Studies On The Degradation Of Organophosphorous Pesticides By Chitosan Metal Complexes

Organophosphorus pesticides are one of the most important groups of insecticides and are widely applied to pest control in agriculture. It plays a very important role in prevention of pests and plant diseases. The extensive application of organophosphorus pesticides can subsequently release organophosphorus pesticides into environment which may pose a seriously adverse impact to non-target organisms and humans due to various toxicities of OPs. We could not ban organophosphorus pesticides at present as they are efficient and have relatively short half-life. However, the improper use of pesticide makes pesticide residues in agricultural products excessive. Therefore, technique of degradation of organophosphorus pesticides must be studied.In this paper, the optimal organophosphorus pesticide detection methods were explored. Chitosan which has a range of molecular weight was used as ligand, and four kinds of metal (Ca,Fe,Zn,Mg) were chosen. Chitosan metal complexes were used to act on dichlorvos, omethoate, dimethoate and chlorpyrifos. The complex was characterized by IR and DSC. The degradation products were analysed. The research refers to the following paragraph:1. The condition of separating mixed dichlorvos, chlorpyrifos, parathion, parathion-methyl, dimethoate, omethoate, methamidophos, malathion methamidophos by solid phase extraction (SPE) and gas chromatography (GC) was developed. The orthogonal experiment design was used to define the best operation parameter, the effects of sensitivity, recovery and peak shape to obtain the optimization resolution. Detection limit, recovery and linear range were studied. Comparing with methods reported, better sensitivity, peak shape and shorter analysis time were obtained. The detection limit was 1.1μg/L-2.5μg/L. The linear range was 0.1 mg/L-4 mg/L. The relative standard deviation ranged from 2.0% to 7.4%. The average recovery was in the range of 69.1% -108.2%. The method discussed could be applied for quick and accurate simultaneous determination for organophosphorous pesticides.2. The degradation of dichlorvos, omethoate, dimethoate and chlorpyrifos with chitosan Ca complex,chitosan Fe complex,chitosan Zn complex and chitosan Mg complex were studied. The complex with degradation of organophosphorus pesticides will be preliminarily characterized. The results of the study show that CTS-Fe (Mv=5.89×10oC) and COS-Zn(Mv=2298.9) were good for degradation of organophosphorus pesticides. The degradation rate of dichlorovos,omethoate and dimethoate were 55.6%, 23.2% and 37.8% by CTS-Fe. The degradation rate of dichlorovos, omethoate and dimethoate were 50.5%, 100%, 65.2% by COS-Zn. Different composition conditions, metal and molecular of chitosan will effect degradation of organophosphorus pesticides. The best condition of degradation were: pH4.0, 20oC, 6h and the molar ratio of amino-metal is 1:2.3. The condition of degradation was studied. For control group, the degradation was influent by pH and temperature. The half-life was shorten at high temperature and pH. For test groups, complexes were the most important, while pH and temperature were not primary factors.4.Degradation products of organophosphorus pesticides by complexes were studied. Pesticide intermediates were detected by GC-MS. Different condition may change structure of intermediates and different degradation pathway of ops. The final degradation products of ops by complexes were inorganic substance and inorganic ion.