The Preparation Of Molecularly Imprinted Microspheres For Binding Nicosulfuron And Its Application In Detection Of Pesticide Residue

Molecularly imprinted polymer is a high molecular compound, which has specific adsorption capacity to target compound. Due to their high selectivity and practicability to template molecules, now molecularly imprinted polymers are used widely in various fields,such as trace analysis or residue detection. Nicosulfuron (NS) is a new type of high efficiency,low toxicity herbicide, It is used widely due to the advantages of high biological activity and easily degradable. But NS in crop residues can also damage human health. In this thesis, using NS as molecular templates, imprinted polymers with high selectivity to NS were prepared in two different methods:precipitation polymerization and suspension polymerization.Then the two methods were compared, the adsorption mechanism was discussed and these polymers were used in NS residue detection.Molecularly imprinted microspheres (MIPMs) were preparaed by precipitation and suspension polymerization for binding and recognition of NS. Methacrylic Acid (MAA)was used as the functional monomer, Trimethylolpropane three methyl acrylate (TRIM) as the linking agent,Azodiisobutyronitrile (AIBN) as the initiator and chloroform as the porogen solvent. The preparation conditions was optimized and the results show that (1) precipitation polymerization: MIPMs have the best absorption capacity when the molar ratio of NS/MAA/TRIM/AIBN is 1:4:4:1 and the volum of the porogen is 90 ml; (2) suspension polymerization: MIPMs have the best absorption capacity when the molar ratio of NS/MAA/TRIM is 1:4:4, the weight of AIBN is 45 mg and the volum of the porogen is 6 ml.The rebinding capacity of two MIPMs was evaluated according to adsorption kinetics and adsorption isotherm of the imprinted microspheres.By analysis using scatchard plot, the experimental results revealed the maximum rebinding to NS at 11370.48 ?g/g (precipitation)and 20726.34 ?g/g (suspension) respectively, specific adsorption rates to NS and its structural analogs are 36% (precipitation) and 54% (suspension). The experimental results above showed MIPMs prepared by suspension is better than precipitation. UV-Vis spectrophotometric and Fourier Transform Infrared Spectroscopy were employed to demonstrate the mechanism of the interaction between NS and MAA, the results showed that the NS-MAA complexes of 1:1 mole ratio were obtained, and -NH in NS and -COOH in MAA are combined by hydrogen bond in the pre-polymerization phase. And a rapid method for the determination of NS residues in soil and corn was developed using MISPE as sample preparation methods. The analytes were extracted using acetonitrile and phosphate buffer,cleaned-up by MISPE and analyzed by HPLC. The results showed that good linearity in the range of 0.01 ?1 mg/kg was obtained for NS,the correlation coefficient is 0.9986. Recovery tests in soil were performed for concentrations between 0.02?1 mg/kg; recoveries were in the range between 82.2%?86.3%? relative standard deviation varied between 1.9%?4.3%;Recovery tests in corn were performed for concentrations between 0.02?1 mg/kg; recoveries were in the range between 89.1%?92.2%, relative standard deviation varied between 2.3%?3.3%. The proposed method has the advantage of being quick and easy to operate, it is reliable and applicable to analyze NS residues in soil and corn samples.