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  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Chromatographia 42 (1996), S. 263-268 
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Local anaesthetics ; Enantiomer separation ; Triethanolamine ; Dimethyl-β-cyclodextrin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A chiral capillary electrophoresis system for the highresolution separation of the enantiomers of the local anaesthetics mepivacaine, ropivacaine, bupivacaine and prilocaine is described. Triethanolamine was added to the background electrolyte to obtain a negative electroosmotic flow and hence higher resolutions. The interactions of the local anaesthetics and their chemical analogues with the chiral selector, dimethyl-β-cyclodextrin, were studied. From a model describing chiral capillary electrophoresis, the association equilibrium constants were determined by curve-fitting. The separation of mepivacaine, ropivacaine and bupivacaine was due to the different mobilities of the free analytes in solution, whereas the separation of a pair of enantiomers of a single analyte was due to differences between the association equilibrium constantsK 1 andK 2. Branching of the alkyl chain, which was situated close to the cavity in the inclusion complex, had strong effects on the chiral separation of the enantiomers.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1612-1112
    Keywords: Micellar electrokinetic capillary chromatography ; Enkephalin related peptides ; Response surface modelling ; Central composite designs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A simultaneous optimization of resolution, efficiency and migration times of enkephalin-related peptides in micellar electrokinetic capillary chromatography (MEKC) was performed. Six experimental variables; the surfactant concentration, the percentage of organic modifier, the ionic strength of the buffer, the injected plug length, the applied temperature and the sample solution composition were studied via central composite design (CCD). Large differences in separation performance were observed at a commonly used level of organic modifier in the background electrolyte. Partial least squares regression of the responses revealed that the experimental domain was too large and complicated to be explained by the model. A new CCD model was obtained with improved prediction ability at narrower ranges of the experimental factors, especially of the organic modifier. A conflict between maximum resolution and efficiency within the shortest analysis time was observed. Therefore, constraints were set on maximal resolution and analysis time, while solving for maximum efficiency. Optimal operating conditions were found at 35 mM sodium dodecyl sulfate (SDS), 5% v/v of acetonitrile, 1.9 mm injected plug length, 35°C and sample solution with no added micelles, giving high efficiency and resolution at short analysis time. The value predicted by the model was found to agree very well to the observed values, at the optimal experimental conditions, even on a new capillary.
    Type of Medium: Electronic Resource
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