SPECTROPHOTOMETRIC METHODS FOR THE DETERMINATION OF FENOTEROL HYDROBROMIDE IN PURE AND DOSAGE FORMS

Abstract

Two sensitive, simple and rapid spectrophotometric methods for determination of fenoterol either in pure or pharmaceutical preparation are described. The first proposed method (A) is based on coupling fenoterol-with 3-Methylbenzothiozolin-2-one-hydrazone-hydrochloride (MBTH) in presence of ferric chloride hexahydrate in acid medium. The resulting stable coloured product showed an absorption maximum at 485 nm against reagent blank. The second proposed method (B) is based on the oxidative coupling of fenoterol with 4-Aminoantipyrine (4-AAP) in presence of potassium dihydrogenphosphate and potassium ferricyanide. The stable coloured product showed an absorption maximum at 528 nm. Appropriate conditions were established for both methods. Beer's law is obeyed in the concentration range 4-12 µgml-1 and 10-20 µgml-1 for method A & B respectively. Molar absorptivity and Sandell sensitivity for method A 8.05x104 Lmol-1 cm-1 and 4.8x10-3 µgcm-2, while for method B is 3.194x104 L mol-1 cm-1 and 1.202x10² µgcm-2. The detection and quantification limits are calculated. The developed methods are applied successfully for the determination of fenoterol in pure and in pharmaceutical formulation without interference from common excipients.