Fluorimetric Methods for the Determination of Terazosin HCl in Drug Substance and Dosage Forms

Determination of terazosin hydrochloride dihydrate (TRZ) in drug substance and tablets was studied by fluorimetric techniques. The fluorimetric methods are based on: (1) measurement of the native fluorescence of the drug in water at 750 nm after excitation at 330 nm. (2) sensitizing the native fluorescence by formation a binary complex of drug with aqueous uranyl acetate (0.1% w/v) at the same Ex / Em. under the described condition. the proposed methods were applicable over the concentration range of (10 -1000 and 0.5-12 ng mL-1) with good correlation ((r2=0.9982 and 0.9987), limit of detection of  ( 3.47 and 0.198 ng/mL) and a lower limit of quantification of (10.5 and 0.6 ng mL-1) for method (1) and (2), respectively. The described methods were successfully applied for the determination of TRZ in its commercial tablets without interference from common excipients.