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

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 analyti cally important Cd isotopes in both matrices, being particularly severe wit h the latter matrix. To overcome this problem, chemometric methods were app lied. Metals incorporated in this study were Cd, Mo, Zr, Pd and Sn, while R h was used as internal standard, the recorded mass numbers (m/z) ranging fr om 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 evalua ted separately. The root mean square error of cross-validation (RMSECV) for the fly ash domain was 0.64 mu g l(-1) and 1.42 mu g l(-1) for the metal a lloy domain. The Cd concentrations in the reference materials were predicte d accurately, and since the same sample was wet-digested and analysed sever al times and in different runs, figures of reproducibility are reported. Mu ltivariate and univariate regression approaches were also compared. Univari ate models were comparable in terms of predictive ability for the fly ash d omain, but not for the metal alloy domain.