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

Five poly(vinyl chloride) matrix membrane sensors responsive to some beta-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 beta-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 x 10(-7) mol l(-1) of different beta-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 beta-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.

Polarographic determination of propranolol in pharmaceutical formulation.

Propranolol was reacted with nitric acid to give nitropropranolol and was then measured in Britton-Robinson solutions in the pH range 2.0-12.0 by differential-pulse polarography. Nitropropranolol gave rise to a well-resolved differential-pulse polarographic peak at pH 2.0. A linear calibration graph in the range 5.0 x 10(-7)-5.0 x 10(-5) M and a detection limit of 5 nM was obtained. The relative standard deviation was 1.95% (n = 10) at 5 x 10(-6) M. The effect of common exceipient on the peak height was evaluated. The method was applied for the determination of the drug in the tablet dosage form.