Voltammetric Determination of Tryptophan and 5-Hydroxytryptophan Using Graphite Electrode Modified with a Thin Film of Graphite/Diamond Nano-mixture And Determination of omeprazole Using Graphite Electrode

Bayat, Maryam | 2010

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 40927 (03)
  4. University: Sharif University of Technology
  5. Department: Chemistry
  6. Advisor(s): Shahrokhian, Saeed
  7. Abstract:
  8. At the first part of this thesis, a pyrolitic graphite electrode (PGE) modified with graphite/nanodiamond film (GND) was applied as a sensitive electrochemical sensor for determination and study of electrochemical behavior of tryptophan (Trp) and 5-hydroxytryptophan (5-HTP) in aqueous solutions. The results showed that GND caused a remarkable increase in the peak currents so the GND/PGE electrode surface was more sensitive to the concentration of Trp and 5-HTP than the PGE surface. The determination of Trp and 5-HTP were investigated by stripping voltammetry. Experimental parameters such as scan rate, pH, accumulation conditions and amount of the modifier used on the PGE surface were optimized by monitoring the CV responses toward Trp and 5-HTP. A maximum current response obtained at pH 3.0 after accumulation at open circuit. Two linear dynamic ranges of 1.0×10−7 to 8.0×10−6M and 1.0×10−5 to 8.0×10−5M with a detection limit of 30 nanomolar were obtained for Trp, also two linear dynamic ranges of 2.0×10−8 to 2.0×10−6M and 4.0×10−6 to 1.0×10−5M with a detection limit of 6 nanomolar for 5-HTP. The modified electrode shows several advantages such as simple preparation method, high stability, high sensitivity, sharp and symmetric peaks, long-term stability and remarkable voltammetric reproducibility. At the second part of this thesis, a pyrolitic graphite electrode (PGE) was used for determination and study of electrochemical behavior of omeprazole in aqueous solutions. The results of CV investigations were shown a considerable enhancement in the peak current of omeprazole. Corresponding to the results, pyrolytic graphite has an electrocatalytic influence on oxidation of omeprazole. Furthermore, simplicity, high reproducibility and low detection limit (3 nanomolar) of the electrode response as well as wide linear range (1.0×10−8 to 4.0×10−6M) can be stated as significant features of this electrode. The electrode also used for determination of omeprazole in commercial drugs and showed satisfying results.

  9. Keywords:
  10. Electrochemical Sensor ; Nanodiamond ; Cyclic Voltammetry ; Modified Electrodes ; Graphite Electrode ; Tryptophan ; 5-Hydroxytryptophan ; Omeprazol

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