Preparation And Evaluation Of Novel Stationary Phase For Capillary Electrochromatography

Capillary electrochromatography(CEC) is a novel micro-separation technology, which combines the advantage of high separation efficiency of capillary electrophoresis(CE) and high selectivity of high performance liquid chromatography(HPLC). It is well known that the technology of chromatographic columns is the key for the theory and application of CEC. A series of polymers with different matrix were synthesized and used as the stationary phase in CEC for separation application.Firstly, molecularly imprinted polymers(MIPs) nanoparticles were synthesized with a size 50-80 nm via precipitation polymerization, and then the MIPs nanoparticles were used in CEC with partial filling technique. Baseline separation of rac-zopiclone(rac-ZOP) was obtained with resolution(Rs) of 4.75. The influence of some important parameters on the size and separation capability of the MIPs nanoparticles were investigated, including template to monomer ratio, type and amount of cross-linking monomer, and functional monomer composition ratio. In addition, we also studied the effect of separation condition, e.g., ACN content, pH value and salt concentration of buffer, on the electrochromatographic behavior of the MIP nanoparticles. The result showed that the size of the d-ZOP MIPs nanoparticles could be carefully controlled around 80 nm, which was benefit to the accessibility of imprinted sites and stability of MIPs suspension. High column efficiency(41,400 plates/m), good peak symmetry and reproductivity could be achieved in CEC enantioseparation. It illustrated that the precipitation polymerization was a feasible method to obtain MIPs nanoparticles with smaller size, in which the imprinted sites were easily accessible. The results indicated that MIPs nanoparticles can show high suspension stability in electrolyte, and provide with high column efficiency and good peak symmetry.In the second part, it is the first time to prepare MIPs nanoparticles with a low level of crosslinking in the presence of liquid crystalline monomer as physical crosslinker to replace part of chemical crosslinker, via precipitation polymerization method. When the d-ZOP imprnted MIPs nanoparticles with low level of crosslinking were used in CEC with partial filling technique, the chiral separation for rac-ZOP was obtained with Rs of 3.29, as well as high column efficiency(up to 66,900 plates/m) and good peak symmetry at a level of crosslinking as low as 5%. Furthermore, the chiral separation for rac-AML and rac-IBU on the S-AML and S-IBU imprinted nanoparticles could be obtained, respectively. Compared with the MIPs nanoparticles with high crosslinking in the first part, the liquid crystal-based MIPs nanoparticles with low crosslinking showed similar separation property, but better uniformity and monodispersity, and higher binding capability. Therefore, the liquid crystal based MIPs with low level of crosslinking is a good alternative to improve the low mass transfer and accessibility of imprint cavity.For the third part, by combining the merits of metal organic framework MOF(Cu)(mesopores donor) and porous monoliths(macropores donor), MOF(Cu)-poly(BMA-EDMA) monolith was developed as the stationary phase in CEC mode for the first time, for the separation of various analytes, including alkylbenzenes, aromatic ketones and aromatic carboxylic acid derivatives. The crosslinking degree of the monolith to achieve the optimal separation of three kinds of analytes was 40%, and the porogen system was [C6min][BF4]-DMF-H2 O with the amount of 1-Acrylanmido-2-methylpropane sulfonic acid(AMPS) of 1 mg. By investigating the effect of ACN content on the effect of retention of toluene, acetophenone and fenbufen on the monolith, we concluded that the behaviour of retention of the analytes on the MOF(Cu)-poly(BMA-EDMA) monolith was the mechanism of reversed phase. Van Deemter analysis showed that eddy diffusion, longitudinal diffusion andmass transfer all had impacts on the column efficiency. Owing to the presence of MOF(Cu) material of meso- and micropores and high specific surface area, the separation for the above analytes was improved on MOF(Cu)-poly(BMA-EDMA) monolith compared with poly(BMA-EDMA) monolith without MOF(Cu). Compared with the MIL-101(Cr)-organic polymer monolith reported, the column efficiency of our MOF(Cu)- organic polymer monolith was increased more than two times in CEC mode.