Spectrophotometric Determination of Finasteride Using Diazotization and Coupling

Abstract

An accurate and sensitive spectroscopic method was developed for the determination of finasteride based on the azo-coupling reaction. 4-Aminoacetophenone was diazotized to form the corresponding diazonium salt, which was subsequently coupled with FIN in the presence of sodium hydroxide. The resulting complex was then heated to 50 °C to produce a yellow-colored azo dye. The absorbance of the product was measured at a wavelength of 425 nm. The reaction conditions were optimized to achieve maximum complex formation. The results indicated that the method exhibited good linearity over the concentration range of 2.5–22.5 µg/mL, with a determination coefficient (R² = 0.9994). The method showed good sensitivity, with a molar absorptivity of 8829 L·mol⁻¹·cm⁻¹, Sandell’s sensitivity of 0.04219 µg/cm², a limit of detection (LOD) of 0.1164 µg/mL, and a limit of quantification (LOQ) of 0.3530 µg/mL. The accuracy and precision of the method were evaluated, and the recovery percentage (Rec%) ranged from 96.6244 to 101.8987%, while the relative standard deviation (RSD%) was less than 0.1111-0.5268% The proposed method demonstrated high accuracy and sensitivity and was successfully applied to the determination of FIN in pharmaceutical formulations.