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  • 1
    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.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 3 (1991), S. 229-239 
    ISSN: 1040-7685
    Keywords: sample introduction ; injection ; supercritical fluid chromatography ; open tubular columns ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: As in the case of all chromatographic methods, the ideal sample introduction method for supercritical fluid chromatography (SFC) would provide a narrow and sharp solvent peak (or no solvent peak), quantitative transfer of the sample into the column, and high reproducibility. Elimination of the solvent before the solutes enter the column would be preferred; however, this practice is always associated with the risk of partial solute elimination. In open tubular column SFC, samples are normally introduced using a smallvolume internal loop valve. These valves can be operated such that none, some, or all of the solvent is eliminated. Several approaches were quantitatively evaluted, and optimized conditions were determined. Particular attention was given to trace analysis. The minimum detectable levels (S/N 〉4) achievable using a flame ionization detector were determined to be approximately 30 ng (150 ppm) for split injection, 4 ng (20 ppm) for delayed split injection, and 1 ng (5 ppm) for direct injection.
    Additional Material: 8 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 7 (1995), S. 207-212 
    ISSN: 1040-7685
    Keywords: charcoal ; active carbon ; PLOT column ; column technology ; gas chromatography ; permanent gases ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The preparation of charcoal porous layer open tabular (PLOT) columns, and their application to the separation of permanent gases and light hydrocarbons are reported. Two types of charcoal, coconut and darco charcoal, were used to prepare columns from fused silica capillaries. The performance of these columns was compared to that of a commercially available carbon molecular sieve PLOT column. The coconut charcoal PLOT column produced good retention and resolution for both permanent gases and light hydrocarbons; all separations were achieved in less than eight minutes under isothermal conditions. © 1995 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
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  • 4
    ISSN: 1040-7685
    Keywords: multidimensional ; supercritical fluid chromatography ; liquid crystal polysiloxane ; polycyclic aromatic hydrocarbons ; coal tar ; petroleum distillate ; carbofuran ; capillary columns ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A multidimensional system based on capillary supercritical fluid chromatography (SFC) was constructed that utilizes a simple flow-switching interface between two open-tubular 50-μm i.d. columns. A novel solvent-venting injection technique was incorporated in the system that enables single or multiple 0.5-μL volumes to be injected into an uncoated, yet deactivated, length of capillary precolumn without flooding of the analytical column. The effectiveness of multidimensional capillary SFC (SFC-SFC) for complex mixtures is demonstrated by the analysis of polycyclic aromatic hydrocarbons (PAH) in a coal tar extract, the trace determination of a methylcarbamate pesticide and its metabolites in a bird extract, and a group-type separation of hydrocarbons in a high-boiling petroleum distillate. These examples show for the first time that capillary SFC-SFC is a complementary alternative to other multidimensional chromatographic methods involving liquid or gaseous mobile phases.
    Additional Material: 12 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 1 (1989), S. 207-211 
    ISSN: 1040-7685
    Keywords: supersonic jet spectroscopy ; supercritical fluid chromatography ; sheath-flow nozzle ; capillary columns ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Supersonic jet spectroscopic detection has been successfully coupled to capillary supercritical fluid chromatography by introduction of the supercritical effluent into a secondary flow of argon, before supersonic expansion of the combined flow through a converging nozzle. At pressures of 6-10 atm, the flowing sheath of argon efficiently carries eluting sample through a 25-p.m nozzle orifice into the supersonic jet. Dead volumes are negligible in this arrangement, and high-resolution fluorescence excitation spectra are obtained. Perylene and benzo[a]pyrene were selectively detected in a standard reference coal tar sample at detection limits of 150 pg and 5 ng, respectively.
    Additional Material: 4 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 3 (1991), S. 521-529 
    ISSN: 1040-7685
    Keywords: solvent vent ; large volume injection ; open tubular columns ; supercritical fluid chromatography ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The use of small internal diameter precolumns (11-25-μm i. d.) helped solute focussing when using solvent vent sample introduction in open tubular column supercritical fluid chromatography (SFC). Column efficiencies were similar to those obtained with split injection (3000-5000 plates m-1). Trace analysis in SFC was improved because large volumes (1 μL) could be introduced for analysis with little sacrifice in column efficiency.
    Additional Material: 11 Ill.
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 7 (1995), S. 153-158 
    ISSN: 1040-7685
    Keywords: silica gel ; PLOT column ; column technology ; gas chromatography ; light hydrocarbons ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We report a simple method for the preparation of silica PLOT columns using fused silica capillaries. In this method, silica particles were suspended in a methylene chloride/pentane solution containing polymethylhydrosiloxane and passed through the capillary tubing. This caused the silica particles to be dynamically coated on the inner wall of the fused silica capillary. The column was dried and heated, which facilitated the simultaneous deactivation and bonding of a uniform mono-layer of porous silica on the inner wall of the capillary tubing. These columns were used to separate light hydrocarbons, chlorinated hydrocarbons, and aromatic compounds.
    Additional Material: 6 Ill.
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  • 8
    ISSN: 1040-7685
    Keywords: gas chromatography ; open tubular columns ; sulfonyl-containing polysiloxane ; polar stationary phase ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new polar polysiloxane stationary phase for capillary column gas chromatography containing 4-(methylsulfonyl)phenyl substitution was synthesized and compared to a cyanophenylpolysiloxane, OV-225. The sulfonylphenylpolysiloxane phase was useful and stable over a wide temperature range from 70°C to 320°C, and it exhibited similar overall polarity to OV-225. However, because of the specific chemical properties of the 4-(methylsulfonyl)phenyl group, this phase demonstrated unique selectivities for certain classes of compounds including basic nitrogen heterocycles and polychlorinated biphenyls.
    Additional Material: 5 Ill.
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  • 9
    ISSN: 1040-7685
    Keywords: supercritical fluid chromatography ; mass spectrometry ; negative ion ; chemical ionization ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The application of mass spectrometry in the negative ion mode with capillary column supercritical fluid chromatography is described. The supercritical fluid chromatography mobile phase (CO2) was used as the primary reagent gas to generate thermalized electrons and reagent anions (such as O- and CO2-). When trace amounts of CH4 or NH3 gas were also introduced into the chemical ionization source, the mass spectrometer sensitivity was increased. Detection limits (S/N = 5) for heptachlor were determined to be 20 pg and 200 fg for full scan and selected ion monitoring modes, respectively. Mass spectra of a cyclic peptide, valinomycin, obtained with these mixed reagents (CH4 + CO2 and NH3 + CO2) gave the molecular anion at m/z 1110 as the most abundant ion and additional fragment ions that yielded peptide sequence information.
    Additional Material: 9 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 6 (1994), S. 409-414 
    ISSN: 1040-7685
    Keywords: open tubular columns ; liquid chromatography ; high temperature ; UV-absorption detection ; optical fibers ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A new UV-absorption detector cell for on-column detection in open tubular column liquid chromatography was evaluated. Optical fibers and quick-fit connections were employed for flexibility and ease in alignment and mounting in an oven for high temperature detection. Different optical fiber diameters were evaluated for 50 μm i.d. capillary columns. The best combination of optical fibers (200 μm source and collector) resulted in a detection limit of 2 × 10-6 M for acetophenone. No dramatic change in the signal-to-noise ratio was found when the temperature was raised to 150°C.
    Additional Material: 3 Ill.
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