Preparation Ofamphiphilic Polymeric Micelle And Preliminary Application In Capillary Electrophoresis

Electrokinetic chromatography (EKC) is one mode of capillary electrophoresis (CE). Based on pseudostationary phase (PSP), such as micelle and microemulsion, EKC could extend analytes from charged substances to neutral, water-insoluble molecules. Recently, a large number of novel surfactants such as biosurfactant and gemini surfactant, dendrimers, liposomes, vesicles, ionic polymers have been used as PSP in EKC. However, to my knowledge, self-assembly of amphiphilic polymer micelles as PSP in MEKC has not been reported. The present work firstly used polymeric micelle as PSP in CE to attempt to overcome difficulties in MEKC or MEEKC. On the one hand, conventional SDS micelles as PSP in MEKC the is limited to separate highly lipophilic substances.On the other hand, high concentration of ionic surfactant to form microemulsion results in high joule heating, longer analysis time. The thesis mainly included the following three parts.1. A series of random copolymers poly(methyl methacrylate-co-methacrylic acid) (P(MMA-co-MAA)) with different feed monomer ratio and different molecular weight were synthesized by radical polymerization, using methyl methacrylate (MMA) and methacrylic acid (MAA) as monomers, 2,2-Azobis (isobutyronitrile) (AIBN) as initiator, 1,4-dioxane as solvent. The random copolymers P(MMA-co-MAA) were characterized by means of FTIR, 1H NMR and Gel Permeation Chromatography (GPC). The results show that the proportion of the MMA and MAA groups on the chain of random copolymer is similar as the feed monomer molar ratio and the molecular weight of the polymer was controlled by changing the initiator content, its molecular weight is between 20000 and100000 and distribution was narrow.2. A fast, simple and green method of the preparation of polymeric micelles has been invented, according to the characteristics of the amphiphilic polymer. The micelle of amphiphilic random polymer P (MMA-co-MAA) is prepared by dissolving certain quantity of the polymer in alkaline solution (sodium hydroxide solution used in this experiment) and the pH is adjusted in light of the experiment. The aqueous self-assembly of the random polymers were investigated by using transmission electron microscopy (TEM), dynamic laser light scattering (DLS) and Zeta potential. The effects of concentration of polymer, pH of the running buffer, molecular weight of polymer and different feed monomer ratio of MMA and MAA were investigated. Results showed the shape and the size of polymeric micelle were mainly influenced by the concentration of polymer and different feed monomer ratio of MMA and MAA, respectively. The Zeta potential of micelle was controlled by pH of the running buffer. At the concentration of 0.048 mmol/L, feed monomer ratio of 6:4 (MMA to MAA) and pH 9.2, the polymeric micelles were of monodispersity and perfect spheres. The optimum conditions of preparation polymeric micelle were utilization of the polymeric micelle as a pseudostationary phase to improve MEKC performance.3. The polymeric micelle with amphiphilic random copolymer P (MMA-co-MAA) via neutralization in aqueous medium was firstly applied as a pseudostationary phase (PSP) in electrokinetic chromatography (EKC) in the present work. Three structurally similar corticosteroids namely hydrocortisone, prednisolone and prednisone were separated with EKC using polymeric micelle as PSP to assess the separation performance. The concentration of polymer, pH of the running buffer, molecular weight of polymer and different feed monomer ratio of MMA to MAA on EKC performances have been investigated, and the optimum condition is at the concentration polymer( MMA:MAA 6:4 and Mn=88924, Mw=104213, Mw/Mn=1.17) of 0.048 mmol/L and pH 9.2. With separation voltage of 20 kV, electrokinetic injection of 3s/20 kV and capillary temperature of 20℃, prednisone, hydrocortisone and prednisolone were baseline separated within 7.4 min. The RSDs of migration time for three analytes were all less than 0.17% and peak area were less than 3.7% (n=7). Excellent linearity was obtained ranged from 2 to 100 mg/L, the detection limits based on ratio of signal to noise of 3 were 0.63, 0.94 and 1.2 mg/L for three analytes respectively. Compared with typical MEKC, MEEKC and MEKC modified with IL ([Bmim]BF4), the developed method was more rapid, efficient and higher selective. The separation mechanism using polymeric micelle as PSP was reverse-phase interaction. The method has been applied to determination of the three corticosteroids in actual cosmetic samples, the recoveries of three analytes were between 97.7% and 113%.