Browsing by Author "Leisegang, E C"

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    The application of gas-liquid chromatography to the structural investigation of Polysaccharides
    (1965) Kaplan, Morris; Stephen, A M; Leisegang, E C
    This work constitutes the first reported analysis of carbohydrate derivatives by gas-liquid chromatography, using the hydrogen-flame ionization detector. The conditions used compared favourably with conditions reported by other workers and were well suited to the quantitative analysis of methanolysis products from methylated polysaccharides. Excellent separations were achieved, and at the same time a wide range of sugars could be estimated quantitatively using a single column. The detector response was shown to be linearly related to sample size. Authenticated standards were converted to their methyl glycosides by heating with methanolic hydrogen chloride, and their relative molar responses (R ' values) to the hydrogen-flame ionization detector were determined. R values were also obtained by calculations based on recent theories accounting for the observed ionization of organic compounds in the hydrogen flame, but the calculated values were not in agreement with the R values found experimentally. The experimental results obtained suggest that, under the conditions used, the response of the sugar is related to its retention time but not to the mechanism of ionization of the sugar molecule in the flame. From the observed relationship between R values and relative retention times, relative molar responses were predicted for those sugars which were not available as standards. The possible sources of error in quantitative analysis have been discussed. Errors resulting from degradation during the methylation procedures and incomplete methylation of the polysaccharides, and from the demethylation and degradation of methylated sugars during methanolysis, were found to be greater than experimental errors arising from small variations in operating conditions and the measurement of peak areas. Using the R values already determined, the methanolysis products from twelve methylated polysaccharides were separated quantitatively by gas chromatography. The structural significance of the results obtained were discussed and possible model structures for ten of the polysaccharides investigated were presented. As far as possible, the structural models were based on the findings of previous investigations, and in those cases where published data were available, gas chromatography results were in good agreement with the published results. The hydrogen-flame ionization detector was found to be ideally suited to the analysis of methylated sugars. The greater resolving power, sensitivity of detection and, in particular, the speed with which quantitative analyses can be performed, are the major advantages which make gas-liquid chromatography superior to other techniques in this area of polysaccharide chemistry.
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    Factors affecting the separation of organic compounds by gas liquid chromatography
    (1965) Hagens, Rodger Graham Robertson; Leisegang, E C; Stephen, A M
    The objects of this thesis have been threefold. In the first place it has been an investigation of the factors which influence retention time in an attempt to predict the retentions of new compounds. Secondly it has been an investigation into the conditions for the best separation of diastereoisomers, and thirdly it has been an application of gas chromatography in the study of the forces of intermolecular interaction in solution. To carry out these investigations, the retention times of twenty five monofunctional and bifunctional compounds have been determined on four stationary liquids at 130°C. It was found that by dividing the retention time of a solute by that of a hypothetical normal hydrocarbon of the same molar volume of the solute, a functional group constant was obtained. By means of this constant, termed the Group Retention Factor, it was found that it is possible to predict the retention of bifunctional compounds. The separation of diastereoisomeric pairs is discussed in terms of the Group Retention Factors of the functional groups on the diastereomers. The molar volume is also utilized in order to develop an equation by means of which the ratio of retention times on two solvents can be related to the forces of interaction between solute and solvent.
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    Infra-red studies of carbon monoxide and hydrogen absorbed on silica supported metal catalysts
    (1976) Heal, Martin James; Leisegang, E C; Torrington, R G
    The interaction of carbon monoxide and hydrogen on silica supported nickel, cobalt, and iron catalysts was studied using infrared spectroscopy. The products occurring in the gas phase, as well as spectra of adsorbed CO surface species in the frequency range 2300 - 1700 cm−¹ for different order of addition of the two reactants was examined. Bulk powdered samples and conventional thin transparent sample discs were used to study either the products in the gas phase or the adsorbed CO species respectively.
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    Infra-red studies of carbon monoxide chemisorbed on iron triad elements
    (1970) Ferreira, Leonardus Cornelius; Leisegang, E C
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    An investigation of cation-exchange in aqueous pyridine
    (1968) Ilsley, Bruce Meredith; Leisegang, E C; Arnold, R
    This thesis presents a comparative investigation of the ion-exchange behaviour of a typical carboxylic acid resin, Amberlite IRC 50, and a typical sulphonic acid resin Zeo-Karb 225, in aqueous and aqueous pyridine solutions of the alkaline earth metal cations. The ion-exchange phenomena investigated included: swelling, preferential sorption of solvent and selectivity variations with loading, degree of neutralization of the resin, solvent composition and choice of solution phase anion. The chromatographic separation of the alkaline earth metals using aqueous pyridine eluants was also investigated.
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    The determination of trace metals in sea water
    (1965) Orren, Michael John; Leisegang, E C
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    The ion-exchange behaviour of niobate and tantalate in alkaline solution
    (1967) Smith, Francis White; Leisegang, E C