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Insertion of an electrochemical cell in a flow injection system to evaluate the on-line reduction of ionic species is presented. The cell comprised Pt electrodes installed in two sections separated by a Nafion membrane. The sample was injected into an acidic carrier stream and passed through the cathode compartment of the electrolytic chamber where the species were reduced as consequence of an applied DC voltage. The sample solution leaving the cell received a confluent reagent stream (1,10-phenanthroline buffered at pH 4.7) and the reacted products were dropped off in an open tube for gas/liquid separation. Efficiency of the Fe(3+) to Fe(2+) reduction in acidic medium was evaluated in the presence of strongly reducing species of V and Mo by monitoring the Fe(II) colored complex. Interferences from Pb(2+), Co(2+), Ni(2+), Zn(2+), Cu(2+), V(5+) and Mo(6+) were evaluated. Production of strongly reducing species of V at the electrolytic cell presented higher efficiency for Fe reduction than the electrolytic chamber itself. Total reduction of Fe(3+) in solutions containing up to 10 mg l(-1) Fe plus 100 mg l(-1) V or 100 mg l(-1) of Mo was achieved by the electrolytic process at 2 A. The quantitative determination of Fe and V in low silicon Fe/V alloys was achieved. Accuracy was assessed with the certified Euro-standard 577-1 ferrovanadium alloy produced by the Bureau of Analysed Samples Limited and no difference at the 95% confident level was found. |
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