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  • 1
    Electronic Resource
    Electronic Resource
    Chromatographic evaluation of chiral (1R-trans)-N, N′ -1,2-cyclohexylenebisbenzamide-oligodimethylsiloxane copolymeric stationary phases for capillary supercritical fluid chromatography (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 4 (1992), S. 155-162 
    Details
    ISSN: 1040-7685
    Keywords: chiral stationary phase ; copolymeric stationary phase ; supercritical fluid chromatogrphy ; open tubular columns ; enantiomers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A novel approach to the design of chiral stationary phases (CSPs) is illustrated by the synthesis and evaluation of selective and efficient copolymeric CSPs with alternating chiral (1R-trans)-N, N′-1,2-cyclohexylenebisbenzamide and achiral (oligodimethylsiloxane) blocks. These materials are shown to resolve a variety of chiral diols. Evaluation of the performance of one of these phases in GC and SFC suggests that SFC can produce higher resolution because of its lower operating temperature which facilitates solute-stationary phase interactions. The influence of different chiral (position of substitution) and achiral (chain length) blocks of the copolymer on solute retention, efficiency, chiral selectivity, and resolution were studied, as well as the reproducibility of the column preparation method.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mcs.1220040207
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  • 2
    Electronic Resource
    Electronic Resource
    Silver-complexed dicyanobiphenyl-substituted polymethylsiloxane encapsulated particles for packed capillary column supercritical fluid chromatography (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 7 (1995), S. 279-287 
    Details
    ISSN: 1040-7685
    Keywords: supercritical fluid chromatography ; packed capillary columns ; dicyanobiphenyl-substituted polymethylsiloxanes ; silver chelated packing materials ; polymer encapsulated packing materials ; fatty acid methylesters ; double bond selectivity ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: High nitrile content cyano-substituted polymethylsiloxane encapsulated particles were prepared for double bond selectivity in packed capillary column supercritical fluid chromatography (SFC). Silica particles were deactivated with 50% cyanopropyl-substituted polymethylhydrosiloxane, and coated with 25% o,p-dicyano-p-biphenyl-substituted polymethylsiloxane (o,p,p-DCBP), and 25% m,m-dicyano-p-phenyl-substituted polymethylsiloxane (m,m,p-DCBP) stationary phases. Argentation of the particles was carried out by complex formation between silver ions and the cyano groups on the particles. Unsaturated fatty acid methylesters (FAMEs) were used to investigate the selectivity of these packing materials to double bonds using packed capillary column SFC. Separations were performed according to the degree, position, and geometrical configuration of the double bonds. The effect of temperature on selectivity was also investigated. The stability of the packing materials was evaluated by monitoring the loss in selectivity of the oleate/elaidate isomers after washing the column with supercritical CO2 at 300 atm and 85°C. The separation of FAMEs in a commercial fish oil was compared using capillary columns packed with DCBP coated and silver-complexed particles.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mcs.1220070312
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  • 3
    Electronic Resource
    Electronic Resource
    Cyanobiphenyl-substituted polymethylsiloxane encapsulated particles for packed capillary column supercritical fluid chromatography (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 7 (1995), S. 411-419 
    Details
    ISSN: 1040-7685
    Keywords: supercritical fluid chromatography ; stationary phases ; packing materials ; packed capillary columns ; cyanobiphenyl-substituted polymethylhydrosiloxane ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nine isomeric cyanobiphenyl-substituted (25%) polymethylsiloxane (CBP) stationary phases were coated and immobilized by free-radical crosslinking on silica packing materials for use in supercritical fluid chromatography (SFC). The selectivities of these packing materials to benzene derivatives, polycyclic aromatic hydrocarbons (PAHs), and double bonds in fatty acid methylesters (FAMEs) were determined. Among the nine isomeric CBP-coated packing materials, the o, p-CBP phase was found to be the most selective to both double bonds and aromatic isomers under SFC conditions. The durability of the packing materials was evaluated by measuring the changes in selectivity with SFC use. The loss in selectivity was less than 0.20% after being continuously washed by supercritical carbon dioxide at 100°C and 300 atm for more than 100 h.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mcs.1220070414
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  • 4
    Electronic Resource
    Electronic Resource
    Syntheses of isomeric cyanobiphenyl-substituted polysiloxanes for stationary phases in gas chromatography (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 4 (1992), S. 521-527 
    Details
    ISSN: 1040-7685
    Keywords: cyanobiphenyl polysiloxanes ; gas chromatography ; stationary phases ; synthesis ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nine isomeric cyanobiphenyl-substituted polysiloxanes were synthesized using a four-step procedure and tested as stationary phases in open tubular column gas chromatography.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mcs.1220040610
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  • 5
    Electronic Resource
    Electronic Resource
    Novel cyanobiphenylpolysiloxane stationary phases for gas and supercritical fluid chromatography (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 4 (1992), S. 529-540 
    Details
    ISSN: 1040-7685
    Keywords: stationary phases ; cyanobiphenylpolysiloxanes ; gas chromatography ; supercritical fluid chromatography ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Nine different 25% cyanobiphenyl-substituted polysiloxane (CBP) stationary phases were evaluated for use in gas and supercritical fluid chromatography. They were easily coated and cross-linked on fused silica capillaries to produce highly efficient columns. For a 200 μm i.d. column, an efficiency of as high as 5,100 plates m-1 was obtained. For most of the new phases, the upper temperature limit was 300°C. A comparative study of the chromatographic behaviors of the cyanobiphenyl and commercial reference phases was made. Some of the cyanobiphenyl stationary phases showed polarities higher than those for carbowax 20M or 50% cyanopropyl. All six positional isomers of dodecylxylene and the five isomers of four-ring polycyclic aromatic hydrocarbons were baseline resolved on GC capillary columns with certain of the cyanobiphenyl phases, demonstrating higher selectivity over SE-54 or Carbowax 20M phases. In SFC, a cyanobiphenyl column provided better separation of a standard coal tar sample than columns with biphenyl or cyanopropyl phases. The retention behavior of fatty acid methyl esters and a mixture of polar solutes was investigated on the cyanobiphenyl and references phases. With respect to certain solute pairs, the selectivities of the new stationary phases were found to increase with temperature. The new cyanobiphenyl phases were found to be useful for GC and SFC separations of various classes of complex mixtures including essential oils, explosives, and polycyclic aromatic hydrocarbons.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mcs.1220040611
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  • 6
    Electronic Resource
    Electronic Resource
    Structural characteristics of pendant and copolymeric cyclodextrin polysiloxane stationary phases and their influence on chiral selectivity and resolution in capillary gas chromatography (1995)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 7 (1995), S. 91-105 
    Details
    ISSN: 1040-7685
    Keywords: cyclodextrin stationary phases ; polysiloxane stationary phases ; structural characteristics ; gas chromatography ; chiral selectivity ; enantiomers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The dependence of gas chromatographic properties on stationary phase structural characteristics was evaluated for three different types of cyclodextrin-bonded polysiloxanes: small-rim-tethered, large-rim-tethered, and copolymeric. Separation efficiency, chiral selectivity, and resolution were investigated as functions of stationary phase structural features such as length and chemical composition of the connecting arms, chemical composition of the substituent groups on the small rim of the cyclodextrin toroid, and the position(s) of connecting arm attachment(s) on the cyclodextrin rims. For all of the solutes and experimental conditions used in this study, the small-rim-tethered cyclodextrin phases were found to provide superior chromatographic performances compared to the other two types of cyclodextrin phases. The chiral selectivities of the investigated phases were found to depend both on chemical composition and length of the connecting arm(s). Shorter connecting arms were found to provide improved chiral selectivities. Stationary phases having a four-carbon connecting arm with an etheric oxygen linkage in the chain provided higher chiral selectivities compared to stationary phases with hydrocarbon or phenoxy group-containing connecting arm(s). The chiral selectivities of the studied phases did not change when the substituents at the C-6 positions were changed from -CH2OCH2 to -CH3. Efficiency values of up to 5,000 theoretical plates per meter were obtained using 200 μm i.d. columns. Column efficiency was found to be independent of structural features of the cyclodextrin toroid and the connecting arms.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mcs.1220070202
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