ELECTROCHEMICAL BEHAVIOR OF DISOPYRAMIDE AND ITS ADSORPTIVE STRIPPING DETERMINATION IN PHARMACEUTICAL DOSAGE FORMS AND BIOLOGICAL FLUIDS
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Electrochemical behavior of disopyramide (DPA) and optimum conditions to its quantitative determination were investigated using voltammetric methods. Some electrochemical parameters such as diffusion coefficient, surface coverage of adsorbed molecules, electron transfer coefficient, standard rate constant and number of electrons were calculated using the results of cyclic and square-wave voltammetry. All studies were based on the quasi-reversible and adsorption-controlled electrochemical reduction signal of DPA at about -1.60 V vs Ag|AgCl at pH 10.0 in Britton-Robinson buffer. This adsorptive character of molecule was used to develop fully validated, new, rapid, selective and simple square-wave cathodic adsorptive stripping voltammetric (SWCAdSV) method to the direct determination of DPA in pharmaceutical dosage forms and biological samples without time-consuming steps prior to drug assay. Peak current of electrochemical reduction of DPA was found to change linearly with the concentration in the range from 7.15 x 10(-8) mol l(-1) (0.024 mg l(-1)) to 1.43 x 10(-6) mol l(-1) (0.49 mg l(-1)). Limit of detection (LOD) and limit of quantification (LOQ) were found to be 5.65 x 10(-8) mol l(-1) (0.019 mg l(-1)) and 1.88 x 10(-7) mol l(-1) (0.064 mg l(-1)), respectively. The method was successfully applied to assay the drug in tablets, human serum and human urine with good recoveries at about 100%.