Selective electrochemical determination of dopamine, using a poly(3,4-ethylenedioxythiophene)/polydopamine hybrid film modified electrode

• We report obtaining a new electrode modified with a hybrid film PEDOT/PDA.
• PEDOT/PDA is a selective electrode for dopamine in the presence of interferents.
• The hybrid film PEDOT/PDA displays good stability and reproducibility.
• PEDOT/PDA presents detection limits of 0.6 μM and limit of quantification of 1.7 μM.

The selective determination of dopamine (DA) was performed in the presence of ascorbic (AA) and uric acid (UA), using a platinum electrode (Pt) modified with a hybrid film of poly(3.4-ethylenedioxythiophene)/polydopamine (PEDOT/PDA). PEDOT was obtained using a potential step technique on a bare Pt electrode. PDA was subsequently obtained on the PEDOT coated electrode by cyclic voltammetry. The PDA thickness effect allows observing just the DA oxidation signal in the presence of some interferents, e.g. uric acid (UA) and ascorbic acid (AA). The formed PEDOT/PDA hybrid film was compared with PEDOT in a K4[Fe(CN)6] solution in PBS of pH 7.4. Inhibition of the [Fe (CN)6]4−/[Fe(CN)6]3− redox couple on the PEDOT/PDA surface was observed, indicating the film bears a negative surface charge. The different electrodes were characterized by SEM and FTIR. DA amperometric determination was performed in the presence of AA and UA. The sensor proved to be selective toward DA. Calibration curves, with a linear range 1.5 × 10−6 to 50 × 10−6 mol L−1, enabled the limit of detection and quantification to be determined, namely 0.65 × 10−6 mol L−1 and 1.77 × 10−6 mol L−1, respectively. The described methodology permits, therefore, to propose this modified electrode as a new electrode for DA determination in the presence of interferents.