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  • Gas chromatography, capillary  (4)
  • Coupled HPLC-capillary GC  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Capillary columns with immobilized stationary phases. Part 3: The basic influence of vinyl groups (1981)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 4 (1981), S. 491-494 
    Details
    ISSN: 0935-6304
    Keywords: Gas chromatography, capillary ; Column preparation ; Immobilization of stationary phases ; Influence of vinyl groups ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This article presents a preliminary description of the influence exerted by vinyl groups on the process and on the result of immobilization. Vinyl groups may occur in the stationary phase (e. g. in SE-54) or may be bound to the support surface by persilylation with divinyltetramethyldisilazane. In the first case they promote the crosslinking process in the stationary phase. In the second case bonding to the solid surface is intensified. We have observed that vinyl groups in both situations contribute with comparable efficiency to the final non-extractability of the stationary phase. A further, yet entirely independent influence of surface-bonded vinyl groups concerns the acidity of the column. Whereas regular persilylation produces slightly acidic columns, a substantial shift to basic column behavior is observed after persilylation with a vinyl-containing reagent. The potential future importance of both kinds of influence is discussed.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240041003
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  • 2
    Electronic Resource
    Electronic Resource
    Capillary columns with immobilized stationary phases. Part 4: A moderately polar phase, OV-1701 (1982)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 5 (1982), S. 13-18 
    Details
    ISSN: 0935-6304
    Keywords: Gas chromatography, capillary ; Column preparation ; Immobilization of stationary phases ; Procedure for polar phases ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Whereas the immobilization of apolar silicone phases is essentially understood and mastered, the corresponding treatment of even moderately polar phases remains problematical. Upon attack by peroxide radicals, these phases respond by forming active transformation products rather than by bonding to the support surface or to neighboring molecules. OV-1701 is at present the most polar stationary phase which can reasonably be immobilized. An essential feature of the practical procedure is the prevention of film breakage after coating the inert support surface and before immobilization. Two ways of overcoming this problem are presented.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240050103
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  • 3
    Electronic Resource
    Electronic Resource
    Capiliary columns with immobilized stationary phases. Part 5: Determination of column bleeding; re-silylationPart 4: HRC & CC5 (1982) 13. (1982)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 5 (1982), S. 349-354 
    Details
    ISSN: 0935-6304
    Keywords: Gas chromatography, capillary ; Persilylated, apolar columns ; Immobilized coatings ; Determination of column bleeding ; Re-silylation of fresh and used columns ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The bleeding of apolar high temperature columns may well be the critical factor limiting their applicability for GC/MS-coupling, and for high temperature analyses. Therefore, a bleeding determination procedure has been designed as a basis for a systematic approach to the production of low-bleed columns. Re-silylation is a traditional method of reducing column bleeding. Increased efficiency of re-silylation becomes feasible with immoblized coatings. Experience gained so far shows that resilylation of immoblized coatings may indeed result in the expected strongly reduced bleed rates and in improved overall column quality. Re-silylation may also contribute to column washing by enhancing the solubility of adsorbed contaminants.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240050703
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  • 4
    Electronic Resource
    Electronic Resource
    Coupled HPLC-capillary GC - state of the art and outlook (1985)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 8 (1985), S. 726-733 
    Details
    ISSN: 0935-6304
    Keywords: Coupled HPLC-capillary GC ; Retention gap ; Concurrent solvent evaporation ; Extraction techniques ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: HPLC fractions involving eluents of low to intermediate polarity can be introduced into capillary GC using the retention gap technique. Partial or complete solvent evaporation during sample introduction reduces the length of, or almost eliminates, the zone in the column inlet (retention gap) flooded by the introduced liquid, allowing introduction of larger HPLC fractions and/or use of shorter retention gaps. The corresponding techniques are reviewed. The retention gap technique is poorly suited for water-containing HPLC eluents (reversed phase HPLC) and fails completely if HPLC eluents contain, e.g., buffer salts. Various techniques for extracting such HPLC eluents are considered, preference being given to extraction into GC stationary phases from where solutes are thermally desorbed into the GC separation column. Limiting factors are diffusion of solutes within the liquid phase to be extracted and retention power of the extraction tubes.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240081107
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  • 5
    Electronic Resource
    Electronic Resource
    Concurrent solvent evaporation for on-line coupled HPLC-HRGC (1986)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 95-101 
    Details
    ISSN: 0935-6304
    Keywords: Coupled HPLC-capillary GC ; Concurrent solvent evaporation ; Retention gap ; Solvent effects ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A technique is proposed which allows introduction of very large volumes of liquid (10 ml were tested) into capillary columns equipped with short (1-2 m long) retention gaps. It is based on concurrent solvent evaporation, i.e. evaporation of the solvent during introduction of the sample. The technique presupposes high carrier gas flow rates (at least during sample introduction) and column temperatures near the solvent boiling point. The major limitation of the method is the occurrence of peak broadening for solutes eluted up to 30°, in some cases up to 100°, above the injection temperature. This is due to the absence of solvent trapping and a reduced efficiency of phase soaking. Therefore, use of volatile solvents is often advantageous. Application of the concurrent solvent evaporation technique allows introduction of liquids which do not wet the retention gap surface. However, the method is still not very attractive for analysis of aqueous or water-containing solutions (reversed phase HPLC).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240090208
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  • 6
    Electronic Resource
    Electronic Resource
    Pressure and flow changes in vaporizing GC injectors during injections and their impact on split ratio and discrimination of sample components (1979)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 2 (1979), S. 563-569 
    Details
    ISSN: 0935-6304
    Keywords: Gas chromatography, capillary ; sampling, sample discrimination, split ratio ; many factors influencing real amount sampled ; external calibration to be replaced by inner standard technique ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The effect of pressure changes in the vaporizing GC injectors on the split ratio is investigated. It is shown that the true split ratio depends on a number of parameters and may strongly differ from the split ratio expected from the flows set before injection. Quantitation with split injection based on external standards has to be carried out very carefully (or should be replaced by the method with internal standard). The split ratio may strongly change during the splitting of the sample. There are a number of mechanisms causing some sample components to be retarded and hence to be split by a different ratio. The split injector is a device which still requires further development.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240020905
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