A new coated-wire electrode based on clopidogrel-hexathiocyanato ferrate (III) ion-pair

A plasticized coated-wire PVC-membrane electrode for determination of clopidogrel bisulfate (CLPB), based on the formation of CLP-hexathiocyanato ferrate (III) ion-pair, was constructed and studied. The effect of different parameters including membrane composition, temperature, conditioning time, pH of the test solution, response time, and interferent species on the electrode performance, was also studied. The optimum electrode performance was accomplished with a membrane composition of 49.38% PVC and DOP, and 1.25% ion-pair complex. This electrode showed a linear response with a Nernstian slope of 59.58±1.19mV/decade over the concentration range 1.0×10^-4 - 5.0×10^-2 M and was usable within the pH range 1.1-2.8. This sensor exhibited a relatively fast response time (about 22 s), a low detection limit (6.48×10^-5 M), a long lifetime (>4 months, 2 h a day) and good thermal stability. The standard electrode potentials, E°, were determined at 25 - 80°c and used to calculate the isothermal temperature coefficient (dE°/dT) of the electrode. The highly selective electrode was successfully applied for the determination of clopidogrel bisulfate both in pure and pharmaceutical forms using potentiometric measurements. The obtained results were statistically analyzed in regards to both accuracy and precision and were compared to the U.S. pharmacopeial method where there no significant difference was observed.