Electrochemical determination of l-dopa in the presence of ascorbic acid on the surface of the glassy carbon electrode modified by a bilayer of multi-walled carbon nanotube and poly-pyrrole doped with tiron

There are high attractions in the development of conducting polymer (CP) coatings to improve the electrochemical properties and biocompatibility of electrodes in the area of biosensors. A new type of the modified electrodes is prepared in a layer-by-layer process by using multi-walled carbon nanotube (MWCNT) and poly-pyrrole. In this procedure, the glassy carbon electrode is casted by a drop suspension of MWCNT, which leads to form a thin film of nanotube on its surface. In the second step, electrochemical polymerization of pyrrole in the presence of tiron (used as doping anion) is performed on the surface of the MWCNT pre-coated electrode. The modification procedure led to fabrication of a modified electrode that can be used as a sensitive and selective sensor for voltammetric determination of l-dopa. The electrochemical behavior of l-dopa is investigated on the surface of the modified electrode using cyclic voltammetry (CV) in various potential sweep rates and pHs of the buffer solution. The effect of drop size of MWCNT suspension and the number of cycles in the electro-polymerization process on the electrode response toward l-dopa has been optimized. The results of CV and DPV investigations showed a considerable enhancement in the anodic peak current of l-dopa (up to seven times) associated with decreasing about 180 mV in the corresponding peak potential. Furthermore, high reproducibility as well as low detection limit of the electrode responses can be considered as significant features of the prepared modified electrode.