Polymeric matrix membrane sensors for sensitive potentiometric determination of some β-blockers in pharmaceutical preparations

Five poly(vinyl chloride) matrix membrane sensors responsive to some β-blockers (atenolol, bisoprolol, metoprolol, propranolol and timolol) are described and characterized. The sensors are based on the use of the ion-association complexes of the β-blocker cations with tungstophosphate anion as electroactive materials. The performance characteristics of these sensors, evaluated according to IUPAC recommendations, reveal fast, stable and near-Nernstian response for 10 −2–2×10 −7 mol l −1 of different β-blockers over the pH range 2–9. Many inorganic and organic cations as well as drug excipients and diluents normally used in drug formulations do not interfere. The sensors are used for direct potentiometry of β-blockers in some pharmaceutical preparations. Validation of the method according to the quality assurance standards shows suitability of the proposed sensors for use in the quality control assessment of these drugs. Results with an average recovery of 99.1% and a mean standard deviation of ±1.3% of the nominal are obtained which compare fairly well with data obtained using the British Pharmacopoeia method.