A New Mechanism for Resonance Rayleigh Scattering Detection of Minoxidil Based on Catalytic Oxidation of Silver Nanoparticles

This study introduces a novel method for detecting minoxidil using silver nanoparticles (AgNPs) through a catalytic oxidation process. Minoxidil reduces to its pyrimidine form, causing AgNPs to oxidize and decrease in size and number, which in turn reduces their resonance Rayleigh scattering (RRS) signal. The method is simple, rapid, and involves mixing minoxidil with AgNPs in an acidic buffer, with the reaction completing in 2 minutes. The RRS intensity at 409 nm linearly correlates with minoxidil concentration in the range of 0.5 to 5.0 mM, achieving a detection limit of 0.35 mM. This technique was successfully applied to quantify minoxidil in hair-growth formulations.