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

Abstract

An electrochemical sensor for simultaneous quantification of Levodopa (L-dopa) and Carbidopa (C-dopa) using a b-cyclodextrin/poly(N-acetylaniline) (b-CD/PNAANI) modified carbon paste electrode has been developed. Preconcentrating effect of b-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 0.5-117 mM and 1.6-210 mM with detection limits down to 0.2 and 0.8 mM 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.

Ternary mutual diffusion coefficients of aqueous {l-dopa (1)+β-CD (2)} solutions at T=298.15K

“…The 1 H NMR spectra of b-CD in the presence of L-dopa (5 mmol Á dm À3 : 5 mmol Á dm À3 , pH of dissolution) displays significant shifts in the signals for H-3 0 and H-5 0 , towards higher and lower frequencies, respectively, accompanied by a visible narrowing of the signal of H- signals inside the b-CD cavity, and the corresponding changes for all the protons of L-dopa in the 1 H NMR spectra of mixtures of L-dopa and b-CD support formation of a complex between L-dopa and b-CD, and analogy with previous studies [5,29] points to the inclusion of L-dopa in the hydrophobic cavity of b-CD.…”

“…Using D 21 /D 11 values, at the same concentrations, we can expect that a mole of diffusing L-dopa co-transports, at most, 0.09 mol of b-CD. These observations can readily be explained by considering the binding interactions between L-dopa and b-CD molecules, leading to formation of inclusion complexes in solution, as shown from our NMR data and other studies [5]. As a consequence, the L-dopa molecules will have reduced mobility and, therefore, this can be responsible by the relatively large decrease in D 11 .…”

“…Electrochemical sensors have been developed for quantification of this drug in recent years, which use a b-cyclodextrin/poly (N-acetylaniline) [5]. For example, Aslanoglu et al [6] proposed a b-cyclodextrin doped poly(2,5-diami nobenzenesulfonic acid) modified glassy carbon electrode for detection of the L-dopa/cyclodextrin species.…”

Development of a Modified Carbon Electrode With Ionic Liquid and Its Application for Electrocatalytic Oxidation and Voltammetric Determination of Levodopa

“…Numerous methods have been used for the determination of levodopa in matrices such as in raw material, pharmaceutical formulations and biological fluids, including spectrophotometry, liquid chromatography, capillary zone electrophoresis and electrochemistry. [3][4][5][6][7][8] The electrochemistry of the oxidation of levodopa has been described using different electrodes, including carbon, platinum or gold electrodes. This has enabled the electrochemical characterization and determination of levodopa.…”

“…The as-obtained LOD is on the order of than those reported for some modified electrodes used in the electrocatalysis of levodopa, for example 0.17 μg/mL for a basal plane pyrolytic graphite electrode modified with chloro(pyridine) bis-(dimethylglyoximato)cobalt-(III)6, 0.01-0.05 μg/mL for modified glassy carbon and CPE. 5,7,30,31 13.4 μg/mL in a gold screen-printed electrode.…”