Theoretical And Experimental Studies On Fluorescence Spectra Of Pesticides

The application of pesticide promoted the development of modern agriculture. However, with the increasing use of pesticide, serial problems in nature environment and human health coursed by the pesticide residua becomes more and more outstanding, coursing widely international attention. So high-sensitivity detection method becomes greatly important to the pesticide residua and their metabolites.The traditional analysis methods for pesticide residues, such as Thin Layer Chromatography (TLC), Gas Chromatography(GC), High Performance Liquid Chromatography(HPLC) and Biological Analysis, have the disadvantages including complicated sample preprocessing, consuming more reagent and more time etc. Thus, it is impossible to carry out a fast and green detection with the traditional methods. The fluorescence analysis method has advantages of high sensitivity, little sampling,fast detecting and simple operation, and shows unique superiority in environmental monitoring. In this paper the technology of fluorescence spectroscopy is applied to theoretical and experimental study of pesticide residua detection.Starting with the basic principle of fluorescence measurement, the feasibility of fluorescence origin of some common pesticides, such as carbamate, benzoylurea and fungicide is analyzed in theory, and the fluorescence property of carbaryl,metolcarb,pirimicarb,isoprocarb,iprodione,imidacloprid,acetamiprid were experimental studied The relationships between the characteristics of natural fluorescence and molecular structures were also researched, as well as the excitation and emission spectra of these pesticides and the fluorescence spectra of background solvent. Moreover, their optimum excitation wavelength and emission wavelength are studied and chosen. The fluorescent property of carbaryl and metolcarb in different pH was studied, and the working curve was established according to the optimized experiment condition.The standard pesticides and the pesticide residues in rice, vegetables and water sample have been studied by the fluorescence measurement system. Their fluorescence spectra and the analytical parameter of this system, such as the detection limit, recovery are achieved successfully. The rationality and practicability of this system and the measurement method were validated.The method of quantum chemistry was used for studying the fluorescence spectra of three common pesticide compounds. Firstly, the geometries of these three compounds were fully optimized using density functional theory(DFT) method. After vibrational analysis, the fluorescence spectra of the three compounds have been studied by configuration interaction method (CIS). The results of calculation are in better agreement with the experimental values. The mechanism of fluorescence emission has been studied theoretically. The conformation which is fit the hydrolysis reaction of imidacloprid was also analyzed in theoretical aspect. The results provided a new and theoretical method to study the fluorescence analysis of pesticide compounds. These results will provide pesticide degradation with some useful information for the further study.