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Silica-based Capillary Monolithic Column For μ-HPLC: Studies Of Fabrication, Modification And Chromatographic Characterization

Posted on:2005-02-17Degree:DoctorType:Dissertation
Country:ChinaCandidate:J Y GuoFull Text:PDF
GTID:1101360125467520Subject:Analytical Chemistry
Abstract/Summary:PDF Full Text Request
Column technology in HPLC has now reached a high standard. Chromatographer can obtain higher efficiency in a short period of time by reducing the size of HPLC spherical porous materials. However, disadvantages of columns made from the smaller particles are the inevitable resulting increased in back pressure, which can damage the system or column. The monolithic column technology developed in these years has overcome the problem of high-pressure drop associated with the use of small particles. This technique use continuous porous polymers beds from organic or inorganic materials as separation media. However, the tendency of the monolithic column made of organic materials to expand and contract reduces its stability, and such columns show relatively low efficiency for small solutes. The monolithic silica columns overcome the problems mentioned above, and the porosity and plate height of which have proven to be better than in conventional packed columns. The invention of monolithic silica columns can be regarded as a major technological change in column technology. However, the facture procedure is very complicated and only several groups have mastered this technique. In this thesis, the facture and chemical modification of new type monolithic silica column were studied. The optimized process conditions were established; the C18 bonded monolithic silica column with high efficiency was manufactured, and its chromatographic behavior was studied; the new type organic polymer coated monolithic silica column was manufactured, its chromatographic behavior was studied. Main points of this thesis are listed as following:The new progress and important achievements on HPLC packing materials and monolithic column were reviewed in Chapter 1.The fire-new fabrication process of monolithic silica capillary columns by sol-gel method was firstly reported in this thesis. The factors affecting the skeleton structure of silica monoliths were studied, including the aging temperature, the reaction time, the pH value, the reactant ratio, the drying process, etc. New idea was presented and the sol-gel method reported in literatures was improved in this thesis.The study of tailoring the size of mesopores and the surface modification of monolithic silica capillary columns were carried out. The mechanism of mesopores formation was studied. The optimized process conditions were established to ensure the monolithic silica capillary columns having enough specific area, and the factors affecting the on-column surface modification of monolithic silica capillary columns including the reaction temperature, reaction time and catalyzer, etc, were discussed in detail.The structure and chromatographic behavior of C18 bonded monolithic silica capillary columns were characterized in this thesis. Under optimum mobile phase composition and flow velocity, the column efficiency of the C18-silica monoliths fabricated by the method established in this thesis was evaluated by separating alkylbenzenes and aromatic compounds. It is proved that the C18-monolithic column provides better performance than packed column, especially at high linear velocities. We describe an application of monolithic silica C18 capillary columns for the study of metal–ion interactions with sugars. It could be shown that the use of a long capillary column in HPLC is an easy and effective approach to study the stabilities of the complexes from D-fructose in aqueous solution. The linear solvation energy relationships (LSERs) were used to evaluated the retention of the C18-monolithic column, and the variables of , and were found influence the retention of the column, which is similar to that in packed column.The Divinyl benzene-styrene encapsulated copolymerization monolithic silica column was firstly manufactured in this thesis which having the advantages of both organic and inorganic packing materials, and its chromatographic behavior was studied. The alkylbenzenes and aromatic compounds were separated successfully.The polybutadiene-coated silica monolithic column...
Keywords/Search Tags:HPLC, capillary, silica monolithic column, chemical modification, C18 bonded, Divinyl benzene-styrene coated, polybutadiene-coated, LSERs
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