| Enantioseparation is one of the main approaches to obtain the optical purity substances, which has important significance in organic chemistry, medicinal chemistry and life science and has become a hot research issue in the world. There are several approaches to obtain enantiomerically pure chemicals, such as crystallization, chemical derivation, biotransformation, extraction, asymmetric conversion and chiral chromatography. The chiral chromatography is more attractive and has been developed rapidly in recent years, and research was concentrated on the chiral stationary phases.In my research, two methods were used in preparing cellulose 3,5-dimethylphenylcarbamate chiral stationary phases, which were through bonding and radical polymerization.Bonded chiral stationary phases: Cellulose 3,5-dimethylphenylcarbamate were chemically bonded to macroporous silica gel at 6-position of the primary hydroxyl group of the glucose unit of cellulose with hexamethylene diisocyanate as a new spacer to form a new CSP. Cellulose derivative bonded at 6-position to silica gel possessed a higher chiral recognition than that either regioselectively bonded at the 2-,3-position to silica gel or non-regioselectively bonded at 2-,3-and 6-positions to silica gel. It was observed that bonded-type CSPs usually showed a lower separating abilities than those of coated-type CSPs. However, the bonded-type CSPs were able to be used with eluents such as tetrahydrofuran in wich the coated-type CSPs were not able to be used because the cellulose derivatives were soluble or swollen.Plysaccharide-immobilized chiral stationary phases: Cellulose derivative with a vinyl group were prepared by reacting with 3,5-dimethylphenyl isocyanate and ally isocyanate , then chiral stationary phase was prepared by the polymerization of cellulose 3,5-dimethylphenylcarbamate having a polymerizable vinyl group at the 6-position with vinyl monomers on silica gel(MA-silica). The vinyl group on the silica surface resulted in a more efficient immobilization of the cellulose derivatives on the silica gel.Chromatography performance of bonded CSP: Benzoin and trans-stilbene oxide enantiomers were resolved on the prepared bonded stationary phase under the mobile phases of hexane/iso-propanol or ethanol/tetrahydrofuran or dichloromethane. The retention factors decreased with the increase of the tetrahydrofuran or dichloromethane concentration. The separation factors ofbenzoin and trans-stilbene oxide enantiomers were more than 1.2 at almost all experimental conditions. The prepared CSPs were stable under different mobile phases, even with 23% tetrahydrofuran in mobile phase.Chromatography performance of immobilized CSP: Benzoin enantiomers were resolved on the prepared plysaccharide-immobilized stationary phase under the mobile phases of hexane/iso-propanol or ethanol /tetrahydrofuran. The separation condition of benzoin on the prapared immobilized stationary phase through radical polymerization was conformed with the resolution on the bonded stationgary, but trans-stilbene oxide enantiomer can not be resolved. The retention factors decreased with the increase of the tetrahydrofuran. When the content of tetrahydrofuran was low, the obtained phase exhibited higher chiral recognition abilities. This immobilized CSPs could be stably used with the eluent containing 10% tetrahydrofuran, which cannot be used for the phase prepared by coating the derivatives on silica gel.The work validated that the bonded and the immobilized chiral stationary phases possess good chiral separation capability. The two CSPs are capable of operating in different mobile phase systems: normal phase, reversed phase, and polar organic mode. Since the two CSPs are covalently bonded to silica gel through chemical reaction, there is no detrimental effect when a column switches from one mobile phase mode to another.
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