No abstract

The oxidative behavior of pramipexole was studied at modified electrodes in various buffer solutions and at different pH values using cyclic and square wave voltammetry. Glassy carbon electrode (GCE) was modified using graphene (GRP) and bismuth (III) oxide (Bi 2 O 3 ) nanoparticles. Different conditions were investigated to optimize the analytical methodology for determination of pramipexole in pharmaceutical formulation. Square-wave voltammograms of pramipexole showed higher current response at GRP/GCE, 88.66% and Bi 2 O 3 /GCE, 20.70% whereas; cyclic voltammograms at GRP/GCE, 82.94% and Bi 2 O 3 /GCE, 18.03% as compared to bare GCE. Electrochemical impedance spectra (EIS) showed the reduction in charge transfer resistance of modified electrodes and enhancement in current response due to higher electrocatalytic behavior of GRP/GCE and Bi 2 O 3 /GCE. The relationship between oxidation peak current and concentration of pramipexole was linear in the range of 40−300 ng mL −1 with the detection limit 12.79 ng mL −1 . The morphological characteristics of GRP and Bi 2 O 3 nanoparticles were studied by atomic force microscopy (AFM). This method was employed for quantification of pramipexole in different pharmaceutical formulations.

Voltammetric behaviour and assay of nicorandil were investigated using square-wave and cyclic voltammetry. Voltammograms in Britton-Robinson (BR) buffer exhibited one well-defined and two merged reduction peaks. The influence of different buffers, electrolytes, pH, scan rates, and concentration of the drug on cathodic peak current was studied. On the basis of electrochemical behaviour of nicorandil, a direct square-wave voltammetric procedure for quantitation of nicorandil has been developed and validated. The proposed square-wave voltammetric method allows quantitation over the range 12.5-62.5 µg mL(-1) with correlation coefficient of 0.992. The limit of quantification and limit of detection were 21.95 µg mL(-1) and 6.58 µg mL(-1) , respectively. Precision and accuracy were also checked and found within limits. The developed square-wave method has also been successfully applied for the determination of nicorandil in pharmaceutical formulations.

Redox behavior of midazolam was studied at a glassy carbon electrode in various buffer systems, supporting electrolytes and pH using differential pulse, square-wave and cyclic voltammetry. Based on its reduction behavior, a direct differential pulse voltammetric method has been developed and validated for the determination of midazolam in parenteral dosage. Three well-defined peaks were observed in 0.1% SLS, Britton–Robinson (BR) buffer of pH 2.5. The effect of surfactants like sodium lauryl sulfate (SLS), cetyl trimethyl ammonium bromide (CTAB) and Tween 20 was studied. Among these surfactants SLS showed significant enhancement in reduction peak. The cathodic peak currents were directly proportional to the concentration of midazolam with correlation coefficient of 0.99.

The present study reports voltammetric reduction of nitazoxanide in Britton–Robinson (B–R) buffer by cyclic and square-wave voltammetry at glassy carbon electrode. A versatile fully validated voltammetric method for quantitative determination of nitazoxanide in pharmaceutical formulation has been proposed. A squrewave peak current was linear over the nitazoxanide concentration in the range of 20–140 µg/mL. The limit of detection (LOD) and limit of quantification (LOQ) was calculated to be 5.23 μg/mL and 17.45 μg/mL, respectively.