Preparation And Application Of Organophosphorus Imprinted Sol-gel Coatings For Solid-phase Microextraction And Array Solid-phase Microextraction

Molecularly imprinted polymers(MIPs),acclaimed as the artificial antibody,possess predetermined recognition sites able to selectively rebind template molecules and have been extensively applied in sample preparation.The molecularly imprinted solid-phase microextrction(MISPME)technique integrates the MIPs characteristics of high selectivity with the advantages of SPME technique,and could be applied for selective separation of analytes and eliminate matrix interference.By far the most widely used method for the preparation of MIP fibers is the co-polymerization method using methacrylic acid and its derivatives as monomers.Moreover,the coating volume of the conventional MISPME fiber is insufficient.Anyhow,there is an urgent need for the development of monomers,MIPs preparation methods and multi-residue analytical methods for simultaneous determination have become a focus and hotspot.In this work,several kinds of MISPME fibers using organophosphorus pesticides as the templates,polyethylene glycol(PEG-20M)and 5,11,17,23-tetra-tert-butyl-25,27-dicyanomethoxyl-26,28-dihydroxy calix[4]arene(C[4])as the functional monomers,were prepared by sol-gel method.A hybrid array SPME device was also constructed by packing three different kinds of imprinted fibers.Characteristics of the fibers and array SPME device were evaluated.The optimized methods based on imprinted MISPME combined with gas chromatography(GC)were applied for the determination of organophosphorus pesticides(OPPs)in vegetable and fruit samples.The main contents were as following.1.Preparation and application of diazinon imprinted sol-gel coating for SPME.A novel MISPME fiber with diazinon as a template was prepared by sol-gel technique.PEG-20M was chosen as the functional monomer.Characteristics of the fiber were evaluated.The fiber exhibited excellent thermal and chemical stability,demonstrated high selectivity to diazinon and its structural analogues,and showed higher extraction capacity than commercial PDMS and DVB/CAR/PDMS fibers.A method based on MISPME combined with gas chromatography was developed for the determination of OPPs in vegetable samples.The linear ranges were achieved at the ?g kg-1 levels and the linear correlation coefficients for all analytes were greater than 0.995.The recoveries for five OPPs in spiked cucumber,green pepper,Chinese cabbage,eggplant and lettuce were 82.7-113.5%,88.9-109.9%,89.7-106.8%,93.7-110.9%,and 81.2-112.6%,respectively.2.Preparation and application of parathion-methyl imprinted sol-gel coating for SPME.C[4]was firstly synthesized as functional monomer and introduced for preparation of MISPME fibers by sol-gel technique.The average thickness of fiber was 50 ?m.The characteristics,selectivity and possible recognition mechanism and extraction efficiency of MIP-coated fiber were investigated.A method for the determination of four OPPs by the MISPME coupled with GC was developed.All the compounds exhibited wide linear ranges and good correlation coefficients(R2>0.997).The limits of detection(LODs)ranged from 0.0019 to 0.065 ?g kg-1 and the relative standard deviation(RSD)for OPPs was in the range 3.4%-7.0%.Liquid-liquid extraction(LLE)coupled to GC was also developed according to the industrial standard of agriculture ministry(NY/T 761-2008)as a comparison.The results indicated SPME technique was more convenient,rapid,without solvent and better recoveries than LLE.3.Preparation and application of molecularly imprinted coating for array SPME.MIPs with diazinon,parathion-methyl and isocarbophos as template,respectively,were prepared and coated on the surface of stainless steel fiber through sol-gel technique.A novel array SPME device was designed and evaluated by selecting three different kinds of imprinted fibers.By contrast,other SPME devices by packing the same imprinted fibers also prepared.Extraction kinetics,and selectivity were evaluated.Furthermore,the extraction capability was investigated in comparison with the commercial fibers,the non-imprinted polymer coated fiber,different SPME devices prepared by the usage of various kinds of MIP-coated fibers.A new multi-residue method was presented for simultaneously quantitative and qualitative analysis of five OPPs in fruit and vegetable samples.The lowest concentrations of linear ranges were achieved in the range of 0.1-1?g kg-1,the linear correlation coefficients for all analytes were greater than 0.995,the RSD was in the range 3.5%-6.6%and the LODs ranged from 0.0052 to 0.23 ?g kg-1.The experimental results showed that the selected vegetable samples were free of OPPs contamination.The recoveries of spiked apple,cucumber,Chinese cabbage and cherry tomatoes samples were 75.8%-122.3%,91.6%-120.7%,81.1%-123.2%and 75.1%-104.4%,respectively.