Square-wave adsorptive voltammetry of dexamethasone: redox mechanism, kinetic properties, and electroanalytical...

The electrochemical reduction behavior of dexamethasone at a hanging mercury drop electrode was investigated by cyclic and square-wave adsorptive voltammetries in a Britton-Robinson buffer at pH 2.0. The optimized experimental conditions consisted of a pulse potential frequency of 100 s(-1), a pulse amplitude of 15 mV, and a potential step height of 2 mV, with E(acc)=-0.60V and t(acc)=15s. From these parameters, it was also possible to develop a detailed study about the kinetic and mechanistic events involved in the reduction process. Two well-defined peaks were observed in the cathodic scan, and peak 2 was used to obtain analytical curves. A linear range between 4.98×10(-8) and 6.10×10(-7)mol L(-1), with a detection limit of 2.54×10(-9)mol L(-1) and a quantification limit of 8.47×10(-9)mol L(-1), was observed. Moreover, it was possible to achieve a simple, selective, and versatile methodology adaptable to the quantification of dexamethasone because common excipients used in multicomponent commercial formulations caused no interference. The satisfactory recoveries and the low relative standard deviation data reflected the high accuracy and precision of the proposed method for the determination of dexamethasone in injectable eye drops and elixir samples.