Trace Electroanalysis for the Pesticides Determination

• Main Authors: Bor Iuan Jan, 詹博淵
• Other Authors: Meng Shan Lin
• Format: Others
• Language: zh-TW
• Published: 1999
• Online Access: http://ndltd.ncl.edu.tw/handle/19487556896203929846

博士 === 淡江大學 === 化學學系 === 87 === Abstract： The schemes of modified electrodes for the electrochemical pesticides determination have been developed to improve the sensitivity, selectivity and speed. These schemes also are suitable for the developing to the environmental trace analysis. These chemical modified electrodes, as well as cleansing pulse training and adsorptive accumulation process, have been employed previously. The MnO2 modified electrodes are used to develop a new type of aromatic amines and dinitrophenol based pesticide electrochemical determination. A dual carbon paste and carbon ink electrodes use as the analyte generator electrodes. A sonication process induces the chemical reaction is used to develop a new electrochemical scheme for the parathion determination. The selective advantage is attributed to the lower applied potential for the reductive determination between the modified electrode and analyzes. The MnO2 is a strong oxidative agent for the aromatic amine and its deviation and produce benzoquinone and quinone-like products, respectively. These oxidative chemical reactions also give the advantages for electrochemical scheme from oxidative mode to reductive mode and avoid the electropolymerization on the electrode surfaces. The lower applied potential and improvement reproducibility are the characteristics of MnO2 modified electrode for the aromatic amine and its deviation determination. The sonication induces process and the flow injection system with the dual working electrodes for the parathion pesticide determination is developed. In contrast to the natural parathion hydrolytic reaction, the sonication induces scheme can improve the hydrolytic rate of parathion in acidic solution effectively. The sonication process will produce a high temperature and a high pressure for the chemical reaction when the bubble collapsed. The electrochemical measurement used the reductive mode to eliminate the easily oxidizable species interference. A rapid in situ electrochemical scheme- cleaning pulse train for the regenerated of the surface of the glassy carbon electrode is developed. The cleaning pulse train can remove the passive layer from the oxidative process of maleic hydrazide effectively. In contrast to the untreated glassy carbon electrode, the treated electrode provides significant stability in measurements, which are demonstrated by a series of cyclic voltammetry and differential pulse voltammetry, respectively. Also, the cleaning pulse train provided a constant electrode surface and improved the sensitivity for the maleic hydrazide measurements. An effective accumulation scheme, followed by a differential pulse voltammetric measurement, or cathodic stripping voltammetry, was used to measure the dithiocarbamate-based pesticides. The accumulation step will improve the sensitivity up to submicro-molar level of dithiocarbamate pesticides. The preconcentration scheme was achieved by the optimization of preconcentration potential, deposition time, solution pH, and ionic strength. These strategies enhance greatly the power of electroanalysis in the area of environmental analysis.