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  • Coupled HPLC-GC  (5)
  • Gas chromatography, capillary  (4)
  • Coupled HPLC-capillary GC  (2)
  • Gas Chromatography, capillary, glass  (2)
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  • 1
    Electronic Resource
    Electronic Resource
    Analysis of petroleum fractions by on-line micro HPLC-HRGC coupling, involving increased efficiency in using retention gaps by partially concurrent solvent evaporation (1985)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 8 (1985), S. 601-606 
    Details
    ISSN: 0935-6304
    Keywords: Coupled HPLC-GC ; Retention gap ; Partially concurrent solvent evaporation ; Gasoline ; Group-type separation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Two-dimensional chromatography of gasoline by on-line coupled HPLC-HRGC, as described in this paper, allows separate GC analysis of paraffins and aromatics. The GC system contains a retention gap of only 10 m length for introducing HPLC fractions of 100 μl volume. This becomes possible through evaporation of part of the solvent during introduction of the HPLC eluent. This “partially concurrent solvent evaporation” technique allows transfer of large volumes of HPLC eluent into relatively short retention gaps, maintaining the full efficiency of the solvent effects in reconcentrating the bands of the early eluted solutes.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240080925
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  • 2
    Electronic Resource
    Electronic Resource
    Practical capillary gas chromatography - a systematic approachPlenary Lecture to the Thirtieth Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, March 6, 1979. (1979)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 2 (1979), S. 109-117 
    Details
    ISSN: 0935-6304
    Keywords: Gas Chromatography, capillary, glass ; Capillary versus packed column ; Small sample width at inlet important ; Optimized sampling by on-column injection ; Hydrogen as ideal carrier gas ; Efficient and stringent testing of columns needed ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Capillary gc is now rapidly expanding. Naturally, initiation is most often attempted on the basis of the experience acquired with packed columns. However, such an extrapolation is successful only if a number of essential peculiarities of capillary gc are considered. Based on practical examples this paper discusses six essential details: 1) design and maintenance of the gas flow paths, 2) the greatly increased importance of sampling technique, which should not be confined just to stream splitting, 3) the problems in quantitative analysis arising from small sample size, 4) specific sources of trouble related to small amounts of liquid phase, 5) specific arguments for the choice of the carrier gas, clearly pointing to hydrogen as the ideal carrier and, 6) the different way to approach column production. Figures for all selected examples are given.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240020303
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  • 3
    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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  • 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
    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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  • 6
    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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  • 7
    Electronic Resource
    Electronic Resource
    GC column effluent splitter for problematic solvents introduced in large volumes: Determination of di-(2-ethylhexyl) phthalate in triglyceride matrices as an application (1988)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 11 (1988), S. 135-139 
    Details
    ISSN: 0935-6304
    Keywords: Solvents and GC detectors ; Coupled HPLC-GC ; Column effluent splitter ; Di-(2-ethylhexyl) phthalate ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Introduction of solutions of up to several milliliters by on-column injection of large volumes or by coupled HPLC-GC may cause problems with GC detectors (FID, AFID, MS). For instance, dichloromethane forms large amounts of hydrochloric acid and carbon black in FIDs.A column effluent splitter was developed for keeping the major portion of the solvent vapors away from the detector; approximately 99% of the vapor is vented while the remaining 1% of vapor is used for detecting the widths of the solvent peaks. During analysis, the split ratio is reversed by a strong increase of the resistance to the gas flow through the split exit line.The system was used for the determination of di-(2-ethylhexyl)-phthalate (DEHP) in triglyceride matrices of various foods. Direct determination by HPLC is not sufficiently sensitive, whereas direct analysis by GC is hindered by the triglycerides. Solutions of fats or oils were pre-separated on a silica column using dichloro-methanelcyclohexane 1:l with addition of 0.05 % acetonitrile as eluent. The HPLC fraction containing the DEHP was transferred to GC through a loop-type interface using concurrent solvent evaporation. Detection limits were around 0.1 ppm.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240110135
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  • 8
    Electronic Resource
    Electronic Resource
    Coupled HPLC-GC for determining PCBs in fish (1987)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 10 (1987), S. 416-417 
    Details
    ISSN: 0935-6304
    Keywords: Coupled HPLC-GC ; Loop-type interface ; Concurrent solvent evaporation ; PCBs in fish ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240100713
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  • 9
    Electronic Resource
    Electronic Resource
    Co-solvent effects for preventing broadening or loss of early eluted peaks when using concurrent solvent evaporation in capillary GC. Part 1: Concept of the technique (1988)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 11 (1988), S. 388-394 
    Details
    ISSN: 0935-6304
    Keywords: Solvent effects ; Co-solvent effects ; Concurrent solvent evaporation ; Large sample volumes ; Coupled HPLC-GC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The concept and some first results of a method are described for evaporating large volumes of solvent in a relatively short pre-column (retention gap) in such a way that solvent trapping retains volatile components in the inlet up to completion of solvent evaporation. The method was developed for transferring large volumes (easily exceeding 1 ml) of HPLC eluent to GC when using on-line coupled HPLC-GC, but is equally suited for injecting large sample volumes (at least some 50 μl) and could be particularly useful for introducing aqueous solutions.Concurrent solvent evaporation allows introduction of very large volumes of liquid into GC. However, peaks eluted up to some 40-80° above the column temperature during introduction of the liquid are strongly broadened due to the absence of solvent trapping. On the other hand, previous retention gap techniques involving solvent trapping were not suited for transferring very large volumes of liquid into GC. Using a relatively high boiling co-solvent added to the sample or the HPLC eluent, advantages of concurrent solvent evaporation can be combined with solute reconcentration by solvent effects, allowing elution of sharp peaks starting at the column temperature during introduction of the sample.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240110506
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  • 10
    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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