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Electrochemical Determination of Tyrosine and Tryptophan at the Surface of Pyrolytic Graphite Electrode Modified with Multi-Walled Carbon Nanotubes, New Coccine and Nitrazine

Ebrahimi, Shiva | 2011

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 42126 (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 new coccine/multi-walled carbon nanotubes film (NC/MWCNT) was applied as a sensitive electrochemical sensor for determination and study of electrochemical behavior of tyrosine (Tyr) in aqueous solutions. The results showed that NC/MWCNT caused a remarkable increase in the peak current so the NC/MWCNT/PGE electrode surface was far more sensitive to the concentration of Tyr than the PGE surface. The determination of Tyr was investigated by linear sweep voltammetry (LSV). Experimental parameters, such as scan rate, pH and amount of the modifier used on the PGE surface were optimized by monitoring the LSV responses toward Tyr. A maximum current response obtained at pH 7.0. Two linear dynamic ranges of 5.0×10−7 to 7.0×10−6M and 7.0×10−6 to 7.0×10−5 M with a detection limit of 1.5×10−7 M were obtained for Tyr. The modified electrode shows several advantages such as simple preparation method, high stability, high sensitivity, sharp peaks and remarkable voltammetric reproducibility. At the second part of this thesis, a pyrolitic graphite electrode (PGE) modified with nitrazine/multi-walled carbon nanotubes film (NI/MWCNT) was used for determination and study of electrochemical behavior of tryptophan (Trp) in aqueous solutions. The results of LSV investigations were shown a considerable enhancement in the peak current of Trp. Simplicity, high reproducibility and low detection limit (30 nanomolar) of the NI/MWCNT/PGE electrode response as well as wide linear range (1.0×10−7 to 1.0×10−3 M) can be stated as significant features of this electrode. The modified electrode also used for determination of Trp in commercial drugs and showed satisfying results.
  9. Keywords:
  10. Graphite Electrode ; Multi-Walled Carbon Nanotube ; Modified Electrodes ; Tryptophan ; Tyrosine ; New Coccine ; Linear Sweep Voltammetry

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