Electrochemical and catalytic investigations of levodopa and folic acid by modified carbon nanotube paste electrode

A sensitive and selective electrochemical method for the determination of levodopa (LD) was developed using a ferrocenemonocarboxylic acid modified carbon nanotubes paste electrode (FMCNPE). The modified electrode exhibited good electrocatalytic activity for electrochemical oxidation of LD at pH 7.0 phosphate buffer solution. The diffusion coefficient (D = 1.44 x 10(-6) cm(2) s(-1)), and the kinetic parameters such as the electron transfer coefficient (alpha = 0.4) and catalytic rate constant (k = 1.8 x 10(3) M-1 s(-1)) of LD at the surface of FMCNPE were determined using electrochemical approaches. Differential pulse voltammetry (DPV) of LD at the modified electrode exhibited linear dynamic range with a detection limit (3 sigma) of 70 nM. DPV was used for simultaneous determination of LD and FA at the modified electrode. Finally, this modified electrode was also examined for the determination of LD and FA in urine samples.