Electrooxidation of the antiviral drug valacyclovir and its square-wave and differential pulse voltammetric determination in pharmaceuticals and human biological fluids

The electrochemical properties of valacyclovir, an antiviral drug, were investigated in pH range 1.8–12.0 by cyclic, differential pulse and square-wave voltammetry. The drug was irreversibly oxidized at a glassy carbon electrode in one or two oxidation steps, which are pH-dependent. For analytical purposes, a very resolved diffusion controlled voltammetric peak was obtained in Britton–Robinson buffer at pH 10.0 using differential pulse and square-wave modes. Limits of detection were 1.04 × 10−7 and 4.60 × 10−8 M for differential pulse and square-wave voltammetry, respectively. The applicability to direct assays of tablets, spiked human serum and simulated gastric fluid, was described.