Study On New Method Of Selective Clean-up And Analysis Of Pesticide Residues

Organophosphorus pesticides(OPPs)and organochlorine pesticides(OCPs)are two classes of pesticides that are generally used for the control of a broad range of pests on cotton,rice,tobacco,sorghum,sugarcane and vegetables.The selective extraction/clean-up and determination of OPPs and OCPs in soils,water and foods has received considerable attention in recent years.Molecularly imprinting technique(MIT)is an emerging interdisciplinary methodology of molecular recognition that is developing in recent years.Molecularly imprinted polymers(MIPs)can discriminate template molecule and related analogs selectively.Because of their good affinity,sensitivity and stability,MIPs have been rapidly developed and used extensively in biotechnology,environmental monitoring, inartificial drugs,food industries and so on.During the process of matrix solid-phase dispersion(MSPD),the dispersant and sample is blended fully.The dispersant is an abrasive,producing shearing and grinding forces that induced disruption of the sample architecture,and accomplishing complete sample disruption and dispersion, the extraction and clean-up are achieved in one-step.Accelerated solvent extraction (ASE)is one of the latest techniques developed for extraction of solid/semi-solid samples.ASE operates at high temperatures(40-200℃)and high pressures (1000-2500psi),and allows faster extraction of analytes and requires only small volume of solvents.In this dissertation,molecularly imprinted polymers were synthesized with methamidophos(MAP)and acephate(APA)as template respectively.The interaction mechanisms between the template and the monomers were researched thoroughly by spectroscopy methods.The appearance,molecular affinity ability and specificity recognition characteristics of these MIPs were studied by physical and chemical methods.Selecting a right dispersant,a new method of selective extraction and clean-up of OCPs in complicated samples was developed by combining MSPD and ASE.The main work of this thesis is summarized as follows: 1.Molecular imprinting was used to develop a method based on noncovalent interaction for the synthesis of a MAP-specific polymer.The mechanism and selective binding characteristics of the imprinted polymer were evaluated by ~1H NMR,FT-IR and UV spectrometry.The results illustrated the interaction should be cooperative hydrogen bonds produced by self-assembling of the template and monomers.The stoichiometric mole ratio of MAP-methacrylic acid complex is 1:2.The Freundlich isotherm(FI)illustrated the MIP had better affinity capacity for MAP.The specificity of MIP for MAP was studied by FT-IR.The results illustrated that there were carboxyl in MIP combined with the template by cooperative hydrogen bonds.The hydrogen atom of NH and oxygen atom of P=O in MAP molecular would be the hydrogen-bonding sites with carboxyl.The results of molecularly imprinted solid-phase extraction(MISPE)also showed the specificity of MIP for MAP.The high affinity of the MIP to MAP could be applied in fast preconcentration,clean-up and determination of MAP in soil and water samples.2.Relative to MAP(pK_a=10.0),the basicity(pK_a=8.5)and toxicity Of APA are all weaker.Molecular imprinting was used to develop a method based on noncovalent interaction for the synthesis of a new MIP using APA as the template.The mechanism and selective binding characteristics of the imprinted polymer were evaluated by ~1H NMR,FT-IR and UV spectrometry.The results illustrated the interaction should be cooperative hydrogen bonds produced by self-assembling of the template and monomers.The stoichiometric mole ratio of APA-methacrylic acid complex is 1:2. The results of single-analyte binding assay showed the MIP had better affinity capacity for APA and smaller MAR The results of MISPE showed the specificity of MIP for APA and MAP.The high affinity of the MIP to APA and MAP could be applied to fast preconcentration,clean-up and determination of APA and MAP simultaneously.3.A 3.5μm diameter of microspheric molecularly imprinted polymer(MIP)was synthesized by precipitation polymerization.The shape,adsorption capability,thermal stability and porosity of microspheric MIP were compared with the bulk MIP.The microspheric MIP owned regular shape,stronger affinity capability,the more surface area,porosity and better thermal stability.The specificity of microspheric MIP for MAP was studied by FT-IR.The results illustrated that there were carboxyl in microspheric MIP combined with the template by cooperative hydrogen bonds.The results of MISPE also showed the specificity of microspheric MIP for MAP.4.The matrix solid-phase dispersion(MSPD)and accelerated solvent extraction(ASE) were combined to develop a fast,sensitive and accurate method for the determination of organochlorine pesticides(OCPs)in complicated samples.The Florisil was used as dispersant for the determination of 16 OCPs in soils.The recoveries were from 77.4% to 101.3%,and the limit of determination(LOD)were from 0.01 to 0.04 ng/g.The acid alumina was used as dispersant to adsorb the fat for the determination of OCPs in fish.The extraction and clean-up were completed in one-step.The extracts were clean enough to GC-ECD and GC-MS(SIM)analysis,nonother clean-up step was needed.