Stable silicon isotope analysis on nanomole quantities using MC-ICP-MS with a hexapole gas-collision cell

Abstract

We demonstrate in this study that a single focusing multiple collector inductively coupled plasma mass spectrometer (MC-ICP-MS) equipped with a hexapole gas-collision cell (GV-instrument®Isoprobe) can precisely determine the δ29Si (2S.D., 0.2‰) using a total Si consumption of less than 14 nmole (390 ng Si). Testing and evaluation of background, rinse time, and major matrix effects have been performed in a systematic way to establish a procedure to measure δ29Si in small quantities. Chemical purification prior to analysis is required to remove potential interferences. For data collected during a four-year period, the average δ29Si value of IRMM-018 relative to NBS-28 was found to be −0.95‰ (n = 23, 2S.D. 0.16‰) with a 95% confidence interval (−0.95 ± 0.028‰). The mean δ29Si value of the Big-Batch standard was found to be −5.50‰ (n = 6, 2S.D. 0.26‰). Although determination of the δ30Si measurements is not possible, with our current instrument we demonstrate that this system provides a fast and long-term reliable method for the analysis of δ29Si in purified samples with low Si concentration (18 µM Si).