Determination of cadmium in fly ash and metal alloy reference materials by inductively coupled plasma mass spectrometry and chemometrics

Abstract

Inductively coupled plasma mass spectrometry (ICP-MS) was used to determine Cd in five certified reference materials consisting of fly ashes and metal alloys following dissolution. Spectral overlap is observed for all analytically important Cd isotopes in both matrices, being particularly severe with the latter matrix. To overcome this problem, chemometric methods were applied. Metals incorporated in this study were Cd, Mo, Zr, Pd and Sn, while Rh was used as internal standard, the recorded mass numbers (m/z) ranging from 90 to 124. Regression models were based on data derived from hundreds of standards, and it was shown that it is possible to use results of several ICP-MS runs in the same model. Fly ash and metal alloy matrices were evaluated separately. The root mean square error of cross-validation (RMSECV) for the fly ash domain was 0.64 µg l ^–1 and 1.42 µg l ^–1 for the metal alloy domain. The Cd concentrations in the reference materials were predicted accurately, and since the same sample was wet-digested and analysed several times and in different runs, figures of reproducibility are reported. Multivariate and univariate regression approaches were also compared. Univariate models were comparable in terms of predictive ability for the fly ash domain, but not for the metal alloy domain.