| Summary: | 碩士 === 國立嘉義大學 === 應用化學系研究所 === 96 === The antibiotic thiostrepton is structurally modified with achiral reagents containing aromatic moieties and isocyanate- or isothiocyanate-terminated fragments to improve its enantioselectivity for LC resolution in the polar-organic mode. The resolution, not found in the native form of thiostrepton under the same chromatographic conditions, is further enhanced by increasing the number of moles of reagents added in the chemical derivatization reaction. It is believed that the resolution is obtained mainly as a result of the p-p interaction between the analyte and chiral selector in a cleft. Consequently a proper fitting in a cleft, which is highly dependent on the size of analyte, is crucial for a chiral recognition to be possible. Other effects such as steric hindrance, dipole-dipole interaction and hydrogen bonding from the isocyanate and isothiocyanate functional fragments of reagents also are beneficial to the resolution.
In light of the difficult LC separation of pharmaceutical and biological enantiomers which each for aromatic moiety on the structure, developing a GC stationary phase that meets the need is necessary. In this part of research, an attempt of applying previously developed material for LC stationary phase to GC separations is made. Instead of bonding the material to the inner wall of a capillary tube, a coating procedure is adopted. Also, the material is modified with silver nanoparticles for separating geometric isomers of unsaturated compounds through complexation between the double bond and nanoparticle. The preliminary results show that factors such as the type of additive or coating material, and its percentage in the coating matrix all affects the resolution. The resolution, confirmed by the data of mass spectrometry, also is subjected to the influence of conditioning temperature of capillary tube in the water bath to remove the solvent. At this stage, the research is still in its infancy. More effort is needed to explore the separation mechanism and make this GC stationary phase more practical in applications.
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