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1.
Porous zirconia monolith (ZM) modified with cellulose 3,5-dimethylphenylcarbamate (CDMPC) was used as chiral stationary phase to separate basic chiral compounds in capillary electrochromatography. The electroosmotic flow behavior of bare and CDMPC-modified zirconia monolithic (CDMPC-ZM) column was studied in ACN/phosphate buffer eluents of pH ranging from 2 to 12. The CDMPC-ZM column was evaluated by investigating the influences of pH, the type and composition of organic modifier of the eluent on enantioseparation. CEC separations at pH 9 provided the best resolutions for the analytes studied, which are better than those observed on CDMPC-modified silica monolithic columns under similar chromatographic conditions. No appreciable decline in retention and resolution factors after over 200 injections, and run-to-run and day-to-day repeatabilities of the column of less than 3% indicate the stability of the zirconia monolithic column in basic media. 相似文献
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A membrane-based chiral separation system for the separation of racemic tryptophan solutions is developed by the covalently binding beta-cyclodextrin onto the surface of commercial cellulose membranes. The immobilization process is monitored by XPS. AFM demonstrates the evolutionary transition of membrane surface morphology before and after the CD immobilization. Due to their different complexation with immobilized CD, dialysis transport experiments show d-tryptophan preferential permeability through the immobilized CD membranes, and the enantioselectivity is 1.10. A model based on the existence of a thin chiral solution layer of amino acid at the interface between the feed solution and the membrane has been proposed. This chiral separation model has been verified using the chiral separation results of racemic amino acids and binding constants of amino acids with CD. The effect of membrane's pore size on enantioselectivity has also been investigated. The immobilized CD membrane, having MWCO 1000, exhibits the highest enantioselectivity to the racemic tryptophan solution. 相似文献
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纤维素在离子液体[AMMor]Cl/[AMIM]Cl混合溶剂中的溶解性能 总被引:6,自引:0,他引:6
研究了纤维素在混配离子液体N-甲基-N-烯丙基吗啉氯盐[AMMor]Cl/3-甲基-1-烯丙基咪唑氯盐[AMIM]Cl中的溶解性能, 结果表明, [AMMor]Cl/[AMIM]Cl混配溶剂能有效溶解天然纤维素, 且在相同条件下, 溶解能力要优于离子液体[AMIM]Cl; 随着溶解温度的升高, 溶解时间大大缩短. 利用FTIR, XRD和TGA方法分析了再生纤维素的化学结构和热稳定性, 结果表明, 未经活化的纤维素可直接溶于[AMMor]Cl/[AMIM]Cl而不发生其它衍生化反应, 且天然纤维素在该溶剂体系中纤维素聚合度下降较小. 相似文献
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A series of cellulose benzoates with different degrees of substitution (DS) were prepared by aminolysis under homogeneous conditions. Using them as a stationary phase, the dependence of the chromatographic chiral recognition of cellulose benzoate (CB) on its DS was studied under normal phase conditions. For most enantiomeric pairs, chiral recognition decreased along with the decrease in DS. However, some enantiomeric pairs were resolved only by CBs carrying unsubstituted hydroxyl groups. Many of the compounds were quite strongly retained by cellulose benzoate with a DS of 2.8. A study of the retention behaviors of simple achiral compounds led us to the conclusion that the change in the retention behaviors by introducing free hydroxyl groups into tribenzoate is not caused by hydrogen bonding including the hydroxyl groups, but by a specific unidentified change. 相似文献
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Chiral stationary phases (CSPs) for high-performance liquid chromatographic (HPLC) have been prepared by coating silica gel with cellulose tribenzoate or cellulose trisphenylcarbamate. The effect of chiral additives on preparation of the CSPs was studied with (+)-l-mandelic acid, (−)-2-phenyl-1-propanol, (+)-1-phenyl-1,2-ethanediol and (−)-1-(1-naphthyl)ethanol as chiral additives for cellulose tribenzoate and (−)-2-phenyl-1-propanol and (+)-phenylsuccinic acid as chiral additives for cellulose trisphenylcarbamate. The results showed that chiral recognition by these stationary phases was increased in comparison with the original CSPs, especially the resolution (R
S) obtained. The method can be used to improve the efficiency of enantiomer separation by silica gel stationary phases coated with polymers. 相似文献
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The 3,5-dichlorophenylcarbamates (2) of cellulose bearing a small amount of 3-(triethoxysilyl)propyl residues were synthesized by a one-pot process and immobilized onto a silica gel through intermolecular polycondensation of the triethoxysilyl groups. The obtained cellulose derivatives were characterized by (1) H NMR and elemental analysis (EA), and their recognition abilities were evaluated by high-performance liquid chromatography (HPLC). The cellulose derivatives containing about 1-5% of the 3-(triethoxysilyl)propyl residue were efficiently immobilized with a high chiral recognition ability. The immobilized chiral packing materials (CPMs) could be used with the eluents containing chloroform and tetrahydrofuran (THF), which cannot be used with the conventional coated-type chiral packing materials. By using these eluents, the chiral recognition for many racemates was improved. 相似文献
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Summary L-N-(3,5-dimethoxyoxybenzoyl)isoleucine, ionically bonded to γ-aminopropyl silica, has been tested as a chiral stationary
phase for the separation of racemates by HPLC. The phase shows good selectivity towards different types of racemates and in
particular for those having an electron-poor aromatic group in their molecule. The separation of benzoin racemate can be achieved
on the developed chiral phase with an α value of 1.10. 相似文献
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萘普生是一种消炎镇痛药 ,其 S对映体的抗炎作用是 R构型的 2 8倍 ,萘普生及其衍生物的拆分具有重要意义 .手性固定相 HPLC直接拆分 [1~ 4 ] 是最简便的分析方法 .氧化锆是近年来备受关注的色谱载体 [5,6 ] .Carr等 [7] 对碱性药物快速拆分表明氧化锆在手性分离Scheme1 Structuresof chiral naproxen and its derivatives中的独特选择性 .萘普生及其衍生物在锆基手性固定相上的分离未见文献报道 .本组利用自制的球形氧化锆制备了涂敷型纤维素 -三 ( 3,5 -二甲基苯基氨基甲酸酯 ) -Zr O2 手性固定相 ( CDMPC- Zr O2 - CSP) ,在正… 相似文献
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Jinming Zhang Jin Wu Yan Cao Shengmei Sang Jun Zhang Jiasong He 《Cellulose (London, England)》2009,16(2):299-308
The ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl) as a reaction medium was studied for the synthesis of cellulose
benzoates by homogeneous acylation of dissolved cellulose with benzoyl chlorides in the absence of any catalysts. Cellulose
benzoates with a degree of substitution (DS) in the range from about 1 to 3.0 were accessible under mild conditions. The DS
of cellulose derivatives increased with the increase of the molar ratio of benzoyl chloride/anhydroglucose unit (AGU) in cellulose,
reaction time, and reaction temperature. Benzoylation of cellulose with some 4-substituted benzoyl chlorides including 4-toluoyl
chloride, 4-chlorobenzoyl chloride and 4-nitrobenzoyl chloride was also readily carried out under mild conditions. Furthermore,
regioselectively substituted mixed cellulose esters were synthesized in this work. All products were characterized by means
of FT-IR, 1H-NMR, and 13C-NMR spectroscopy. In addition, at the end of benzoylation of cellulose, the ionic liquid AmimCl was easily recycled. When
the recycled AmimCl was used as the reaction media, the cellulose benzoate with a similar DS was obtained under comparable
reaction conditions. 相似文献
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Mari Granström 《Tetrahedron letters》2009,50(15):1744-1747
Increased reactivity of cellulose in ionic liquids was revealed when cellulose was protected with a 4-methoxytrityl moiety in the imidazolium-based ionic liquid, 1-allyl-3-methylimidazolium chloride ([amim]Cl). Selectively protected 2,6-di-O-(4-methoxytrityl)cellulose was obtained in one reaction step with a DS of close to 2, and was characterised by NMR. 相似文献
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Four alkenoxy leucine-based surfactants with C8-C11 chains containing a terminal double bond, and one C11 chain surfactant with a terminal triple bond are synthesized and characterized in monomeric and polymeric forms. These polymeric pseudophases are then utilized to study the influence of chain length and DP for the enantioseparations of seven beta-blockers in MEKC. Variations in chain length and concentration of polymeric surfactants showed significant effects on the chiral resolution (Rs) and efficiency (N). A relatively large elution range combined with the highest polarity and aggregation number (A) but the lowest retention time, partial specific volume, and optical rotation generated with C8-polymeric surfactant results in simultaneous enantioseparation of all seven beta-blockers with higher N and R(s). In particular, highly hydrophobic beta-blockers are better resolved with shorter hydrocarbon chain even at higher surfactant concentration, which is unachievable with longer chain surfactant. On the other hand, polymer derived from C11-triple bond provided smaller A value compared to C11-double bond surfactant. However, chiral Rs of hydrophobic beta-blockers are still achievable with the C11-triple bond surfactant with enhanced N and shorter analysis time. In addition, effect of polymerization concentration is evaluated by polymerizing all five surfactants at five times their respective CMCs and 100 mM equivalent monomer concentrations. Polymerization of shorter chain (C8 and C9) double-bonded surfactants at five times their respective CMCs results in higher A values with better chiral Rs and N compared to the same two surfactants polymerized at 100 mM. 相似文献
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Mari Granström Jari Kavakka Alistair King Johanna Majoinen Valtteri Mäkelä Juho Helaja Sami Hietala Tommi Virtanen Sirkka-Liisa Maunu Dimitris S. Argyropoulos Ilkka Kilpeläinen 《Cellulose (London, England)》2008,15(3):481-488
Tosylation and acylation of cellulose were performed under mild reaction conditions using imidazolium based ionic liquids
(ILs) as solvents. The non-degradative nature, lower viscosity, as well as higher solubility of cellulose in [amim]Cl encouraged
us to carry out the reactions in this media. The reactions described here were optimised for this particular solvent in order
to obtain different cellulose derivatives with high yields, homogeneity and degree of substitution (DS). Two reagents employed
for the in situ activation of carboxylic acids were N,N′-carbonyldiimidazole (CDI) and 1-ethyl-3-(3′-dimethylaminopropyl)carbodiimide hydrochloride (EDCI). Final products were characterised
by solution and solid-state NMR techniques.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
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Enantiomeric separation of six antihistamine agents was first systematically investigated on a cellulose-based chiral stationary phase (CSP), that is, cellulose tris-(3,5-dimethyl phenyl carbamate) (Chiralcel OD-RH), under the reversed-phase mode. Orphenadrine, meclizine, terfenadine, dioxopromethazine, and carbinoxamine enantiomers were completely separated under the optimized mobile phase conditions with resolutions of 5.02, 1.93, 1.68, 1.67, and 1.54, respectively. Mequitazine was partially separated with a resolution of 0.77. The influences of type and concentration of buffer salt, the pH of buffer solution, and the type and ratio of organic modifier on the chiral separation were evaluated and optimized. For a better insight into the enantiorecognition mechanisms, molecular docking was carried out via the Autodock software. The lowest binding energy and the optimal conformations of the analytes/CSP complexes were supplied, and the mechanisms of chiral recognition were determined. According to the results, the key interactions for the chiral recognition of these six analytes on CDMPC were π–π interactions, hydrophobic interactions, hydrogen bond interactions, and some special interactions. 相似文献