ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
Filter
  • Capillary GC  (7)
  • Coupled HPLC-GC  (5)
  • Solvent effects  (4)
  • Column preparation  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 17 (1983), S. 357-360 
    ISSN: 1612-1112
    Keywords: Capillary GC ; Peak deformation ; Solvent trapping
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In capillary GC the analysis of solutes eluted before the solvent is often precluded because of severe broadening and distortion of the peaks. This problem has three sources: a) most solutes are partially solvent trapped; b) phase soaking broadens peaks eluted shortly before the solvent and c) slow sample transfer from the injector to the column in splitless injection creates broad initial bands which cannot be re-concentrated to narrow bands. The most important (and troublesome) broadening effect is partial solvent trapping. Full solvent trapping of solutes eluted before the solvent only occurs under special conditions. Most solutes are either partially trapped or non-trapped. Partial solvent trapping is mostly of the weak type, broadening the solute bands less than that due to the evaporation time of the solvent at the column inlet. Deformation of peaks eluted before the solvent by solvent trapping can only be avoided by the selection of conditions which create non-trapping. Rapid introduction of the sample into the column is required, which calls for split or on-column injection.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 18 (1984), S. 197-201 
    ISSN: 1612-1112
    Keywords: Capillary GC ; Co-injection ; Solvent effects
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Co-injection techniques (introducing additional pure solvent with the sample) were tested to eliminate peak distortion due to partial solvent trapping. Co-injections of solvent identical with the sample solvent were not successful, because first only partial solvent trapping of the strong type could be eliminated and second, there was no practicable method of placing a band of pure solvent ahead of the sample in the column inlet. Successful co-injections have to accept mixing of the sample with the pure solvent. Either the solvent trapping is improved by co-injection of a solvent which enhances solution of the critical solutes in the sample layer, or it creates a phase soaking effect in the stationary phase and reconcentrates broadened bands beyond the flooded inlet. The added solvent must have the appropriate polarity and some of it must remain in the column inlet at least until the sample solvent has completely evaporated.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 7 (1984), S. 319-326 
    ISSN: 0935-6304
    Keywords: Capillary GC ; Band broadening in space ; Flooded column inlet ; Retention gap ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In on-column or in splitless injection with recondensation of the solvent, the length of the flooded zone in the column inlet depends primarily on the wettability of the internal wall of the inlet. For columns with a coated inlet this explains why peak distortion due to band broadening in space by a certain sample volume is pronounced in one case and hardly observable in another. Glass or fused silica capillaries silylated with diphenyltetramethyldisilazane were found to give optimal retention gaps. They combine thorough and thermostable deactivation with good wettability and low retention power. On the other hand it is very easy to deactivate fused silica capillaries with Carbowax. The resulting retention gaps are suitable for a wide range of applications and are particularly attractive for the analysis of dirty samples which require frequent replacement of the inlet.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 4
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 5 (1982), S. 13-18 
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 518-523 
    ISSN: 0935-6304
    Keywords: Coupled HPLC-GC ; Concurrent solvent evaporation ; Loop-type interface ; Raspberry ketone ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Presently, two coupling techniques are used for directly introducing HPLC fractions into capillary GC: The retention gap technique (involving negligible or partially concurrent solvent evaporation) and fully concurrent solvent evaporation. While the former involves use of a conventional on-column injector, it is now proposed that concurrent solvent evaporation technique be carried out using a switching valve with a built-in sample loop. The technique is based on the concept that the carrier gas pushes the HPLC eluent into the GC capillary against its own vapor pressure, generated by a column temperature slightly exceeding the solvent boiling point at the carrier gas inlet pressure. Further improvement of the technique is achieved by flow regulation of the carrier gas (accelerated solvent evaporation) and backflushing of the sample valve (improved solvent peak shape).Concurrent solvent evaporation using the loop-type interface is easy to handle, allows transfer of very large volumes of HPLC eluent (exceeding 1 ml), and renders solvent evaporation very efficient, allowing discharge of the vapors of 1 ml of solvent through the column within 5-10 min.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 405-407 
    ISSN: 0935-6304
    Keywords: Capillary GC ; Solvent effects ; Solvent trapping ; Phase soaking ; Large sample volumes ; 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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 7
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 4 (1981), S. 491-494 
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 8
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 9 (1986), S. 593-594 
    ISSN: 0935-6304
    Keywords: Capillary GC ; HPLC ; Adulteration of cold pressed olive oil ; 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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 10 (1987), S. 416-417 
    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
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...