Study On Electrochemical Feature Of Seleno-amino Acids And Its Application In Analysis

In recent years, the biology and chemistry of selenium including the analysis of its various species have been the subject of increasing attention, due to the importance of selenium both as an essential trace and toxic element. Se is a nutritional or toxic element depending on the concentration and chemical form in which it enters the organism. Compared inorganic selenium with organic selenium compounds , the first is more toxic and has lower bioavailability than the second . From a nutritional point of view, Se is found existing in the organism mainly as organic selenium such as selenoproteins, selenosugars, Se-lipids and seleno-amino acids etc. ,and through these species the organism takes up the necessary amount of this element , removing the excess. In mammalian tissues, selenoamino acids are the predominant forms of selenium. Furthermore, it has been demonstrated that the main form of selenium in grains is selenomethionine, which is used as selenium supplement in the diet of man and animals. Because of the importance of the organic selenium , it has become the subject of increasing interest in recent years , and much effort has been devoted to the development of analytical methods for the selective determination of the organic selenium compounds.SeCys and SeMet as investigated objects, this paper reports their electrochemical behavior at silver electrode ,respectively. The research results indicate that both SeCys and SeMet possess good electrochemical response signal in the medium of sodium borate-NaOH(PH9.45). A pair of redox peaks are observed at .62v(oxidation) and ?O.68v(reduction) ( u s. SCE). After optimizing the experimental conditions, the cyclic voltammetry and the 2th order differential linear sweep voltammetry are used to detect SeCys and SeMet. The detection limit of SeCys is 4.32X 1O?mol/L and 8.6X 10 11mo1/L, respectively. The detection limit of SeMet is 8.OX 1O?mol/L and 4.OX 10mol/L, respectively. Reaction mechanism of SeCys and SeMet at silver electrode is discussed. The SeCys modified silver electrode has also been used for determining inorganic metal ion by the anodic stripping voltammetry and the potentiometric stripping analysis. The result of determination is satisfactory.