【作者】 李蕊；

【导师】 白燕；

【作者基本信息】 暨南大学 ， 分析化学， 2004， 硕士

【摘要】 硒是人体必需的微量元素之一，其生物活性和生理作用主要是源于含硒氨基酸的电子传递和电子转移。因此采用电化学方法研究含硒氨基酸的电子转移特性，可以更简便地探讨其生物氧化还原作用机理，开展含硒氨基酸的形态分析。含硒氨基酸是人体获取硒的主要来源，测定食品硒源及富硒保健品中的含硒氨基酸含量对研究其生物作用机理、充分利用硒资源具有非常重要的意义。 在硒-金膜修饰玻碳电极（（Se-Au）／GC）上，采用循环伏安法研究了硒代胱氨酸（SeC）和硒代蛋氨酸（SeMet）的电化学特性，SeC在-654 mV和-327 mV附近出现一对氧化还原峰（峰Ⅱ和峰Ⅲ），均为扩散控制。探讨了pH值，扫描速度，各种干扰等对SeC电化学信号的影响。利用伏安法、计时电量法及旋转圆盘电极法对其氧化还原过程进行研究，得出其的电子转移数均为2。推断SeC的电化学反应机理为：除氧条件下SeC的二硒键（Se-Se）在电极表面断裂，电还原生成硒代半胱氨酸（SeCys）：SeCys与电极上的单质硒形成类似于二硒键的分子间作用力，使SeCys保持相对的稳定性，其电氧化生成SeC。而在相同条件下，因硒代蛋氨酸（SeMet）没有二硒键，没有产生电化学信号。在空气饱和的底液中，还原产生的SeCys有一部分会被溶液中的氧气氧化成SeC，从而构成一个平行催化体系。而另一部分则继续在电极上氧化产生SeC。 依据SeC的还原峰电流（ip_Ⅱ）与其浓度成线性递增关系，在充分探讨多种影响因素的基础上建立了（Se—Au）／GC电极上微分脉沖伏安法测定SeC含量的新方法，其线性范围为5.0×10^-8～7.0×10^-4 mol·L^-1，检出限为3×10^-8 mol·L^-1。测定了富硒酵母和富硒茶叶中SeC的含量。采用常用的DAN荧光法测定了普通茶叶、普通茶汤、普通茶叶水解液、富硒茶叶、富硒茶汤、富硒茶叶水解液中的总硒量，并对样品中的硒的存在形态进行了探讨，富硒酵母中的硒大部分为氨基酸状态的硒，其中硒代胱氨酸约占总硒量的40％。富硒茶叶水解液中的硒大部分为氨基酸状态的硒，其中硒代胱氨酸约占总硒量的24％，一小部分为浸出的无机硒和小分子的硒物质。在饮茶时，富硒茶叶的茶汤中浸出的仅为较少的水溶性的硒（无机硒和小分子的硒物质），大部分的硒还留在茶叶中，饮用茶水并未充分利用茶叶中的硒。 摘要 根据150“测量不确定度表示导则”对（Se一Au）/GC电极上微分脉冲伏安法测定富硒酵母及富硒茶叶中的SeC含量所产生的不确定度进行了研究，对所建立的新方法及其测定结果进行了评估。结果表明新方法结果可靠，与其他成熟方法所产生的不确定度结果相当，具有实际应用价值。更多还原

【Abstract】 Selenium is one of biotrace elements, and its biological activation and physiological function is based on the electron transmition and shift of selenium amino acid mainly. Studies of the electron transmit characteristics of selenoamino acids using the electrochemical methods to can probe into their biological oxidize and reduce mechanism simply and conveniently, and develop the specific analysis of selenoamino acids. Selenoamino acids are the main selenium-source in people’s daily meal. Determination of selenoamino acids in the food selenium-source and rich selenium health products has very important meanings to their biological mechanism and fully using.The electrochemical characteristics of SeC and SeMet on Se-Au film modified glassy carbon electrode ((Se-Au) /GC) are studied with cyclic voltammetry. It’s showed that SeC has one cathodic peak-654mV and one anodic peak at -327mV, respectively. Several parameters of the voltammetric determination, such as the kind of electrolytes scan rate, pH value, were investigated. Electrochemical process of SeC was 2H+/2e- by voltammetry, chronocoulometry and rotating disk electrode. The electrochemical reaction mechanism of SeC was that SeC in solution was reduced to SeCys at the electrode surface by cracking the Se-Se bond, then, SeCys was oxidized to SeC. Under the air-saturated condition, a part of SeCys was oxidized to SeC by O2 in solution and this chemical reaction catalyzed the electrochemical reduce process of SeC. SeMet was electrochemically inactive due to no Se-Se bond.At (Se-Au) / GC electrode the peak current (ipn) and the concentration of SeC had linear relationship. Its linear range is 5.0X 10-8~7.0X 10-4 mol L-1, and a 3 detection limit is 3.0 X 10-8 mol L-1 SeC. This paper set up a new method of SeC determination by differential pulse voltammetry at the (Se-Au) / GC electrode. The content of SeC of the selenized yeast and selenized tea was determined. By using DAN fluorescence method, the paper determined the total selenium of the ordinary tea, ordinary tea lixivium solution, ordinary tea hydrolysis solution, selenized tea,selenized tea lixivium solution, and selenized tea hydrolysis solution. The result indicates that the state of selenium in the selenized yeast is selenoamino acids mostly, and SeC accounts for 40%. There are selenoamino acid states mostly in selenized tea hydrolysis solution. SeC accounts for 24%, and one small part is inorganic selenium and small molecule state selenium. When people drink tea, only less water soluble selenium (mainly on inorganic selenium and small molecule state selenium) was drunk, and most selenium still stay in tea-leaf, so drinking tea has not fully utilized selenium in tea.According the"guide to the expression of uncertainty in measurement (ISO: 1993E)", uncertainty was calculated of determination of SeC in selenized yeast and selenized tea by differential pulse voltammetry at the (Se-Au) / GC electrode. Result indicates that the new method is reliable. Uncertainty of this new method was equal to that of other mature methods, so the new method can be used in practical application.更多还原