Avaliação da determinação de arsênio por espectrometria de absorção atômica com Geração de hidretos (HG-AAS) frente a interferentes metálicos

Abstract

Arsenic is a metalloid of significant environmental and toxicological concern, mainly because of the adverse effects associated with prolonged exposure to its inorganic forms. Its determination in aqueous samples requires sensitive analytical techniques and adequate control of the chemical conditions involved in the analysis. In this study, arsenic determination by hydride generation atomic absorption spectrometry (HG-AAS) was evaluated in the presence of metallic interferents and under different conditions related to arsine formation. Fe3+ and Cu2+ were evaluated individually at concentrations of 1, 5, 10, and 20 mg L−1 and jointly at 10 mg L−1 each. Pb2+, Mn2+, Cr3+, Zn2+, Cd2+, Al3+, and Co2+ were also investigated individually and in a multielement mixture at a concentration of 10 mg L−1. The NaBH4 concentration was evaluated from 0.25 to 1.75% (m/v), whereas the influence of HCl during the pre-reduction step was investigated at concentrations of 0, 5, 10, 20, and 25% (v/v). For total arsenic determination, As(V) was pre-reduced to As(III) using potassium iodide and L-ascorbic acid, both at 2% (m/v), in an acidic medium. The selected NaBH4 concentration was 1.25% (m/v), and the condition containing 20% (v/v) HCl provided the highest analytical response during the pre-reduction step. Under the evaluated conditions, the investigated metals did not cause significant suppression of the analytical signal. The multielement mixture produced the greatest signal reduction, corresponding to 4.96%. The procedure was applied to two water samples collected in Ouro Preto, Minas Gerais, Brazil, yielding arsenic concentrations of 18.38 ± 0.32 μg L−1 for the Mina do Jeje sample and 90.77 ± 1.12 μg L−1 for the residential sample. Post-digestion spike recovery tests ranged from 86.0 to 95.5%. The results indicated that, under the studied conditions, HG-AAS showed good tolerance to the evaluated metallic interferents and an adequate analytical response for arsenic determination in the analyzed samples, provided that the chemical conditions involved in the pre-reduction and arsine generation steps were properly controlled.