The effect of boron doped diamond (BDD) surface termination immediately after cathodic and anodic electrochemical pre-treatment, and the influence of the pre-treatment in different supporting electrolytes, on the electrochemical oxidation potentials of dsDNA. DNA bases, nucleotides, homopolynucleotides and biomarker 8-oxoguanine was investigated, using differential pulse voltammetry in aqueous media at different pH. The anodic and cathodic BDD surface pre-treatments were performed in three different solutions, pH 4.5 0.1 M acetate buffer, pH 7.0 0.1 M phosphate buffer and pH 0.55 0.5 M sulphuric acid and the electrochemical response at the BDD surface varied as a function of the potential applied in the surface pre-treatment and also on the electrolyte used. All results demonstrated that the electrochemical properties of the BDD electrode are very dependent on the state of the surface termination, due to oxygen and hydrogen terminations. Concerning the compounds studied a better response was obtained when the BDD surface was pre-treated cathodically. The interaction and adsorption of the electrochemical species with the SOD surface pre-treated cathodically was facilitated due to a higher conductivity of the BDD electrode surface. On the other hand, after anodic pre-treatment a wider potential window of BDD surface was obtained enabling the detection of the pyrimidine bases. However, the hydroxyl radicals produced on BDD surface during the anodic pre-treatment are highly reactive, and consequently the BDD surface is not completely inert. (C) 2010 Elsevier B.V. All rights reserved.