Functional Cyromazine Molecularly Imprinted Polymers: Preparation, Characterization And Applications

In recent years, a huge progress of determination of harmful substances in foodhas achieved with the development of analytical instrumentation. Sample pretreatment,as one of the critical procedures in quantitative analysis, directly influences theprecision and accuracy of the analytical method. However, large amounts of matrixinterferences being extracted simultaneously with the target analyte, known as thematrix-effect, leads to poor selectivity of the conventional solid phase extraction (SPE)technique, as well as low separation and enrichment efficiency. Molecularly imprintedpolymers can specifically recognize the imprinted molecules. When acting as SPEmaterial, molecularly imprinted polymers are selectively capable of enrich targetmolecules on the matrix without matrix interference, which makes it a potentialmaterial in the field of pretreatment of complex sample.Recently, a large number of chemicals were brought into human foods, includingfeed additives, pesticides, veterinary drugs and food additives. Some of them werecarcinogenic, teratogenic and mutagenic, which was a grave threat to public health.Cyromazine, which possesses less toxicity, is an insect growth regulator used for flycontrol in crop production and protecting animal feed by inhibiting insects growing. Itcan also be metabolized to melamine through environmental degradation viadealkylation reaction in both plants and animals. Melamine would lead tocrystallization and subsequent renal failure and even cause urolithiasis and bladdercancer by forming insoluble complexes with cyanuric acid in the kidneys. So it is veryimportant to determine cyromazine and melamine simultaneously. There are manymethods for their determination, but they all involve in poor selectivity and a largenumber of interfering substance. In the thesis, some molecularly imprinted polymerfor cyromazine and melamine were prepared and used to determine cyromazine andmelamine in complex sample. The details of this thesis are outlined as follows:1) Cyromazine imprinted polymers were prepared, and used as SPE materials.The combination of cyromazine imprinted polymer solid-phase extraction with highperformance liquid chromatography has been developed to isolate, enrich anddetermine cyromazine and its metabolic melamine in some samples. In lake watersamples, good recoveries of cyromazine and melamine were obtained as 98.0%-90.7%; in the milk samples, good recoveries were obtained as86.3%-91.5%.These results show that cyromazine imprinted polymer could effectively reduce thematrix interference and improve the accuracy in determining cyromazine andmelamine.2) To avoid the possible risk of template leakage for using cyromazine imprintedpolymer to determine cyromazine and melamine, psuedo template molecularlyimprinted polymers for cyromazine and melamine were firstly prepared, The resultingpseudo molecularly imprinted polymers were used as a solid-phase extraction materialto enrich cyromazine and melamine, and different protocols were optimized. Thecombination of pseudo template molecularly imprinted solid-phase extraction withhigh performance liquid chromatography has been developed to determinecyromazine and melamine in egg and milk samples. In the standard addingexperiment, the mean recoveries ranged from89.80to98.14%for cyromazine andmelamine, respectively. Compared to cyromazine imprinted polymer, pseudo templatemolecularly imprinted polymers could effectively reduce the matrix interference, butalso completely avoid the possible risk of template leakage. And it would be easy tomass produce and extende3) The above pseudo template molecularly imprinted polymers were prepared byusing toluene as a porogen, so it had a poor affiniting and selectivity in water solution.For this reason, hydrophilic-hydrophobic balance molecules imprinted polymers werefirstly prepared with glycidilmethacrylate as co-monomer. In water solutions, thepolymer had more excellent affinity and selectivity for cyromazine and melamine thanpseudo molecularly imprinted polymers. The hydrophilic-hydrophobic balancemolecules imprinted polymers were used as a solid-phase extraction material to enrichcyromazine and melamine in lake water. When cyromazine and melamine were allspiked at0.1μg/g, the recoveries of hydrophilic-hydrophobic balance moleculesimprinted solid-phase extraction were improved1.5%and3.6%compared topseudo template molecules imprinted solid-phase extraction respectively.Hydrophilic-hydrophobic balance molecules imprinted solid-phase was more suitablefor extraction cyromazine and melamine in water and could avoid the possible risk oftemplate leakage.4) In order to realize quickly high-throughput and automated detection, magneticmolecularly imprinted polymers for cyromazine and melamine were prepared bysimple suspension polymerization. It was characterized by VSM, TEM, FT-IR and used as a solid-phase extraction material. A method based on molecularly imprintedsolid-phase extraction assisted by magnetic separation was developed to extractcyromazine and melamine from egg and milk samples. When cyromazine andmelamine were at different fortified concentrations, the mean recoveries ranged from71.86%to80.56%. Compared to above three kinds of molecularly imprintedpolymers, magnetic molecularly imprinted polymers could shorten the analytical timeand was suitable for high-throughput selection, miniaturization and automation.