Application Of Magnetic Mulit-walled Carbon Nanotubes In The Electrochemical Analysis Of Dopamine And Quercetin

Electrodes modified with carbon nanotubes (CNTs) exhibited significantly enhanced electron transfer efficiency owing to the excellent conductivity and the large surface area to volume ratio. However, CNTs are insoluble in most solvents, and the physical stability of electrode is weak which modified by CNTs through the casting method or the straightforward manual method. In this thesis, the magnetic muilt-walled carbon nanotubes (Fe3O4-MWCNTs)was synthesised successfully. The superparamagnetism of Fe3O4 can provide an easy and simple way to load CNTs on electrodes with the aid of a magnet. The Fe3O4-MWCNTs modified SPE (Fe3O4-MWCNTs/SPE) could determinate DA at trace concentration. The linearity was found between 5 to 180 ?M, with the limit of detection of 0.43 ?M. In the mean time, this modified electrode exhibited excellent selectivity for DA detection with almost no interference from the high concentrations of ascorbic acid (AA). In addition, this novel electrode has been applied to determine DA concentration in spiked human blood serum and satisfactory recovery was found in the range of 97.43-102.94% with the relative standard deviations (RSDs) of less than 2.27%. This work developed a sensitive and reliable electrochemical analytical method for determination of DA, which is useful for judgment of some nerve cell damage relating to abnormity of DA.The shape of ?-Cyclodextrin (?-CD) resembles a truncated cone with a hydrophobic inner cavity and a hydrophilic exterior, which enables ?-CD to selectively bind with guest molecules into its hydrophobic inner cavity to form host-guest inclusion complexes. The interaction between the host and the guest can further strengthen the accumulation effects of?-CD modified electrode and accordingly, increase the concentration of the guest molecules on the interface of the modified electrode, which results in the significantly enhancement of the peak current. In this thesis, the magnetic muilt-walled carbon nanotubes functionalized by?-CD (Fe3O4@?-CD-MWCNTs) was synthesised successfully. The Fe3O4@P-CD-MWCNTs modified SPE (Fe3O4@?-CD-MWCNTs) through magnetic adsorption method could determinate quercetin (QR). The linear range of QR was found between 0.95 to 100 ?M, with the limit of detection of 0.084 ?M. In the meantime, this modified electrode has been applied to determine QR concentration in real samples such as blood serum, onion, orange and green tea. The satisfactory recovery was found in the range of 95.92-102.34% with the RSDs of less than 2.54%. This work developed a sensitive and reliable electrochemical analytical method for determination of QR, which exhibits great potential for determination of QR in biological samples.