Study Of The Preparation Of Several Monolithic Columns With High Selectivity

With the rapid development of nanoscale chromatographic separation systems, micro-column, the heart of chromatography system, is becoming an increasing concern. Among various micro-columns, capillary monolithic columns have been received greatest attention due to easy preparation, good permeability, versatility in surface modification, low solvent consumption, high efficiency of transmission and good separation ability. In the past decades, a great number of monolithic columns with various functionality groups have been studied. However, there is an abysmal lack of monolithic columns with unique affinity or separation ability for some special analytes in environment samples or biomatrix. Based on this situation, we select several special monomers and prepare several monolithic columns, main contents are as follows:First, the traditional precursor composition (TMOS and VIMS) are replaced by y-methacryloxypropyltrimethoxysilane (y-MAPS), a monomer with higher activity. The organic-inorganic hybrid fluorous monolithic capillary column was synthesized by the improved "one-pot" approach via the polycondensation of γ-MAPS and in situ copolymerization of1H,1H,7H-dodecafluoroheptyl methacrylate (DFHMA) and vinyl group on the precondensed siloxanes through one-step thermal treatment. The pore properties and permeability could be tuned by the composition of the polymerization mixture. A series of perfluorocarboxylic acids and perfluoroalkyl sulfonates with different C-Fchains were employed to investigate the mechanism of fluorine-fluorine interaction. The results revealed that fluorine-fluorine interaction increased as the C-F chain of fluorous compounds increased. Then the adsoption capacities of y-MAPS-DFHMA hybrid monolithic column for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) were examined via the online breakthrough curves of the two compounds. It was found that the adsorption capacities of the monolithic column for PFOA and PFOS were0.257and0.513μg/mg, respectively. In addition, the trace amounts of PFOA and PFOS in water samples can be successfully concentrated about160times to their original concentrations by this monolithic column.Polyhedral oligomeric silsesquioxane (POSS) is a type of cagelike silsesquioxane, which embodies a truly inorganic-organic hybrid architecture containing an inner inorganic framework made up of silicon and oxygen. A monolithic column with good mechanical stability, homogenuous porosity, low swelling and high affinity to fluorous compounds was prepared using a polyhedral oligomeric silsesquioxane (POSS) reagent as the cross-linker and pentadecafluorooctyl methacrylate (PDFOMA) as the functionality monomer. The chromatographic evaluation results showed that alkylbenzenes and phenyl amines were separated with good peak shapes on the POSS-PDFOMA hybrid monolithic column based on reversed-phase chromatography mode, respectively. A series of perfluoroalkyl methacrylates were baseline resolved on the optimized monolithic column under isocratic elution of70%acetonitrile aqueous solution. Such a resolution could not be achieved on a silica-based C18monolithic column. In addition, several perfluoroalkyl sulfonates were also baseline separated on the fluorous monolith applying0.1%(v/v) acetic acid aqueous solution containing75%acetonitrile as mobile phase without the addition of ammonium. This advantage is very significant for the LC-MS high sensitive analysis of perfluoroalkyl sulfonates because the ion suppression can be decreased effectively.Due to the combination of merits of POSS and fluorous phase with no residual silanols and low interaction with nonfluorinated compounds, the POSS-PDFOMA hybrid monolithic column was supposed to have low nonspecific interaction with biomacromolecules. The pore properties and permeability were retuned by the composition of the ternary porogenic solvent. The monolithic columns provided size separation of three proteins in the range of MWs from20000to250000in water. The pore size distributions were examined using inverse size-exclusion chromatography (ISEC) of a series of proteins and peptides covering a wide MW range. It was found that the best monolith had relatively large fractions of mesopores (10%), which is important for size-exclusion separation of peptides and proteins.A PEG-silica hybrid monolithic column was synthesized via one-pot approach using tetramethoxysilane (TMOS) and vinyl trimethoxysilane (VTMS) as precursor and polyethylene glycol diacrylate (PEGDA, Mn-700) as organic monomer. The obtained PEG-silica hybrid monolithic column owned better mechanical stability over previously reported pure PEG-based organic polymer monolithic columns. The characterization and evaluation results demonstrated that the obtained PEG-silica hybrid monolithic columns provided hydrophilic interaction as well as hydrophobic interaction. The optimized PEG-silica hybrid monolithic column provided hydrophobic interaction chromatography of five proteins.A novel, facile process was developed for the preparation of surface-glycosylated porous monolithic columns via aqueous two phase graft copolymerization of polyethylene glycol diacrylate (PEGDA) and dextran. In this method, porous poly(PEGDA) skeletons and surface glycosylation were synthesized via one-step process without perturbing the backbone structure of dextran. In addition, dextran not only took part in the graft copolymerization, but also played an important role in the phase separation process. The pore properties and skeletons could be tuned by the composition of the polymer mixtures.Ternary phase diagrams and SEM images of the corresponding monolithic columns were obtained after systematical investigations. The results exhibited that the bicontinuous porous structure could be formed by moderate proportion of the three conditions.On the basis of the optimal conditions of graft copolymerization of PEGDA and dextran, poly (PEGDA) grafted-dextran monolithic column and poly (PEGDA) grafted-dextran sulfate monolithic column were synthesized. FI-IR and thermal gravimetric analysis proved that polysaccharides were chemically bonded to the PEG skeletons. These results revealed this novel approach showed high versatility for preparation of series of surface-glycosylated porous monolithic columns with water-soluble polysacchrides. The obtained monolithic columns provided typical hydrophilic interaction chromatography of five nucleosides. In addition, poly (PEGDA) grafted-dextran monolithic column provided size-exclusion of BSA and several peptides.