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Simultaneous Voltammetric Determination of Epinephrine and UricAcid in Presence of Ascorbic Acid Using Pyrolytic Graphite Electrode Modified with Nano- diamond/graphite Film & Voltammetric Determination of Levothyroxine at the Surface of Edge Plane Pyrolytic Graphite Electrode

Khafaji, Mona | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 41011 (03)
  4. University: Sharif University of Technology
  5. Department: chemistry
  6. Advisor(s): Shahrokhian, Saeed
  7. Abstract:
  8. Part 1: A novel modified pyrolytic graphite electrode with nanodiamond/graphite was fabricated. The electrochemical response characteristics of the modified electrode toward the epinephrine (EN) and uric acid (UA) are studied by means of cyclic and linear sweep voltammetry. The structural morphology and thickness of the film was characterized by SEM technique.The prepared electrode shows an excellent catalytic activity in the electrochemical oxidation of EN and UA, leading to remarkable enhancements in the corresponding peak currents and lowering the peak potentials. The prepared modified electrode acts as a highly sensitive sensor for simultaneous determination of EN and UA in the presence of ascorbic acid (AA). The electrode showed an excellent activity to resolving EN and UA peaks and completely eliminates the interfering effect of AA. The current response of the electrode showed a linear relationship with the concentrations of EN and UA in the range of 0.01–10 M and 0.01–60 M, respectively. In the semeasurements a detection limit of 3 nM is resulted for both compounds. This sensor exhibited very good reproducibility, repeatability and sensitivity for the determination of EN in the human blood serum, urine and the corresponding injecting samples. Moreover, the linear range and the detection limit of the determinations in the real samples remained constant in comparison with the measurements in the pure buffer solution. Part 2: The electrochemical response of sodium levothyroxine (T4) at the unmodified edge plane pyrolytic graphite (EPPG) electrode is investigated using cyclic voltammetric technique in the presence of 0.1 M HCl as supporting electrolyte.T4 underwent totally irreversible oxidation at this system and a well-defined peak at 821 mV is obtained. Compared to the signals obtained in the optimized conditions at bare glassy carbon and carbon paste electrodes, the oxidation current of T4 at EPPG electrode shows a greate enhancement. The electrochemical process of T4 is explored and the experimental conditions are optimized. The oxidation peak current represented a linear dependence on T4 concentration from 0.01 to 10 M. The detection limit of 3 nM (S/N = 3) is obtained for 250 s accumulation at 0.3 V. Determination of T4 in a synthetic serum sample demonstrated that this sensor has good selectivity and high sensitivity.
  9. Keywords:
  10. Epinephrine ; Uricacid ; Ascorbic Acid ; Modified Electrodes ; Cyclic Voltammetry ; Graphite Electrode ; Nano Diamond/Graphite ; Levothyroxine

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