Spectrophotometric and spectrofluorimetric methods for the determination of terazosin in dosage forms

Five simple and accurate methods are presented for the determination of terazosin (TZ) in tablets. These methods are based on the direct measurements of the first and second derivative spectra of samples (A), the reaction of TZ with chloranil (CPT) in aqueous solution of pH 9 to give an intense yellow color measured at 340 nm (B), the reaction of the drug with mercurochrome (MER) in aqueous alkaline medium to give an intense red color measured at 543 nm (C) the formation of an ion-pair salt between the drug and bromocresol purple (BCP) with subsequent absorbance measurements at 412 nm (D), and a sensitive fluorimetric method (E). The latter method was extended to determine TZ in presence of its degradation products. All variables were studied to optimize the reaction conditions. Beer's law was valid within the specified concentrations and conditions.The proposed methods have been applied for the assay of terazosin in commercial tablets with coefficient of variation less than 1%.