Development of an analytical scheme for the direct determination of antimony in geological materials by automated ultrasonic slurry sampling-ETAAS

The ongoing application of ultrasonic probes for slurry homogenization give s new additional advantages with respect to the traditional slurry analyses by ETAAS, namely speed, automation, improved reproducibility, etc. Despite all these advantages, there are still difficulties in the optimization sta ges of the analytical procedures because of the large number of variables t o take into account. Accordingly, several chemometric techniques were appli ed to help in the development of a systematic analytical scheme to determin e Sb directly in soils and sediments by means of ultrasonic slurry sampling (USS)-ETAAS. They are intended not only to optimize the slurry preparation but also to diminish the amount of benchwork to be done. The chemometric t echniques and their objectives were as follows: Plackett-Burman designs, to assess the influence of six analytical variables; optimization of the impo rtant analytical variables; a two-way ANOVA, to investigate the influence o f sample cups and replicates; and control charts, to monitor the graphite t ube performance. Additionally, two pipetting options and three quantificati on methods were evaluated. Analytical results for Sb determined in five cer tified reference materials confirmed the usefulness of the ultrasonic slurr y sampler (USS-100) combined with ETAAS for a direct and almost fully autom atic analysis of complex matrices.