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 x 10(-6) to 1 x 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. (c) 2005 Elsevier B.V. All rights reserved.