A new strategy to monitor instrumental blank samples based on multivariate control charts

This paper proposes a methodology to monitor and assess the stability of instrumental blank samples of four elements (lead, cadmium, nickel and chromium), analysed through inductively coupled plasma mass spectrometry (ICP-MS). The proposed methodology, which is based on multivariate control charts, comprises an intra-day control, used as an internal quality control tool, to monitor and detect possible contaminations that may occur in the measurement process. The strategy used to evaluate the multivariate control chart performance was a direct comparison with a set of four univariate control charts build for each element. The findings (of this exploratory study) suggest that multivariate control charts have potential to be effectively used as an internal quality control tool in a daily base in IPC-MS. Taking into account the statistics used in this chart, Q-Statistics, their sensitivity should be improved, as well as the mathematical complexity involved.