Amperometric sensor for thiosulphate based on cobalt hexacyanoferrate modified electrode

A chemically modified amperometric sensor was constructed by mechanically immobilizing cobalt hexacyanoferrate onto the surface of a paraffin impregnated graphite electrode (PIGE). The cyclic voltammogram of the electrode exhibited two reversible redox peaks corresponding to Co2+/Co3+ and Fe(CN)64−/Fe(CN)63− reactions. Thiosulphate was found to undergo electrocatalytic oxidation at a reduced overpotential with good sensitivity in a wider pH range at the modified electrode. The sensor showed good stability and reproducibility. Under optimal condition, the sensor showed a linear response for thiosulphate in the concentration range from 4×10−5 to 4.8×10−4 M with a correlation coefficient of 0.9972 and the detection limit was 1.8×10−5 M (S/N=3). The sensor has been applied for the determination of thiosulphate in the photographic effluents.