液晶作为气相色谱固定液的研究

1888年F.Reinitzer发现了液晶,直到二十世纪五十年代人们才对液晶的应用作了尝试。1963年H.Kelker首先提出用对.对’-二甲氧基氧化偶氮苯液晶作为气相色谱固定液分离二甲苯异构体.近年来液晶固定相在苯二取代化合物、多环芳烃、甾族差向异构体、取代萘类、氮杂环化合物、顺反异构体、对映异构体等的分离研究取得了较大进展.     

液晶气相色谱固定液特殊选择性的研究——Ⅱ.评价液晶固定液的一个新参数

本文提出用探索样在被考察液晶固定液的液晶态和液态的保留指数差值ΔI来表征液晶固定液的特有效应。选择了一系列不同极性、不同结构的化合物作为探索样,在液晶固定液PBOB和MPBOB上进行了考察。根据各探索样ΔI值的大小,解释了两种液晶固定液特殊选择性的规律。     

聚硅氧烷液晶作为毛细管色谱固定液的研究

]本文研制了聚硅氧烷液晶玻璃毛细管柱,考察了其色谱性能,结果表明这种柱柱效高,对多环芳烃选择性好,热稳定性好,使用温度范围宽,适于分析组成复杂的多环芳烃混合物,高分子液晶是一类兼具有液晶优点和硅油优点的固定液。     

高分子液晶作气相色谱固定液的进展

自从1963年Kelker把液晶用作气相色谱固定液以来已有24年的历史,经过研究和使用的液晶固定液有200多种,在分离位置异构体方面获得了很大的成功,特别是对多环芳烃异构体的分离得到很好的效果。但是低分子液晶用于毛细管柱时有两个致命的弱点:在高温下挥发性大;液膜在毛细管壁上不稳定。因此1982年Finkelmann等人首次把聚硅氧烷侧链高分子液晶用作气相色谱固定液,     

液晶用作气相色谱固定液的研究(Ⅱ)——混合液晶的色谱行为

本文研究混合液晶作气相色谱固定液的色谱行为,比较了混合液晶和单个液晶的温度特性、过冷状态稳定性;测定了一些液晶及其混合物的相常数,并对一些难分离物质和复杂天然产物进行了分离和鉴定。实验证明,用混合液晶作固定液常较单种液晶优越。     

有机硅席夫碱聚氨酯液晶色谱固定液的合成及性能研究

以对羟基苯甲醛、3-氯-1-丙醇、对苯二胺合成液晶基元—1,4-二(4-丙氧基醇苯亚胺基)苯,液晶基元与对苯二异氰酸酯和1,3-双(3-氨基丙基)四甲基二硅氧烷反应合成有机硅席夫碱聚氨酯液晶聚合物。采用红外光谱、X射线衍射、差式扫描量热分析、偏光显微镜、X射线能谱等手段对液晶聚合物的结构、热稳定性、液晶性能、元素组成及分布进行了测试与表征。用此液晶聚合物作为气相色谱固定液,制备成气相色谱填充柱,测定了该色谱柱的相对极性,苯取代物及二氯苯的同分体异构体的分离性能。该液晶聚合物作为色谱固定液具有较强的分离能力。     

几种新液晶作固定液分离二元取代苯异构体

Kelker和Dewar等人曾把液晶用作气相色谱固定液分离二元取代苯异构体取得很好的效果,此后很多研究者把近两百种液晶亦都用于气相色谱固定液。在研究和使用的液晶固定液中,芳羧酸酯类液晶被认为具有较好的热稳定性和分离选择性,国内研究较多的也是这一类液晶,而且已有商品。为了进一步研究这类液晶以扩大品种,我们在对苯二酚酯液晶的苯环上引入不同类型和数量的极性基团,并在玻璃毛细柱上考查其对二元取代苯异构体的分离性能。     

新型侧链聚硅氧烷液晶高分子用作毛细管柱气相色谱固定液

1 引 言寻求高选择性固定液是当今毛细管柱气相色谱研究的重要课题之一。1982年,Finkelmann等首次把侧链聚硅氧烷高分子液晶用作气相色谱固定液,成功地分离了二环芳烃异构体2,3－二甲萘、1,4－二甲萘和二苯甲烷。侧链聚硅氧烷高分子液晶易涂渍,选择性和热稳定性皆优于低分子液晶。本文对两种新型侧链聚硅氧烷液晶高分子用作气相色谱固定液进行了探讨。2 实验部分2.1 仪器与试剂 SP－3400气相色谱仪(北京分析仪器厂),氢火焰离子化检测器（FID）。蒽、菲、芴混合物（溶剂二氯甲烷),邻、间、对二甲苯混合物,二甲酚异构体混合物（溶剂…     

新型侧链聚硅氧烷高分子液晶作毛细管柱气相色谱固定液的研究

 以合成的新型胆甾酯类侧链聚硅氧烷高分子液晶作固定液 ,涂渍在弹性石英毛细管柱上 ,获得了具有较高的柱效和选择性、良好的热稳定性、适于分离多种异构体混合物的毛细管柱。     

用高分子冠醚和高分子液晶混合物作毛细管气相色谱固定液的研究

作为毛细管气相色谱固定液,对高分子液晶和高分子冠醚的共混物和含冠醚的高分子液晶单一固定液进行了比较,结果表明它们具有大致相同的保留性能。     

Studies on the special selectivity of the liquid crystal stationary phase used in gas chromatography: II. A new parameter for characterization of the liquid crystal stationary phase

In this paper, the special effect of liquid crystal stationary phase is expressed in terms of ΔI, the difference of the retention index of probed solute between mesomorphic phase and isotropic phase. A series of compounds with different structures and polarities are selected as probed solutes for the investigation of their retention behavior on liquid crystal PBOB and MPBOB. According to the differences of ΔI of various solutes, the rule of special selectivity on liquid crystal is explained.     

Chromatographic characterization of a bonded liquid crystal stationary phase for HPLC

Summary A chromatographic and thermodynamic study of the compound [4-(allyloxy)benzoyl]-4-methoxyphenyl (ABMP) as a model of a chemically bonded liquid crystal stationary phase for HPLC was undertaken. A number of polycyclic aromatic hydrocarbons (PAHs) and two small solutes, carvone and pulegone, were studied under varying solvent and temperature conditions. Plots of log k vs. % organic in the mobile phase were not completely linear in all cases. The van't Hoff plots revealed at least one phase transition. The enthalpies of solute transfer from the mobile phase to the ABMP phase were determined for several PAHs. All tests indicate that ABMP possess liquid crystal properties when bonded to particulate silica.     

Gas-chromatographic separation of underivatized steroids using a BPhBT liquid crystal stationary phase

A gas-chromatographic separation of underivatized steroids is described, in which the liquid crystal N,?-bis(p-phenylbenzylidene)α,α′-bi-p-toluidine (BPhBT) was used isothermally at 265°C for the stationary phase. The nematic range of this crystal is 247 to 403°C. Use of the BPhBT crystal allowed operations in a temperature range where steroids are volatile and unlikely to display broad elution peaks and long retention times. With columns precoated with 2.5 weight percent of BPhBT, steroids containing minor structural differences in the ring system were readily differentiated. For example, 5-androsten-17α-ethinyl-3β, 17β-diol was found to elute more rapidly than its 3-keto analog, ethisterone. Ethisterone was distinguished readily also from its 19-nor analog, norethisterone. Additionally, differences in side-chain functionality and resultant molecular dimensions facilitated the separation of steroids of identical ring structure, as in the comparison of cholesterol with methyl 3β-hydroxy-5-cholenate and 25-hydroxycholesterol. An enhancement of separation according to the molecular length-to-breadth ratio was observed; in general, the larger this length-to-breadth ratio, the greater the retention period on the column.     

Evaporation of the liquid stationary phase in gas chromatography

Summary The theory of the evaporation of the liquid stationary phase is elaborated and experimentally verified. On the basis of this theory the role played by the losses in the amount of liquid phase present is quantitatively determined. General techniques are examined which minimize the losses; these techniques are based on saturating the incoming carrier gas with liquid phase vapours and raising the pressure of the carrier gas in the column, e.g. by connecting a capillary to the column outlet in order to offer resistance to the gas flow. The application of these techniques ensures stable performance of the gas chromatographic columns using a volatile liquid phase.     

A chemically bonded liquid crystal as a stationary phase for high performance liquid chromatography. Synthesis on silica via an organochlorosilane pathway

Chromatographia - A compound which becomes a liquid crystal when bonded to a polysiloxane was reacted with dimethylchlorosilane to produce a reagent suitable for bonding to a silica surface. After...     

Synthesis and characterization of a new type of chemically bonded liquid crystal stationary phase for HPLC

Summary Two commercially available liquid crystals, 4-cyano-4′-n-pentyl-1,1′-bipheny and 4-cyano-4′-n-pentoxy-1,1′-bipheny, are bonded to a silica hydride surface via hydrosilation in the presence of a free radical iniator, t-butyl peroxide. Elemental analysis, diffuse reflectance Fourier trans-form infrared spectroscopy, and¹³C and²⁹Si CP-MAS NMR spectroscopy are used to confirm the success of the bonding reaction. The¹³C CP-MAS spectra suggest a difference in the bonded phase morphology of the two materials. Static hydrolytic stability tests indicate these materials do not degrade significantly in both acidic and basic solutions. Chromatographic tests confirm that these two bonded phase behave differently with respect to their retention of PAHs, alkyl-substituted benzenes and benzodiazepines.     

Thermodynamic study of a liquid crystal as a liquid phase in gas-liquid chromatography. II. A cholesteric liquid crystal.

Gas-liquid chromatography is utilized for the determination of thermodynamic solution parameters for various organic solutes at infinite dilution in the meso- and isotropic phases of cholesteryl palmitate. The thermodynamic data and trends in values of the activity coefficients for the solutes are discussed in relation to their structure and to the orientations of the liquid crystal.     

The selectivity of the stationary liquid in vapour phase chromatography

Vapour phase chromatography is a highly efficient analytical technique for the separation of gases and volatile liquids. The stationary phase in this percolation process is a liquid supported by an inert solid carrier material of a suitable particle size. The important role played by this liquid in the separation of a mixture into its components is discussed.