Preparation And Application Of Novel Polymeric Capillary Monolithic Columns

Polymeric capillary monolithic columns have attracted great attention due to their merits of easy fabrication, versatile surface modification, wide pH range tolerance and high permeability. Various great progresses on the methods and technologies for the fabrication of polymeric capillary monoliths have been developed. It is significant to develop novel kinds of polymeric capillary monoliths for enriching and improving the capillary chromatographic techniques.Main points of this thesis are listed as followed:In chapter 1, the development of capillary monoliths has been introduced. The progress on preparation and application of polymeric capillary monoliths are reviewed, and then the aim and design of this thesis have been briefly presented.In chapter 2, a novel ionic liquid (IL) functionalized urea-formaldehyde resin (UF) monolith has been prepared by using the polycondensation of urea, formaldehydeand and IL. Rapid preparation of this monolith was achieved within 10 minutes. The optimal composition, the optimal preparation conditions, the separation mechanism and the performance of the monolith were discussed. The permeability and mechanical stability of the obtained column were acceptable. Due to the innate polarity (hydrophilicity) of the UF matrix, the resultant capillary monolithic column reveals excellent hydrophilic interaction (HI) and normal-phase (NP) mechanism. For the modified positively charged IL groups, the monolithic stationary phase exhibited anion-exchange interaction and cation-exclude interaction. Various analytes were used to evaluate the electrochromatographic characterization on the novel IL-functionalized UF monolith. Different neutral polar solutes could be well separated in HI mechanism. The separation of the model acidic analytes was realized by mixed-mode of HI/anion-exchange. The cation-exclude interaction has been also proved by the separation of the positively charged enkephalins.In chapter 3, a novel phenylalanine-functionalized zwitterionic monolith for hydrophobic electrochromatography was prepared by a two-step procedure involving the synthesis of Glycidyl methacrylate (GMA) based polymer monolith and subsequent on-column chemical modification with phenylalanine via ring opening reaction of epoxides. Benefitting from the hydrophobicity of both methacrylate-based matrix and aromatic group of phenylalanine, this monolith exhibited good hydrophobic interaction for the separation. Typical reversed-phase (RP) chromatographic behavior was observed toward various solutes. The well-controlled cathodic or anodic electroosmotic flow (EOF) of the prepared column could be facilely switched by altering the pH values of running buffers. The separation mechanism of this phenylalanine-functionalized zwitterionic monolith was discussed. Two mixed-mode mechanisms of RP/cation-exchange and RP/anion-exchange could be further realized on the same monolith in different pH condition of the mobile phase. Versatile separation capabilities of neutral, basic and acidic analytes had been successfully achieved in this zwitterionic monolith by CEC.In chapter 4, a chiral monolithic capillary column for rapid enantioseparation was prepared by covalently bonding of cellulose tris(4-methylbenzoate) (CTMB) on N-acryloxysuccinimide-based monolith. The preparation conditions and the derivatization conditions of the monolith were optimized. The successful grafting of CTMB was confirmed on the characterization of the Infrared spectrum and the cathodic EOF. Effects of acetic acid concentration and methanol content on the enantioseparation had been discussed. The solvent resistance, reproducibility and stability of the monolithic column had been investigated. Rapid enantioseparation of five solutes (phenylalanine, tyrosine, tryptophan, propranolol and phenylethanol) with Rs value up to 1.31 were achieved within 1 minute on the resultant chiral capillary monolith by CEC.In chapter 5, a capillary monolithic column was used as the solid phase micro-extraction column to build in tube SPME-HPLC system, and employed to determinate the residues of five phenoxyl acid herbicides (2,4-D; PPA; 2,2-CPPA; 2,3-CPPA; 2,4-DP). Operating parameters of in tube SPME-HPLC system, such as the length of the monolithic column, sampling flow rate, sampling time, elution flow rate and elution time had been investigated. Optimum separation conditions that the mobile phase compoesd of 0.1% TFA and ACN in a ratio of 55:45 (v/v) was obtained and the best system operation parameters were gained as follow:20 cm of the length of monolithic column, 0.04mL/min of the sample flow rate for 13min; 0.02 mL/min of elution flow rate for 5min. Under the optimum conditions, the detection limit of five phenoxyl acid herbicides were achieved as 8.69μg/L,3.79μg/L,3.65μg/L,5.12μg/L, 4.65μg/L, respectively. The recoveries of five phenoxyl acid herbicides were ranged in 79.0～98.0%(R.S.D≤3.9%). This method was successfully used to monitor the residues of five phenoxyl acid herbicides in farmland water samples with satisfactory results.