Supramolecular Recognition Reaction Studied By Fluorescence Spectroscopy For Pesticide Residue Analysis And Application

Host compounds have high molecular recognition ability towards guest molecules and their application opened up broad prospects for developing the specific exclusive and highly selective methods to some molecules. In new types of host compounds, cyclodextrin(CD) is selected firstly. Cyclodextrins(CD), the cyclic oligosaccharides consisting of six or more D-(+)-glucopyranose units, are well known to have the property of forming inclusion complexes with guest molecules which possess suitable polarity and dimension. The formation of the inclusion complex can alter the photochemical and photophysical properties of the guest molecules. Based on the ability of supramolecular recognition, cyclodextrins has been widely used in the studies of general inclusion phenomena, enzyme-substrate interactions and analytical methods including the luminescence application of the cyclodextrins.With the improvement of environmental protection thoughts, people pay great attention to the determination and control of pesticide residue. At present, the determination of pesticide and other bioactive substances-drugs almost entirely use organic solvents as medium under the limit of some factors in aqueous solution such as poor solubility, small fluorescence quantum yield and so on. Most of these non-spectroanalysis methods needed expensive instrumentation, required strictly controlled reaction condition, involved some time-consuming and troublesome steps and what's more important, they were less sensitive. So, for routine quality control, the development of some simple, rapid, selective and sensitive spectrofluorimetric methods for the determination of pesticide in aqueous phase is highly desirable. The low fluorescence quantum yield or small molar absorption coefficient of the analyte in aqueous solution precludes their trace amount determination. So, the remarkable enhancement of the fluorescence emission or absorbance of the bio-pertinent substances due to their complexations with β -CD might be very useful from an analytical point of view.In this paper, based on the supramolecular interactions between host and guest, the sensitive spectrofluorimetry for the determination of tetramethrin carbaryl and napropamide in aqueous solution by using β-CD as sensitizing reagent has been established. The experiment conditions such as pH dependence, the kinds and the volumes of some buffersolutions and the interaction time were studied, and the optimum conditions were found at last. The experiment results showed that these methods are simple, selective and sensitive. The application of the proposed methods to the determination of the analyzed substances in river water or cottonseeds gave satisfactory results. It is very useful that the research results give new theory and experimental method to the establishment of standard analytical methods on pesticide residue.