PRECISE AND ACCURATE NEODYMIUM ISOTOPIC MEASUREMENTS BY PLASMA-SOURCE MASS SPECTROMETRY

Abstract

The plasma-source mass spectrometer equipped with both a magnetic mass filter and multiple collection (PSMS) of Lyon was tested for high-precision analysis of neodymium isotopic compositions. These can be determined on as little as 70 ng Nd by PSMS with an internal precision of 10 ppm and an external reproducibility of #30 ppm. A magnetic mass filter, which provides flat top peaks, multiple collection, which integrates plasma instabilities, and steady-state nebulization, which enables accurate cross-calibration with standards, bring precision of PSMS within the range of that achieved by thermal-ionisation mass spectrometry. The molecular oxide and hydride peaks are undetectable. The Sm isobaric interferences can be accurately corrected which relieves the requirement of Nd purification and allows the separation procedure to be reduced to a one-step elution on a cation-exchange column. Very fast sample throughput (18 min per analysis) makes this technique a powerful tool for isotopic stratigraphy. This is illustrated by a preliminary study at high resolution of the neodymium isotopic compositions of the basalts from the Piton de la Fournaise volcano (Renion Island).