Preparation Of Magnetic Molecularly Imprinted Polymers And Its Application In Essential Oils

Essential oil known as liquid gold is widely used for the preparation of variousfragrances and food additives, there are nearly119relevant ISO standards on essentialoils. In European Union and the United States, some stringent standards have beenperformed, especially for the trace elements which have a larger impact on essentialoil quality. China is the major supplier of the world fragrance industry, Xinjiang is themain essential oil producing region of China. In recent years, the domestic essentialoils industry has greatly developed. But compared with European Union and theUnited States, standards of China were too simple, and just limited in the physical andchemical factor of the oil, and largely hinder the improvement of essential oil quality.One important reason is that no detection methods were proposed to the lowconcentration components. To improve the essential oil quality of Xinjiang, it’snecessary to establish a rapid detect method for local essential oil products. Molecularimprinting technology (MIT) is a novel type of separation technique with highefficient separation and molecular recognition. In this study, the magnetic molecularlyimprinted polymers (MMIPs) were prepared by combining with MIT and magneticseperation technology for separating and enriching the characteristic components ofthe oil.In this thesis, two methods are used to prepare MMIPs of camphor andcitronellol. Specific content as follows:(1) MMIPs were successfully prepared by using camphor or citronellol astemplate molecule. Methyl acrylic acid as functional monomer and Fe3O4as magneticcomponent, Ethylene glycol dimethacrylate as crosslinking agent,2,2’-azobisisobutyronitrile as initiator, chloroform as solvent as well as nonimprintedpolymers (MNIPs) without addition of template molecule. The morphological, sizeand polymeric characteristics of MMIPs were characterized by X-ray diffraction,scanning electron microscope, transmission electron microscope and fourier transforminfrared spectroscopy. The diameter of Fe3O4with good monodispersity is in therange of70-270nm. The prepared MMIPs showed good selectivity to camphor orcitronellol.(2) Hollow porous magnetic molecularly imprinted polymer microspheres wasprepared with camphor and citronellol as template molecule respectively,P(St-co-MAA) as functional monomer and Fe3O4as magnetic component, as well asnonimprinted polymers without addition of template molecule. In order to obtain the best condition, the polymerization formula was optimized via orthogonal experiment.The morphological, size and polymeric characteristics of hollow porous magneticmolecularly imprinted polymer microspheres were characterized by X-ray diffraction,scanning electron microscope, transmission electron microscope and fourier transforminfrared spectroscopy. The orthogonal experiment results showed that the optimalpreparation formula for camphor hollow porous magnetic molecularly imprintedpolymer was as follows: P(St-co-MAA)0.06mmol, Fe3O4500μL, NaOH400μL,chloroform6mL, speed at250r/min. Camphor hollow porous magnetic molecularlyimprinted polymer of good adsorption properties can be produced. The optimalpreparation formula for citronellol hollow porous magnetic molecularly imprintedpolymer was as follows: P(St-co-MAA)0.02mmol, Fe3O4500μL, NaOH300μL,chloroform2mL, speed at500r/min. Citronellol hollow porous magnetic molecularlyimprinted polymer of good adsorption properties can be produced.(3) The binding affinity and selectivity to camphor and citronellol of MMIPs andMNIPs were evaluated by equilibrium adsorption experiments and their adsorptionkinetics were observed, respectively. Camphor MMIPs exhibited good adsorptionaffinity and selectivity toward camphor, and citronellol MMIPs exhibited goodadsorption affinity and selectivity toward citronellol and its analogues. The Scatchardplot for MMIPs consisted of two linear parts with different slopes, while theScatchard plot for MNIPs was a single linear curve. It revealed that binding sites ofMMIPs and MNIPs were heterogeneous and homogeneous, respectively. Thecamphor in the essential oil of Lavandula angustifolia and the citronellol in theessential oil of Rose were enriched and determined by gas chromatography. Therecoveries of camphor in the essential oil of Lavandula angustifolia adsorbed bycamphor MMIPs ranged from52.68%-60.20%with low RSD (<6.52%); Therecoveries of camphor in the essential oil of Lavandula angustifolia adsorbed bycamphor hollow porous MMIPs were in the range of66.98%-75.76%with low RSD(<4.53%) and the limit of detection for camphor was3.160μg/mL. The recoveries ofthe citronellol in the essential oil of Rose dealt with citronellol MMIPs were in therange of47.96%-51.02%with low RSD (<8.18%). The recoveries of the citronellolin the essential oil of Rose dealt with citronellol hollow porous MMIPs were in therange of54.36%-62.23%with low RSD (<7.18%) and the limit of detection for citronellol was3.030μg/mL.