Cyclodextrin-based dextromethorphan potentiometric sensors

The construction and performance characteristics of different dextromethorphan (DXM) potentiometric sensors are described. Three types of electrodes are demonstrated, namely silver coated wire electrode (CWE), coated graphite electrode (CGE) and the conventional PVC membrane electrodes (CE). The cited electrodes are based on cyclodextrins (CDs) ionophores and show a considerable selectivity towards DXM with Nernstian slopes depending on the type of the electrode and the ionophore used. Matrix compositions of each electrode are optimized on the basis of effects of type and concentration of the ionophore as well as influence of the selected plasticizers. CWE incorporated with heptakis (2,3,6-tri-o-methyl)-β-CD and sodium tetrakis (4-fluorophenyl) borate (NaTFPB) with o-nitrophenyloctylether (o-NPOE) as membrane plasticizer, showed the best electroanalytical performances. CWEs work satisfactorily in the concentration range from 10−7 to 10−2 mol L−1 with Nernstian compliance 59.0 ± 0.22 mV decade−1 and detection limit 7.0 × 10−8 mol L−1. Fast response time of about 4 s and adequate shelf-life (4 weeks) was achieved. The developed electrodes have been successfully applied for the potentiometric determination of DXM in pharmaceutical formulation under batch and flow injection analysis (FIA) conditions. FIA allows the analysis of 90 samples h−1 and offer the advantage of simplicity, accuracy and automation feasibility. Comparison of the obtained results with those provided by reference method revealed adequate accuracy for control assay.