Parallel factor analysis for the study of systematic error in inductively coupled plasma atomic emission spectrometry and mass spectrometry

This paper describes the application of a trilinear parallel factor analysi s (PARAFAC) to study systematic error during the multi-element determinatio n of a range of analytes in acid digests of solid samples (tea leaves) by I CP-AES and ICP-MS. The three variables studied were the "number of digestio ns", in order to assess the systematic error associated with the sample pre -treatment, and the "number of replicates" and "calibration", to provide in formation on the systematic error associated with the analytical determinat ion itself. The elements under study were Co, Cr, Cu, Ni, Pb, Rb and Ti by ICP-MS, and Ba, Ca, Fe, Mg, Mn, Sr and Zn by both ICP-MS and ICP-AES. For s ome elements flame atomic absorption spectrometry was used for comparative purposes. A Chinese tea certified reference material containing many of the metals above was used in the study. The results obtained were compared to results from ANOVA. It was found that the systematic error, expressed as th e sum of squares after PARAFAC, was quite different from the results obtain ed using ANOVA due to the very different way in which the models are built. The PARAFAC approach is shown to be straightforward to implement and robus t.