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  • Central composite designs  (1)
  • Enantiomer and rotamer resolution  (1)
  • 1995-1999  (2)
  • 1
    ISSN: 1612-1112
    Keywords: Capillary electrophoresis ; Surface modified capillaries ; Derivatized cyclodextrins ; Peak shape optimisation ; Enantiomer and rotamer resolution ; Remoxipride and local anaesthetic drugs
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Dynamic coating of bonded C8 fused silica capillaries with cationic amphiphiles is shown to minimize adsorption of basic drug molecules but also to facilitate control/reversal of electroosmotic flow. Optimization of the peak shapes was achieved by addition of cationic amphiphiles with a suitable mobility and adsorption to the capillary surface. The surface modification described, combined with the addition of cyclodextrins as selectors into the background electrolyte, resulted in unique CE systems showing excellent resolution for structural analogues. The separation of rotamers and enantiomers is demonstrated. Applications to the antipsychotic compound remoxipride and its related substances and to the chiral separation of asthma- and local anaesthetic drug enantiomers are given.
    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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