A GRAPHITE SILVER(I) HEXACYANOFERRATE(III) COMPOSITE ELECTRODE FOR THE DETERMINATION OF IRON(III) IONS

A reactive electrode (reactrode) made of silver(I) hexacyanoferrate(II I) (Ag-hcf), graphite and paraffin has been developed for the determin ation of iron(III) ions in solutions down to a concentration of 0.12 m g L-1. Silver ions are reduced to Ag-0 and the liberated hecacyanoferr ate ions react with iron(III) ions from the solution to form Prussian blue. After this preconcentration step, the iron ions can be determine d electrochemically by the characteristic signals of Prussian blue in differential pulse voltammetry. A nonlinear calibration plot is obtain ed which has a standard deviation of 13 %. Pb2+, Cu2+ and Ni2+ interfe re when they are at the same concentration as iron(III), whereas Cd2does nor interfere even at higher concentrations. The incorporation of an active reagent into the electrode material remarkably facilitates the analytical procedure and makes the use of a mercury electrode unne cessary.