Sol-gel coated prussian blue modified electrode for electrocatalytic oxidation and amperometric determination of thiols

A sol gel coated chemically modified prussian blue electrode has been prepared successfully by means of mechanical immobilization of prussian blue on graphite electrode followed by a coating of a thin layer of silicate by sol-gel method. The sol-gel coating enhanced the stability of the modified electrode. This electrode was characterized by cyclic voltammetry tinder different experimental conditions. The electrocatalytic oxidation of thiols such as cysteine and glutathione with the modified electrode was investigated. The high spin it-on of the prussian blue could not bring about any catalytic oxidation of the thiols, while the low spin iron of the prussian blue in the oxidised form shows catalytic oxidation. Using the catalytic oxidation shown by the low spin iron, amperometric method has been developed for the determination of thiols. A linear response in catalytic current has been observed from 34.3-193.5 muM for cysteine and 34.3-150.9 muM for glutathione. The modified electrode showed very stable response due to the presence of silicate coating. Hydrodynamic voltammetric studies have also been carried out to study the suitability of the electrode for use in flow systems and a good reproducible response could be obtained with the electrode.