Cyclodextrin Host-Guest Recognition Approach for Simultaneous Quantification and Voltammetric Studies of Levodopa and Carbidopa in Pharmaceutical Products

An electrochemical sensor for simultaneous quantification of Levodopa (L-dopa) and Carbidopa (C-dopa) using a beta-cyclodextrin/poly(N-acetylaniline) (beta-CD/PNAANI) modified carbon paste electrode has been developed. Preconcentrating effect of beta-CD as well as its different inclusion complex stability with L-dopa and C-dopa was used to construct an electrochemical sensor for quantification of these important analytes. The overlapping anodic peaks of L-dopa and C-dopa at 810 mV on bare carbon paste electrode resolved in two well-defined voltammetric peaks at 450 and 880 mV vs. Ag/AgCl, respectively, with a drastic enhancement of the anodic peak currents. Under optimized conditions, linear calibration curves were obtained in the ranges of 0.5117 mu M and 1.6210 mu M with detection limits down to 0.2 and 0.8 mu M for L-dopa and C-dopa, respectively. The proposed electrode was successfully applied for the determination of L-dopa /C-dopa in pharmaceutical formulations and the results were in close agreement with the labeled values.