Carbon paste and PVC electrodes for the flow injection potentiometric determination of dextromethorphan

The construction and performance characteristics of dextromethorphan (DXM) carbon paste (CPEs) and polyvinyl chloride (PVC) electrodes are described. Different modes for electrode modification, including incorporation of ion pairs (IPs), ion pairing agent or soaking the plain electrode in IPs suspension, have been used. Matrices compositions were optimized referring to the effect of modifier and plasticizer. The fabricated electrodes work satisfactorily in the concentration range from 10−5 to 10−2 mol L−1 with fast response time (1.6 s) and long operational lifetime (2 months). The developed electrodes have been successfully applied for the potentiometric determination of DXM in pharmaceutical formulation under batch and flow injection analysis (FIA) conditions. Under FIA conditions, the proposed electrodes allow the analysis of 90 samples h−1 and offer the advantage of simplicity, accuracy and automation feasibility. The solubility products of various DXM-IPs were determined conductometrically.