ELECTROCHEMICAL STUDIES OF GANCICLOVIR AS THE ADSORBED CATALYST ON MERCURY ELECTRODE

Although ganciclovir (gan) as a purine analogue is a compound of biological interest (antiviral drug), it has been rarely electrochemically studied. In this paper surface catalytic electrode mechanism based on the hydrogen evolution reaction is analyzed under conditions of square-wave voltammetry and differential capacity curves of double layer measurements. The electrode mechanism is assumed to involve a preceding chemical reaction in which the adsorbed catalyst (gan(ads)) is protonated at the electrode surface, i.e., gan(ads) + H-aq(+) -> ganH+(ads). The protonated form of the catalyst (ganH+(ads)) is irreversibly reduced at potential about -1.35 V vs Ag|AgCl, yielding the initial form of the catalyst and atomic hydrogen, i.e., ganH+(ads) + e -> gan(ads) + H-aq. Changes of zero charge potential and surface tension point to the adsorption of ganciclovir molecule directed with guanine group to the mercury surface and suggests that ganciclovir molecules are not placed flat on the mercury surface. The effect of adsorption on mercury electrode was studied in detail in respect to analytical usefulness of the obtained results. A new catalytic method for voltammetric determination of ganciclovir was developed. The detection and quantification limits were 1.3 x 10(-7) and 4.3 x 10(-7) mol l(-1) for square-wave voltammetry, and 1.4 x 10(-7) and 4.7 x 10(-7) mol l(-1) for linear-sweep voltammetry.