Potentiometric membrane sensors for the selective determination of cinnarizine in pharmaceutical preparations

The construction and general performance characteristics of four novel potentiometric PVC membrane sensors responsive to the cinnarizinium cation are described. These sensors are based on the use of the ion-association complexes of the cinnarizinium cation with tetraphenylborate, flavianate, reineckate and 12-molybdatophosphate counter anions as ion exchange sites in a plasticized PVC matrix. These sensors exhibit fast, stable and near-Nernstian response for the doubly charged cinnarizinium cation over the concentration range 10(-2) to 10(-6) M and pH 2-3. No interferences are caused by many inorganic and organic cations. Direct potentiometric determination of 4-400 mu g ml(-1) cinnarizine shows an average recovery of 99.5% and a mean standard deviation of +/-0.5%. The sensors proved useful for determining cinnarizine in various dosage forms, monitoring tablet dissolution rates and testing tablet uniformity. The results compare favourably with data obtained by liquid chromatography.