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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 detailDevelopment and validation of a nonaqueous capillary electrophoretic method for the enantiomeric purity determination of a synthetic intermediate of new 3,4-dihydro-2,2-dimethyl-2H-1-benzopyrans using a single-isomer anionic cyclodextrin derivative and an ionic liquid
Rousseau, Anne ULg; Florence, Xavier ULg; Pirotte, Bernard ULg et al

in Journal of Chromatography. A (2010), 1217(51), 7949-55

The enantiomeric purity determination of a synthetic intermediate of new 3,4-dihydro-2,2-dimethyl-2H-1-benzopyrans, i.e. 4-amino-2,2-dimethyl-6-ethoxycarbonylamino-3,4-dihydro-2H-1-benzopyran, was ... [more ▼]

The enantiomeric purity determination of a synthetic intermediate of new 3,4-dihydro-2,2-dimethyl-2H-1-benzopyrans, i.e. 4-amino-2,2-dimethyl-6-ethoxycarbonylamino-3,4-dihydro-2H-1-benzopyran, was successfully carried out using an anionic cyclodextrin (CD) derivative combined with a chiral ionic liquid (IL). In order to obtain high resolution and efficiency values, the addition of a chiral IL, i.e. ethylcholine bis(trifluoromethylsulfonyl)imide (EtChol NTf2), to the background electrolyte containing heptakis(2,3-di-O-methyl-6-O-sulfo)-β-CD (HDMS-β-CD) was found to be essential. A simultaneous increase in separation selectivity and enantioresolution seems to indicate a synergistic effect of HDMS-β-CD and EtChol NTf2. The best enantioseparation of the key intermediate was achieved using a methanolic solution of 0.75 M formic acid, 10 mM ammonium formate, 1.5 mM HDMS-β-CD and 5 mM EtChol NTf2. Levamisole was selected as internal standard. The optimized conditions allowed the determination of 0.1 % of each enantiomer in the presence of its stereoisomer using the method of standard additions. The NACE method was then fully validated with respect to selectivity, response function, trueness, precision, accuracy, linearity and limits of detection and quantification. [less ▲]

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See detailInfluence of the BGE composition on analyte response in CD-mediated NACE-MS
Servais, Anne-Catherine ULg; Fillet, Marianne ULg; Mol, Roelof et al

in Electrophoresis (2010), 31(7), 1157-1161

The influence of the BGE composition, including the addition of a single-isomer sulfated beta-CD derivative, on the ionization performance of the model compound carvedilol in NACE-ESI-MS was studied using ... [more ▼]

The influence of the BGE composition, including the addition of a single-isomer sulfated beta-CD derivative, on the ionization performance of the model compound carvedilol in NACE-ESI-MS was studied using an alternative infusion method. This approach employs voltage-induced infusion of the BGE containing the analyte, and takes into account the effects of variations in EOF and effective analyte mobility on the ESI-MS intensity. First, the optimal composition of the sheath liquid for CE-MS in terms of signal abundance and stability was determined. The BGE ammonium formate, acetate, and camphorsulfonate were found to have similar effects on analyte ionization. Addition of single-isomer sulfated beta-CD derivatives (available as sodium salt) to the BGE revealed that the anionic CD derivatives did not give rise to the same ionization suppression effect. This result can be attributed to differences in the dissociation state of these sodium salts. Finally, it is shown that information about chiral selectivity can also be obtained with the applied infusion method. [less ▲]

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See detailSeparation of propranolol enantiomers by CE using sulfated beta-CD derivatives in aqueous and non-aqueous electrolytes: Comparative CE and NMR study.
Servais, Anne-Catherine ULg; Rousseau, Anne ULg; Fillet, Marianne ULg et al

in Electrophoresis (2010), 31

Separations using CE employing non-aqueous BGE are already as well established as separations in aqueous buffers. The separation mechanisms in achiral CE with non-aqueous BGEs are most likely similar to ... [more ▼]

Separations using CE employing non-aqueous BGE are already as well established as separations in aqueous buffers. The separation mechanisms in achiral CE with non-aqueous BGEs are most likely similar to those in aqueous buffers. However, for the separation of enantiomers involving their interaction with chiral buffer additives, the interaction mechanisms might be very different in aqueous and non-aqueous BGEs. While the hypothesis regarding distinct mechanisms of enantiomer separations in aqueous and non-aqueous BGEs has been mentioned in several papers, no direct proof of this hypothesis has been reported to date. In the present study, the enantiomers of propranolol were resolved using CE in aqueous and non-aqueous methanolic BGEs with two single isomer sulfated derivatives of beta-CD, namely heptakis (2,3-diacetyl-6-sulfo)-beta-CD and heptakis (2,3-dimethyl-6-sulfo)-beta-CD. The enantiomer migration order of propranolol was inverted when an aqueous BGE was replaced with non-aqueous BGE in the case of heptakis (2,3-dimethyl-6-sulfo)-beta-CD but remained the same in the case of heptakis (2,3-diacetyl-6-sulfo)-beta-CD. The possible molecular mechanisms leading to this reversal of enantiomer migration order were studied by using nuclear overhauser effect spectroscopy in both aqueous and non-aqueous BGEs. [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 detailFactors Influencing Cyclodextrin-Mediated Chiral Separations
Servais, Anne-Catherine ULg; Crommen, Jacques ULg; Fillet, Marianne ULg

in Chiral Separations by Capillary Electrophoresis (2010)

In this chapter, several factors likely to infl uence cyclodextrin (CD)-mediated enantioseparations, such as CD type and concentration, pH and ionic strength of the background electrolyte (BGE), addition ... [more ▼]

In this chapter, several factors likely to infl uence cyclodextrin (CD)-mediated enantioseparations, such as CD type and concentration, pH and ionic strength of the background electrolyte (BGE), addition of organic solvents, injection mode as well as temperature are discussed from a practical point of view and illustrated by examples. Finally, several types of dual systems including at least one CD are also presented. [less ▲]

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See detailAssociation of two single-isomer anionic CD in NACE for the chiral and achiral separation of fenbendazole, its sulphoxide and sulphone metabolites: Application to their determination after in vitro metabolism
Rousseau, Anne ULg; Gillotin, Florian; Chiap, Patrice ULg et al

in Electrophoresis (2010), 31

A NACE method was developed for the separation of fenbendazole (FBZ), a prochiral drug giving rise to chiral (oxfendazole or OFZ) and nonchiral (FBZ sulphone or FBZSO2) metabolites. First, the effect of ... [more ▼]

A NACE method was developed for the separation of fenbendazole (FBZ), a prochiral drug giving rise to chiral (oxfendazole or OFZ) and nonchiral (FBZ sulphone or FBZSO2) metabolites. First, the effect of the nature and the concentration of CD as well as that of the acidic BGE on the enantiomeric separation of OFZ were studied. OFZ enantiomers were completely resolved using a BGE made up of 10 mM ammonium formate and 0.5 M TFA in methanol containing 10 mM heptakis(2,3-di-O-acetyl-6-O-sulfo)-beta-CD and 10 mM heptakis(2,3-di-O-methyl-6-O-sulfo)-beta-CD. Moreover, the NACE method was found to be particularly well suited to the simultaneous determination of FBZ, OFZ enantiomers, and FBZSO2. Thiabendazole was selected as an internal standard. The CD-NACE potential was then evaluated for in vitro metabolism studies using FBZ as a model case. The OFZ enantiomers and FBZSO2 could be detected after incubation of FBZ in the phenobarbital-induced male rat liver microsomes systems. [less ▲]

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See detailComparison and combination of spectroscopic techniques for the detection of counterfeit medicines
Sacré, Pierre-Yves ULg; Deconinck, Eric; De Beer, Thomas et al

in Journal of Pharmaceutical & Biomedical Analysis (2010), 53

During this study, Fourier transform infrared spectroscopy (FT-IR), near infrared spectroscopy (NIR) and Raman spectroscopy were applied to 55 samples of counterfeit and imitations of Viagra® and 39 ... [more ▼]

During this study, Fourier transform infrared spectroscopy (FT-IR), near infrared spectroscopy (NIR) and Raman spectroscopy were applied to 55 samples of counterfeit and imitations of Viagra® and 39 samples of counterfeit and imitations of Cialis®. The aim of the study was to investigate which of these techniques and associations of them were the best for discriminating genuine from counterfeit and imitation samples. Only the regions between 1800-400 cm-1 and 7000-4000 cm-1 were used for FT-IR and NIR spectroscopy respectively. Partial Least Square analysis has been used to allow the detection of counterfeit and imitation tablets. It is shown that for the Viagra® samples, the best results were provided by a combination of FT-IR and NIR spectroscopy. On the other hand, the best results for the Cialis® samples were provided by the combination of NIR and Raman spectroscopy (1400-1190 cm-1). These techniques permitted a clear discrimination between genuine and counterfeit or imitation samples but also the distinction of clusters among illegal samples. This might be interesting for forensic investigations by authorities. [less ▲]

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See detailEnantioresolution of basic pharmaceuticals using cellulose tris(4-chloro-3-methylphenylcarbamate) as chiral stationary phase and polar organic mobile phases.
Dossou, Katina Sourou Sylvestre ULg; Chiap, Patrice ULg; Chankvetadze, Bezhan et al

in Journal of Chromatography. A (2009), 1216(44), 7450-5

A polysaccharide-based chiral stationary phase (Sepapak-4), with cellulose tris(4-chloro-3-methylphenylcarbamate) as chiral selector, has been investigated in liquid chromatography (LC). Its ... [more ▼]

A polysaccharide-based chiral stationary phase (Sepapak-4), with cellulose tris(4-chloro-3-methylphenylcarbamate) as chiral selector, has been investigated in liquid chromatography (LC). Its enantioresolution power was evaluated towards 13 basic amino-drugs with widely different structures and polarities, using polar organic mobile phases. After preliminary experiments, acetonitrile was selected as the main mobile phase component, to which a low concentration of diethylamine (0.1%) was systematically added in order to obtain efficient and symmetrical peaks. Different organic solvents were first added in small proportions (5-10%) to acetonitrile to modulate analyte retention. Polar organic modifiers were found to decrease retention and enantioresolution while hexane had the opposite effect, indicating normal-phase behaviour under these conditions. The addition of an organic acid (formic, acetic or trifluoroacetic acid) was found to strongly influence the retention of the basic amino drugs in these nonaqueous systems. The nature and proportion of the acidic additive in the mobile phase had also deep impact on enantioresolution. Therefore, the studied compounds could be subdivided in three groups in respect to the acidic additive used. All analytes could be enantioseparated in relatively short analysis times (10-20min) using these LC conditions. [less ▲]

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See detailEffect of the nature of the single-isomer anionic CD and the BGE composition on the enantiomeric separation of beta-blockers in NACE.
Rousseau, Anne ULg; Chiap, Patrice ULg; Oprean, Radu et al

in Electrophoresis (2009), 30(16), 2862-8

The separation of ten beta-blockers has been investigated in NACE systems using heptakis(2,3-di-O-methyl-6-O-sulfo)-beta-CD (HDMS-beta-CD) and heptakis(2,3-di-O-acetyl-6-O-sulfo)-beta-CD (HDAS-beta-CD ... [more ▼]

The separation of ten beta-blockers has been investigated in NACE systems using heptakis(2,3-di-O-methyl-6-O-sulfo)-beta-CD (HDMS-beta-CD) and heptakis(2,3-di-O-acetyl-6-O-sulfo)-beta-CD (HDAS-beta-CD). The influence on enantioresolution, mobility difference and selectivity of the nature of both anionic CD and BGE anion as well as their concentrations were studied by means of a multivariate approach. A D-optimal design with 25 experimental points was applied. For all studied analytes, the enantiomeric resolution was shown to be significantly influenced by both CD nature and concentration. Except for two compounds, HDAS-beta-CD was found to give higher enantioresolution values than HDMS-beta-CD. The best enantioseparation for all compounds was achieved in the presence of a high chiral selector concentration and for most of them at a low BGE anion concentration. For each investigated compound, operating conditions leading to the best enantiomeric resolution were deduced. A generic NACE system was then recommended, namely 10 mM ammonium acetate and 40 mM HDAS-beta-CD in methanol acidified with 0.75 M formic acid. This generic system was able to completely resolve the enantiomers of all beta-blockers, with a R(s) value of at least 4. Finally, the optimal conditions obtained modelling resolution, mobility difference and selectivity were compared. [less ▲]

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See detailCE-MS method development for peptides analysis, especially hepcidin, an iron metabolism marker.
Martin, Gaëlle ULg; Mansion, François ULg; Servais, Anne-Catherine ULg et al

in Electrophoresis (2009), 30(15), 2624-31

A method for the resolution of a peptides mixture including hepcidin-25, an iron metabolism marker, was developed by CE-ESI-MS. Several strategies were tested to optimize peptide separation, such as the ... [more ▼]

A method for the resolution of a peptides mixture including hepcidin-25, an iron metabolism marker, was developed by CE-ESI-MS. Several strategies were tested to optimize peptide separation, such as the addition of cyclodextrins or organic solvents in the BGE or the use of coated capillaries. Best results in terms of resolution, symmetry and efficiency were obtained with a BGE made of 500 mM ammonium acetate pH 4.5/ACN 70:30 v/v. Using the methodology of experimental design, BGE concentration, sheath liquid composition and MS-coupling parameters were then optimized in order to obtain the best signal intensity for hepcidin. Finally, a 225 mM BGE and a sheath liquid composed of isopropanol/water 80:20 v/v containing 0.5% v/v formic acid were selected as it constitutes the best compromise for selectivity, peak shape and sensitivity. [less ▲]

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See detailLiquid chromatographic determination of enrofloxacin in nasal secretions and plasma of healthy pigs using restricted access material for on-line sample clean-up
Bimazubute, M. A.; Rozet, Eric ULg; Dizier, Isabelle ULg et al

in Journal of Chromatography. A (2008), 1189(1-2), 456-466

A new fully automated method was developed for the quantitative analysis of an antibacterial drug, enrofloxacin (ENRO), in both nasal secretions and plasma samples of healthy pigs. The method is based on ... [more ▼]

A new fully automated method was developed for the quantitative analysis of an antibacterial drug, enrofloxacin (ENRO), in both nasal secretions and plasma samples of healthy pigs. The method is based on the use of a pre-column packed with restricted access material (RAM), namely RP-18 ADS (alkyl diol silica), for on-line sample clean-up coupled to a liquid chromatographic (LC) column containing octadecyl silica. The only off-line sample preparation was the 50-fold dilution of nasal secretions and plasma samples in the washing liquid composed of 25 mM phosphate buffer of pH 7.4. A 10 μl diluted sample volume was injected directly onto the pre-column and washed for 7 min. By rotation of a switching valve, the analyte of interest was eluted in the back-flush mode with the LC mobile phase which consisted in a mixture of 25 mM phosphate buffer of pH 3.0 and acetonitrile according to a segmented gradient elution. By a new rotation of the switching valve, the pre-column and the analytical column were equilibrated for 3 min with the initial mobile phases. The flow-rate was 0.8 ml min−1 for the washing liquid and 1.5 ml min−1 for the LC mobile phase. ENRO was detected by fluorescence at excitation and emission wavelengths of 278 and 445 nm, respectively. Finally, the developed method was validated using an original strategy based on total measurement error and accuracy profiles as a decision tool. The limits of quantitation of ENRO in plasma and in nasal secretions were 30.5 and 91.6 ng/ml, respectively. The validated method was then applied successfully to the determination of ENRO in healthy pigs treated by intramuscular injection at different doses (2.5, 10 and 30 mg/kg bodyweight) for a pilot study. This method could be also used for the simultaneous analysis of ENRO and its main metabolite, ciprofloxacin (CIPRO). [less ▲]

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