Liquid crystal stationary

A number of analytical methods have been developed for the determination of chlorotoluene mixtures by gas chromatography. These are used for determinations in environments such as air near industry (62) and soil (63). Liquid crystal stationary columns are more effective in separating m- and chlorotoluene than conventional columns (64). Prepacked columns are commercially available. ZeoHtes have been examined extensively as a means to separate chlorotoluene mixtures (see Molecularsieves). For example, a Y-type 2eohte containing sodium and copper has been used to separate y -chlorotoluene from its isomers by selective absorption (65). The presence of ben2ylic impurities in chlorotoluenes is determined by standard methods for hydroly2able chlorine. Proton (66) and carbon-13 chemical shifts, characteristic in absorption bands, and principal mass spectral peaks are available along with sources of reference spectra (67). [Pg.54]

Separation of Stereoisomers Osing Liquid Crystal Stationary Phases... [Pg.463]

Janini, G.M., Recent usage of liquid crystal stationary phases in gas chromatography, Adv. Chromatogr., 17, 231, 1979. [Pg.58]

Smith, T.R. and Wozny, M.E., Gas chromatographic separation of underivatized steroids using BPhBT liquid crystal stationary phase, J. High Resolut. Chromatogr. Chromatogr. Commun., 3, 333, 1980. [Pg.58]

A commercially available semetic phase composed of biphenylcarbox-ylate ester attached to the polysiloxane backbone of a fused silica column has been shown to be ideal for the separation of geometric isomers of polycyclic aromatics of various classes of compounds [14,15]. This column exhibits a wide semetic temperature range of 100-300°C and has been shown to be stable to at least 280°C. Liquid-crystal stationary phases have also been employed in SFC [16]. [Pg.46]

S. Rokushika, K. Naikwadi, et al., Liquid crystal stationary phases for gas chromatography and supercritical fluid chromatography, HRC CC J. High Res. Chromatogr. Chromatog. Commun., 5 480-484(1985). [Pg.322]

Betts, T.J., Charmaine, M.M. and Tassone, A.I. (1991) Use of a liquid crystal stationary phase at temperatures below its melting point for the gas chromatographic study of some volatile oil constituents, journal of Chromatography A 547, 335-344. [Pg.239]

To improve the effectiveness of the chromatographic separation, a comparison study has been carried out on cyclodextrin and liquid crystal stationary phases Both materials function as "ordered" media with cyclodextrins the inclusion complex formation predominates, whereas the liquid crystals enable interaction of compounds with the ordered structure of the mesophase ... [Pg.247]

Naikwadi KP, Wadgaonkar PP. Liquid crystal stationary phases for chromatography. US patent 5900145, assigned to J K Environmental Ltd., Sydney, CA 1999. [Pg.399]

Witkiewicz, Z. Mazur, J. Liquid-crystal stationary phases in capillary columns. LC-GC 1990, 8 (3), 224-234. [Pg.1413]

The surface order and diffusion in 5CB liquid crystal confined to porous glass have been studied using NMR spectroscopy. and Si NMR spectroscopy has been used to characterise a new type of chemically bonded liquid crystal stationary phase for... [Pg.167]

Liquid crystals have found widespread use as stationary phases in gas chromatographic applications due to the benefits of coupling the usual analytical strengths of gas chromatography with the unique structure and shape selective properties of the liquid crystalline phase. Interaction of solutes with the orientational order provided by the anisotropy of the liquid crystal stationary phase allows for the effective and selective separation of positional and geometric isomers. This remarkable solute structural discrimination is especially important for the separation of isomers that have similar physical properties and thus cannot be conveniently separated on conventional capillary columns that mainly differentiate on the basis of boiling point/molecular weight or polarity differences. The mechanism of separation in liquid crystalline stationary phases is based on specific intermolecular inter-... [Pg.889]

Early studies on the use of liquid crystals as stationary phases focused on packed columns however as with other gas chromatographic applications, the technology has now almost exclusively shifted to capillary columns. Several reviews outlining the fundamentals and applications of liquid crystal stationary phases in both packed and capillary columns are available [444-449]. Stationary phases can be prepared from either monomeric or side-chain polymeric liquid crystals. Particularly relevant to the latter is the increased use of polysiloxane and poly-arylate backbones for the attachment of... [Pg.889]

Application of Liquid Crystal Stationary Phases for the Determination of Thermodynamic Data for Nonmesogenic Solutes... [Pg.891]

Solute (number of isomers) Liquid crystal stationary phase (phase types) Refs. [Pg.916]

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