STABLE ISOTOPE COMPOSITIONS OF CADMIUM IN GEOLOGICAL MATERIALS AND METEORITES DETERMINED BY MULTIPLE-COLLECTOR ICPMS

Abstract

A new technique for the precise and accurate determination of Cd stable isotope compositions has been developed and applied to geological materials and meteorites. The Cd isotope analyses are performed by multiple collector inductively coupled plasma mass spectrometry (MC-ICPMS) using external normalization to Ag for mass bias correction. The accuracy of the new procedure was ascertained by the comparison of data for meteorites with published results acquired by thermal ionization mass spectrometry and double spiking. Some results were also confirmed by measurements using external normalization to Sb on a different MC-ICPMS instrument. A long-term reproducibility of ± 1.1 εCd/amu (2 sd) was obtained for separate dissolutions and multiple analyses of several rock and meteorite samples (εCd/amu represents the deviation of a Cd isotope ratio of a sample relative to the JMC Cd standard in parts per 10^4, normalized to a mass difference of 1 amu). As little as 5–20 ng of Cd are sufficient for the acquisition of precise and accurate data.