Application And Research For Electrochemical Characteristics Of Selenoamino Acids

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.