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  • 1
    Electronic Resource
    Electronic Resource
    Determination of solvent recondensation or evaporation in the GC-precolumn by measurement of temperature changes on the column wall (1997)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 20 (1997), S. 657-664 
    Details
    ISSN: 0935-6304
    Keywords: Temperature measurement on column wall ; Solvent recondensation in the precolumn ; Closure of Vapor exit ; Vaporizer/precolumn solvent split ; Loop-type interface ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Temperature measurements on the column outer well were used for detecting recondensation or evaporation of solvent inside the precolumn during injection or on-line transfer of large solvent volumes. This facilitates the choice of the most critical parameter of these techniques, i.e. oven temperature. When using the vaporizer/precolumn solvent split/gas discharge system, the dew point of the solvent is determined, either to just prevent solvent recondensation or to limit it to the capacity of the precolumn to retain liquid. In concurrent eluent evaporation through the loop type LC-GC interface, temperature measurement enables the determination of whether or not the flooded zone exceeds a given limit. Fanally, when solvent trapping is used (on-column injector/partially concurrent solvent evaporation evaporation or vaporizer/partial recondensation), temperature measurement near the front end of the flooded zone is used as a signal for accurate closure of the vapor exit shortly before the end of solvent evaporation.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240201208
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  • 2
    Electronic Resource
    Electronic Resource
    Ruined GC column performance due to ferrule particle (1990)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 13 (1990), S. 658-659 
    Details
    ISSN: 0935-6304
    Keywords: Capillary GC ; Ferrule particle ; Column performance ; Column installation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240130919
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  • 3
    Electronic Resource
    Electronic Resource
    Distorted solvent peaks in capillary GC: A symptom of porous column surfaces (1990)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 13 (1990), S. 803-810 
    Details
    ISSN: 0935-6304
    Keywords: Capillary GC ; Uncoated precolumns ; Solvent peak ; Porosity of capillary surfaces ; Deactivation methods ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Many uncoated precolumns, and to a lesser extent separation columns, strongly retain some of the solvent. Retarded release of such solvent elevates the baseline after the solvent peak and causes ugly “humps” of eluted solvent as the temperature is increased. The problem is probably a result of retention by a porous surface, e.g. surfaces obtained by leaching or hydrothermal treatment of capillaries prior to silylation. It is assumed that other problems with capillary columns can be explained by the same mechanism, including: a kind of adsorption including apolar compounds, and “ghost” peaks as well as “memory” effects. Fused silica capillaries are superior to glass, but even for these special procedures are required in order to achieve thorough deactivation of the internal surface without introducing porosity.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240131203
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  • 4
    Electronic Resource
    Electronic Resource
    Carbowax-deactivated GC precolumns capable of resisting water? (1991)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 14 (1991), S. 212-214 
    Details
    ISSN: 0935-6304
    Keywords: Capillary GC ; Uncoated precolumn ; Water-resistant deactivation ; Coupled LC-GC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240140317
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  • 5
    Electronic Resource
    Electronic Resource
    PTV vapor overflow  -  principles of a solvent evaporation technique for introducing large volumes in capillary GC (1990)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 13 (1990), S. 540-546 
    Details
    ISSN: 0935-6304
    Keywords: PTV Injection ; Vapor overflow ; Sample introduction at reduced pressure ; Evaporation rates ; Large sample volumes ; Coupled LC-GC ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The concept of a GC solvent evaporation technique is outlined that involves a modified Programmed Temperature Vaporizing (PTV) injector. The vapor overflow technique is intended for introducing samples in large volumes of solvent by syringe injection of strongly diluted samples or by coupled LC-GC. The liquid is introduced into a packed vaporizing chamber kept above the solvent boiling point at a pressure which is near or below ambient. The carrier gas is essentially switched off. Evaporation and discharge of the solvent vapors occurs by expansion of the vapors, driven by the solvent vapor pressure. For transferring the sapmple into the column, the carrier gas is switched on again and the vaporizing chamber heated.Compared to PTV solvent split injection, vapor overflow offers the following advantages: It automatically optimizes operational parameters, therefore facilitating its application. Losses of volatile materials are minimized by a minimal flow rate through the injector.Vapor overflow is a promising technique for transferring watercontaining eluents in coupled LC-GC since no wettability is required and leaching of pre-column surfaces is avoided.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240130803
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  • 6
    Electronic Resource
    Electronic Resource
    Modified cyclodextrins as stationary phases for capillary GC: Consequences of dilution in polysiloxanes (1991)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 14 (1991), S. 207-210 
    Details
    ISSN: 0935-6304
    Keywords: Capillary GC ; Cyclodextrin stationary phases ; Dilution of cyclodextrins ; Chiral resolution ; Glass capillary columns ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240140315
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  • 7
    Electronic Resource
    Electronic Resource
    Coupled LC-GC: Evaporation rates for partially concurrent eluent evaporation using an early solvent vapor exit (1989)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 12 (1989), S. 721-726 
    Details
    ISSN: 0935-6304
    Keywords: Coupled LC-GC ; Partially concurrent eluent evaporation ; Evaporation rates ; Early solvent vapor exit ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Partially concurrent eluent evaporation presupposes an eluent evaporation rate in the GC pre-column that approaches the LC flow rate. Discharging the vapors through the whole GC column, evaporation rates reach 10-30 μl/min, i.e. are suitable just for LC flow rates typical for packed capillary LC columns. With an early vapor exit, evaporation rates are increased to 100-200 μl/min (under extreme conditions to some 800 μl/min), thus fitting the LC flow rates of 2 mm i.d. columns.Evaporation rates were measured for a standard set of pre-columns and conditions. The dependence of the evaporation rate on temperature, inlet pressure, carrier gas, and internal diameter of the retaining pre-column are discussed in order to allow the design of a GC system producing a desired evaporation rate.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240121106
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  • 8
    Electronic Resource
    Electronic Resource
    High temperature vaporizing chambers for large volume GC injections and on-line LC-GC (1995)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 18 (1995), S. 573-578 
    Details
    ISSN: 0935-6304
    Keywords: Large sample volumes ; Vaporizing chambers ; Evaporation rates ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The suitability of some chambers for sample evaporation at high input flow rates (〉100 μl/min) was studied by visual experiments. The chambers were at temperatures far above the solvent boiling point in order to achieve the heat transfer required. Shooting liquid owing to violent evaporation, flooding of the chamber as a result of cooling, and excessively high vapor pressure causing backflow into the gas supply system were found to be the limiting factors. Fused silica capillaries into which a piece of wire or polyimide-free fused silica capillary had been inserted were found to be suitable for the vaporization of “easy” solvents, such as alkanes (up to some 1.7 ml/min), but packed beds were required to achieve favorable evaporation of dichloromethane or methanol/water (up to some 800 and 300 μl/min, respectively).
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240180912
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  • 9
    Electronic Resource
    Electronic Resource
    GC “ghost” peaks caused by “fingerprints” (1991)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 14 (1991), S. 558-559 
    Details
    ISSN: 0935-6304
    Keywords: Capillary GC ; Coupled LC-GC ; Contamination of solvent ; “Ghost” peaks ; “Fingerprints” ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240140809
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  • 10
    Electronic Resource
    Electronic Resource
    Mixing in the sample loop of the loop-type interface in coupled LC-GC (1992)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 15 (1992), S. 71-74 
    Details
    ISSN: 0935-6304
    Keywords: On-line coupled LC-GC ; Loop-type interface ; Mixing in the sample loop ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: During introduction of an LC fraction into the sample loop of the loop-type interface mixing occurs between the fraction of interest and the material previously eluted from the LC. Such mixing may not only result in losses of the solute material of interest, but also in contamination of the fraction of interest with material from which it was supposed to have been isolated. Experimental determination of the extent of mixing has led to the conclusion that whereas the effects are negligible under some conditions, in some circumstances the mixing can cause severe problems.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240150204
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