Electrochemical sensing of levodopa or carbidopa using a glassy carbon electrode modified with carbon nanotubes within a poly(allylamine hydrochloride) film

In this study, the performance of a glassy carbon electrode (GCE) modified with functionalized multi-walled carbon nanotubes (MWCNT) immobilized within a poly(allylamine hydrochloride) (PAH) film for the electrochemical determination of the catecholamines, levodopa (LD) and carbidopa (CD) is evaluated. The electrochemical behaviour of the MWCNT-PAH/GCE sensor was investigated via cyclic voltammetry. Under the optimum experimental conditions, the LD and CD analytes were determined by differential pulse voltammetry (DPV) using their oxidation redox processes at −24 mV and +490 mV (versus Ag/AgCl (3.0 mol L−1 KCl)), respectively. The obtained analytical curves were linear from 2.0 to 27 μmol L−1 for LD and from 2.0 to 23 μmol L−1 for CD, with limits of detection of 0.84 μmol L−1 for LD and 0.65 μmol L−1 for CD. The proposed DPV method was successfully employed for LD and CD determination in commercial pharmaceutical formulation samples, and the collected results were consistent with those obtained by the respective standard methods at a confidence level of 95%. In addition, the potentiality of the DPV method was tested for LD and CD quantification in human serum samples.