Determination of Iron and Copper by Spectroelectrochemistry

A new spectroelectroanalytical method for the simultaneous determination of iron and copper is presented in terms of the spectroelectrochemical properties of complexes of iron and copper with 2,2′-bipyridine. By using long optical pathlength thin-layer cells, the differences in the absorbance after complete potential-controlled redox reactions of the two complexes (ΔA) were proportional to the investigated concentration over ranges from 2×10−7 M to 5×10−5 M for iron and from 4×10−7 M to 1×10−4 M for copper, respectively. The proposed method offers a higher selectivity than conventional spectrophotometry. In addition, a preconcentration proceudre for copper was taken in 0. 2 M NH3·H2O-NH4Cl for 1 min; the deposited copper was then dissolved into a solution containing 2,2′-bipyridine as a chromogenic reagent; ΔA, recorded as before, was used as the analytical signal to determine trace copper. The apparent molar absorptivity obtained was ca. 6 times that without electrodeposition. Iron and copper in aluminum alloys and pig serum were satisfactorily determined by the proposed methods.