Flow-injection pulse amperometric detection based on ion transfer across a water-plasticized polymeric membrane interface for the determination of verapamil

A flow-injection pulse amperometric method for determining verapamil, based on ion transfer across a plasticized poly(vinyl chloride) (PVC) membrane, was developed. A four-electrode potentiostat with ohmic drop compensation was used, while a flow-through cell incorporated the four-electrode and the membrane, which contained tetraphenylpyridinium tetraphenylborate. The influence of the applied potential and of the flow-injection variables on the determination of verapamil was studied. In the selected conditions, a linear relationship between current peak height and verapamil concentration over a range of 5 × 10−6 to 1 × 10−4 M verapamil was found. Good repeatability and between-day reproducibility were obtained. Some common ions and pharmaceutical excipients did not interfere. The method proposed has been applied satisfactorily to the determination of verapamil in pharmaceuticals and human urine.