ABSTRACT

A method for the rapid determination of Re-Os isotopes by multi-collector inductively coupled plasma mass spectrometry (MC-ICP-MS) was developed. For Os measurements, samples were introduced into the plasma through conventional solution mode. The main Os memory occurs in the nebulizer; therefore, the use of a glass nebulizer rather than a Teflon nebulizer leads to a significant reduction in the Os memory effect. The Os memory is quickly and easily eliminated by washing the inlet system with 5% HCl-EtOH. The external reproducibility of the ¹⁸⁷Os/¹⁸⁸Os ratio of the Johnson-Matthey Chemical ICP (JMC) Os standard solution, as measured using the multi-ion counter system, is 0.07% (2σ, n = 12) for analyte amounts ranging from 0.1 to 1 ng total Os. Using MC-ICP-MS, the mean values of ¹⁸⁷Os/¹⁸⁸Os obtained for standards were found to be within analytical uncertainty of values obtained by negative thermal ionization mass spectrometry (N-TIMS). An improved mass-fractionation correction technique using Ir was applied to the isotopic analysis of Re. The present methods demonstrate the feasibility of MC-ICP-MS for precision measurements of the ¹⁸⁷Re-¹⁸⁷Os isotope system.