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91.
Enantiomeric amide derivatives of (S)- and (R)-1-phenyl-2-aminopropane (dextro- and levoamphetamine, respectively) were resolved by high performance liquid chromatography on commercially available ionically and covalently bonded chiral stationary phases ((R)-N-(3,5-dinitrobenzoyl)phenylglycine). Ten enantiomeric amide pairs were synthesized and chromatographed on the columns by using a mobile phase of hexane-isopropanol (97 : 3), a flow rate of 2 ml/min, and a column temperature of 20°C. The (R)-isomer of all 10 amides eluted first on the covalent column as did the (R)-isomer of nine derivatives on the ionic column. however, the 3,5-dinitrobenzoyl amide of (S)- amphetamine eluted before the (R)-isomer on the ionic column. This reversal in enantiomeric elution order reveals the complexity of the interactions occurring on these columns and emphasizes the hazards of relying on observed elution order as an a priori indication of absolute configuration. 相似文献
92.
Application of mono (6A-N-ethylenediamine-6A-deoxy) perphenylcarbamoylated β-cyclodextrin (β-CD) bonded stationary phase (CSP) in micro-high performance liquid chromatography (micro-HPLC) and pressurized capillary electrochromatography (p-CEC) was firstly presented. A series of racemic α-amidophosphonates were resolved in reversed- and normal-phase modes on this CSP. The investigated chromatographic parameters include retention factor (k′), separation factor (α) and resolution (Rs) of solutes. In addition, the structural variation of the solutes and the experimental factors affecting chiral separations have been examined, including the percentage of alcohol modifier, the linear velocity (u) of the mobile phase, electrical field strength, etc. Baseline separation was achieved for most of the entities. Hydrophobic interaction, steric effect and π-π interaction contribute to the possible mechanism. Comparative results indicate that higher Rs value up to 3.1 was found in micro-HPLC, higher efficiency up to 29,970 in p-CEC. 相似文献
93.
C. Brenier-Maurel C. Delaurent G. Pages M. -C. Guilhem A. M. Siouffi 《Chromatographia》2002,56(5-6):277-282
Summary An optimization procedure for the separation of flavonoids from St John's Wort by reversed-phase high-performance liquid chromatography
on monolithic stationary phase is described. Three-component mobile phase systems are studied using experimental design methodology.
The starting experimental domain is a triangle, each vertex of which is a pure component. From preliminary isocratic experiments,
truncations in the domain are performed leading to a quadrilateral shape working domain with no symmetry. To cope with both
separation and analysis time, desirability functions are used. Optimal conditions are finally given by binary systems and
the four flavonoids are separated in less than seven minutes. 相似文献
94.
高效液相色谱氮杂冠醚键合固定相的合成及性能研究 总被引:2,自引:0,他引:2
我们曾用γ-氯丙基键合硅胶(CPS),在氢化钠(NaH)作用下合成了3-(氮杂-18-冠-6)丙基键合固定相(BCP)[1].该固定相对碱基、核苷酸、硝基苯酚等有较好的分离选择性,但由于NaH对硅胶基质腐蚀作用较大,导致BCP柱效及渗透性较低.本文采... 相似文献
95.
一种包覆型聚合物高效液相色谱固定相的制备与评价 总被引:1,自引:1,他引:1
当代应用最广的HPLC固定相中,硅胶基质填料化学稳定性较低,并且由于残存硅羟基而表现所谓第二效应,特别使碱性化合物的峰形拖尾;聚合物基质填料虽提高了化学稳定性,没有离子基团,但刚性降低,并且由于溶胀难于进行梯度淋洗;面包覆型聚合物填料则可综合二者的优点,本文对我们制备的这种固定相作初步报道。 相似文献
96.
97.
J. Neveu 《Stochastic Processes and their Applications》1985,19(2):237-258
Given a stationary stochastic continuous demand of service σ(θtω) dt with ∫ σ(ω)P(dω) < 1, we construct real stationary point processes such that for a given constant D \2>0. These point processes correspond to a service discipline for which a single server services during the time intervals [Tn, Tn+1[ the demand of service accumulated during the proceding intervals [Tn?1, Tn[ and take a rest of fixed duration D. 相似文献
98.
99.
The ideal way to prepare efficient, yet robust stationary phases for microanalytical high-resolution methods such as capillary chromatography and electrochromatography remains to be defined. In this contribution a one step sol-gel process is proposed for the production of monolithic, macroporous nanocomposite phases in fused silica capillaries, which require no additional derivatization, since they already bear the interactive (C8) moieties. The effect of the catalyst, the water content, the pH, as well as that of certain additives on monolith formation and porosity is investigated. Volume shrinkage and a tendency to crack were the major obstacles to overcome. Homogeneous stationary phases could be produced by applying a pH gradient during sol formation, thereby changing the catalytic principle from acidic (0.1 M HCl) to basic (gradual formation of OH– as a consequence of the hydrolysis of N-methylformamide). Gelation/coacervation of suchgels could be induced by the addition of N,N-diethylamine. The water content during sol formation was determined as decisive for pore formation, with 250% of the amount theoretically needed for complete hydrolysis of all precursors giving optimal results. The volume shrinkage problem during xerogel formation was resolved by integrating dialkyldialkoxysilane units (dimethyldiethoxysilane 35 mol%) into the silica network. 相似文献
100.
用高效液相色谱法(HPLC)在正相条件下,用自制的涂敷直链淀粉-三(3,5-基苯基氨基甲酸酯)(ADMPC)手性固定相直接拆分了高效低毒的抗心绞痛药物雷喏嗪外消旋体(Ranolazine),并考察了二元及三元流动相体系对样品分离的影响,结果表明,三元流动相中的拆分结果远远好于二元流动相,流动相中不同种类醇改性剂及含量对样品保留时间和立体选择性有不同程度的影响. 相似文献