Simple self-referenced ratiometric electrochemical sensor for dopamine detection using electrochemically pretreated glassy carbon electrode modified by acid-treated multiwalled carbon nanotube

In this work, a simple self-referenced ratiometric electrochemical dopamine (DA) sensor was described based on electrochemically pretreated glassy carbon electrode (EPGCE) modified by acid-treated multiwalled carbon nanotube (MWCNT). The quinone-type group on the surface of the EPGCE and acid-treated MWCNT was used as an inner reference electrochemical probe in phosphate buffer solutions (pH 3.0). At the same time, it was demonstrated that the electrochemical pretreatment of the GCE and the introduction of acid-treated MWCNT could greatly enhance the electrical conductivity and the electroactive surface area of the electrode. The MWCNT/EPGCE-based ratiometric sensor exhibited high sensitivity, high selectivity, good reproducibility, and good stability for DA detection. The high sensitivity was demonstrated to be predominately ascribed to the fast electron-transfer kinetics and high surface coverage of DA on the electrode surface. The calibration curve for DA was obtained in the concentrations range of 1.0 to 20.0 μM, with a detection limit of 0.23 μM. In addition, the ratiometric electrochemical sensor allowed the detection of DA in human serum samples.