Visible Spectrophotometric Determination of Olmesartan Medoxomil in Pharmaceutical Formulations

Two simple and sensitive spectrophotometric methods (method A and method B) in the visible region have been developed for determination of olmesartan medoxomil in bulk and in pharmaceutical formulations. Method A is based on oxidative coupling of olmesartan medoxomil with 3-methylbenzothiazolin-2-one hydrazone (MBTH). The resulting green complex has lambda(max) at 631 nm. Method B is based on the reduction of ferric to ferrous ions followed by complexation with 1,10-phenanthroline to produce an orange red chromogen at lambda(max) 510 nm. Beers law is obeyed in the concentration range of 10-45 mu g/mL and 5-35 mu g/mL respectively. These methods were extended to pharmaceutical formulations and there was no interference from excepients and diluents. The proposed methods are simple, sensitive, accurate and suitable for quality control applications.