Electrochemical Oxidation and Thermodynamic Parameters for an Anti-viral Drug Valacyclovir

The electro-oxidation of valacyclovir has been studied at a glassy carbon electrode in phosphate buffer media by using cyclic voltammetric technique. Effects of anodic peak potential (Epa), anodic peak current (ipa), pH and heterogeneous rate constant (ko) have been discussed, single irreversible voltammogram was observed. The effects of scan rate, pH, concentration and temperature were evaluated. The electrode processes were shown to be diffusion controlled and irreversible involving adsorption effects. The electro-oxidation product of valacyclovir has been identified by MALDI2-((2-amine-6,8-dioxo-7,8-dihydro-3H-purin9(6H)-yl)methoxy)ethyl2-amino-3-methylbutanoate), involving 2-electron and 2-porton oxidation. Thermodynamic parameters such as activation energy Ea=27.51 kJmol-1, enthalpy ΔH#=25.03 kJmol-1, entropy ΔS#=-284.8 JK-1mol-1, Gibbs free energy ΔG#=109.9 kJmol-1 and Arrhenius factor, logA=-2.08 and analytical parameters linearity range 5.0×10-3 to 7.5×10-5 M, LOD=1.44 μM, LOQ=4.83 μM and RSD=5.26% were calculated and presented.