Silica modified with zirconium oxide for on-line determination of inorganic arsenic using a hydride generation-atomic absorption system

In the present work, an on-line pre-concentration system, using SiO₂/ZrO₂ as solid phase adsorbent, for the determination of low concentrations of arsenic was developed.In this procedure, total inorganic arsenic present in the sample is reduced to As (III) with l-cysteine and the solution is passed into a glass column (?_i = 3 mm; h = 35 mm) containing 70 mg of SiO₂/ZrO₂ (100-230 mesh) to retain the As (III), with the solution flowing at 3.2 mL min⁻¹. After 2 min, the concentrated species are eluted with 3 mol L⁻¹ HCl (3.2 mL min⁻¹) loading a 150 μL loop while a 1.0% (m/v) sodium borohydride solution loads the other loop of a FI-HG AAS system. The elution step is carried out during 7 s and, at the same time, the SiO₂/ZrO₂ phase is regenerated for the next concentration cycle. The arsine generated is carried with N₂ (flow rate = 90 mL min⁻¹) to a quartz cell where the electrothermal atomization process occurs.Under these conditions, a 20-fold enrichment factor is obtained considering the increase of sensitivity in the analytical curve after the concentration step. The limits of detection and quantification were 0.05 and 0.35 μg L⁻¹, respectively, with an injection frequency of about 28 h⁻¹ and relative standard deviation lower than 8%. Four metallurgical reference materials were analyzed with the proposed method after their acid dissolution. The results obtained were in good agreement with certified values.