Abstract

Background: The electrochemical oxidation of antiviral drug valacyclovir was first investigated in aqueous and aqueous/surfactant solutions by cyclic and linear sweep voltammetry using a borondoped diamond electrode. The compound was oxidized in one, two or three steps at high positive potentials, depending on pH and composition of the supporting electrolyte, scan rate and surfactant type.

Method: It underwent irreversible oxidation within the potential window from 0 to +1.8 V, which was a diffusion-controlled process. Using differential pulse wave-form, the drug could be determined in the concentration range 8×10^-7 M – 6×10^-5 M in phosphate buffer pH 3.0 alone, and 8×10^-8 M – 8×10^-6 M in 0.2 M H₂SO₄ containing 1×10^-3 M sodium dodecylsulfate (anionic surfactant).

Results: The limits of detection were 1.0×10^-7 M (32.43 ng mL^-1) and 2.1×10^-8 M (6.81 ng mL^-1) in both of the media, respectively.

Conclusion: Practical applicability of the newly developed approach was verified by the assays of pharmaceutical formulations (tablets), spiked human urine and simulated gastric fluid samples.

Keywords: Valacyclovir, boron-doped diamond electrode, sodium dodecylsulfate, tablet, biological samples.

Graphical Abstract