Espectrometria de Emissão Atômica em Filamento de Tungstênio (WCAES) : potencialidades e aplicações

Abstract

This thesis describes the analytical application of WCAES for the determination of Ca, Al, Cs, Sr and Cr in samples with different compositions. In all studies the observation zone of the detector related to the coil was critically evaluated. In the first study, Ca was determined in mineral water, coconut water and juice samples. It was necessary the dilution of the coconut water and juice samples with an oxidizing mixture composed by HNO3 and H2O2 in order to perform in situ digestion of the samples. The results obtained by WCAES were compared with those obtained by ICP OES and no significant difference was observed. The same mixture was used in a second study where WCAES was evaluated for the determination of Al in tea infusion and iced tea samples. The heating program composed by drying, pyrolysis and atomization steps was optimized. The Al concentrations determined by WCAES were compared with those obtained by ICP OES and no difference was observed. In the third study, a portable WCAES was employed in the determination of Cs and Sr in fish samples. The fish samples were homogenized using enzymatic digestion promoted by papain. The oxidizing mixture was also added in the slurries of fish samples in order to promote the decomposition of the organic concomitants. The limits of detection were comparable to conventional methods, such as ICP-MS for example. Finally, the effect of cobalt in the determination of Cr by WCAES was evaluated. A high concentration of this element caused a significant increase in the emission signals of Cr. The presence of cobalt also allowed the application of higher temperatures during the pyrolysis step. Then, cobalt acts as chemical modifier improving figures of merit for Cr determination using WCAES.