Abstract
Electrochemical oxidation of theophylline was investigated at the surface of carbon paste electrode with methylene blue dye as an electron mediator. The electrode surface was characterized by atomic force microscopy (AFM) and XRD. Methylene blue a cationic dye is an excellent redox mediator. Cyclic voltammetric technique was used to investigate the electrochemical behaviour of modified electrode. There was enormous increase in the peak current as compared with bare electrode. The effect of pH on oxidation behaviour of theophylline in the pH range of 3.0-11.2 was carried out. Electrochemical oxidation of theophylline was predominant in pH 3.0. In addition, the effect of scan rate variation was used to calculate the number of electrons transferred and heterogeneous rate constant. Further, a possible electrode reaction mechanism was proposed. Differential pulse voltammetric method in the linear range 0.2 -10 µM was performed and limit of detection and quantification were calculated 2.25 nM and 7.52 nM respectively. The developed electrode was further successfully employed for the determination of theophylline in pharmaceutical and human urine samples.
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