Spectroscopic Determination of Two Beta-Blockers – Atenolol and Propanolol by Oxidative Derivatization Using Potassium Permanganate in Alkaline Medium

Abstract A simple, rapid, sensitive, cheap and accurate oxidative method for two beta-blockers in pharmaceutical dosage forms was developed and evaluated. The method involved the oxidimetric treatment of atenolol and propanolol with 2 x 10-3 mol L-1 KMnO4 in alkaline medium (pH ≥ 9). Scanned spectra of oxidized complex showed distinctive absorptions at 460, 520, 540 and 570 nm. Arrays of colour changes were observed - from violet to blue; blue to bluish-green and yellow. Exhibited colours were due to ligand-metal charge transfer. An indirect spectrophotometric determination of atenolol and propranolol was done after 12-15 minutes at 520 nm. The optimum assay conditions showed linearity ranged from 0 – 15.0 μg mL-1 for both beta-blockers (R= 0.9997 – 0.9999). Molar absorptivity values were 4.79 x 103 and 4.88 x 103 L mol-1 cm-1 for atenolol and propanolol respectively, with corresponding Sandell’s sensitivity values of 0.056 and 0.053 μg cm-2. Limits of detection and quantification were 0.50 and 1.65 μg mL-1 for atenolol respectively and 0.58 and 1.91 μg mL-1 for propanolol, while relative standard deviation for intra-and inter-day precision were < 2.0%. The applicability, accuracy and reliability of the method were demonstrated by the determination of atenolol and propanolol in tablet formulations. The recovery studies ranged from 93.33 - 103.00% for both beta-blockers and the amounts in brands were from 97.53 ± 2.68 to 100.84 ± 1.82%.