Determinação de espécies de arsênio, antimônio e chumbo em antimoniato de meglumina por espectrometria de absorção atômica após extração em fase sólida

Abstract

In this study, two flow systems with a solid phase extraction were developed for the determination of Sb(III), Pb(II) As(V) and total As by atomic absorption spectrometry in sample of meglumine antimonate, which is the chosen medication in Brazil for treating leishmaniasis. For the determination of Sb(III) and Pb(II) with solid phase extraction and flame atomic absorption spectrometry (FI SPE F AAS), the species were retained in a micro-column containing 8-hydroxyquinoline as a chelating agent, supported in glass with controlled porosity (CPG 8HQ). The principal experimental parameters established were, respectively for Sb(III) and Pb(II): pH 5.8 and 6.8; HCl 2 and 1 mol L-1 as eluent; limit of detection (LOD) 0.1 mg L-1 and 2.0 μg L-1; analytical frequency 9 and 13 cycles h-1. The determinations of Sb(III) were carried out on two different batches of meglumine antimoniate, and values varied from 2.65 to 2.97 mg mL-1, which correspond to approximately 3.5% of Sb(III) in relation to the total concentration of antimony. For the speciation study of arsenic, a flow system with a solid phase extraction and hydride generation atomic absorption spectrometry (FI SPE HG AAS) were used. The sorbent used in the pre-concentration phase was a Dowex ion-exchange resin. Among the principal parameters optimized for the selective determination of As(V), we can highlight the following: eluent H2SO4 1 mol L-1; reducing reagent NaBH4 0.5% m/v; NaOH 0.001 mol L-1 for pH adjustment. The LOD value calculated for the determination of As(V) was 2.65 mg L-1 and the analytical frequency was 20 cycles h-1. For the determination of total As, an initial stage for the oxidation of the species As(III) with a 3+1 mixture of concentrated hydrochloric and nitric acid was necessary, and the limit of detection calculated for total As was 6 mg L-1. Based on the results demonstrated, the use of the FI SPE F AAS procedure is proposed for the selective determination of Sb(III) in meglumine antimoniate, which contains close to 81,000 mg L-1 of Sb(V). Furthermore, the use of the FI SPE F AAS and FI SPE HG AAS systems is proposed for the determinations of lead and arsenic, respectively, in the same pharmaceutical products, being that the limit for the total concentration of heavy metals, according to current pharmacopoeias, is 10 mg L-1, greater than the limit of detection of the proposed methods.