Abstract
Background: The aim of this work was to develop an efficient voltammetric method for rapid analysis and simultaneous determination of L-dopa and benserazide (Bz) in pharmaceutical formulations. To the best of our knowledge simultaneous electrochemical determination of the mentioned compounds based on an activated screen-printed carbon electrode (SPCE*) has not been reported in the literature, this paper being the first example of an electrochemically pre-treated disposable carbon sensor for the direct and simultaneous determination of L-dopa and Bz in pharmaceutical formulation
Methods: Cyclic voltammetry (CV) was used to investigate the suitability of the SPCE* for the oxidation of L-dopa and Bz on the electrode surface in Britton-Robinson buffer solution (BRB) of pH 2.21. The validity of the proposed differential pulse voltammetry (DPV) method was successfully assessed for analysis of both drugs in a commercial pharmaceutical tablet formulation (Madopar). For comparison the determination of L-dopa and Bz in tablets was also carried out by a HPLC method. Results: Cyclic voltammetry studies showed that activated SPCE* lowers overpotentials and improve electrochemical behavior of L-dopa and Bz, compared to untreated SPCE. Under optimum differential pulse voltammetry conditions, the oxidation peak current of L-dopa in Britton-Robinson buffer solution of pH 2.21 showed a linear calibration range from 1x10-6 – 1x10-4 M with a limit of detection of 0.47x10-6 M. In case of Bz a linear calibration range from 6x10-6 M to 1x10-4 M and a detection limit of 2.6x10-6 M were obtained. Conclusion: In this work a simple and cost effective voltammetric method for the simultaneous determination of L-dopa and Bz in BRB solution of pH 2.21 was developed using activated SPCE. The current sensitivity and good limit of detection for L-dopa and Bz at the SPCE* prove its potential sensing applications for the determination of both compounds in Madopar pharmaceutical formulation with good recovery results. Some important advantages of the proposed method such as no need to use chemical modifiers and of sample pretreatment or any time-consuming extraction step prior to the drug assay and the disposability of the sensor strip that avoids poisoning from repeated use, along with its low cost, potential for miniaturization hold considerable promise for routine pharmaceutical analysis in evaluating the quality of some medicines in market places.Keywords: L-dopa, benserazide, electrochemically pretreated, screen-printed carbon electrode, voltammetry, pharmaceutical formulation.
Graphical Abstract
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