Studies On The Electrochemical Behaviors Of The Selenium, Iron, Nitrite And Its Application

Selenium and iron are trace elements that indispensable and available to the life body. And the content of trace elements have great relation to human health. The determination of trace elements play an important role in the essay of environmental, science, medicine, food and clinic. Nitrite is serious pollution that lies in natural waters and foods. Nitrite amine that has changed by nitrite will do harm to human health and even cause cancer. So, establishing quick, simple, sensitive and less disruptive methods to determine trace elements and nitrite are very valuable in application. Electrochemistry method has the advantages of quickness, convenience, sensitivity and not being interfered by the color of the solution, therefore, the electrochemical behaviors of selenium and iron and nitrite were studied by polorgraphic method.1. Study on Catalytic Adsorptive Wave of Selenium (IV) and Copper(II) System and Its ApplicationThe electrochemical behaviors of selenium (IV) and copper( II) system has been studied in polarographic method. In 0.4 mol.L^HAc solution, a sensitive derivative polarographic of the Se (IV)-Cu( II) system appears at -0.76V (vs. SCE).The peak current is proportional to selenium concentration in the range of 5 X 10-8 ~ 7 × 10-6 mol.L01, the detection limit is 2×10-8 mol/L. Several electrochemical methods have been used to study the properties of the polarographic wave and the mechanism of electrode. It is proved that the wave is a catalytic adsorptive one. The number of electrons transferred (n) is 2 and the transfer coefficient (α) is 0.61~ 0.68 and the rate constant of surface electrode reaction (Ks) is 1.41/s. This method has been successfully applied to the determination of trace selenium in human hair samples.2. Study on Catalytic Adsorptive Wave of Fe3+/2+-MTB-NO2- and Its Application-Determination of total ironIn 0.04 mol/L NHs-NRjCl buffer solution, at pH 8.5, a sensitive second derivative polarographic wave of Fe3+/2+-MTB-NO2" complex appears at -1.10V (vs. SCE). The peak current is proportional to iron concentration in the range of 3 × 10-8 ~ 5 × 10-6 mol.L-1 , the detection limit is 1 × 10-8 mol.L-1. Several electrochemical methods have been used to study the properties of the polarographic wave and the mechanism of electrode. It is proved that the wave is a catalytic adsorptive one. The peak current is produced by the reduction of Fe(II). The molar ratio of Fe( II) to MTB is 1:1 .The saturated adsorption amount of the complex at Hg electrode is 1.92×10-9 mol/cm2 and the adsorption obeys Frumkin adsorption isotherm. The adsorption coefficient(P) is 4.05 ×105 and G0 is 31.99kJ/mol. The number of electrons transferred (n) is 2 and the transfer coefficient (a ) is 0.42~0.45 and the rate constant of surface electrode reaction (Ks) is 1.01/s. This method has been successfully applied to the determination of trace total iron in medicine and water samples.3. Determination of Nitrite by PolarographyThe electrode reaction of vitamin 812 with nitrite was studied, and a sensitive derivative polarographic was given by the reaction product at the potential -0.82V(v.s. SCE) in HAc and KC1 solution. The peak current is proportional to nitrite concentration in the range of 5 × 10-8 ~3 × 10-6 mol.L-1, the detection limit is 1×10-8 mol.L-1. Several electrochemical methods have been used to study the properties of the polarographic wave and the mechanism of electrode. It is proved that the wave is a adsorptive one. The number of electrons transferred (n) is 2 and the transfer coefficient (α) is 0.54~0.58 and the rate constant of surface electrode reaction (Ks) is 1.26/s. This method sensitive, simple and rapid, it has been successfully applied to the determination of trace nitrites in natural water samples.