Electro-oxidation of cytostatic drugs: Experimental and theoretical identification of by-products and evaluation of ecotoxicological effects

Methotrexate (MTX) and Capecitabine (CPC) as mostly used cytostatic drugs were degraded by electro-oxidation process in this study. Ti/IrO2-RuO2 electrode was used to provide anodic oxidation. The effect of change of current density, initial pH of the solution and supporting electrolyte concentration on electro-oxidation of cytostatic drugs was evaluated. Current density of 30 mA/cm(2), neutral pH and supporting electrolyte concentration of 200 mg L-1 were determined as optimum operational parameters. After oxidation process, the transformation by-products of cytostatic drugs were identified by LC-MS-MS analysis. Density functional theory (DFT) modelling was performed and the calculations were given in harmony with analytic results. In addition, toxicity evaluation on the electro-oxidation was assessed due to the possible toxic effect of the metabolites after treatment process. Indeed, the transformation by-products of MTX showed toxic effects after treatment, however; the metabolites CPC did not cause toxicity although lower removal efficiency.