abstract

This paper presents an analytical technique to determine the concentrations of Te and Se, and the stable isotope composition of Te. The outlined analytical protocol combines Se single-spike and Te double-spike methods to determine the Se and Te concentrations using the isotope dilution method and mass dependent fractionation of Te isotopes using the double-spike method. Selenium and Te separation from the sample matrix utilized thiol cotton fibre. For the Te isotope analyses, a desolvating nebulizer system (dry plasma) and wet plasma were tested. The reproducibilities of isotope analyses for an in-house standard solution were 0.027‰ and 0.035‰ for δ^130/125Te under dry and wet plasma conditions, respectively. The sample consumptions per run for isotope analysis were 20 and 260 ng of Te for the dry and wet conditions, respectively. Correction for the Te hydride ions was necessary for analysis using the wet plasma but not for the dry plasma condition. Barium interferences did not affect the accuracy of the isotope analysis when Ba/Te < 10⁻² and <10⁻³ for either the dry or wet plasma conditions, respectively. We analysed five distinct Te standards, three natural ferromanganese nodule reference materials, and a jasperoid reference material. The measured Te isotope compositions of these samples were identical for the dry and wet plasma setups. Four different standard solutions of Te from different suppliers showed variable Te isotope compositions with a range of 1.25‰ for δ^130/125Te, indicating different Te isotope compositions in their source materials and/or that isotope fractionation occurred in their manufacturing processes. A positive correlation was observed between δ^130/125Te and Te/Se for the ferromanganese nodules and the jasperoid sample, which potentially suggests that elemental and isotope fractionation of Te occurred simultaneously, and the Te isotope composition may reflect changes in the environmental conditions.