| This thesis involves two parts:Part one Documents reviewExcepting with special properties of nano-materials, such as surface effect, small size effect, quanta-size effect and tunneling effect, carbon nanotube also with attractive electronic and mechanical properties. Based on its particular characteristics, carbon nanotube currently under intense investigation and widely applied in electrocatalytic and electroanalytical chemistry. In this article, the structure, purification method, characteristic of carbon nanotube and its application in analytical chemistry was studied.Part two Research reportsIn this thesis, carbon nanotube was chosen as electrode materials. Carbon nanotubes paste electrode was prepared as the way of making carbon paste electrode and can be used to study the voltammetric behavior of some organic pharmaceuticals and their determination. On the other hand, molecular wires and multiwalled carbon nanotubes have been combined to prepare a modified carbon nanotube paste electrode. The voltammetric response of the electrode to the reactant was significantly greater than that of electrodes prepared from other materials, which demonstrated that combination of different nanomaterials with different functions would enlarge their range of application in electroanalytical chemistry. In additional, the voltammetric behavior of two organic pharmaceutical and their determination were studied on CPE. The concrete contents are described as follows:Chapter one Determination of metformin based on amplification of its voltammetric response by a combination of molecular wire and carbon nanotubesMolecular wires, in the form of the coordination polymer (Cu(II)4(bpp)4 (maa)8(H2O)2). 2H2O (bpp=1,3-bis(4-pyridyl)propane, maa=2-methylacrylic acid), and multiwalled carbon nanotubes (CNT) have been combined to prepare a paste electrode (CuMW/CNT/PE). The voltammetric response of the CuMW/CNT/PE to metformin (MET) was significantly greater than that of electrodes prepared from other materials, which demonstrated that combination of different nanomaterials with different functions would enlarge their range of application in electroanalytical chemistry. A novel voltammetric method for determination of MET is proposed. In pH 7.2 Britton-Robinson buffer, the second- order derivative peak current for oxidation of MET at 0.97 V (relative to SCE) increased linearly with MET concentration in the range 9.0×10-7-5.0×10-5 mol L-1 and the detection limit was6.5×10-7mol L-1.Chapter two Catalytic Action of Copper (II) Ion on Electrochemical Oxidation of Metformine and Voltammetric Determination of Metformine in PharmaceuticalsIn NH3-H2O-NH4Cl (pH 8.9±0.1; 0.1M)- 2.0×10-4 M Cu(II) medium, the imino-group in guanidino-group of MET yields a sensitive catalytic oxidation wave with peak potential 0.95 V on CPE. The enhancement action of Cu (II) ion on the oxidation peak suggests that an unknown Cu (II)-oxo complex of Cu (II) ion with the electro-generated active oxygen species from the oxidation of H2O reduces the oxidization product of imino-group to original one, forming the catalyzed cycle. From the view of biochemistry, the catalyzed cycle may predict that the Cu (II)-oxo complex can inhibit the oxidation of MET. Moreover, the oxidation peak current of MET at multiwalled carbon nanotube paste electrode (MWCNT/PE) was further increased by about 3 times compared with that at C/PE in the same medium. Based on this, a voltammetric method for the determination of MET by using MWCNT/PE is developed. The second-order derivative peak current of the catalytic peak is proportional to MET concentration in the range 2.0×10-7～1.0×10-5M. The detection limit is 6.7×10-8M.Chapter three Voltammetric Behavior and Determination of Tanshinone IIA at Carbon Paste ElectrodeThe voltammetric behavior of tanshinone IIA (TS) on carbon paste electrode (CPE) was studied. In 0.2 mol L-1 BR (pH 2.36)-ethanol/water (40:60 v/v) medium, the carbonyl group of TS went a one-electron and one-proton redox reaction at CPE, which was a reversible process with adsorption character. The semiquinone radical of TS as reduction product existed stably on CPE, which might be due to hydrophobic organic phase inhibiting the disproportionation reaction of the radical of TS. The peak potentials of the reduction and oxidation peaks were—0.31 V and—0.24 V (vs, SCE), respectively. The second-order divertive oxidation peak current showed a linear relationship with the concentration of TS in the range of 1.2×10-8～8.2×10-7 mol L-1, and the detection limit was 4.1×10-9 mol L-1. The voltammetric method was proposed and was used to determine the total tanshinone in compound Danshen tablet.Chapter four The Voltammetric Behavior of Tamoxifen at Carbon Paste Electrode and Its DeterminationThe voltammetric behavior of tamoxifen (TAM) on carbon paste electrode (CPE) was studied. In BR buffer (pH 3.29±0.1) - methanol/water (18: 82 v/v) medium, TAM yields a oxidation peak with the peak potential 1.0 V on CPE. the second-order derivative peak current for oxidation of TAM at 1.0 V (relative to SCE) increased linearly with TAM concentration in the range 7.0×10-10～3.0×10-8 mol·l-1 and the detection limit was 1×10-10mol·l-1. The propoused method can be used to determine the content of TAM in pharmaceuticals. |
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