Simultaneous determination of trace iron(III) and copper(II) by dual-wavelength dual-indicator catalytic spectrophotometry

A new dual-wavelength dual-indicator catalytic kinetic spectrophotometric method for the simultaneous determination of trace iron (Ⅲ) and copper (Ⅱ) was studied.The method is based on the iron (Ⅲ) and copper (Ⅱ)catalyzing oxidation of methyl orange and methylene blue by hydrogen peroxide in the Na2SO4 medium.The absorbances of the systems of catalysis and uncatalysis are measured at 440 nm and 664 nm.The linear ranges are 0.0050～0.50 μg/25 mL for iron and 0.0025～0.75 μg/25 mL for copper.The detection limits are 6.9×10-11 g/mL for iron and 8.7×10-11 g/mL for copper.The method has been used for the determination of trace iron and copper in water with satisfactory results.