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  • 1
    Electronic Resource
    Electronic Resource
    Determination of heats of vaporization and gibbs free energies of alkylbenzenes on GC stationary phases of different polarity (1998)
    Springer
    Chromatographia 48 (1998), S. 89-94 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography ; Heats of vaporization ; Gibbs free energies ; Kováts retention indices ; Alkylbenzenes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary In our paper we propose a new method for the determination of heats of vaporization (ΔH vap(i)) and the Gibbs free energies of vaporization (Δμp(i)) for individually selected alkylbenzenes, chromatographed on stationary phases of low and medium polarity. The method is based on a new thermodynamic description of the Kováts retention index (I (i)) making use of Trouton's rule. In fact, we attribute physical significance to two empirical relationships, well known from the literature. We can describe thermodynamically the magnitude ofI (i) using two relations, each of them potentially useful for further determination of δH vap(i) and Δμp(i). A comparison was made of the results obtained with the use of our new approach and of those already existing in the literature attained in a completely different way. The comparison suggests that the calculated δH vap(i) and Δμp(i) values are thermodynamically acceptable and hence correct, and the data suit into the series of similar values determined on stationary phases of different polarity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02467523
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Quantitative Analysis of aliphatic aldehydes by headspace SPME sampling and ion-trap GC-MS (1998)
    Springer
    Chromatographia 48 (1998), S. 127-132 
    Details
    ISSN: 1612-1112
    Keywords: Gas chromatography-mass spectrometry ; Solid-phase microextraction ; Headspace analysis ; Unsaturated aldehydes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A fast and simple headspace SPME sampling method has been developed for quantification of volatile aliphatic aldehydes in sunflower oil. Analysis has been performed by gas chromatography, on a 30m×0.25 mm i.d. ×0.25 μm CP-Wax 52CB column, with mass spectrometric detection. Carryover from the SPME fiber could be eliminated by heating the fiber in the injection port between runs. Response factors of all the compounds were linear for concentrations up to 100 ng μL−1. The slopes of the calibration curves decrease with the amount of saturation of the aldehydes. The average responses for unsaturated aldehydes were twice as high as those for the saturated variety. Responses for dienes were approximately one order of magnitude higher than for saturated aldehydes. Depletion of the analyte was examined by repeated extraction from the same vial. SPME was optimized—after 30 min extraction most components were found to have reached equilibration. The detection limit for the compounds studied varied between 0.1 and 1 ng μL−1. Distribution constants were determined for ten different aldehydes and Henry's constants were calculated for unsaturated aldehydes. There was a definite relationship between the response factors and the amount of saturation of the aldehydes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02467528
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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