Modern porous monoliths have been conceived as a new class of stationary phases for high performance liquid chromatography(HPLC) in classical columns in the early 1990s and later extended to the capillary format.These...Modern porous monoliths have been conceived as a new class of stationary phases for high performance liquid chromatography(HPLC) in classical columns in the early 1990s and later extended to the capillary format.These monolithic materials are prepared using simple processes carried out in an external mold(inorganic monoliths) or within the confines of the column(organic monoliths and all capillary columns).These methods afford macroporous materials with large through-pores that enable applications in a rapid flow-through mode.Since all the mobile phase must flow through the monolith,the convection considerably accelerates mass transport within the monolithic separation medium and improves the separations.As a result,the monolithic columns perform well even at very high flow rates.The applications of monolithic capillary columns are demonstrated on numerous separations in the HPLC mode.展开更多
Surfactant template synthesis of mesoporous silica monolith was carried out via modified fast sol gel process. It was easy to obtain crack free silica monolith due to low volume shrinkage during the gelation. The morp...Surfactant template synthesis of mesoporous silica monolith was carried out via modified fast sol gel process. It was easy to obtain crack free silica monolith due to low volume shrinkage during the gelation. The morphology of the titled silica was characterized by transmission electron microscopy and X ray diffraction. The results showed that the pores were worm like and the pore size was about 4 nm. Further nitrogen isothermal absorption experiment indicated that the specific area of the titled material was 391 m 2/g, which was comparable with the reported value 306 m 2/g in literature.展开更多
An improved bulk sol-gel process was found to prepare transparent, non-cracking, highly pure and mono-component monolithic silica gels with a low volume shrinkage. HSi（OC2H5）3 was used as a gel acceleration to short...An improved bulk sol-gel process was found to prepare transparent, non-cracking, highly pure and mono-component monolithic silica gels with a low volume shrinkage. HSi（OC2H5）3 was used as a gel acceleration to shorten the whole sol-gel processing time in the place of the carbonate powders in bulk sol-gel process. The mono-component silica gel monoliths prepared via the improved bulk sol-gel process possess a microporous structure and a good transmittance in the UV-Vis region, and the mass fraction of silica is 89%, the mass fraction of small molecules is 11%.展开更多
A new approach of preparing monolithic silica column was founded by adopting an improved sol-gel technology with tetramethoxysilane and polyethylene glycol as the matrix materials. The reason of resulting in crack and...A new approach of preparing monolithic silica column was founded by adopting an improved sol-gel technology with tetramethoxysilane and polyethylene glycol as the matrix materials. The reason of resulting in crack and deformation of monolithic column was explained. By using N,N-dimethylformamide and a heat treatment procedure, the problems of crack and deformation in preparing the column were solved and the drying time was shortened greatly. In addition, the methods of fabricating mesopore and the effects of porogen solvent of different concentrations on monolithic silica column were investigated. The results show that the column prepared possessed bimodal pores structures with micrometer-size co-continuous through-pores and silica skeletons which have nanometer-size mesopores, straight appearance, high porosity, good chemical and mechanical stability. The characteristics would favour the separation with a rapid speed and high efficiency for both small molecules and macromolecules.展开更多
基金Supported by grants of the National Institute of General Medical Sciences,National Institutes of Health(GM-48364),and the Materials Sciences and Engineering Division of the U.S.Department of Energy(DE-AC02-05CH11231).
文摘Modern porous monoliths have been conceived as a new class of stationary phases for high performance liquid chromatography(HPLC) in classical columns in the early 1990s and later extended to the capillary format.These monolithic materials are prepared using simple processes carried out in an external mold(inorganic monoliths) or within the confines of the column(organic monoliths and all capillary columns).These methods afford macroporous materials with large through-pores that enable applications in a rapid flow-through mode.Since all the mobile phase must flow through the monolith,the convection considerably accelerates mass transport within the monolithic separation medium and improves the separations.As a result,the monolithic columns perform well even at very high flow rates.The applications of monolithic capillary columns are demonstrated on numerous separations in the HPLC mode.
文摘Surfactant template synthesis of mesoporous silica monolith was carried out via modified fast sol gel process. It was easy to obtain crack free silica monolith due to low volume shrinkage during the gelation. The morphology of the titled silica was characterized by transmission electron microscopy and X ray diffraction. The results showed that the pores were worm like and the pore size was about 4 nm. Further nitrogen isothermal absorption experiment indicated that the specific area of the titled material was 391 m 2/g, which was comparable with the reported value 306 m 2/g in literature.
文摘An improved bulk sol-gel process was found to prepare transparent, non-cracking, highly pure and mono-component monolithic silica gels with a low volume shrinkage. HSi（OC2H5）3 was used as a gel acceleration to shorten the whole sol-gel processing time in the place of the carbonate powders in bulk sol-gel process. The mono-component silica gel monoliths prepared via the improved bulk sol-gel process possess a microporous structure and a good transmittance in the UV-Vis region, and the mass fraction of silica is 89%, the mass fraction of small molecules is 11%.
文摘A new approach of preparing monolithic silica column was founded by adopting an improved sol-gel technology with tetramethoxysilane and polyethylene glycol as the matrix materials. The reason of resulting in crack and deformation of monolithic column was explained. By using N,N-dimethylformamide and a heat treatment procedure, the problems of crack and deformation in preparing the column were solved and the drying time was shortened greatly. In addition, the methods of fabricating mesopore and the effects of porogen solvent of different concentrations on monolithic silica column were investigated. The results show that the column prepared possessed bimodal pores structures with micrometer-size co-continuous through-pores and silica skeletons which have nanometer-size mesopores, straight appearance, high porosity, good chemical and mechanical stability. The characteristics would favour the separation with a rapid speed and high efficiency for both small molecules and macromolecules.
