In the present work, an on-line pre-concentration system, using SiO(2)/ZrO(2) 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 (varphi(i)=3mm; h=35mm) containing 70mg of SiO(2)/ZrO(2) (100-230 mesh) to retain the As (III), with the solution flowing at 3.2mLmin(-1). After 2min, the concentrated species are eluted with 3molL(-1) HCl (3.2mLmin(-1)) loading a 150muL 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 7s and, at the same time, the SiO(2)/ZrO(2) phase is regenerated for the next concentration cycle. The arsine generated is carried with N(2) (flow rate=90mLmin(-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 0.35mugL(-1), respectively, with an injection frequency of about 28h(-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.711150-4