Catalytic determination of nanogram amounts of iron(III) using its catalytic effect on the oxidation of chromotropic acid by hydrogen peroxide

Abstract

A simple and sensitive catalytic method is proposed for the determination of Fe^III; the method is based on the catalytic effect of Fe^III on the oxidation of chromotropic acid (the disodium salt of 4,5-dihydroxynaphthalene-2,7-disulphonic acid) by hydrogen peroxide. The reaction was followed spectrophotometrically by measuring the rate of change in the absorbance of the coloured product at 440 nm. Micro-amounts of Fe^III(11.2–167.6 ng ml^–1) can be determined with good accuracy and reproducibility. The influence of foreign ions on the accuracy of the results was investigated and the method was found to be adequately selective and has been satisfactorily applied to the determination of Fe^III in tap and sea water samples and in biological materials.