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See detailOptimization of the separation of beta-blockers by ion-pair capillary electrophoresis in non-aqueous media using univariate and multivariate approaches
Servais, Anne-Catherine ULg; Fillet, Marianne ULg; Chiap, Patrice ULg et al

in Journal of Separation Science (2002), 25(15-17), 1087-1095

The separation of four beta-blocking drug substances (atenolol, sotalol, betaxolol, and metoprolol) selected as model basic analytes has been investigated in non-aqueous capillary electrophoresis (NACE ... [more ▼]

The separation of four beta-blocking drug substances (atenolol, sotalol, betaxolol, and metoprolol) selected as model basic analytes has been investigated in non-aqueous capillary electrophoresis (NACE) using the principle of ion-pair formation. Camphorsulphonate was selected as the counter-ion in a background electrolyte (BGE) made up of formate buffer in a mixture of acetonitrile/methanol or acetonitrile/ethanol. The influence on resolution of the concentration of the counter-ion, the nature and proportion of the organic solvents, as well as the concentration of the ionic components of the BGE was first studied by a univariate approach. An experimental design was then applied to estimate possible quadratic effects and first-order interactions. To identify the most important factors affecting the separation of the four beta-blockers, a two-level fractional factorial design with 16 experimental points was applied as a screening test. A three factor Box-Behnken design with 12 experimental points was used to predict and optimize the selectivity. Finally the optimal conditions obtained by the univariate and the multivariate, approaches were compared. [less ▲]

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See detailPrediction of selectivity for enantiomeric separations of uncharged compounds by capillary electrophoresis involving dual cyclodextrin systems
Abushoffa, Adel M.; Fillet, Marianne ULg; Hubert, Philippe ULg et al

in Journal of Chromatography. A (2002), 948(1-2), 321-9

The single-isomer polyanionic cyclodextrin (CD) derivative heptakis-6-sulfato-beta-cyclodextrin (HSbetaCD) has been tested as chiral additive for the enantioseparation of non-steroidal anti-inflammatory ... [more ▼]

The single-isomer polyanionic cyclodextrin (CD) derivative heptakis-6-sulfato-beta-cyclodextrin (HSbetaCD) has been tested as chiral additive for the enantioseparation of non-steroidal anti-inflammatory drugs, such as fenoprofen, flurbiprofen, ibuprofen and ketoprofen, in capillary electrophoresis, using a pH 2.5 phosphoric acid-triethanolamine buffer in the reversed polarity mode. In most cases, the enantiomers of these acidic compounds, present in uncharged form at that pH, were only poorly resolved with HSbetaCD alone. However, the use of HSbetaCD in combination with the neutral CD derivative, heptakis-(2,3,6-tri-O-methyl)-beta-cyclodextrin (TMbetaCD), which has a particularly high enantioselectivity towards these compounds, has led to complete enantioresolution in reasonably low migration times in most cases. Affinity constants for the enantiomers with the two cyclodextrins were determined, using linear regression in a two-step approach. Affinity constants with the charged HSbetaCD were first calculated in single systems while those with the neutral TMbetaCD were determined in dual systems. Selectivity for the enantiomeric separation of these compounds in dual CD systems could be predicted using recently developed mathematical models. [less ▲]

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See detailSeparation, identification and quantitation of ceramides in human cancer cells by liquid chromatography–electrospray ionization tandem mass spectrometry
Fillet, Marianne ULg; Van Heugen, Jean-Claude ULg; Servais, Anne-Catherine ULg et al

in Journal of Chromatography. A (2002), 949

Ceramides are important intracellular second messengers that play a role in the regulation of cell growth, differentiation and programmed cell death. Qualitative and quantitative analysis of these second ... [more ▼]

Ceramides are important intracellular second messengers that play a role in the regulation of cell growth, differentiation and programmed cell death. Qualitative and quantitative analysis of these second messengers requires sensitive and specific analytical methods to detect endogenous levels of individual ceramide species and to differentiate between them. Nine synthetic ceramides were separated by liquid chromatography coupled to tandem mass spectrometry on a C bonded silica 18 column. The lipids were eluted in gradient elution mode using a mixture of water, acetonitrile and 2-propanol as mobile phase. They were detected by reaction monitoring performed on positive ion electrospray generated ions. Collision-induced fragmentations conducted on ceramides produced a well characteristic product ion at m/z 264, making multiple reaction monitoring (MRM) well suited for various ceramides quantitative measurements. After optimization of the extraction step, the proposed methodology was able to identify and quantify different ceramide species issued from human cancer cells. The method could be validated for C , C and C ceramides, quantified at the nanogram level. The validation exhibits good 16 18 20 results with respect to linearity, accuracy and precision. [less ▲]

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See detailEnantiomeric Separations of Drugs Using Mixtures of Charged and Neutral Cyclodextrins
Fillet, Marianne ULg; Hubert, Philippe ULg; Crommen, Jacques ULg

in Journal of Chromatography. A (2000), 875(1-2), 123-34

An overview on the use of mixtures of neutral and charged cyclodextrins as chiral additives for the enantioseparation of drugs by capillary electrophoresis is presented. These so called dual cyclodextrin ... [more ▼]

An overview on the use of mixtures of neutral and charged cyclodextrins as chiral additives for the enantioseparation of drugs by capillary electrophoresis is presented. These so called dual cyclodextrin systems can often provide unique selectivities. A brief theoretical background illustrating the influence of the chiral discrimination ability and the effective mobility of the two cyclodextrins on the overall selectivity of the enantiomeric separation is given. Typical examples of applications in the pharmaceutical field, based on the simultaneous use of a charged (cationic or anionic) and neutral cyclodextrins, are described. [less ▲]

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