【作者】 党雪平；

【导师】 胡胜水；

【作者基本信息】 武汉大学 ， 分析化学， 2004， 硕士

【摘要】 表面活性剂在电分析中的研究和应用日益活跃，它可以显著改善待测物质的电化学响应，提高分析的灵敏度和选择性。另外，表面活性剂膜电极的结构与生物细胞膜中的类脂所组成的双层结构类似，所以对表面活性剂膜电极电化学行为的研究有助于认识生物体内的电子传递过程。本论文考察了不同类型的表面活性剂对生物分子和药物分子的电化学响应的影响，并利用表面活性剂的强吸附性能制备了表面活性剂膜修饰电极，采用扫描电子显微镜（SEM）探索了其表面形貌，并运用多种电化学技术考察了该修饰电极对氧分子的电化学响应。主要研究内容如下： （1）制备了聚乙烯吡咯烷酮（PVP）修饰碳糊电极，在表面活性剂CTAB存在下，用循环伏安法考察生物分子甲状腺素（T₄）在该修饰电极上的氧化过程，发现T₄在该电极上表现出完全不可逆的氧化过程。考察了不同类型表面活性剂对T₄氧化的影响，发现阳离子表面活性剂十六烷基三甲基溴化铵（CTAB）对T₄的氧化有明显的催化作用。采用计时库仑法和交流阻抗法研究了T₄在该修饰电极上的氧化过程，发现T₄的氧化涉及到四个电子和四个质子的转移，CTAB加快了T₄在电极表面的电子转移速度。T₄的浓度在2×10^-7-9×10^-6mol／L时，其氧化峰电流与浓度呈现出良好的线性关系。在开路条件下富集40s，T₄的检出限为8×10^-8 mol／L。 （2）采用具有较大比表面积的乙炔黑作为电极的基体材料，制备乙炔黑电极。在不同类型的表面活性剂存在下，考察四环素（TC）在该电极表面的电化学氧化。发现TC在阴离子表面活性剂十二烷基硫酸钠（SDS）存在下表现出一灵敏的氧化峰，峰电位为0.58 V，说明SDS对TC有明显的催化作用。采用交流阻抗法、计时库仑法和循环伏安法研究TC在该体系的氧化过程，发现SDS加快TC在溶液中的扩散系数和在电极表面的电子转移速度。TC的氧化为其C₁₀位上的酚羟基的氧化，涉及到四个电子和四个质子的转移。推测出TC的酚羟基开始可能被氧化成苯醌。而苯醌在电极上又被还原成对苯二酚，且对苯二酚／苯醌电对则容易吸附在电极表面，表现出一对比较可逆的氧化还原峰。TC的浓度在1.2×10^-7-1.5×10^-5mol／L时，其氧化峰电流与浓度呈现出良好的线性关系。在开路条件下富集150s后，Tc的检出限为6.。/10一“mollL。干扰实验证明，该体系有较好的选择性。在最优化的实验条件，实现了蜂蜜和药物中四环素的检测。 （3）采用乙炔黑电极，在不同类型的表面活性剂存在下，考察去甲肾上腺素（NA）在该电极表面的电化学行为。循环伏安法和交流阻抗法的实验结果表明阴离子表面活性剂SDS对强酸介质中NA的氧化还原有明显的催化作用。NA的氧化还原峰对应于NA结构中的邻苯二酚的氧化还原，即邻苯二酚/邻苯醒电对。NA的浓度在6.0/10一8一7.2/10’6mol/L时，其氧化峰电流与浓度呈现出良好的线性关系。在开路条件下富集70:后，Tc的检出限为6.0/10一9 mol/L。该体系有望应用于NA的高灵敏检测。 （4）采用吸附法将不同类型的表面活性剂吸附到电极表面，得到各种类型的表面活性剂膜修饰乙炔黑电极。采用SEM研究了乙炔黑电极修饰前后的表面形貌，发现表面活性剂修饰电极表现出更大的比表面积。考察氧分子在各种修饰电极上的电化学还原响应。发现氧分子在该修饰电极上表现出完全不可逆的还原过程，且其还原电流增大，电位比裸的乙炔黑电极有不同程度的正移。cTAB膜修饰电极的较大的比表面积和饰:效应”两种因素导致氧分子在Cl…AB膜修饰电极上的还原电位变得更正，还原电流变得更高。计时库仑法和控制电位电解法的研究表明氧分子在乙炔黑电极表面的还原过程为两个电子过程，还原产物为HZOZ。另外，采用Tafel曲线研究了氧分子的还原动力学过程。 通过总结不同类型的表面活性剂对T4、TC和NA电化学响应的影响，讨论了表面活性剂的增敏作用和其在疏水性碳糊类电极表面的吸附状态。初步的实验结果.表明表面活性剂是通过非极性亲油的碳氢链吸附在电极表面的。阳离子型和阴离子型表面活性剂的极性端可以与带相反电荷的物质发生静电作用，增加该物质的扩散系数和在电极表面的吸附量，使物质与电极之间的电子转移更加畅通，从而对其电氧化有明显催化作用。非离子型表面活性剂因与这两种带电荷的物质作用较小而不能促进它们的电氧化。更多还原

【Abstract】 The studies and applications of surfactants become more and more popular in electroanalysis since surfactant can change the structure of electrode/solution interface, and consequently improve the sensitivity and selectivity of electroanalytical methods. Additionally, the structure of surfactant film modified electrode is similar to the double-layer of biologic cell film, which is composed of lipoid. So the study of the electrochemical behavior of surfactant film modified electrode is of great benefit to get information of the electron transfer in the biologic body. In this thesis, the effects of different types of surfactants on the electrochemical response of some biological molecules and drugs were investigated. Moreover, different types of surfactant film modified electrodes were prepared, and characterized by scanning electron microscopy (SEM). Various electrochemical techniques were used to investigate the electrochemical responses of dioxygen on the modified electrode. The work is summarized as follows:(1) Polyvinylpyrrolidone (PVP) was used to modify carbon paste electrode. In the presence of cetyltrimethylammonium bromide (CTAB), the electrooxidation of thyroxine (T4) was studied by cyclic voltammetry on the modified electrode. T4 underwent totally irreversible oxidation at this system and a well-defined peak at 0.42 V was obtained. The influence of various surfactants on the oxidation of thyroxine was examined. The oxidation of T4 was facilitated by cationic surfactants CTAB. Chronocoulometry and AC impedance were also used to investigate the electrode process. T4 undergoes a four-proton and four-electron process, and the electron transfer rate of T4 was facilitated by CTAB. In the range of 2 x 10-7 - 9 x 10-6 mol/L, the oxidation peak current of T4 was linear with the T4 concentration and a low detection limit of 8 x 10-8 mol/L was obtained for 40s accumulation.(2) The acetylene black particle with high specific area was used to prepare the acetylene black electrode. In the presence of different surfactants,the electrooxidation of tetracycline (TC) was studied on the electrode. A sensitive oxidation peak appears at 0.58 V in the presence of the anionic surfactant sodium doddecyl sulfate (SDS), indicating that the oxidation of TC was facilitated by SDS. AC impedance, chronocoulometry and cyclic voltammetry were used to investigate the electrode process, indicating the diffuse coefficient of and electron transfer rate of TC was facilitated by SDS. The phenolic substituent in position ten of TC is responsible for the oxidation peak. The phenolic substituent may have lost four protons and four electrons and can be oxidized to benzoquinone. The benzoquinone was also reduced, forming a reversible redox couple hydroquinone / benzoquinone, which was adsorbed at the acetylene black electrode surface. In the range of 1.2 10-7 -1.5 10-5 mol/L, the oxidation peak current was linear with the TC concentration and a low detection limit of 6.0 10-8 mol/L was obtained for 150s accumulation. The good reproducibility and sensitivity were obtained. Under optimized experiment conditions, the method has been used to determine TC in honey and pharmaceutical, and the results compared favorably.(3) In the presence of different surfactants, the electrochemical response of noradrenalin (NA) was studied on the acetylene black electrode. The results of cyclic voltammetry and AC impedance indicated that the electrochemical response of NA in acid media was facilitated by the anionic surfactant SDS. The redox peak of NA is corresponding to the redox of the oxophenic acid part in the structure of NA, i.e. the reversible redox couple oxophenic acid / o-quinone. In the range of 6 10-8- 7.2 10-6 mol/L, the oxidation peak current of NA was linear with the NA concentration and a low detection limit of 6.0 x 10-9 mol/L was obtained for 70s accumulation. Under optimized experiment conditions, the method could be used to determine NA in biological sample.(4) Different type更多还原