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See detailAnalysis of mainstream tobacco smoke particulate phase using comprehensive two-dimensional gas chromatography time-of-flight mass spectrometry
Brokl, Michal ULg; Bishop, L; Wright, C et al

in Journal of Separation Science (2013), 31

In tobacco research, the comparison of different tobacco blends as well as the puffdependent <br />behaviour of cigarettes is a matter of particular interest. For the investigation <br />of smoke ... [more ▼]

In tobacco research, the comparison of different tobacco blends as well as the puffdependent <br />behaviour of cigarettes is a matter of particular interest. For the investigation <br />of smoke characteristics, GC6GC offers different ways for data analysis, <br />namely, compound target analysis, automated peak-based compound classification <br />and comprehensive pixel-based data analysis. This study will show the application <br />as well as the pros and cons of these types of data analysis for very complex matrices <br />like cigarette particulate matter. In addition, new aspects about the recently discovered <br />puff-dependent behaviour of compounds in cigarette smoke will be presented. <br />Automated peak-based compound classification including mass spectrometric pattern <br />recognition is used for the classification of tobacco particulate matter samples <br />and the puff-dependent investigation of different compound classes. This compound <br />group specific analysis is further reinforced by applying an even more comprehensive <br />pixel-based analysis. This kind of analysis is used to generate fingerprints of <br />different types of cigarettes. The combination of fast feature reduction methods like <br />analysis of variance (ANOVA) and t-test with multivariate feature transformation <br />methods like partial least squares discriminate analysis (PLSDA) for feature selection <br />provides a powerful tool for a detailed inspection of different types of cigarettes. [less ▲]

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See detailFast microwave assisted extraction of rotenone for its quantification in seeds of yam bean (Pachyrhizus sp.)
Lautié, E.; Rasse, C.; Rozet, Eric ULg et al

in Journal of Separation Science (2013), 36

The aim of this study was to find if fast microwave assisted extraction could be an alternative to the conventional soxhlet extraction for the quantification of rotenone in yam bean seeds by solid phase ... [more ▼]

The aim of this study was to find if fast microwave assisted extraction could be an alternative to the conventional soxhlet extraction for the quantification of rotenone in yam bean seeds by solid phase extraction and HPLC-UV. For this purpose, an experimental design was used to determine the optimal conditions of the microwave extraction. Then the values of the quantification on three accessions from two different species of yam bean seeds were compared using the two different kinds of extraction. A microwave extraction of 11 min at 55°C using methanol/dichloromethane (50:50) allowed rotenone extraction either equivalently or more efficiently than the 8h soxhlet extraction method and was less sensitive to moisture content. The selectivity, precision, trueness, accuracy and limit of quantification of themethod with microwave extraction were also demonstrated. [less ▲]

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See detailMicellar electrokinetic chromatography systems for the separation of mixtures of charged and uncharged compounds
Lamalle, Caroline ULg

in Journal of Separation Science (2012)

In this study, the migration behavior of charged and uncharged analytes was investigated under different conditions. Effective mobilities - electrophoretic mobilities under the influence of micelles - of ... [more ▼]

In this study, the migration behavior of charged and uncharged analytes was investigated under different conditions. Effective mobilities - electrophoretic mobilities under the influence of micelles - of cations, anions, and neutrals were measured at neutral, basic, and acidic pH (7.5, 11, and 2.2) using background electrolytes containing different sodium dodecyl sulfate (SDS) concentrations (0-90 mM) and acetonitrile (ACN) proportions (0-75%). SDS concentration and ACN proportion were found to have a tremendous effect on the effective mobilities and migration order of the model compounds. Although the SDS micelles preferably interact with neutrals and cations, hydrophobic bonds can also occur with anions. Cations, anions, and neutrals having rather different migration behaviors, it is possible to considerably enhance the selectivity of the method by adjusting properly the SDS concentration and the ACN proportion. These observations confirm the interest of using micellar electrokinetic chromatography not only for the separation of neutral substances but also to analyze charged compounds. [less ▲]

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See detailOptimization of micro-HPLC peak focusing for the detection and quantification of low hepcidin concentrations.
Mansion, François ULg; Chiap, Patrice ULg; Houbart, Virginie ULg et al

in Journal of Separation Science (2011), 34(15), 1820-1827

Micro-high-performance liquid chromatography is a miniaturized, economic and ecological chromatographic system allowing the use of reduced size chromatographic columns. Coupled with electrospray ... [more ▼]

Micro-high-performance liquid chromatography is a miniaturized, economic and ecological chromatographic system allowing the use of reduced size chromatographic columns. Coupled with electrospray ionization tandem mass spectrometry, this technique can be used to detect and quantify low concentrations of peptides. In this study, hepcidin was used as the model compound and analysed using octadecylsilica stationary phase by means of a gradient elution mode at a flow rate of 4 muL/min. Several parameters were studied to optimize peak focusing. Using the methodology of experimental design, the mobile-phase gradient conditions and the sample composition were optimized in order to maximize the sensitivity and minimize retention time. Stability of the target peptide in solution was also demonstrated. [less ▲]

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See detailDetermination of enantiomeric purity of S-amlodipine by chiral LC with emphasis on reversal of enantiomer elution order.
Dossou, Katina ULg; Edorh, P. A.; Chiap, Patrice ULg et al

in Journal of Separation Science (2011), 34

An LC method was developed and prevalidated for the enantiomeric purity determination of S-amlodipine in polar organic solvent chromatography using a chlorine-containing cellulose-based chiral stationary ... [more ▼]

An LC method was developed and prevalidated for the enantiomeric purity determination of S-amlodipine in polar organic solvent chromatography using a chlorine-containing cellulose-based chiral stationary phase (CSP). The concentration of formic acid (FA) (0.01-0.2%) in the mobile phase containing acetonitrile as the main solvent was found to influence the elution order of amlodipine enantiomers as well as the enantioresolution. A reversal of the enantiomer elution order of amlodipine was only observed with chiral stationary phases with both electron-withdrawing (chloro) and electron-donating groups (methyl) on the phenyl moieties of the chiral selector, namely cellulose tris(3-chloro-4-methylphenylcarbamate) and cellulose tris(4-chloro-3-methylphenylcarbamate). The highest enantioresolution (R(s) : 4.1) value was obtained at the lowest FA concentration (0.01%) using cellulose tris(4-chloro-3-methylphenylcarbamate) as the chiral selector and the enantiomeric impurity, R-amlodipine, eluted first under these conditions. Therefore, the mobile phase selected for the prevalidation of the method consisted of ACN/0.1% DEA/0.01% FA and the temperature was set at 25 degrees C. The method was prevalidated by means of the strategy based on the total measurement error and the accuracy profile. The method was found to be selective and the limit of quantification was found to be about 0.05% for R-amlodipine, while the limit of detection was close to 0.02%. [less ▲]

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See detailEvaluation of chlorine containing cellulose-based chiral stationary phases for the LC enantioseparation of basic pharmaceuticals using polar non-aqueous mobile phases.
Dossou, Katina S. S.; CHIAP, Patrice ULg; Servais, Anne-Catherine ULg et al

in Journal of Separation Science (2011), 34(6), 617-22

The discrimination ability of three cellulose-based chiral stationary phases (CSPs) was evaluated towards the enantiomers of basic drugs, using ACN as the main solvent in polar organic mobile phases. The ... [more ▼]

The discrimination ability of three cellulose-based chiral stationary phases (CSPs) was evaluated towards the enantiomers of basic drugs, using ACN as the main solvent in polar organic mobile phases. The study was focused on CSPs containing cellulose tris(3-chloro-4-methylphenylcarbamate) (3-Cl-4-MePC), cellulose tris(4-chloro-3-methylphenylcarbamate) (4-Cl-3-MePC) or cellulose tris(3,5-dichlorophenylcarbamate) (3,5-diClPC) as the chiral selector. The behaviour of these CSPs was studied systematically in order to investigate the influence of the presence and position of the chlorine substituents on the phenylcarbamate moieties on the retention and resolution of the enantiomers. The evaluation was made with three different generic mobile phases, namely ACN/0.1%DEA/0.1% TFA (DEA, diethylamine), ACN/0.1%DEA/0.2% FA and ACN/0.1%DEA/0.2%AcA, deduced from the previous study. The nature of the acidic additive and of the chiral selector was found to be particularly important for the retention and enantioresolution of these basic compounds. High-resolution values could be obtained for most studied enantiomers with these CSPs, clearly demonstrating the interest of using them in combination with polar organic mobile phases. However, significant differences in enantioresolution between the CSPs have been observed for many compounds, indicating that these phases seem to be quite complementary. [less ▲]

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See detailCapillary electrophoretic and nuclear magnetic resonance studies on the opposite affinity pattern of propranolol enantiomers towards various cyclodextrins
Servais, Anne-Catherine ULg; Rousseau, Anne ULg; Fillet, Marianne ULg et al

in Journal of Separation Science (2010), 33

In the present study the migration order of the propranolol enantiomers with various native CDs and neutral and charged CD derivatives was examined in capillary electrophoresis (CE). The reversal of the ... [more ▼]

In the present study the migration order of the propranolol enantiomers with various native CDs and neutral and charged CD derivatives was examined in capillary electrophoresis (CE). The reversal of the enantiomer migration order was observed due to sulfation of β-CD on its primary hydroxy groups. The structures of intermolecular selector-selectand temporary diastereomeric associates in solution were elucidated based on 1D rotating frame nuclear Overhauser effect spectroscopy (1D ROESY) experiments. Major structural differences were observed between the propranolol complexes with native β-CD and heptakis(6-O-sulfo)-β-CD. [less ▲]

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See detailOptimization of the LC enantioseparation of chiral pharmaceuticals using cellulose tris(4-chloro-3-methylphenylcarbamate) as chiral selector and polar non-aqueous mobile phases
Dossou, Katina Sourou Sylvestre ULg; Chiap, Patrice ULg; Chankvetadze, Bezhan et al

in Journal of Separation Science (2010), 33

The resolving power of a new commercial polysaccharide-based chiral stationary phase, Sepapak-4, with cellulose tris(4-chloro-3-methylphenylcarbamate) coated on silica microparticles as chiral selector ... [more ▼]

The resolving power of a new commercial polysaccharide-based chiral stationary phase, Sepapak-4, with cellulose tris(4-chloro-3-methylphenylcarbamate) coated on silica microparticles as chiral selector, was evaluated toward the enantioseparation of ten basic drugs with widely different structures and hydrophobic properties, using ACN as the main component of the mobile phase. A multivariate approach (experimental design) was used to screen the factors (temperature, n-hexane content, acidic and basic additives) likely to influence enantioresolution. Then, the optimization was performed using a face-centered central composite design. Complete enantioseparation could be obtained for almost all tested chiral compounds, demonstrating the high chiral discrimination ability of this chiral stationary phase using polar organic mobile phases made up of ACN and containing an acidic additive (TFA or formic acid), 0.1% diethylamine and n-hexane. These results clearly illustrate the key role of the nature of the acidic additive in the mobile phase. [less ▲]

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See detailMicroanalytical systems for separations of stratum corneum ceramides
Quinton, Loïc ULg; Gaudin, Karen; Baillet, Arlette et al

in Journal of Separation Science (2006), 29(3), 390-398

The small amount of lipids from human skin obtained with noninvasive sampling method led us to investigate microanalytical separation techniques. The lipid class analysis was performed with a micro ... [more ▼]

The small amount of lipids from human skin obtained with noninvasive sampling method led us to investigate microanalytical separation techniques. The lipid class analysis was performed with a micro polyvinyl alcohol-silica (PVA-Silm) column. The gradient elution was from heptane to acetone/butanol 90:10 v/v in 4%/min at 78 lL/ min. In addition an evaporative light scattering detector (ELSD) was modified for micro-LC. All solvents contained 0.1% of triethylamine and formic acid in stoichiometric amount, which increased the ELSD response. In these conditions, the cholesterol eluted before free fatty acid, and squalene and triglycerides close to the dead volume. The various ceramide classes eluted following the order of the increased number of hydroxyl groups. The LOD for ceramides was 2.2 ng. The advantages of this method are the use of a normal stationary phase more reliable due to its chemical stability, its surface homogeneity and its development in microchromatography without chlorinated solvents which offers small LOD and the whole profile of lipids present in stratum corneum (SC). A method using a narrow-bore PVA-Sil column was used to collect ceramide fraction. Then the molecular species were analysed with a porous graphitic carbon column in capillary LC using a gradient from CH3OH/CHCl3 70:30 v/v to CHCl3 at 2%/min with a flow rate at 5 lL/min. The LOD obtained for ceramide was 1 ng. Both methods were assessed with SC samples obtained by rinsing a 5.7 cm2 area of the forearm with 25 mL of ethanol. [less ▲]

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See detailLC method for the simultaneous determination of R-timolol and other closely related impurities in S-timolol maleate: Optimization by use of an experimental design
Marini Djang'Eing'A, Roland ULg; Chiap, Patrice ULg; Boulanger, Bruno ULg et al

in Journal of Separation Science (2003), 26(9-10), 809-817

A liquid chromatography (LC) method using cellulose tris(3,5-dimethylphenylcarbamate) (5 mum) as chiral stationary phase (CSP) and a mixture of hexane, 2-propanol, and diethylamine as mobile phase was ... [more ▼]

A liquid chromatography (LC) method using cellulose tris(3,5-dimethylphenylcarbamate) (5 mum) as chiral stationary phase (CSP) and a mixture of hexane, 2-propanol, and diethylamine as mobile phase was developed for the simultaneous determination of R-timolol and other potential related substances in S-timolol maleate samples. An experimental design was elaborated in order to test the effects of the different selected factors. Three factors were studied simultaneously, namely the concentrations of 2-propanol and diethylamine as well as the column temperature. The effects of these factors were evaluated statistically. Optimal LC conditions were then deduced by applying a multicriteria decision making approach, namely Derringer's desirability function, for the responses of interest. The developed LC method was compared to the European Pharmacopoeia method and was applied to the determination of R-timolol and other related substances in several samples of S-timolol maleate from different sources. [less ▲]

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See detailEnantiomeric separation of aminoglutethimide by capillary electrophoresis using native cyclodextrins in single and dual systems
Abushoffa, A. M.; Fillet, Marianne ULg; Marini Djang'Eing'A, Roland ULg et al

in Journal of Separation Science (2003), 26(6-7), 536-542

Aminoglutethimide (AGT) is one of the few examples of chiral drugs that can be enantioseparated by capillary electrophoresis using any of the three native cyclodextrins: alpha-, beta-, or gamma-CD. A ... [more ▼]

Aminoglutethimide (AGT) is one of the few examples of chiral drugs that can be enantioseparated by capillary electrophoresis using any of the three native cyclodextrins: alpha-, beta-, or gamma-CD. A complete resolution of the enantiomers of this compound in cationic form could be achieved with each of the three CDs, using a pH 3 phosphoric acid-triethanolamine buffer. Affinity constants for AGT enantiomers with the three native CDs were determined, confirming that the highest selectivity was given by gamma-CD while the strongest complexation was obtained with beta-CD. However, an opposite affinity pattern was observed with the latter. Selectivity was lower for AGT enantiomers in dual CD systems, compared to that obtained with a single selector at its optimal concentration, which confirms that dual systems are of more limited interest when the two selectors have a similar effect on the analyte mobility. These results are in good agreement with those predicted using recently developed mathematical models. [less ▲]

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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 detailComparative study on the enantioseparation of glutethimide using dual cyclodextrin systems and cyclodextrin modified MEKC in capillary electrophoresis
Abushoffa, Adel M.; Burjanadze, Naira; Blaschke, Gottfried et al

in Journal of Separation Science (2002), 25(1-2), 10-16

In order to critically evaluate the potential of dual cyclodextrin (CD) systems in CE, enantioseparation of the neutral chiral analyte glutethimide (GT) was performed using: a) charged CDs; b ... [more ▼]

In order to critically evaluate the potential of dual cyclodextrin (CD) systems in CE, enantioseparation of the neutral chiral analyte glutethimide (GT) was performed using: a) charged CDs; b) combinations of charged and neutral CDs (dual CD systems), and c) CD-modified micellar electrokinetic chromatography (CD-MECK). The results of this comparative study indicate that properly designed dual CD systems may in certain cases represent a valuable alternative to CD-MEKC and electrokinetic chromatography involving charged CDs for enantioseparation of neutral analytes. [less ▲]

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