| The separation mechanism of capillary electrokinetic chromatography(EKC) is based on electrophoresis coupled with chromatography, which makes it possible to separate neutral and charged analytes simultaneously. The pseudostationary phase(PSP) is the key factor in KEC technology. The typical PSPs are formed by small molecular surfactants. However there are some drawbacks which limit their application. Micelles own the poor ability of solubilzing lipophilic solutes, and are susceptible to organic solvents. Microemulsions consume large amount of surfactants, which leads to large ionic strength. Vesicles are not thermodynamically stable systems, surfactants with specific molecular structure are needed to form vesicles. Because of the low molecular weight and high surface activity of the small molecular surfactants, the mass spectrum of analytes would be interfered seriously and the connector between EKC and mass spectrometer would be polluted by adsorption of surfactants. Therefore, MS coupled with EKC using small molecular surfactant as PSP is not easy.Comparing with the typical PSPs, polymeric PSP have various advantages, such as good adjustability on molecular structures, insusceptible to organic solvents, low critical aggregation concentration(CAC), less consumption, weak influence on mass spectrum owing to large molecular weight. However, recent reports on polymeric PSPs were forced on the development of novel polymers and the improvement of their separation ability. Morphologies and physicochemical properties of the polymeric PSP, especially the amphiphilic polymeric PSP in aqueous solutions, as well as the effects of the morphologies and physicochemical properties of the polymeric PSP on EKC performances were ignored. Thus, the physicochemical properties of the amphiphilic polymeric self-assembly aggregations, the effects of the monomer types and the monomer molar ratios in amphiphilic polymer on the physicochemical properties of the aggregations, the EKC performance of the various kinds of polymeric PSPs were investigated and compared with that of the typical PSPs in the dissertation.The main contents of the dissertation were as follows:(1) The physicochemical properties, such as CAC value, microenvironmental polarity, particle size and surface charge density of the amphiphilic polymeric self-assembly aggregation, which formed by poly(methyl methacrylate-co-methacrylic acid) (P(MMA-co-MAA)), was measured and compared with that of the typical PSPs including sodium dodecyl sulfate(SDS) micelle, SDS swollen micelle(SDS micelle modified with 1-butanol), typical SDS microemulsion and SDS microemulsion modified with ionic liquid. The results were as follows: Firstly, CAC values of P(MMA-co-MAA) are extremely small. Secondly, compared with the typical PSPs, the aggregation formed by P(MMA-co-MAA) have a higher polarity of the inner core, larger particle size and lower surface charge density. Thirdly, the selectivity of the aggregation formed by P(MMA-co-MAA) on separation of three structurally similar corticosteroids was better than that of the typical PSPs. As well, the analysis time was shorter and usage of the polymeric PSP were decreased.(2) The effects of monomer molar ratios on physicochemical and EKC properties of aggregations formed by P(MMA-co-MAA) were investigated. The results were as follows: Firstly, the CAC values of P(MMA-co-MAA) decreased significantly with the increase of the hydrophobic monomer molar ratio. Secondly, for P(MMA-co-MAA) self-assembly aggregations, the polarity of the inner core lowered, the particle size significantly decreased and the surface charge changed slightly with the increase of the hydrophobic monomer molar ratio. Thirdly, using P(MMA-co-MAA) self-assembly aggregations as PSPs, the analysis separation window broadened and the methylene selective was improved with the increase of the hydrophobic monomer molar ratio. Fourthly, the selectivity of the aggregation formed by P(MMA-co-MAA) on eight structurally similar corticosteroids was better than that of the SDS microemulsion modified with ionic liquid. In brief, it is an efficient way to adjust physicochemical and EKC properties of the amphiphilic polymeric self-assembly aggregations by changing monomer molar ratios.(3) The selectivity of polymeric self-assembly aggregations with different kinds of hydrophobic monomers and different monomer molar ratios was investigated by linear salvation energy relationship(LSER) model. The results were as follows: Firstly, hydrophobic interaction and hydrogen-bond acidity were two key factors for all aggregations as pseudostationary phases. Secondly, compared between two kinds of hydrophobic monomers, the larger hydrogen-bond basicity was obtained when methyl methacrylate was used as hydrophobic monomer in the copolymer, while the larger polarizability was obtained when styrene was used as hydrophobic monomer in the copolymer. Thirdly, the hydrophobic interaction of the polymeric aggregation with the analytes could be enhanced by using more hydrophobic monomer in amphiphilic copolymer or increasing the hydrophobic monomer molar ratio, and the polarizability of the polymeric aggregation could be increased with the use of styrene as hydrophobic monomer or with the increase of methyl methacrylate content. Fourthly, compared with SDS micelle, the polymeric self-assembly aggregation owned multiple selectivity because of the good adjustability on type and content of the monomers. In brief, the selectivity of the polymeric self-assembly aggregation could be adjusted by changing monomer type and monomer molar ratio.(4) To enhance the hydrophobicity of the polymeric pseudostationary phase, three kinds of poly(stearyl methacrylate-co-methacrylic acid)(P(SMA-co-MAA)) with different monomer molar ratios were synthesized in the dissertation. Stearyl methacrylate was used as hydrophobic monomer, while methacrylic acid was used as hydrophilic monomer.Polymeric self-assembly aggregations were formed with selective solvent mode, and thephysicochemical and EKC properties of the polymeric aggregations were investigated.The results were as follows: Firstly, the inner cores of the polymeric self-assemblyaggregations owned lower polarity than that of the P(MMA-co-MAA) self-assemblyaggregations. Secondly, the inner cores of the polymeric self-assembly aggregationswould own lower polarity than that of SDS micelle when the molar ratio of stearylmethacrylate was increased, and the methylene selective was improved simultaneously.Thirdly, very small aggregation would be formed with the increase of the hydrophilicmonomer molar ratio.(5) P(SMA-co-MAA) self-assembly aggregation modified with 10%(v/v) 1-butanol and 20%(v/v) acetonitrile was used as novel pseudostationary phase to separate water- and fat-soluble vitamins simultaneous. Eleven kinds of water- and fat- soluble vitamins werebaseline separated within 13 min. The relative standard deviations of the migration timesand peak areas were less than 2.0% and 5.0%, respectively. The recoveries for all vitaminswere between 93% and 111%. This method possessed of rapid analysis as well as goodresolution. The effect of organic solvents on physicochemical properties of theaggregation was also investigated, and there were two speculations. Firstly, 1-butanolcould insert into the polymeric self-assembly aggregation and swell the polymericself-assembly aggregation. Secondly, organic solvents could weaken the electrostaticrepulsion among hydrophilic groups, and promote more polymer molecules to aggregatelarger aggregation.(6) P(SMA-co-MAA) self-assembly aggregation modified with 40%(v/v) methanol and 2%(v/v) 1-butanol was used as novel pseudostationary phase to separate fifteen hydrophobicphthalates by EKC technology. The relative standard deviations of the migration times andpeak areas were less than 1.0% and 3.3%, respectively. Phthalates in six normal foodpacking materials were determined, and the recoveries were between 81% and 118%. |
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