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 gives 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 stages of the analytical procedures because of the large number of variables to take into account. Accordingly, several chemometric techniques were applied to help in the development of a systematic analytical scheme to determine 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 techniques and their objectives were as follows: Plackett-Burman designs, to assess the influence of six analytical variables; optimization of the important analytical variables; a two-way ANOVA, to investigate the influence of sample cups and replicates; and control charts, to monitor the graphite tube performance. Additionally, two pipetting options and three quantification methods were evaluated. Analytical results for Sb determined in five certified reference materials confirmed the usefulness of the ultrasonic slurry sampler (USS-100) combined with ETAAS for a direct and almost fully automatic analysis of complex matrices.