Simultaneous voltammetric determination of 3-methyladenine and adenine at disposable screen-printed carbon electrode

The anodic behavior of 3-methyladenine (3-mAde) and adenine (Ade) were investigated in aqueous media on commercial screen-printed carbon electrodes (SPCEs), using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The electrochemical performance of the SPCEs was first evaluated by CV and using the [Fe(CN)₆]^3- redox probe. The electroactive areas of some SPCEs were also determined and discussed. Overall, the results were very satisfactory and indicated good repeatability and reproducibility of the SPCEs. Regarding 3-mAde its oxidation occurred in a single irreversible step pH dependent controlled by a diffusion layer and at more positive potential, ∼ +200.00 mV, in relation to Ade, demonstrating the possibility of simultaneous detection of these two biomarkers. By DPV experimental conditions were explored to increase the sensitivity and selectivity of the 3-mAde electrooxidation signal, such as influence of the composition and pH of the medium, effect of 3-mAde concentration and presence of possible interferents. A simple, sensitive, selective and fast electroanalytical method, using DPV and commercial SPCE, was developed for determination of 3-mAde in hydrolyzed DNA samples; with a linear range from 2.00 to 10.00 μmol L^-1, limit of detection (LOD) of 0.35 μmol L^-1 and recoveries ranged from 96.0 % to 98.3 % in acetate buffer (pH = 4.10). For the simultaneous quantification of Ade and 3-mAde the analytical data were: concentration range of 0.50-10.00 μmol L^-1, LOD of 0.34 μmol L^-1 and the mean recovery was 95.2 % for Ade and from 2.00 to 10.00 μmol L^-1, LOD of 0.64 μmol L^-1 and the mean recovery was 101.3 % for 3-mAde.