Electrochemistry of moexipril: experimental and computational approach and voltammetric determination

The electrochemistry of moexipril (MOE) was studied by electrochemical methods with theoretical calculations performed at B3LYP/6-31 + G (d)//AM1. Cyclic voltammetric studies were carried out based on a reversible and adsorption-controlled reduction peak at -1.35 V on a hanging mercury drop electrode (HMDE). Concurrently irreversible diffusion-controlled oxidation peak at 1.15 V on glassy carbon electrode (GCE) was also employed. Potential values are according to Ag/AgCl, (3.0 M KCl) and measurements were performed in Britton-Robinson buffer of pH 5.5. Tentative electrode mechanisms were proposed according to experimental results and ab-initio calculations. Square-wave adsorptive stripping voltammetric methods have been developed and validated for quantification of MOE in pharmaceutical preparations. Linear working range was established as 0.03–1.35 M for HMDE and 0.2–20.0 M for GCE. Limit of quantification (LOQ) was calculated to be 0.032 and 0.47 M for HMDE and GCE, respectively. Methods were successfully applied to assay the drug in tablets by calibration and standard addition methods with good recoveries between 97.1 % and 106.2 % having relative standard deviation less than 10 %.