New Spectrophotometric and Spectrofluorimetric Methods for Determination of Prazosin HCl in API and Drug Product

New simple and sensitive spectrophotometric and fluorimetric methods have been developed for the determination of prazosin hydrochloride (PRZ) in its active pharmaceutical ingredient (API) and drug product. The spectrophotometric method (Method I) is based on formation of a binary complex with rose Bengal (RB) at 572 nm. The absorbance-concentration plot is rectilinear over the range 2.5 25 μg/mL. The first fluorimetric method (method II a) depend on measurement of native fluorescence intensity of PRZ at λ emission 388 nm using λ excitation 340 nm. The fluorescence-concentration plot is rectilinear over the range 0.05– 1.4 μg /mL. The second method (method II b) was based on the quantitative quenching effect of PRZ on the native fluorescence of rose Bengal (RB) at the same pH. The quenching of the fluorescence of rose Bengal (RB) was measured at 575 nm after excitation at 483 nm. The fluorescence-concentration plot is rectilinear over the range 0.5–8 μg/mL. The proposed methods were successfully applied to the analysis of commercial tablets. Statistical comparison of the results with the reference method revealed good agreement and proved that there were no significant differences in the accuracy and precision between the two methods respectively