Tessema, Dr. MeridMehretie, Solomon2022-01-252023-11-092022-01-252023-11-092013-05http://etd.aau.edu.et/handle/12345678/29611Electrochemical signals can be enhanced by specifically modifying electrode surfaces with the aim of providing suitable environment to the analyte of interest. Poly(3,4- ethylenedioxythiophene) and activated iron(JlI) doped zeolite were used to modify carbon electrodes for the determination of drugs and biological fluids. 3,4- Ethylenedioxythiophene was electropolymerized on glassy carbon electrode by running multi-sweep cyclic voltammetry whereas iron(lIl) doped zeolite was coated on the electrode surface. Both modified carbon electrodes were characterized by using cycl ic voltammetry. The poly(3,4-ethylenedioxythiophene) modified electrodes were employed for the determination of niclosamide and N-acetyl-p-aminophenol while the iron(JlI) doped zeolite modified electrodes were used to determine pyridine-2-aldoxime methochloride and uric acid. Cyclic voltammetry and differential pulse voltammetry were used to investigate the electrochemical behavior of N-acetyl-p-aminophenol and its degradation product, p-aminophenol at poly(3,4-ethylenedioxythiophene) modified electrode in pH 7.0 buffer solution. Both N-acetyl-p-aminophenol and p-aminophenol showed quasi-reversible redox reactions with formal potentials of 367 m V and 101 m V (versus Ag/ AgCI), respectively. The significant peak potential difference (266 m V) between N-acetyl-p-aminophenol and p-aminophenol enabled the simultaneous III determination of these species using differential pulse voltammetry. The voltammetric responses gave linear ranges of 1.0- 100 /lM and 4.0- 320 /lM, with detection limits of 0.40 /lM and 1.2 /lM for N-acetyl-p-aminophenol and p-aminophenol, respectively. Furthermore, the poly(3 ,4-ethylenedioxythiophene) modified electrode showed a very good electrochemical behavior for niclosamide with a significant enhancement of the peak current compared to the bare electrode. A linear voltammetric response for niclosamide was obtained in the concentration range 0.075- 7.50 /lM, with a detection limit of 0.01 /lM. When the iron(lll) doped zeolite modified glassy carbon electrode was treated with sulfuric acid (2.5 mM), it showed a better electrochemical response compared to the untreated zeolite modified electrode. Cyclic voltammetry and square wave voltammetry were employed to investigate the electrochemical behavior of pyridine-2-aldoxime methochloride and uric acid at the modified electrode. The analytical performance of the modified electrode was evaluated using anodic stripping voltammetry in a buffer solution (PH 7.0), and a linear response for pyridine-2-aldoxime methochloride was obtained in the concentration range 0.5-100.0 /lM with a detection limit of 0.16 /lM. The iron(IIl) doped zeolite was also responsible for the electrocatalytic oxidation of uric acid in a buffer solution (PH 4.6). The analytical performance of the iron(IIl) doped zeolite modified electrode was evaluated using square wave voltammetry. A linear anodic response for uric acid in the concentration range 0.6-6.0.0 /lM, a detection limit of 0.09 /lM and sensitivity of 0.64 /lA /lM- 1 were obtained. Finally, the proposed methods were successfully applied for the determination of the analytes in pharmaceutical formulations and/or biological samples.enDetermination of Drugs and Biological FluidsThesis