Verification of a correction procedure for measurement of lead isotope ratios by inductively coupled plasma mass spectrometry

Abstract

Inductively coupled plasma mass spectrometry (ICP-MS) is a suitable method for determining Pb isotope ratios. This study investigates the effectiveness of a mass discrimination correction technique, which is based upon the addition of TI to the sample and measurement of the ²⁰⁵TI:²⁰³TI ratio. The TI correction method has been found to be highly effective for minimizing bias and drift in Pb isotope ratios under a variety of operating and sample matrix conditions, and for various samples independently analysed by thermal ionization mass spectrometry (TIMS). Biases for ratios with respect to ²⁰⁴Pb are generally controlled at <0.5% and relative standard deviations of 0.2% are attainable. Results using ICP-MS for environmental samples compare favourably with those obtained by TIMS. This correction technique is sutiable for routine analysis of environmental samples.