摘要
分子印迹是指制备对某一特定分子(模板分子或印迹分子)具有特异选择性的分子印迹聚合物的过程。分子印迹聚合物具有亲和性好、稳定性好、抗干扰性强、选择性高、使用寿命长以及应用范围广等优点,在药物、生化、环境以及食品安全分析方面得到迅猛发展。
三唑类杀菌剂是指含有1,2,4-三唑环的化合物,由于其具有低毒、内吸性强、持效期长等优点,被广泛的应用于水果、蔬菜、稻谷等病虫害的防治。随着三唑类农药在水果、蔬菜中的广泛应用,易导致其在农产品和环境中的高残留问题,构成了对食品安全和人类生命健康的重大隐患。因此,对三唑类药物的分离与检测是食品安全与制药生产中质量的控制关键。本论文对三唑酮分子印迹聚合物体系进行了研究,具体内容如下：
1、本文首先采用Hyperchem8.0分子模拟软件,通过半经验算法和从头算法优化,模拟了模板分子三唑酮和4种功能单体的最低能量构象,然后结合Mulliken电荷,分析了三唑酮与功能单体之间的相互作用并计算了相应的结合能,以此表征二者之间相互作用的强弱并指导单体的选择。运用Gaussion03软件将预组装体系置于溶剂模型(PCM)中,计算了模板分子和功能单体在介电常数不同溶剂中的溶剂化能。通过计算可知三氟甲基丙烯酸与三唑酮形成的聚合物稳定性最强,丙烯酸次之,甲基丙烯酸再次之,丙烯酰胺最差。模板分子和功能单体在溶剂中的溶剂化效应与溶剂的介电常数的高低成相关性,在非极性溶剂中溶剂化能最弱。
2、以三唑酮为模板分子,三氟甲基丙烯酸为功能单体,乙二醇二甲基丙烯酸酯为交联剂通过本体聚合的方法制备了分子印迹聚合物(MIP),并结合紫外光谱法研究了该印迹聚合物的结合机理和识别特性。紫外光谱研究证明三唑酮与单体之间可以通过氢键作用形成1∶2型配合物。采用Scatchard模型和Langmuir-Freundlich模型分析表明,以甲基丙烯酸为功能单体的印迹聚合物通过氢键作用可以形成两类结合位点,并用多点结合模型求算了两类不同结合位点的离解常数。
3、以合成的三唑酮分子印迹聚合物为填料,制备了分子印迹固相萃取柱,对上样溶液、淋洗溶液、洗脱溶剂进行优化。固相萃取实验表明,表明当MISPE柱依次用20%的乙腈-水(V/V)上样、淋洗,5mL乙腈洗脱时,20种三唑类农药在分子印迹固相萃取上的同收率均达到85%以上。利用分子印迹固相萃取法对不同食品样品基体进行了前处理,并与ENVI-Carb/SPE小柱在回收率和基体效应上进行对比研究。结果显示：在三个不同加标水平下,三唑类农药的回收率在81.0%～109.7%之间,相对标准偏差小于13%,基质效应在88.8%～126.0%,与ENVI-Carb/SPE小柱相比,能更有效的减弱基体效应。
Molecularly imprinted polymers are specific high polymer material that have the selective binding ability to the particular molecules. MIP has good affinity, good stability, powfull anti-interference, high selectivity, long service life as well as the advantages of wide range of applications. MIP has got rapid development in medicine, biochemistry, environmental and food safety analysis.
Triazoles fungicide is refers to the containing1,2,4-triazole ring compounds. It has been widely used in fruit, vegetables because it has low toxicity, strong systemic and long effective period. Triazoles fungicide is widely applied in fruits, vegetables, which easily lead to its high residues in agricultural products and environment. This constitutes the major hidden dangers of food safety and human health. Therefore, separation and detection of triazole drugs is a key in food safety and pharmaceutical production quality control. The triadimefon molecules is studied in this paper. The main contents and conclusions are as follows:
l.The minimum energy conformations of template and4functional monomers were simulated by a semi-empirical method(PM3) and ab inito algorithm methods with Hyperchem8.0software. The Mulliken charges were used to analys possible interactions between templates and functional monomers and to calculate their binding energies. So as to characterize the strength of the interaction between them and guide the choice of monomer. Calculating the solvent energy of template and4functional monomers in the solvents with different dielectric constants by putting the pre-assembly system into PCM. The results showed that the stability of polymer formed by TFMAA and triadimefon was the most powerful,the second was AA,and then MAA,AM was the last.The salvation energies of template and functional monomers were related to their dielectric constants. The salvation energy in polar solvents is greater than that in non-polar solvents.
2.Molecularly imprinted polymers(MIPs) with high selectivity to triazoles residues were prepared using triadimefon as template,trifluoromethyl acrylic acid (TFMAA) as functional monomer,ethylene glycol dimethacrylate (EGDMA) as cross-linker. The synthesized MIPs was analysed using ultraviolet spectrum. It was showed that the complex ratio between TFMAA and triazolone was1:2. Scatchard and Langmuir-Freundlich analysis indicated that the complex can form two classes of binding sites through hydrogen bonding interaction. The dissociation constants were calculated respectively.
3.The MIPs was applied to solid phase extraction (SPE) of triazoles residues. The sample solution, leaching solution and elution solvent were optimized. The recovery of20triazoles was above85%when the following procedure was applied to MIPs cartridge:loading and cleaning with acetonitrile-water(20:80,V/V) respectively, and eluting with5mL acetonitrile. Under optimized MISPE conditions, recoveries of analytes were in the range of81.0～109.7%with satisfactory precision (RSD%lower than13%) and the matrix effect was in the range of88.8%-126.0%. Compared with ENVI-Carb/SPE columns, MISPE exhibited selective binding properties for triazoles and the matrix effect was significantly decreased.
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