Study On The Rapid Detection Technique Of Organophosphorus Pesticide

The pesticides, an important tool against plant diseases and insect pests, have become an important part for agricultural productions. However, the pesticide residue has gradually become a huge obstruction which greatly impedes the development of the modern agriculture because of the mismanagement and abuse. Organophosphorus pesticide, which brought huge economic benefits, was widely used in modern agricultural due to their broad-spectrum, easy degradation, high effectiveness and short half life in the environment. Meanwhile, they also lead to a series of problems such as environmental pollution and food contamination. The current detection methods of pesticide residues include the instrument detection and rapid detection. The rapid detection method mainly include colorimetric method, enzymatic method and biological sensors method. Compared to traditional methods such as chromatography and spectroscopic method, pesticide residues rapid measuring is suitable for the screening of a large number of samples. In order to guarantee the quality and security of food and promote our agricultural export trade, it is significant to develop effective analytical methods.This thesis comprises four parts, as follows:1. The classification, properties and harmful to human of organophosphorus pesticide were introduced briefly. Current progress of organophosphorus pesticide residue analytical method was summarized finally, the target and content of the dissertation were discussed.2. Low price indoxyl acetate which can be hydrolyzed by acetylcholinesterase was used as substrate. The source of the acetylcholinesterase was from earthworms. The dissolve problems of indigo was overcame with a simple method. Meanwhile, enzyme catalysis and enzyme inhibition were carried out smoothly. The effect of the time of inhibition, pH value and concentration of substrate to reaction system was studyed. In addition, different concentrations of phoxim were tested and reached the standard of the detection of pesticides.3. The strips of cholinesterase and substrate were prepared firstly. According to the principle of enzyme inhibition and polarity difference of pesticide on thin layer chromatography (TLC) plate, the rapid detection of various types of organophosphorus pesticide was completed with enzyme strips and chromogenic substrate strips on TLC before eluted with different proportions of organic solven. Compared to traditional method of spraying to the board thoroughly wet, this method was simple operation, high sensitivity and low prices.4. A simple strategy has been developed for the formation of Ni(OH)2nanoparticle film by oil/water two phase interface. The obtained Ni(OH)2nanoparticle film was easily transferred onto the electrode surfaces and exhibited stable electrochemical performance. The electrochemical behavior of various small biomolecules, including cysteine, homocysteine, glutathione, histidine, glycine, cystine, methionine, lysine, phenylalanine, and dopamine, were studied at the Ni(OH)2nanoparticle-film-modified electrode. The resulted sensor exhibits excellent direct, unmediated electroatalysis toward the oxidation of cysteine in a pH7.4buffer solution with a low onset potential and a high oxidation signal. In addition, chlorinated thiocholine was also studied at the Ni(OH)2nanoparticle-film-modified electrode. According to the size of the electro-catalytic signal, we can indirectly detect organophosphorus pesticide residues. A new method is developed for rapid detection of organophosphorus pesticide.