Polynomial mass bias functions for the internal standardization of isotope ratio measurements by multi-collector inductively coupled plasma mass spectrometry

Abstract

The development and application of a calibration strategy for routine isotope ratio analysis by multi-collector inductively coupled plasma mass spectrometry (ICP-MS) is described and assessed. Internal standardization was used to account for the mass dependant determinate error (mass bias). The general solution for polynomial isotope ratio mass bias functions for use with internal standardization and isotope ratio measurements by multi-collector inductively coupled plasma mass spectrometry was derived. The resulting linear isotope ratio mass bias function was demonstrated to be mathematically consistent and experimentally realistic for the analysis of acidified aqueous solutions of analyte and internal standard elements (clean solutions) by multi-collector inductively coupled plasma mass spectrometry. The calibration strategy was applied to the measurement of Pb, Sm and Ni isotope ratios in clean solutions using Tl, Eu and Cu as internal standards, respectively. Results of the analysis of the standard reference material NBS 982 for 208Pb/ 206Pb, 207Pb/ 206Pb and 204Pb/ 206Pb isotope ratios were 1.000290 ± 0.000025, 0.466994 ± 0.000008 and 0.027218 ± 0.000003 (± 1 standard deviation, n = 48) with errors of (+ 0.0130 ± 0.0025)%, (− 0.0271 ± 0.0017)% and (− 0.005 ± 0.009)%, respectively.