Simultaneous determination of iron and copper in waters by multiligand flow injection analysis

Abstract

Optical characteristics were measured and optimum conditions established for the simultaneous spectrophotometric determination of iron and copper with reagent mixtures of disodium bathocuproinedisulfonate (I) with disodium bathofenanthrolinedisulfonate (II) or ferrospectral (III) in static or dynamic (FIA) conditions. In the FIA method suggested, 30μl water samples containing Fe and Cu in concentration ratios 1 : 10 to 10 : 1 are injected into a stream of I-II mixed reagent at c(I) = 0·6 mmol l-1 and c(II) = 0·2 mmol l-1 in a medium of 0·1M formate buffer pH 3·5 and 0·01M ascorbic acid; for the two metals, present in concentrations of 4 to 40 μmol l-1, the relative standard deviations of determination do not exceed 2 and 5%, respectively. Alternatively, in the reverse FIA method using a multichannel diode array detector, 25 μl of the mixed reagent under the above conditions is injected into the acid sample stream; for samples containing Fe and Cu in concentrations of 1-43 μmol l-1 in ratios of 10 : 1 to 1 : 15, the relative standard deviation of determination is about 2%. The use of mixed reagents makes for a broader variability of the optical characteristics and conditional equilibrium constants of the reaction products as compared to methods employing a single nonselective reagent; owing to this, improved selectivity, accuracy and precision of determination are achieved with multicomponent flow injection analysis (MC-FIA).