Gas Chromatographic Separation of Enantiomers it

Separation methods for the resolution of “optical isomers” (especially enantiomers) are developed to solve either of two basic problems: 1) the need to obtain, in optically pure form, one antipode or the other on a scale suitable for further chemical use-i.e.-“preparative” or 2) the analysis of the extent of racemization or “optical resolution” of a mixture of enantiomorphs on a scale sufficient for quantitative analysis-i.e.-“analytical”. The most economical, large-scale separation methods in use today are not chromatographic in nature but rather range from such common, general unit operations as recrystal1ization to very specific biological degradation.lS2 Chromatographic methods are generally limited to systems in which analytical data is the desired end product or in which only relatively small amounts of resolved material are needed.     

Gas Chromatographic Separation of Enantiomers on Cyclodextrin Derivatives

In investigations concerned with the phenomenon of molecular chirality, the use of gas chromatography for the enantiomeric analysis of stable, volatile compounds is a technique of steadily growing importance. ^[1] In the last three years an important breakthrough in gas-chro-matographic separation of enantiomers has been achieved by using alkylated cyclodextrins (α, β, and γ) as chiral stationary phases in high-resolution capillary columns. In academic and commercial practice two different and complementary strategies have been adopted up to now. In the first, alkylated cyclodextrins are diluted with polysiloxanes and coated on glass or fused silica capillary columns. In the second, lipophilic per-n-pentylcyclodextrins and hydrophilic di-n-pentyl- and hydroxyalkylpermethylcyclodextrins are coated directly in the form of liquid phases onto suitably pretreated glass or fused silica surfaces. These techniques permit enantiomer separations not only for polar diols and alcohols, derivatized hydroxycarboxylic acids, amino acids, sugars, and alkyl halides, but also for nonpolar alkenes, cyclic saturated hydrocarbons, and metal π complexes. An important aspect for practical applications is that in many cases the enantiomers can be separated without previous derivatization. Whereas the resolution of racemates of unfunctionalized hydrocarbons is attributed to an enantioselective host–guest inclusion complex, some observations indicate that for polar guest molecules additional enantioselective interactions are also involved. The new chiral stationary phases can be used over a wide range of temperatures (25 to 250°C). The technique described is likely to become widely adopted as a simple, accurate and highly sensitive method for the enantiomeric analysis of chiral compounds that can be vaporized without decomposition. It will also stimulate future research aimed at finding universal cyclodextrin phases and elucidating the mechanisms of enantioselectivity.     

Chromatographic Properties for Enantiomeric Separation of Amino Acid Derivatives on the Molecularly Imprinted Monoliths

Since their introduction in 1992 by Fréchet and Svec[1], monolithic supports as stationary phases in high performance liquid chromatography (HPLC) and capillary electrochromatography (CEC) have gained significant interest due to a number of unique properties. Their ease of preparation, high reproducibility, versatile surface chemistry and fast mass transport are advantageous in a variety of applications[2-4]. Separations in diverse chromatographic modes have been performed in either HPLC or CEC, showing their strong point for high-speed separations of biological and synthetic molecules[5-12]. Although a number of papers have been reported on the application of monolithic supports as chiral stationary phases in CEC and pressure-assisted capillary electrochromatography (p-CEC)[13-19], few reports have so far been published on chiral monolithic stationary phases for liquid chromatography[20].     

Chromatographic Properties for Enantiomeric Separation of Amino Acid Derivatives on the Molecularly Imprinted Monoliths

Sincetheirintroductionin 1992byFr啨ｃｈｅｔａｎｄＳｖｅｃ[1] ,monolithicsupportsasstationaryphasesinhigh performanceliquidchromatography (HPLC )andcapillaryelectrochromatography (CEC)havegainedsignificantinterestduetoanumberofu niqueproperties .Theireaseo     

三七素手性拆分方法的研究

使用气相色谱法和高效液相色谱法分离了三七素对映体,并探讨了影响液相色谱法分离效果的因素。结果表明,HPLC法利用手性固定相进行直接拆分,无法实现对映体的完全分离;GC法和HPLC的手性试剂衍生化法均可对三七素对映体进行较好的分离。但GC法由于衍生化过程中副产物的存在,干扰了对映体的准确定量。手性试剂衍生化HPLC法,以邻苯二甲醛、N-酰化-L-半胱氨酸为衍生化试剂,反应得到的三七素对映体的衍生物在ODS柱上分离良好,且方法简单、快速。     

高效液相色谱手性流动相添加剂分离肾上腺素类对映体

将β－环糊精、２,６－二甲基－β－环糊精、２,３,６－三甲基－β－环糊精分别作为手性流动相添加剂,较系统地研究了Ｄ,Ｌ－肾上腺素、Ｄ,Ｌ－异丙肾上腺素、Ｄ,Ｌ－麻黄碱在反相ＨＰＬＣ系统中的拆分,建立了甲基化β－环糊精动态手性固定相法分离肾上腺素类药物对映体的方法,探讨了立体选择性与环糊精主体和客体分子结构之间的关系     

气相色谱分析二甲苯异构体的协同效应研究

在以全戊基β－环糊精和ＡｇＮＯ３全戊基β－环糊精和ＴＩＮＯ３以及机皂土－３４和ＡｇＮＯ３为混合固定相对间二甲苯及对二甲苯进行ＧＣ分离的过程中，发现前两种混合固定相具有协同效应，而后一种却是加和效应。     

2-苯基-1-环丙烷羧酸酯对映体的毛细管气相色谱分离研究

使用3-位酰基化的4种2,6-二-O-戊基-3-O-酰基化-β-环糊精衍生物和6-位酰基化的3种2,3-二-O-戊基-6-O-酰基化-β-环糊精衍生物作为毛细管气相色谱手性固定相,对4对2-苯基-1-环丙烷羧酸酯对映体(cis-2-PhCpOMe,cis-2-PhCpOEt,trans-2-PhCpOMe,trans-2-PhCpOEt)进行分离研究。结果表明,对所拆分的4对2-苯基-1-环丙烷羧酸酯对映体而言,3-位酰基化的4种2,6-二-O-戊基-3-O-酰基化-β-环糊精衍生物比6-位酰基化的3种2     

各种氨基酸衍生物在Chirasil—Val固定相上的气相色谱分离

本文叙述氨基酸及其对映体的全氟酰基烷基脂(O-异丙基、-异丁基、-正丁基;N(O,S)-三氟乙酰基,TFA、-七氟丁酰基,HFB)在Chirasil-Val上的洗脱特性。随烷基取代增大,保留时间增加;用HFB代替TFA,对映体的分离因子降低。此外,DL-氨基酸与另丁醇衍生,生成的对映及非对映衍生物在Chirasil-Val上可拆分成四个色谱峰。     

A Two-Factor Simplex Optimization of a Programmed Temperature Gas Chromatographic Separation

Abstract

Simplex optimization was used to optimize the temperature programmed gas chromatographic separation of octane, 2-methyltetrahydrofuran, butylcyclohexane, and ethylbenzene. The initial temperature and the programming rate were the factors studied and a 5 minute time constraint was placed on the system. The Chromatographic Response Function (CRF) used by Deming and Morgan¹ was used as an operational measure of performance. Further experiments in the region of the optimum and regression analysis of the data obtained were carried out to further understand the factor effects.     

气相色谱智能优化在卤代烃分析中的应用

本文研究了气相色谱柱温智能优化软件在卤代烃毒物分析中的应用。智能优化使得包含多个卤代烃与烃的混合样品达到了满意的分离效果，保留值预测误差在１．１％以内，吻合程度很好。     

HPLC法拆分粉唑醇对映体

HPLC法拆分粉唑醇对映体;粉唑醇;对映体;分离;手性固定相     

不同气相色谱固定相对酚类和苯系物的分离

选择一种最佳的分析酚类和苯系物的毛细管气相色谱固定相，比较不同色谱固定相对酚类和苯系物的分离特性；结果发现用环糊精接枝聚硅氧烷作气相色谱固定相可同时分析酚类和苯系物；自制的环糊精毛细管柱有独特的位置异构体分离能力，经济，实用，适用于当前环境污染物的分析。     

Separation and Gas Chromatographic Determination of Free Styrene in Unsaturated Polyester Resins

Abstract

A rapid and efficient method for the separation and determination of free styrene in unsaturated polyester resin samples by gas chromatography was developed. A 10 cm pre-column connected to 1.2 m analytical column, both packed with 20 % carbowax 20M was used at 100°C with isobutylbenzene as an internal standard. Analysis time was two minutes with an accuracy of 0.3 %.     

对映异构体的高效毛细管电泳分离与测定

高效毛细管电泳是８０年代发展起来的一种高效、快速的新型分离技术，在对映异构体分离方面有着广泛的应用前景，本文介绍了这一新型分离技术用于对映体分离的基本原理，并列举了一些对映异构体分离的实例。     

Determination of Enantioselectivity and Enantiomeric Excess by Mass Spectrometry in the Absence of Chiral Chromatographic Separation: An Overview

This review describes the principles and instrumentation for the screening of asymmetric reactions by mass spectrometry. These techniques witnessed a significant advancement in the last few years. Although some of them are still at the proof‐of‐concept development stage, several applications might be foreseen in the field of combinatorial, high‐throughput parallel catalyst screening.