Quantitative Determination of Minoxidil in its Pharmaceutical Formulation and Study of Its Reaction Kinetics with Bromocresol Green

Abstract

This study presents a method involving the reaction of the drug minoxidil with the green bromocresol dye in an aqueous medium at a temperature of 20°C, with a reaction time of 10 minutes for completion. Upon completion of the reaction, the final product displays Greenish blue color, indicating maximum absorption at a wavelength of 617 nm. This method complies with Beer's law across a concentration range of 1-50 µg/mL, featuring a molar absorptivity of 5.377 x 10³ L·mol^-1·cm^-1 and a Sandell index of 0.3766 µg·cm^-2. The detection limit was established at 0.4365µg/mL, and the quantification limit was set at 1.3229 µg/mL. The recovery rate was determined to be 100.4128%, with the relative standard deviation remaining below 0.2519%. This method was effectively utilized to quantify minoxidil in its pharmaceutical formulation presented in tablet form. Furthermore, the kinetics of the resulting complex were examined, indicating that the kinetics are first-order, with an activation energy value of 11825.8336J·K⁻¹·mol⁻¹.