Enantiomer separations by preparative gas chromatography : theory and practice /
Gas chromatography was investigated as a preparative method
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| Format: | Thesis Book |
| Language: | English |
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[Place of publication not identified] :
[publisher not identified] ;
1995.
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| Subjects: | |
| Online Access: | Link to OAKTrust copy http://proxy.library.tamu.edu/login?url=http://proquest.umi.com/pqdweb?did=742745621&sid=1&Fmt=2&clientId=2945&RQT=309&VName=PQD |
| Summary: | Gas chromatography was investigated as a preparative method for the production of pure volatile enantiomers. Two classes of enantiomeric compounds were studied: fluoroether anesthetics, represented by enflurane and isoflurane, were separated using trifluoroacetyl pentyl y-cyclodextrin as stationary phase, and the chiral synthon methyl 2- chloropropionate was separated using trichloroacetyl pentyl @-cyclodextrin as stationary phase. These separations required a custom-designed preparative gas chromatograph. The instrument developed allowed independent temperature control of the injector, the preparative column, the detector, as well as the interface to the analytical column, the analytical column, and another detector. The support type and particle size, the stationary phase concentration and the separation conditions were varied to improve product purity and the production rate in overloaded elution mode separations. The calculation of purity, recovery and production rates for the separations was accomplished by periodically sampling the effluent of the preparative column followed by on-line enantiomeric analysis of the eluting enantiomer bands. Aggressive yet safe fraction pooling schemes result from this near real-time procedure. The gas- liquid partition isotherms of the enantiomers of methyl 2 chloropropionate on the trichloroacetyl pentyl @-cyclodextrin stationary phase were determined using the elution by characteristic points method. The isotherms were described using the single component and competitive biLangmuir isotherm equations. The measured and calculated isotherms as well as the retention factor and separation selectivity data agreed, indicating that the isotherms might be suitable for the modeling of the preparative-scale gas chromatographic separation of the enantiomers. The equilibrium-dispersive model of nonlinear chromatography was used to simulate the band profiles of both the single-component as well as competitive separations of methyl 2-chloropropionate on the trichloroacetyl pentyl @-cyclodextrin stationary phase. The model uses a mass balance equation for each analyte and for the mobile phase, and is completed by the calculated partition isotherm and the integrated Darcy equation for the column pressure profile. The measured and simulated band profiles are compared, and the behavior of both systems discussed. |
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| Item Description: | Vita. "Major Subject: Chemistry". |
| Physical Description: | xiii, 128 leaves : illustrations ; 28 cm. Issued also on microfiche from University Microfilms Inc. |
| Bibliography: | Includes bibliographical references. |