Spectroscopic determination of the minoxidil drug by charge transfer complex using Schiff base

This work includes the synthesis and characterization of a charge transfer complex from Schiff base-minoxidil with a new azo reagent, 1-(4-hydroxy-3-(4-nitrophenyl diazenyl) phenyl) ethan-1-one, and the determination of minoxidil drug in pharmaceuticals. The charge transfer complex gives a red-colored product that gives its highest absorption at the wavelength of 505 nm. UV-visible, FT-IR, and GC-mass characterized azo reagent, Schiff base-drug, and charge transfer complex. The nature of the complex was determined by studying the Job method and the molar ratio method, which showed that the acceptor-to-donor ratio was (1:1). Simple, easy, highly sensitive, and inexpensive spectrophotometric methods for the determination of minoxidil have been developed. Optimal conditions were studied, which gave good sensitivity. It displayed a linear range of 1–12.5 μg mL-1 and a correlation value of 0.9979. The Sandel sensitivity, the detection limit (LOD), and the quantitative limit (LOQ) were obtained at 0.0110 μg/cm², 0.1019 μg mL-1, and 0.3089 μg mL-1, respectively. The average recovery (%) was 102.47.