【作者】 吴影；

【导师】 李念兵；

【作者基本信息】 西南大学 ， 分析化学， 2011， 硕士

【摘要】 化学修饰电极始于1975年,是目前最为活跃的电化学和电分析化学的前沿领域之一。修饰电极应用到电化学分析方法具有分析速度快,操作简便易行,成本低,试剂用量少,检测灵敏度高、具有更好的选择性等优点,现今受到广泛使用。修饰电极的一个重要应用是通过利用修饰物质的电催化活性以达到提高测定灵敏度和选择性的目的。如人体内多巴胺(DA)、尿酸(UA)及抗坏血酸(AA)等生物活性小分子的测定,目前对其研究受到了广大科研工作者的极大重视。本论文主要从以下几个方面开展研究工作：1.多巴胺在L-半胱氨酸修饰玻碳电极上的电化学行为及测定的研究以L-半胱氨酸作为电极表面修饰剂,制得聚L-半胱氨酸修饰电极,并探讨了修饰剂浓度、pH值和循环周数等条件对修饰电极的性能的影响,研究了DA在此修饰电极上的电化学行为及其伏安测定。实验表明,在最优实验条件下研制的修饰电极对DA有较好的电催化响应电流,灵敏度有较大的提高,其氧化峰电流与浓度在1.0×10-6～1.0×10-3 mol/L范围呈现出良好的线性关系,其线性回归方程Ipa(μA)=-9.8038logC(DA)+59.4098,相关系数R2=0.9923。最低检出限可以达到1.0×10-7mol/L(S/N=3).2.L-谷氨酸修饰玻碳电极测定尿酸的电化学研究以L-谷氨酸为电极修饰剂,用于对玻碳电极进行循环扫描修饰,通过循环伏安法(CV)对比研究了UA在裸玻碳电极和聚L-谷氨酸修饰玻碳电极表面的电化学行为,运用线性扫描伏安法(LSV)测定了UA的线性范围和最低检出限,同时对修饰电极的稳定性和重现性进行了探讨研究。实验结果显示,聚L-谷氨酸修饰玻碳电极对UA的电化学氧化反应具有较明显的电催化作用,当响应信号/噪声比值(S/N)为3时,UA的检测限可以达到1.0×10-6mol/L.通过对UA测试条件的优化,得出了UA的氧化峰电流与其浓度在2.5×10-6～1.0×10-3mol/L范围内呈现出较好的线性关系,其线性回归方程为Ipa(μA)=-149.9583+25.5 log C(UA),相关系数R2=0.9948。该实验结果与同类修饰电极测定UA作对比,具有制备简捷,响应灵敏,线性范围宽,检出限低,抗干扰能力强的特点,可望应用于尿液中的UA的测定及相关研究。3.肉桂酸修饰电极在AA存下对UA的研究测定采用恒电位沉积方法在玻碳电极表面制备肉桂酸修饰电极,通过CV法对比研究了尿酸(UA)在裸玻碳电极和肉桂酸修饰玻碳电极表面的电化学行为,研究表明UA在肉桂酸修饰玻电极上具有良好的电化学响应,在1.0×10-3mol/L的高浓度AA共存的情况下,该修饰电极可用于UA的测定,实验考察了检测UA的最佳条件,结果表明UA的氧化峰电流与其浓度在2.0×10-6～2.0×10-4 mol/L范围内呈现出较好的线性关系,其线性回归方程为Ipa(μA)=22.4948 +0.2195 logC(UA),相关系数R2=0.9902,检测限为1.0×10-6mol/L,可望应用于血液中UA含量的快速测定。更多还原

【Abstract】 Chemically modified electrodes (CME) originated in 1975 is one of the foremost fields of electrochemistry and electroanalytical chemistry at present. Nowadays, CME has been widely used in electrochemical analysis because of its fast analysis speed, simple and easy operation, low cost, low reagent consumption, high sensitivity, good selectivity, and other advantages. An important application of CME is applying the electrocatalytic activity of the modifer into the increase in sensitivity and selectivity of analysis. Detection of bioactive small molecules such as dopamine (DA), uric acid (UA), and ascorbic acid (AA) has attracted a wide interest.The main research works of this thesis are the following aspects: Part 1 Electrochemical behavior and determination of dopamine at L-cysteine modified glassy carbon electrodeThe L-cysteine modified electrode was prepared with L-cysteine as the electrode surface modifier and the influence of experimental conditions containing the concentration of modifier, pH value and number of scan round on the performance of the modified electrode was discussed detailedly. Furthermore, electrochemical behavior of dopamine at the modified electrode was studied. The results showed that the modified electrode prepared under the optimum experimental conditions had large electrochemical response. The oxidation peak current presented a good linear relationship in the concentration range of 1.0×10-6～1.0×10-3mol/L with the linear regression equation of Ipa (μA)=-9.8038 logC(DA)+59.4098 (R2=0.9923) and the detection limit of 1.0×10-7 mol/L at signal to noise ratio of 3.Part 2 Voltrammetric detection of uric acid at the poly (L-glutamic acid) modified glassy carbon electrode The glassy carbon electrode was modified with L-glutamic acid modifier and electrochemical behavior of uric acid (UA) at the bare electrode and modified electrode were investigated by cyclic voltammetry. The experimental results showed that the poly (L-glutamic acid) modified glassy carbon electrode has been demonstrated to have obvious electrocatalytical function to electrochemical oxidation reaction of UA. Based on the optimization of UA test conditions, it is concluded that the oxidation peak current has a good linear relationship in the UA concentration range of 2.5 x 10-6～1.0 x 10-3 mol/L with the linear regression equation for Ipa(μA)=-149.9583+25.5 log C(UA) and correlation coefficient of R2=0.9948. The detection limit for UA is 1.0 x 10-6 mol/L at signal to noise ratio of 3. The experimental results, compared with similar modified electrodes, demonstrated the characteristics of simple preparation, wide linear range and low detection limit. It is expected that the modified electrode will be applied to detect UA in urine and related research.Part 3 Electrocatalytic behavior and selective detection of uric acid in the presence of ascorbic acid at the cinnamic acid modified glass carbon electrodeUnder the optimized conditions of electrode preparation, the glassy carbon electrode was modified by constant potential deposition with cinnamic acid modifier. The electrochemical behavior of UA at the bare electrode and cinnamic acid modified electrode was investigated by cyclic voltammetry and the detection of UA was accomplished in the case of high concentration (1.0 x 1O-3 mol/L) of A A coexistence and the stability and reproducibility of the electrode were studied. The experimental results showed that cinnamic acid modified electrode has obvious electrochemical activity to oxidation of UA and the detection limit of 1.0 x 10-6 mol/L at signal to noise ratio of 3. Under the optimum conditions, the oxidation peak current had a good linear relationship in the UA concentration range of 2.0 x 10-6～2.0 x 10-4 mol/L with the linear regression equation of Ipa(μA)=22.4948+0.2195 logC(UA) and correlation coefficient of R2=0.9902. A new electrochemical method for the determination of UA was developed.更多还原