Detail Capillary chromatographic applications in organic geochemistry and natural products Bibliografi Author: Medina, Juan Carlos ; Lee, Milton L. (Advisor) Topik: CHEMISTRY; ANALYTICAL|GEOCHEMISTRY|CHEMISTRY; ORGANIC Bahasa: (EN )    ISBN: 0-599-81902-2     Penerbit: BRIGHAM YOUNG UNIVERSITY     Tahun Terbit: 2000     Jenis: Theses - Dissertation Fulltext: 9976195.pdf (0.0B; 0 download) Abstract Gas chromatography (GC) and capillary electrochromatography (CEC) are high-efficiency modes of chromatography useful for the separation of complex mixtures. The complexity of the mixture may be given either by the presence of compounds with a broad distribution of molecular weights, or by a number of compounds having very similar chemical structures. An example of the first case is the separation of hydrocarbons present in coal. Separation of isomers present in plant extracts is an illustration of the second situation. This dissertation deals with the applications of GC and CEC in solving problems related to fossil fuels and plant extracts, respectively. Despite great interest in evaluation of potential mechanisms contributing to natural gas formation in coalbeds, detailed descriptions of instrumentation for experimentation in such studies are scarcely found in the scientific literature. A state-of-the-art batch reactor system with on-line analysis and data processing for measurement of gas formation rates was built. This computer-controlled system features complete on-line GC analysis of the gaseous compounds produced in the reactor as a function of reaction time. The use of this system allowed quantitative analysis of gaseous products from hydrocarbon hydrogenolysis and CO2 hydrogenation reactions in the presence of Fe/SiO 2 and Ni/SiO2 catalysts. These reactions produced gas that contained methane concentrations greater than 90%, which resembles the composition of natural gas. Reaction temperatures were selected to resemble natural coalbed conditions. CEC is a relatively new microcolumn separation technique that generates column efficiencies higher than HPLC. Because CEC is still in its infancy, no dedicated commercial instruments are available, and most of the research has been conducted using capillary electrophoresis systems without gradient capabilities. A new gradient system for CEC was designed and added to a home-built CEC system. Use of this system significantly reduced analysis time, and demonstrated acceptable reproducibility. It is expected to be well-suited for generating other types of gradients, such as pH and ionic strength gradients, in electroseparation techniques. Separations of oxindole alkaloids present in Cat's Claw, a plant used to treat several diseases, were performed using CEC and HPLC. Results demonstrated that CEC, with its exceptional efficiency, is an excellent complementary technique to HPLC for the analysis of plant extracts. Opini Anda Klik untuk menuliskan opini Anda tentang koleksi ini! Lihat Sejarah Pengadaan  Konversi Metadata   Kembali

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