Total As in seafood as determined by transverse heated electrothermal atomic absorption spectrometry-longitudinal Zeeman background correction: An evaluation of automated ultrasonic slurry sampling, ultrasound-assisted extraction and microwave-assisted digestion methods

Two sample pretreatment methods based on the use of ultrasound [i.e., autom ated ultrasonic slurry sampling (USS method) and ultrasound-assisted extrac tion (UAE method)] were developed for determination of total As in eleven f resh and frozen seafood samples by transverse heated electrothermal atomic absorption spectrometry with longitudinal Zeeman background correction and compared with the conventional microwave-assisted digestion method using th e H2O2-HNO3 mixture (MAD method). Non-parametric tests (i.e., Kruskal-Walli s test and Wilcoxon rank sum test) were used in order to compare analytical results obtained, thus avoiding the influence of outliers. In general, no significant differences in accuracy were observed when comparing the UAE an d MAD methods. Significantly lower arsenic concentrations were observed for several seafood samples with the USS method even using large amounts of ma trix modifier [i.e., 22.5 mu g Pd + 13.5 mu g Mg(NO3)(2)] which were attrib uted to non-spectral interferences caused by the sample matrix. When the so lid particles were allowed to settle in the USS method, an improved arsenic recovery was obtained; the concentration found being similar to that obtai ned by the UAE and MAD methods. Plackett-Burman designs were used to assess the robustness of the USS and UAE methods. The slurry concentration was se en to cause a significant negative effect on As recovery in both the slurry and solid-liquid extraction techniques, whereas nitric acid concentration caused a significant positive effect only in the solid-liquid extraction te chniques. The LOD of arsenic with the USS and UAE methods was 0.5 mu g g(-1 ) and the between-batch precision expressed as relative standard deviation (RSD) was in the range of 1-6%.