Studies Of The Electrochemical Behavior Of Copper, Tungsten, Lipoic Acid And Its Application

With the. rapid development of environment, food,medicine,metallurgy and material sciences, it becomes more and more important to develop rapid and high efficient analytical methods for a trace substance.Electroannalytical methods are characterized by cheap, high sensitivity and selectivity,especially the stripping voltammetry and catalytic polarography. In this thesis, copper, tungsten and lipoic acid are determined by polarography. The mechanisms of electrode reaction are also studied. The main contents of this work are as follows:(1) Study on the adsorptive catalytic polarographic wave of copper (II )-PAN in the presence of per-sulfate kalium (K2S2O8) and its application:In pH= 6.4 KH2PO4-NaOH phosphate buffer, copper (II ) reacts with PAN to form a complex which appears a sharp polarographic wave at -0.23V (vs. SCE). When K2S20g is added, the peak height is increased about 4 times compared that obtained without K2S2O8. The derivative current (ip") is linear with the concentration of copper (II) in the range of 1.5 X 10"8~6 X 10-6 mol/L with detection limit of 8 X 10~9mol/L. The character of polarographic wave is studied, and results shows that this wave is an adsorptive. catalytic wave. The method has been applied to determine copper (II) in rice, mung bean and hair of man samples, the results are satisfied.(2) Study on the adsorptive polarographic wave of tungsten-Perron and its application:An obvious adsorptive wave of W (VI)-Ferron is observed at -0.62V (vs. SCE)in HCl-NaAC medium, and peak current is proportional to the concentration of W(VI) in the rangeof 7.5 ×10-8 - 4.5 ×10-7 mol/L and 5 ×10-7 - 1.1 ×10-5 mol/L(r=0.999), repectively. The detection limit is 2.5 ×10-8 mol/L.The method is usedto detect W (VI) and results are satisfied.(3) Study on the lipoic acid's character of polarographic wave:In the pH 5.0 HCl-NaAC phosphate buffer, lipoic acid (LA) shows a sensitiveadsorptive wave. The ip" shows linear to the concentration range 2.5 × 10-1.5 × 10-5mol/L of LA with a detected limit of 5 X 10-9mol/L (r=0.9996). The character of polarographic wave is studied, and results suggested this polarographic wave is an adsorption polarographic wave.