Determination of Doxazosinmesylate by Ion-pair Complex Formation with Bismuth (III) Tetraiodide Using Spectrophotometric and Atomic Absorption Spectroscopic

Two simple, sensitive spectroscopic and atomic absorption spectrometric (AAS) methods have been suggested for the determination of doxazosinmesylate in pure form and tablet formulations. The methods are based on the formation of ion-pair associate between the drug and the inorganic complex, bismuth(III) tetraiodide. The reaction occurs in nitric acid medium forming orange-reda ion-pair associate which is instantaneously precipitated. The formed precipitate is filtered off and the residual unreacted metal complex in the filtrate is determined either spectrophotometrically at 453 nm or by AAS at 223.1 nm. Also, the precipitatemay be dissolved in acetone and quantified spectrophotometically at 470nm or decomposed by hydrochloric acid, and the bismuth content is determined by AAS at 223.1 nm. The two methods permit the determination of doxoazosinmesylate in the range of 5-80μg L-1. The proposed methods were successfully applied to determine doxazosinmesylate in its tablet formulations without any evidence for interference from pharmaceutical additives. The results were in good agreement with those obtained the reference method. The proposed methods, especially if automated, can be confidently applied for quality control and routine analysis of doxazosinmesylate.