Abstract
Electrochemical behavior of zofenopril (ZOF) was studied via experimental electrochemical methods and theoretical calculations performed at B3LYP/6-31+G(d)//AM1 level. Optimum conditions for quantitative determination were investigated by several electrochemical methods such as cyclic voltammetry, square-wave voltammetry and bulk electrolysis. Electrochemical parameters like charge transfer, diffusion and surface coverage coefficients of adsorbed molecules and also number of electrons transferred in electrode mechanisms were calculated. All studies were based on the irreversible and adsorption-controlled electrochemical oxidation signal of ZOF at about 1.1 V versus Ag/AgCl at pH 5.0 in Britton-Robinson buffer (BR). This adsorptive character of ZOF was used to develop fully validated, new, rapid, selective and simple voltammetric methods for the direct determination of the molecule in pharmaceutical dosage forms and biological samples without time-consuming steps prior to drug analysis. Peak current of electrochemical oxidation of ZOF was found to change linearly with the concentration in the range from 2.0x10-6 molL-1 (0.86 mgL-1) to 1.0x10-4 molL-1 (42.9 mgL-1) in direct voltammetric methods and found to change linearly with the concentration in the range from 2.0x10-8 molL-1 (8.59 μgL-1) to 1.0x10-6 molL-1 (0.43 mgL-1) in adsorptive stripping voltammetric methods. Limit of detection (LOD) and limit of quantification (LOQ) were found to be 1.17x10-8 molL-1 (5.03 μgL-1) and 3.89x10-8 molL-1 (16.8 μgL-1) respectively in anodic adsorptive stripping voltammetry. The methods were successfully applied to assay the drug in tablets, human serum and human urine with good recoveries (between 95.0 % and 104.6 %) and relative standard deviation less than 10 %.
Keywords: Adsorptive stripping voltammetry, AM1, Biological samples, DFT, HOMO-LUMO, Pharmaceuticals, Zofenopril
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