| Molecular imprinting technology(MIT) is a preparation technique to obtain the polymer matched with the molecule(imprinting molecule, the template molecule) in the space structure and the binding sites. Due to the advantages of high selectivity, practicality and reusability, molecularly imprinted polymer(MIP) has been used in many fields such as food safety, medicine and environment. It has been applied widely as solid phase extraction sorbent in various research fields.In this study, MIP was used in the determination of three kinds of hazard factors of food safety, including triazine pesticides, melamine and chloramphenicol. The dummy template imprinting and surface imprinting were studied to deal with the problems of MIT, such as leakage of template molecules, slow transfer kinetics, and uniform sizes of particles. At the same time, a novel, quick and competitive fluorescent assay for melamine was innovatively established based on the surface magnetic molecularly imprinted polymer(SMMIP) as antibody alternatives, the competitive binding of fluorescent tracer and melamine on the SMMIP and the rapid and magnetic separation. Furthermore, the established quick method was attempted to the detection of melamine in milk samples. The main research contents and conclusions were as follows:1. A molecularly imprinted solid-phase extraction(MISPE) method followed by high performance liquid chromatography-tandem mass spectrometry(HPLC-MS/MS) for the determination of 17 kinds of triazine pesticides was established. Two molecularly imprinted polymers for atrazine and prometryn were synthesized using atrazine and prometryn as template separately, methacrylic acid as functional monomer and trimethylolpropane trimethacrylate as cross-linking agent. The molecularly imprinted solid-phase extraction cartridge was obtained by mixing the two molecularly imprinted polymers at proper amount. The adsorption experiment showed that the MISPE had the specificity to adsorb the triazine pesticides that had the similar structures to atrazine and prometryn, hardly to adsorb hexazinone and cyanazine with different structures. It was demonstrated that the MISPE-HPLC-MS/MS method could be applied to the determination of 17 kinds of triazine pesticides, with the recoveries in the range 61.1% and 107.6% and the relative standard deviations(RSD) between 2.0%- 10.7%. The limits of detection were calculated by 3S/N between 0.4 μg/kg and 5.0 μg/kg.2. The sample pretreatment and determination methods for melamine based on molecular imprinting technology were studied.Melamine is also known as 2, 4, 6-three ammonia-1, 3, 5-triazine, and it has the basic ring of triazine. In this study, triazine compounds were investigated as the dummy template to synthesize molecularly imprinted polymer for melamine. The results showed that the dummy template was able to solve the problem of template leakage and improve the reliability of the detection method.(1) The MISPE-HPLC-MS/MS method for melamine was established. Firstly, the molecularly imprinted polymer using melamine as template was synthesized, evaluated and applied in the determination of melamine in milk samples. Secondly, to deal with the leakage of template molecules, 2-chlorine-4, 6-diamine-1, 3, 5-triazine and 2-methyl-4, 6-diamino-1, 3, 5-triazine were selected as dummy templates. Two dummy molecularly imprinted polymers were prepared, and the selectivity and adsorption ability to melamine were evaluated. It was shown that the two dummy molecularly imprinted polymers had the specific adsorption ability with melamine and they could also be applied to the determination of melamine in milk samples with the recoveries between 74.6% and 87.1% and the relative standard deviations(RSD) below 10%.(2) The surface molecularly imprinted polymer(SMIP) using 2-chlorine-4, 6-diamine-1, 3, 5-triazine as dummy template and silica nanoparticles as the core was prepared. The monodispersed silica nanoparticles were modified with vinyl and the molecularly imprinted polymer film was coated onto the silica nanoparticles with the thickness of 30 nm. The adsorption ability and morphology of SMIP were evaluated and characterized. Then the synthesized SMIP was applied as the solid-phase extraction sorbents to the extraction and purification of melamine in milk samples, and the recoveries were between 80.9% and 86.5% with the relative standard deviations in the range 4.9% to 6.4%. Compared with the molecularly imprinted solid-phase extraction cartridge prepared by(1), the operating time was shorten, as well as the efficiency of sample pretreatment was improved.(3) The surface magnetic molecularly imprinted polymer(SMMIP) using 2-methyl-4, 6-diamino-1, 3, 5-triazine as dummy template and Fe3O4 nanoparticles as the core was prepared. A novel, quick and competitive fluorescent assay was studied and established using SMMIP as antibody alternatives for the first time. It was demonstrated that the concentration of melamine(in the range 0.05 mg/L to 80 mg/L) had a negative linear correlation with the bound of the fluorescent tracer on the SMMIP. The limit of detection was 0.05 mg/L. Then the established molecularly imprinted competitive fluorescent assay was attempted to the analysis of melamine in milk samples, and the recoveries were between 70.2% and 85.3% with the relative standard deviations below 12.4%.3. The dummy molecularly imprinted polymer(DMIP) for chloramphenicol and its application in the analysis of chloramphenicol were studied. Thiamphenicol, which has the similar structure with chloramphenicol, was used as dummy template, and the DMIP was synthesized. The adsorption results showed that the DMIP had a good selectivity and adsorption ability to chloramphenicol, and it could be applied to the solid-phase extraction of chloramphenicol in milk samples. The mean recoveries were 72.9% to 81.2% with the relative standard deviations below 8.3%. |
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