Structured approach to achieving high accuracy measurements with isotope dilution inductively coupled plasma mass spectrometry

Abstract

This study investigated a method for simplifying the implementation of ID-ICP-MS, to achieve high accuracy measurements. The method developed is an adaptation of an earlier methodology that utilised an iterative ‘matching’ procedure. While retaining the many advantages of this approach, we have removed the iterative component and simplified the ‘matching’ step between the spiked mass bias calibrant and the spiked sample. Based on a conventional analysis, an approximate ‘match’ (usually within 5%), was made between the spiked reference standard and the spiked sample. This provides the basis for calculating the final result using the normal IDMS equation, while retaining many of the benefits of the full ‘matching’ procedure. These benefits negate many sources of error, such as mass bias, detector dead time and characterisation of the spike material. Many common errors and necessary corrections are negated or eliminated when using the new procedure. Examples are given of the method as applied to the analysis of certified reference materials, such as waters and plastics as well as blind trial data. The accuracy achieved using this procedure, on blind trial solutions, is typically to within 1% (relative to concentration) at the 95% level of confidence.