The Electrochemical Analysis Of Vitamins Drug On Modified Carbon Paste Electrode

In this paper, ionic liquids and ferrocene were chosen as the modifier, theionic liquids and ferrocene modified carbon paste electrodes were prepared andthe electrochemical behaviors of vitamins drug molecules on the modifiedelectrodes were investigated.The thesis was mainly divided into five parts andbriefly described as follows:In chapter1, the development and application of CPE and CMCPE weresummarized. In addition, the electrochemical study methods and the researchprogress of ionic liquid（IL）and ferrocene（Fc）modified carbon paste electrodewere also described respectively.In chapter2, an ionic liquid modified carbon paste electrode（IL/CPE）wasfabricated by employing hydrophobic ionic liquid [BMIM]PF6as a binder. Theelectrochemical behavior of tecored（the oxidation product of vitamin E）at theIL/CPE was investigated.The results show that the tecored has a sensitiveoxidation peak at0.376V in pH=3.29B-R buffer solution, while peak current ipwas significantly increased. At the same time some dynamics parameters of theredox process were determined by potential step techniques: electron transfercoefficient is0.8746, the diffusion coefficient D is1.65×10^-3cm2/s and theelectrode reaction rate constant k_fis6.64×10^-2cm/s.The linear relationshipbetween values of oxidation peak current and concentration of tecored was foundin the range from1.53×10^-4to8.39×10^-7mol/L with a detection limit of1.58×10^-8mol/L（S/N=3）by optimized square wave voltametry（SWV）method.In chapter3, the IL/CPE was characterized by cyclic voltammetry（CV）with the potassium ferricyanide K3[Fe（CN6）] as electrochemical probe.Compared with bare CPE, the ΔE_preduced0.102V and the i_pa/i_pcvalue is moreclose to1, which showed that IL/CPE had a good electrocatalytic activity. Theelectrochemical behavior of ascorbic acid（AA）on IL/CPE was investigated.Theresults showed that the electrode process of AA at IL/CPE was an irreversibleprocess controlled by adsorption. AA oxidation peak current and concentration showed a good linearity in the range from4.0×10^-4to2.0×10^-2mol/L with adetection limit of1.5×10^-4mol/L by differential pulse stripping voltammetry（DPSV）.Through the optimized conditions, the AA oxidation peak and thedopamine（DA）oxidation peak will be separated to245mV, being able to realizethe simultaneous detection of the AA and DA.In chapter4, the ferrocene（Fc）modified carbon paste electrode（Fc/CPE）was prepared and the surface morphology was observed by SEM andcomposition was analyzed by EDS, which indicated that the Fc/CPE had goodperformance for its significantly increased electrical activity area. Theelectrochemical behavior of Quercetin（Que）on Fc/CPE was investigated bycyclic voltammetry（CV）, the results indicated that the peak current response ofQue at Fc/CPE increased ten times compared with bare CPE in pH=6.2PBSbuffer solution, owing to the parallel catalysis produced by the partici_pation offerrocene in electrode reaction. The redox process was a process of two-electronand two-proton transfer controlled by adsorption. Under the optimizedcondition，the oxidation peak currents of Que versus its concentration showed agood linear relationship in the range of8×10^-4～2×10^-6mol/L with a detectionlimit of7×10^-6mol·L-1by differential pulse voltammetry（DPV）.In chapter5, the electrochemical behavior of vitamin K3（VK3）at theFc/CPE was investigated by cyclic voltammetry（CV）and chronocoulometry（CC）, at the same time some kinetic parameters of the VK3were determined,the experimental results indicated that Fc/CPE had an excellent electrocatalyticactivity toward the redox of VK3, the electrode reaction of VK3exhibitedreversible diffusion-controlled redox process of two electrons and two protons,the diffusion coefficient D was9.05×10-5cm2/s.The catalytic reduction peakcurrent of VK3versus its concentration showed a good linear relationship in therange of2.56×10^-4～2.18×10^-6mol/L with a detection limit of1.6×10^-7mol/L bydifferential pulse voltammetry（DPV）.