Horseradish peroxidase immobilized electrode for phenothiazine analysis

A horseradish peroxidase (HRP) immobilized carbon composite electrode has b een developed for the amperometric study of phenothiazine analogues. Flow i njection analysis and batch experiments have been realized in acetate buffe r in the presence of hydrogen peroxide. Cyclic voltammetry and amperometry using a thin-layer Bow cell (dual configuration, serial mode) have permitte d one to suggest the mechanisms governing the biosensor signal at -0.1 V (v s. Ag/Ag+), in the presence of hydrogen peroxide, by addition of a phenothi azine derivative. It was inferred that electron transfer mediation by the p henothiazine occcurred at HRP/graphite adsorbed sites, in addition to perox idation by dispersed HRP with substrate recycling at the graphite array-lik e structure of the biosensor. Thanks to these processes, high sensitivities were achieved especially in batch configurations, with amperometric detect ion capabilities down to 10(-8) M in acetate buffer pH 4.7. Application of the biosensor to the determination of phenothiazines in drug formulations w ere realized.