Preparation And Evaluation Of Molecularly Imprinted Polymers For Solid Phase Microextraction And Their Application To The Analysis Of Pesticide Residues

One of the burning problems facing our society is food security.Pesticide residues in food has brought serious harm to human beings.And it also cause serious pollution to the environment.So it is important to establish an accurate detection technology,which is quick and economical.Chromatography is the preferred method for quantitative analysis of pesticide residues as it's accurate results.However,the traditional sample preparation technology can not satisfy the requirements of pesticide residue analysis.Sample preparation,as the research bottleneck to the analysis of complex samples,has become the hot pursuit in the area of analytical chemistry.Solid-phase microextraction(SPME)has been widely applied to food analysis due to its integrated sampling,extraction,concentration and injection into one single step.Because of the highly complex matrices,target analytes are always subject of interference or inhibited by the matrices,so as to hamper accurate quantification or lower detection sensitivity.The selection of appropriate SPME coatings is therefore indispensable in the whole analytical process.However,only a few types of coating are commercially available,and their use are limited by the lack of selectivity.Promotion of stability and selectivity of SPME fiber is one of the important fields in developing this method.Therefore,the preparation of tailor made fibers has been the focus of interest.Molecularly imprinted polymer(MIP)because of its unique ability of recognition has become a kind of new extraction adsorption material.The combination of MIP and SPME would ideally provide a powerful analytical tool in terms of technology,simplicity,flexibility and selectivity characteristics.In this review,we discussed three main approaches to preparing molecularly imprinted polymer coated solid-phase microextraction fiber,make sure the feasibility and necessity of the sol-gel method of preparation MIP-coated SPME fiber.Two MIP-coated SPME fibers were prepared via sol-gel method with beta-cypermethrin and diazinonas as template molecule,respectively.The characteristics and applications of those fibers were investigated.A method to detect pyrethroid pesticides and organophosphorus pesticides(OPPs)in complex samples such as tea and fruit was presented,which offers a new pretreatment method for quantitative analysis of analytes at trace level in complicated matrix.The main contents in this thesis are described as follows:1.Investigation of the performance of the molecularly imprinted polymers coated solid phase microextraction fibers prepared by different methodsIn this study,three preparation approaches(sol-gel method,co-polymerization method,in-tube polymerization method)were developed for diazinon molecularly imprinted polymer coated fibers used in SPME.The thermal stability of the MIP-coated fiber made through sol-gel method reach a high of 360?,and 300?,320? for MIP-coated fibers which were made by in-tube polymerization method and co-polymerization method,respectively.All of the three MIP-coated fibers had good solvent resistant stabilities.Compared with several commercial fibers,the.three new MIP-coated fibers exhibited high extraction efficiency to diazinon.And the extraction yields of MIP-coated fiber made by sol-gel method were obviously higher than that of MIP-coated fiber made by co-polymerization method.The extraction capacities of OPPs with the MIP-coated fiber by co-polymerization method were about 3.24,2.64,1.61,1.19 and 2.23 times as much as that with the correspond to no imprinting polymer(NIP)coated fiber under direct SPME.And the imprinting factor of MIP-coated fiber made by co-polymerization method under headspace SPME were 2.03,1.19,1.74,1.13 and 1.23.The selectivity of MIP-coated fiber made by sol-gel method was similar under two extraction modes,from 1.19 to 1.77.2.Development of a fiber coating based on molecular imprinting sol-gel technology for selective solid-phase microextraction of pyrethroid pesticides from teaA relatively selective,chemically and physically robust SPME fiber on the basis of MIP was developed via the sol-gel process,using beta-cypermethrin as template,butyl methacrylate(BMA)and divinylbenzene(DVB)as co-functional monomers,and then coupled with gas chromatography/electron-capture detection(GC/ECD)for selective extraction and analysis of pyrethroid pesticides.The MIP-coated fiber were evaluated according to their selective recognition properties for beta-cypermethrin,structure analogues(cyhalothrin,bifenthrin and fenpropathrin)and reference compounds.The new fiber possessed a homogeneous,porous surface and showed excellent thermal(over 340?),chemical and mechanical stability.The optimized extraction conditions were studied.Finally,it was successfully applied to extraction and determination of cyhalothrin,beta-cypermethrin,bifenthrin and fenpropathrin,by the homemade MIP-coated fibers.The linearity was ranging from 10 to 2000?g/kg for bifenthrin,fenpropathrin,beta-cyfluthrin and cyhalothrin.The detection limits of these pesticides were between 1.65 and 5.04?g/kg.The recovery of the pesticides spiked in various tea samples at three different concentrations ranged from78.89%to 121.67%,and the relative standard deviations were less than 12.9%.3.Development of a new molecularly imprinted polymer coated fiber for solid phase microextraction and investigation of the recognition ability for diazinon in fruitsAn MIP-coated fiber was synthesized using BMA and DVB as the functional monomers,diazinon as template.The MIP-coated fiber contain promising mechanical and excellent thermal stability,good durability.Furthermore,special selectivity to other organophosphorus pesticides which have similar structure to diazinon was discovered with the MIP-coated fibers.Parameters affecting SPME were investigated,including extraction temperature,extraction time,ionic strength,desorption temperature and time,based on the MIP-coated fibers were studied and optimized.Under the optimum SPME and GC/NPD conditions,the linear ranges were quit wide for four OPPs in pear with the correlation coefficient of above 0.9986.The detection limits(S/N= 3)were 0.004 to 0.07?g/kg.The precisions of the peak areas for five replicates were less than 7.32%.The recoveries for four OPPs in the spiked apple,pear,strawberry and peach samples at three levels of concentration were 90.01%-117.77%.The proposed method was successfully applied to the selective extraction and determination of organophosphorus pesticides in fruits.