Thesis (M.Sc.) - Cairo University - Faculty of Science - Department of Physical Chemistry

Analyses of important biological species, environmental contaminants, and other important analytes are possible using electrochemical sensing. Among the numerous transduction methods, the electrochemical approach has gained the most focus due to their good sensitivity and high selectivity, accuracy, high dynamic range, lower cost, and simplicity. In this work, assaying uric acid in physiological fluid and Nitrite ion in water samples is achieved with high sensitivity and low detection limit. A simple and efficient electrochemical sensor is fabricated for electrochemical sensing of UA in presence of interfering species: epinephrine (Ep) and tyrosine (Ty). The sensor is fabricated by drop-casting a thin layer of CNTs followed by electrodeposition of two successive thin layers of poly(L-methionine) (PMT) and 18-crown-6 (CW) over a glassy carbon (GC) surface; GC/CNT/PMT/CW. Each of the sensor components' unique property contributes in synergism to the current signal enhancement. Voltammetry determination of UA in presence of Ep and Ty in human blood serum in the concentration ranges (0.04 to 40 oM), (0.04 to 40 oM), and (0.08 to 75 oM) is successfully achieved with low detection limits of 2.7 nM, 2.3 nM and 6.3 nM, respectively. Practical application of the GC/CNT/PMT/CWsensor is efficiently assessed in human serum samples for UA determination with acceptable recoveries, excellent anti- interference ability and long-term stability. Electrochemical determination of nitrite in real water samples is achieved using a simple and efficient electrochemical sensor.The sensor is fabricated by electrodeposition of a thin layer of poly(3,4-ethylenedioxythiophene) sandwiched by drop- casting two thin layers of CNTs and iron oxide nanoparticles (Fe3O4) over a GC electrode surface

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