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 (ϕi = 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.