Development Of Molecularly Imprinted Composite Materials And Their Applications In Rapid Detection Of Organic Pollutants In Food And Environmental Samples

Molecularly imprinted polymers (MIPs) are cross-linked polymers with artificiallygenerated recognition sites, which are able to rebind template molecules or their structuralanalogues. Owing to the general applicability of molecular imprinted technology, differentkinds of MIPs could be prepared to recognize the corresponding template molecular.Although the prepared MIPs exhibite high selectivity, excellent reusability and highstability under extreme conditions of pH or temperature, some problems of MIPs such asincomplete template removal, low binding capacity, and slow mass transfer were revealedand their applications in analytical chemistry are limited to some extent. Furthermore, theapplication of MIPs in complex sample pretreatment always requires multi-step enrichmentand purification procedures. The aim of this paper is to develop new sample pretreatmentmethods based on MIPs in rapid detection of complex samples. The main contents are asfollows:1. Magnetic MIPs (MMIPs) were prepared using the oleic acid modified Fe3O4asmagnetic carriers, and they were applied to extract carbamate pesticides from differentwater samples by simply mixing and stirring with water samples. The MMIPs could beeasily separated from the matrix by adscititious magnetic field, therefore this methodavoided the time-consuming column-passing process of loading large volume samples intraditional SPE. The extraction and clean-up procedures were carried out in a single step.Furthermore, because of the excellent selectivity of adsorbents, matrix effect of the proposed method is much lower than that of conventional SPE method in HPLC-MSanalysis. Under the optimal conditions, the detection limits of carbamates are in the rangeof2.7-11.7ng mL1. In all spiked levels, the recoveries of carbamates are in the range of59–91%.2. Fe3O4@SiO2@MIPs were prepared by surface molecularly imprinting technique. Theprepared Fe3O4@SiO2@MIPs had both high selectivity toward target analytes and highmagnetic response while applying magnetic field. Owing to the multi-layer package, theFe3O4@SiO2@MIPs exhibit good stability. In addition, the interaction between templatemolecular and functional monomer was investigated through the dynamic adsorption study.Furthermore, the adsorption thermodynamics parameters were calculated based on theisothermal adsorption curves of the Fe3O4@SiO2@MIPs. Finally, the preparedFe3O4@SiO2@MIPs were applied to extract triazines from environmental water, and thelimit of detection of this method is0.02-0.08ng L-1. A concentration factor of500isachieved using this method to extract500mL of water samples.3. The molecular imprinted-electrostatic spinning membrane (MIM) was prepared byelectrostatic spinning technique. The morphology and adsorption properties of MIM havebeen characterized. The MIM exhibits good selectivity towards template molecule and itsstructure analgues. The MIM was fixed on the surface of the magnetic stir bar, and theywere used as stir bar adsorbent to extract sulfa antibiotics (SAs) from feed samples. MIMcloud be separated from the sample matrix very quick, the process of the pretreatment wassimplified. Under the optimal conditions, the detection and the quantitative limits of thismethod are1.5-3.4ng g-1and4.6-9.6ng g-1, respectively. In all spiked levels, the recoveriesof SAs are in the range of75–90%.4. Single-hole hollow molecularly imprinted microspheres (h-MIMs) were prepared byhard template method. The morphology and the adsorption performance of the preparedh-MIMs have been characterized. The h-MIMs exhibited bigger specific surface area andmuch higher binding capacity than the molecularly imprinted polymers prepared byprecipitation polymerization (p-MIPs) and surface polymerization (s-MIPs). Besides, theadsorption rate of h-MIMs to template molecule was significantly higher than that ofp-MIPs and s-MIPs. Owing to the hollow structure of the h-MIMs, more binding cavitieswere located both on the inner and outer surfaces of the h-MIMs, which could facilitate theremoval of template molecule from the polymers and the rebinding of the target moleculesto the polymers. Finally, the h-MIMs used as adsorbent were applied to extract six triazinepesticides from cereal samples. Atrazine was found in two rice samples and a wheat sample with the contents of5.1,6.7and5.6ng g1, respectively. Ametryn and prometryn werefound in a maize sample with the contents of7.6and7.3ng g1, respectively.5. The momodisperse MIPs were prepared by emulsion polymerization. Based onmembrane protection solid-phase microextraction, MIPs were successfully applied toextract triazines from tea. The solid phase adsorption package was made by encapsulatingMIPs into polypropylene microporous membrane. The extraction and enrichmentprocedures were carried out simultaneously by simply stirring the sample and the packagesin the extraction solvent. When the extraction completed, the packages could be easilyseparated from the sample matrix by a nipper. After washing and eluting processes, theanalytes were determined by LC-MS/MS. The use of microporous membrane couldeffectively reduce the contact of sample particles and macromolecular impurities withMIPs. Under the optimal conditions, the recoveries of triazines are in the range of81±3%-104±7%.