Flow injection spectrophotometric determination of copper(II) using the iron(III)-thiosulphate catalytic reaction

Abstract

Both 0.65 M iron and 0.067 M thiosulphate solutions are pumped, and mixed in a flow injection analysis (FIA) system to prepare a reddish purple iron(III)-thiosulphate complex. The absorbance at 525 nm is measured after a copper-catalysed colour-reducing reaction in a 4-m coil at 20 °C. The relationship between the logarithm of absorbance and amounts of copper injected is linear up to 180 ng of copper. The relative standard deviation is 3% for five determinations of 100 ng of copper. Forty samples per hour can be analysed. Little interference from various foreign ions was found. Some discussion is given of the particular problems of the design of an FIA manifold using a catalytic reaction.