Emprego de multiatomizador de quartzo para a minimização de interferências e determinação de arsênio por HG AAS em antimoniais pentavalentes

Abstract

A systematic study was made to evaluate the interference of hydride forming elements in conventional quartz tube atomizers as well as to study the performance of multiatomizer of quartz (MMQTA) for minimization of these interferences in determinations by batch hydride generation atomic absorption spectrometry (HG AAS). For the study of interferences, As, Bi, and Sb were selected as analytes and As, Bi, Pb, Sb, Se, Sn as interferents. Except for Bi as analyte, the MMQTA allowed to increase the tolerance limits to interference between 50 and 400% in comparison to the conventional atomizer. For Sn as interferent, no difference was observed in the determination of Sb and Se using MMQTA system. With respect to the linear range better performance was also found for this atomizer. No loss of linearity was observed up to 160 ng for Se and Sb and 80 ng for As. For Bi, the linear range was the same for both atomizers (140 ng). In the second part, the applicability of MMQTA was evaluated in association with citric acid as complexing agent, for the determination of total As by HG AAS in drugs based on Sb (V). The procedure is based on the ability of citric acid to make complexes with Sb (V) and, to the addition of air to the MMQTA system, which provides an increase in the concentration of hydrogen radicals inside the tube. This approach results in a better analyte atomization and consequently reduction of the interfering effect verified in the presence of this element. The experimental conditions were selected for MMQTA: 10% m/v citric acid, 1% m/v NaBH4, 10 s for purge time, 20 mL min-1 air outer gas and 40 s of injection time. The time of contact between the acidic medium and the sample was 1 h and no effects of suppression of signal of As(V) was observed up to 1000 mg of Sb(V). Recovery test for As (V) was carried out and the values obtained remained at approximately 100% of the expected value. The detection limit (3σ) and characteristic mass, using the recommended conditions, were respectively, 0,4 mg L-1 and 160 pg.