| Molecular imprinting technique is one of the emerging technologies containing polymerchemistry, materials science, biochemistry with predetermination, recognition, practicability.Molecular imprinting polymers (MIPs) prepared by molecular imprinting technique promiseunmatched selectivity for template molecules. MIPs have been widely used in enzyme mimicscatalysts, chiral separation, solid-phase exatraction and biosensors due to their high chemicalstability, high selectivity and affinity, easy availability. Imprinting process generally go throughthree steps: firstly, template and monomer form a reversible complex; then template-monomercomplex polymerized to form a crosslinked polymer; Subsequent elimination of the imprintedmolecule tailor a cavity in the polymer matrix that are complementary to the template.Molecular imprinting microspheres have higher surface area-to-volume ratios; thus,imprinted cavities are more easily accessible by the templates and the binding kinetics areimproved. They have already been used as enzyme substitutes drug delivery systems andantibody substitutes as well as in capillary electrophoresis and in sensors.Solid-phase extraction (SPE) is a time efficient technique of sample pretreatment whichcan enriched and purified sample via conditioning, loading, washing and eluting. SPE havebeen well accepted preconcentration technique with the advantages of simple, less cost andpollution compared with the traditional liquid-liquid distribution. Most common sorbents usedin SPE, for example C8, C18, Florisil, lack selectivity for the target compound. However, MIPspossess specific binding sites that are complementary to the template in terms of its shape, size,and functionality. Accordingly, the combination of molecular imprinting and solid-phaseextraction (MISPE) would inherit both advantages of well selectivity and high extractionefficiency.Chloroacetamide herbicides are a class of highly selective herbicide widely used in paddyand upland. Due to the extensive use of chloroacetamide herbicides, they cause a certain degreeof pollution on the environment and endanger human health. The objective of this paper is to prepare MISPE material which has class-specialadsorption to chloroacetamide herbicides using dummy template and this material can beapplied to chloroacetamide herbicides residue analysis. The preparation of chloroacetamideherbicides molecularly imprinted polymers are described in this paper. The performance andmechanism of recognition are researched. The prepared MIPs are used in solid-phase extractionexperiments and the conditions of solid-phase extraction are optimized. At last, the sample ofsoil is analyzedIn chapter1, there is a literature review, we mainly introduce origin, development andapplication of molecular imprinting technology, the latest advances in molecular imprinting isalso introduced. Meanwhile, we describe the solid phase extraction techniques.In chapter2, a series of butachlor molecularly imprinted polymers are prepared viaprecipitation polymerization and bulk polymerization using MAA and4-VP as functionalmonomers, EDMA as crosslinker, AIBN as initiator agent，acetonitrile, chloroform andmethanol as porogen. The conditions of polymerization are discussed and the optimumsynthesis conditions are selected. The results indicate that the MIPs prepared by precipitationpolymerization employing MAA as functional monomer, acetonitrile as porogen with the molarratio of1:4:20(template: functional monomer: crosslinker) show good binding property, theamount of binding is8.98mg·g-1.In chapter3, the structure, particle size distribution and morphology are characterized byinfrared spectrometry, zetasizer and scanning electron microscopy. The kinetics, equilibriumadsorption and selectivity of MIPs are also studied. The results indicate that all componentshave been successfully polymerized, the particles of precipitation polymerization distributeuniformly, D50(MIPs)=0.80μm, the shape of MIPs is microsphere. Kinetic experiments showthat the adsorption of polymer attain equilibrium within60min; Equilibrium adsorption showthat MIPs have better adsorption capacity than NIPs, because there are many specific bindingsites in MIPs; Scatchard analysis prove one specific binding site exist in MIPs, the Kd andQmax are found to be12.95mol/L and25.74mg/g, respectively. One non-specific binding siteexists in NIPs, the Kd and Qmax are found to be42.02mol/L and23.48mg/g, respectively.Selective experiments show that the difference of adsorption are caused by molecular structure,the adsorption of MIPs to chloroacetamide herbicides (butachlor, pretilachlor, acetochlor,alachlor, metolachlor) are occurred in specific binding site of MIPs. MIPs have betterselectivity for acetochlor, α is calculated to be0.79.In chapter4, an annalyticl procedure based MISPE to butachlor and its structuralanalogues is developed. The types of washing solvent and volume of eluting solvent are discussed, and the conditions of solid-phase extraction are optimized. The experimental resultsindicate that MISPE for chloroacetamide herbicides show good adsorption, using1mL of1μg/mL butachlor, pretilachlor, acetochlor, alachlor，metolachlor petroleum ether solution asloading solvent,2mL hexane as washing solvent,15mLmethanol as eluent, the recoveries ofsolid-phase exactration are about90%.In chapter5, the sample of soil spiked with pretilachlor, acetochlor, alachlor，metolachloris analysed. The average spiked recoveries are85.6%88.4%,85.6%and82.2%, respectively.The results meet the requirement of pesticide residue analysis.Therefore, the present study of the molecular imprinted polymers using dummy template isexpected to be used in chloroacetamide herbicides residues of the practical application. |
PDF Full Text Request