References of "Crommen, Jacques"
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See detailOne-step strategy for the synthesis of a derivatized cyclodextrin-based monolithic column.
Guo, Jialiang; Zhang, Qiaoxuan; Yao, Zhe et al

in Journal of separation science (2014), 37(14), 1720-7

Derivatized beta-cyclodextrin (beta-CD) functionalized monolithic columns were prepared by a "one-step" strategy using click chemistry. First, the intended derivatized beta-CD monomers were synthesized by ... [more ▼]

Derivatized beta-cyclodextrin (beta-CD) functionalized monolithic columns were prepared by a "one-step" strategy using click chemistry. First, the intended derivatized beta-CD monomers were synthesized by a click reaction between propargyl methacrylate and mono-6-azido-beta-CD and then sulfonation or methylation was carried out. Finally, monolithic columns were prepared through a one-step in situ copolymerization of the derivatized beta-CD monomer and ethylene glycol dimethacrylate. The sulfated beta-CD-based monolith was successfully applied to the hydrophilic interaction liquid chromatography separation of nucleosides and small peptides, while the methylated beta-CD-functionalized monolith was useful for the separation of nonpolar compounds and drug enantiomers in capillary reversed-phase liquid chromatography. The structures of the monomers were characterized by Fourier transform infrared spectroscopy and mass spectrometry. The physicochemical properties and column performance of monoliths were evaluated by scanning electron microscopy and micro high performance liquid chromatography. This strategy has considerable prospects for the preparation of other derivatized CD-functionalized methacrylate monoliths. [less ▲]

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See detailA novel mixed phospholipid functionalized monolithic column for early screening of drug induced phospholipidosis risk.
Zhao, Xianglong; Chen, Weijia; Liu, Zhenghua et al

in Journal of chromatography. A (2014), 1367

Drug-induced phospholipidosis (PLD) is characterized by the excessive accumulation of phospholipids, resulting in multilamellar vesicle structure within lysosomes. In the present study, a novel mixed ... [more ▼]

Drug-induced phospholipidosis (PLD) is characterized by the excessive accumulation of phospholipids, resulting in multilamellar vesicle structure within lysosomes. In the present study, a novel mixed phospholipid functionalized monolithic column was developed for the first time through a facile one-step co-polymerization approach. The phospholipid composition of the monolith can be adjusted quantitatively and accurately to mimic the mixed phospholipid environment of different biomembranes on a solid matrix. The mixed phospholipid functionalized monolith as a promising immobilized artificial membrane technique was used to study drug-phospholipid interaction. Scanning electron microscopy, elemental analysis, FT-IR spectra, zeta-potential analysis and micro-HPLC were carried out to characterize the physicochemical properties and separation performance of the monolith. Mechanism studies revealed that both hydrophobic and electrostatic interactions play an important role in the retention of analytes. The ratio of their contributions to retention can be easily manipulated by adjusting the composition of the mixed phospholipids, in order to better mimic the interaction between drugs and cell membrane. The obtained mixed phospholipid functionalized monolithic columns were applied to the screening of drug-induced PLD potency. Data from 79 drugs on the market demonstrated that the chromatographic hydrophobicity index referring to the mixed phospholipid functionalized monolith at pH 7.4 (CHI IAM7.4) for the selected drugs were highly correlated with the drug-induced PLD potency data obtained from other in vivo or in vitro assays. Moreover, the effect of the acidic phospholipid phosphatidylserine proportion on prediction accuracy was also investigated. The monolith containing 20% phosphatidylserine and 80% phosphatidylcholine exhibited the best prediction ability for the drug-induced PLD potency of the tested compounds. This research has led to the successful development of a novel and facile approach to prepare a mixed phospholipids functionalized monolith, which offers a reliable, cost-effective and high-throughput screening tool for early prediction of the PLD potency of drug candidates. [less ▲]

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See detailPreparation of a beta-cyclodextrin functionalized monolith via a novel and simple one-pot approach and application to enantioseparations.
Zhang, Qiaoxuan; Guo, Jialiang; Wang, Feng et al

in Journal of chromatography. A (2014), 1325

A novel and facile one-pot copolymerization approach was developed for the preparation of a beta-cyclodextrin (beta-CD) functionalized organic polymer monolith. The proposed one-pot process involved two ... [more ▼]

A novel and facile one-pot copolymerization approach was developed for the preparation of a beta-cyclodextrin (beta-CD) functionalized organic polymer monolith. The proposed one-pot process involved two major reactions occurring in sequence in the same vial: (1) the ring opening reaction between the epoxy groups of glycidyl methacrylate (GMA) and the primary amino groups of ethylenediamine-beta-CD (EDA-beta-CD); (2) the copolymerization of glycidyl methacrylate-ethylenediamine-beta-CD (GMA-EDA-beta-CD) and ethylene dimethacrylate (EDMA) using 2,2'-azobisisobutyronitrile (AIBN) as the polymerization initiator. This approach avoids the time-consuming post-polymerization derivatization of the traditional two-step strategy. Compared to the previously reported two-step strategy, the monolith prepared by this one-pot method exhibited higher beta-CD ligand density and better column efficiency in HPLC. Satisfactory column permeability and separation selectivity were also obtained on the optimized poly(GMA-EDA-beta-CD-co-EDMA) monolithic column. Additionally, the column was also applied to the enantioseparation of some racemic acidic compounds with promising results. [less ▲]

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See detailEnantioseparation of N-derivatized amino acids by micro-liquid chromatography using carbamoylated quinidine functionalized monolithic stationary phase.
Wang, Qiqin; Feng, Jun; Han, Hai et al

in Journal of chromatography. A (2014), 1363

In order to obtain satisfactory column permeability, efficiency and selectivity for micro-HPLC, a capillary monolithic column containing O-9-[2-(methacryloyloxy)-ethylcarbamoyl]-10,11-dihydroquinidine ... [more ▼]

In order to obtain satisfactory column permeability, efficiency and selectivity for micro-HPLC, a capillary monolithic column containing O-9-[2-(methacryloyloxy)-ethylcarbamoyl]-10,11-dihydroquinidine (MQD) as chiral selector was re-optimized. The monolithic column was used to successfully enantioresolve a wide range of N-derivatized amino acids including alanine, leucine, methionine, threonine, phenylalanine, valine, serine, isoleucine, tryptophan, and cysteine. The influence of mobile phase parameters, such as the organic solvent type and concentration, the apparent pH, and buffer concentration, on retention and enantioseparation of N-derivatized amino acids has been investigated. 3,5-dinitrobenzoyl-amino acids and 3,5-dichlorobenzoyl-amino acids were resolved into enantiomers with exceptionally high selectivity and resolution. The chemoselectivity of the monolithic column for a multicomponent mixture of N-derivatized amino acids was also investigated. A mixture of three pairs of 3,5-dichlorobenzoyl-amino acids could be fully resolved in 22.5 min. [less ▲]

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See detailInfluence of the crosslinker type on the chromatographic properties of hydrophilic sulfoalkylbetaine-type monolithic columns.
Liu, Chusheng; Chen, Weijia; Yuan, Guangxin et al

in Journal of chromatography. A (2014), 1373

In order to investigate the effects of the crosslinker on the separation performance of polar zwitterionic sulfoalkylbetaine-type monolithic columns, three crosslinkers, i.e. 1,4-bis(acryloyl)piperazine ... [more ▼]

In order to investigate the effects of the crosslinker on the separation performance of polar zwitterionic sulfoalkylbetaine-type monolithic columns, three crosslinkers, i.e. 1,4-bis(acryloyl)piperazine (PDA), ethylene dimethacrylate (EDMA) and N,N'-methylenebisacrylamide (MBA), were copolymerized with the hydrophilic monomer N,N-dimethyl-N-acryloyloxyethyl-N-(3-sulfopropyl)ammonium betaine (SPDA). The chromatographic properties of the three hydrophilic sulfoalkylbetaine-type monolithic columns, including column efficiency, permeability, porosity and separation mechanism, were systematically compared using scanning electron microscopy or micro-HPLC. Good selectivity in micro-HPLC separations was achieved on all three monolithic columns. The results indicate that the polarity of sulfoalkylbetaine-type monolithic columns may be related to the polarity of the crosslinker, which further affects column selectivity and efficiency. A particularly high column efficiency (100,000 plates/m) was obtained on the novel poly(SPDA-co-PDA) monolithic column at a linear velocity of 1mm/s using thiourea as test analyte. A higher resolution was also observed for nucleobases, nucleosides and hydrophilic organic acids on this novel poly(SPDA-co-PDA) monolithic column compared to the other two columns. [less ▲]

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See detailPreparation and evaluation of a novel monolithic column containing double octadecyl chains for reverse-phase micro high performance liquid chromatography.
Duan, Qianqian; Liu, Chusheng; Liu, Zhenghua et al

in Journal of chromatography. A (2014), 1345

A novel reverse-phase monolithic stationary phase containing double long alkyl chains was prepared based on the thermally initiated co-polymerization of 3-methylacryloyl-3-oxapropyl-3-(N,N ... [more ▼]

A novel reverse-phase monolithic stationary phase containing double long alkyl chains was prepared based on the thermally initiated co-polymerization of 3-methylacryloyl-3-oxapropyl-3-(N,N-dioctadecylcarbamoyl)-propionate (AOD) and ethylene glycol dimethacrylate (EDMA) in the presence of 2-methyl-1-propanol and 1,4-butanediol as the selected porogens. The polymerization was carefully optimized and good permeability, stability and column efficiency were observed for the final monolithic columns. The column also showed good long term stability and reproducibility. The methylene selectivity demonstrates typical reversed phase characteristics. The optimized poly (AOD-co-EDMA) monolith exhibited good selectivity for a range of non-polar test analytes such as PAHs, tocopherols and alkylphenones. A good separation of intact proteins was also observed. [less ▲]

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See detailComparative enantiomer affinity pattern of beta-blockers in aqueous and non-aqueous CE using single-component anionic cyclodextrins
Feng, Y; Wang, T; Chankvetadze, B et al

Conference (2014)

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See detailFunctionalized polymeric monolithic columns in micro-HPLC for pharmaceutical analysis
Jiang, Z; Guo, J; Zhang, Q et al

Conference (2014)

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See detailMicellar electrokinetic chromatography against the counterfeiting of insulin formulations
Lamalle, Caroline ULg; Servais, Anne-Catherine ULg; Crommen, Jacques ULg et al

Poster (2014)

Insulin plays an important role in the homeostasis of blood glucose concentration. A deficiency of this hormone causes diabetes, which can be treated by subcutaneous injection of synthetic insulin ... [more ▼]

Insulin plays an important role in the homeostasis of blood glucose concentration. A deficiency of this hormone causes diabetes, which can be treated by subcutaneous injection of synthetic insulin. Besides human regular insulin, several modified analogues have been developed to accelerate (Lispro, Aspart, Glulisin) or delay (Glargin, Detemir) its absorption. Moreover, protamine is sometimes associated with human, Lispro or Aspart insulin to give a crystalline form, which delays the action of insulin, providing it with a prolonged absorption profile after injection. Diabetes is one of the most common metabolic diseases in the world; its prevalence increases continuously. A lot of patients are therefore concerned with the treatment, which is relatively expensive and requires a prescription. Some pharmaceutical formulations can sometimes be found without prescription on the parallel market but the risk of drug counterfeiting is then considerably increased. The poor quality of these drugs can lead to harmful consequences for the public health. It is therefore essential to develop a suitable method for the identification and quantification of human insulin and its analogues inside formulations. Ortner et al. [1] have already proposed micellar electrokinetic chromatography (MEKC) methods to detect simultaneously human insulin and its five analogues but no quantitative applications were presented. Furthermore, formulations containing protamine were not tested so we included them in our study. The first optimisation step involved the sample preparation procedure. An acidic sample solution (10 mM HCl) was finally selected to solubilise protamine and Glargin. Then the background electrolyte composition was investigated to separate the components present in the formulations. A basic buffer (50 mM ammonium acetate pH 9) was selected, providing an important and stable electroosmotic flow, a negative charge to the insulins and avoiding any adsorption to the capillary wall. The addition of sodium dodecylsulfate (SDS) and acetonitrile (ACN) was also found crucial for selectivity. With 50 mM SDS and 15% ACN the six insulins and the two major excipients (phenol and meta-cresol) were fully separated within 15 minutes. This method was then entirely validated for the human insulin and the quality control of related formulations was performed. The next step will be the validation and the quantification of the other analogues. [less ▲]

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See detailDevelopment and validation of a liquid chromatographic method for the stability study of a pharmaceutical formulation containing voriconazole using cellulose tris(4-chloro-3-methylphenylcarbamate) as chiral selector and polar organic mobile phases.
Servais, Anne-Catherine ULg; Moldovan, Radu-Cristian ULg; Farcas, Elena ULg et al

in Journal of chromatography. A (2014), 1363

The ophthalmic solution of voriconazole, i.e. (2R,3S)-2-(2,4-difluorophenyl)-3-(5-fluoropyrimidin-4-yl)-1-(1H-1,2,4-triazol-1-y l)butan-2-ol, made from an injection formulation which also contains ... [more ▼]

The ophthalmic solution of voriconazole, i.e. (2R,3S)-2-(2,4-difluorophenyl)-3-(5-fluoropyrimidin-4-yl)-1-(1H-1,2,4-triazol-1-y l)butan-2-ol, made from an injection formulation which also contains sulfobutylether-beta-cyclodextrin sodium salt as an excipient (Vfend((R))), is used for the treatment of fungal keratitis. A liquid chromatographic (LC) method using polar organic mobile phase and cellulose tris(4-chloro-3-methylphenylcarbamate) coated on silica as chiral stationary phase was successfully developed to evaluate the chiral stability of the ophthalmic solution. The percentage of methanol (MeOH) in the mobile phase containing acetonitrile (ACN) as the main solvent significantly influenced the retention and resolution of voriconazole and its enantiomer ((2S,3R)-2-(2,4-difluorophenyl)-3-(5-fluoropyrimidin-4-yl)-1-(1H-1,2,4-triazol-1- yl)butan-2-ol). The optimized mobile phase consisted of ACN/MeOH/diethylamine/trifluoroacetic acid (80/20/0.1/0.1; v/v/v/v). The method was found to be selective not only regarding the enantiomer of voriconazole but also regarding the specified impurities described in the monograph from the European Pharmacopoeia. The LC method was then fully validated applying the strategy based on total measurement error and accuracy profiles. Under the selected conditions, the determination of 0.1% of voriconazole enantiomer could be performed. Finally, a stability study of the ophthalmic solution was conducted using the validated LC method. [less ▲]

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See detailL’électrophorèse capillaire micellaire pour la détermination simultanée de l’insuline et de ses analogues dans des formulations pharmaceutiques
Lamalle, Caroline ULg; Servais, Anne-Catherine ULg; Crommen, Jacques ULg et al

Poster (2013, June)

L’insuline joue un rôle important dans l’homéostasie de la concentration sanguine en glucose. Un déficit de cette hormone cause le diabète (de type I) qui peut être traité par injection sous-cutanée ... [more ▼]

L’insuline joue un rôle important dans l’homéostasie de la concentration sanguine en glucose. Un déficit de cette hormone cause le diabète (de type I) qui peut être traité par injection sous-cutanée d’insuline synthétique. En plus de l’insuline humaine, plusieurs analogues ont été développés pour accélérer son absorption (Lispro, Aspart, Glulisin) ou la retarder (Glargin, Detemir). La protamine est également parfois utilisée avec l’insuline humaine, Lispro ou Aspart pour former un complexe et augmenter la durée d’action. Le diabète est une des maladies métaboliques les plus courantes dans le monde; la prévalence ne cesse de s’élever. Beaucoup de patients sont donc concernés par le traitement qui est relativement cher et nécessite une ordonnance. Certaines formulations pharmaceutiques peuvent être trouvées sans ordonnance sur le marché parallèle mais la possibilité de contrefaçon existe. Et la mauvaise qualité de ces médicaments peut entrainer des conséquences néfastes pour la santé publique. Il est donc essentiel de développer une méthode permettant l’identification et la quantification de l’insuline humaine et de ses analogues. Ortner et al. [1] ont déjà proposé une méthode par électrophorèse capillaire micellaire (MEKC) pour séparer simultanément l’insuline humaine et ses 5 analogues, mais ils n’analysaient pas les formulations à base de protamine. Le nombre de ces formulations n’étant pas négligeable, nous les avons incluses dans notre étude. La première étape d’optimisation a été la préparation de l’échantillon. Une solution acide (0.01M d’HCl) a finalement été choisie pour solubiliser la protamine et la Glargine. Ensuite, la composition du background electrolyte a été investiguée pour séparer les composants des formulations. Un tampon basique (50mM d’acétate d’ammonium à pH 9) a été choisi, engendrant un flux électroosmotique important et stable, une charge négative à l’insuline et empêchant l’adsorption à la paroi du capillaire. L’addition de dodécyl sulfate de sodium et d’acétonitrile s’est ensuite révélée déterminante pour la sélectivité. Les 6 insulines et les 2 excipients majeurs (le phénol et le m-crésol) ont été complètement séparés endéans 15 minutes. La méthode précitée a ensuite été adaptée pour permettre la séparation de chaque insuline et de ses produits de dégradation. [less ▲]

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See detailDéveloppement de méthodes de quantification en milieu complexe par chromatographie liquide microfluidique couplée à la spectrometrie de masse
Houbart, Virginie ULg; Rozet, Eric ULg; Crommen, Jacques ULg et al

Conference (2013, June)

L’hepcidine est un biomarqueur peptidique dont l’intérêt tant comme outil de diagnostic que de suivi de pathologies est de plus en plus solidement établi. Il existe donc une demande forte d’outils ... [more ▼]

L’hepcidine est un biomarqueur peptidique dont l’intérêt tant comme outil de diagnostic que de suivi de pathologies est de plus en plus solidement établi. Il existe donc une demande forte d’outils sensibles et robustes afin de la doser au sein de milieux biologiques tels que le plasma ou le sérum. Une méthode analytique a été développée à l’aide d’un système chromatographique miniaturisé (nanoLC-chip) couplé à un spectromètre de masse permettant d’assurer un dosage de l’hepcidine à la fois sensible et fiable. Lors du développement de cette méthode, il a été constaté que la composition de l’échantillon avait une influence majeure sur la réponse analytique. Or, l’utilisation de systèmes chromatographiques miniaturisés implique souvent l’injection de volumes proportionnellement très importants par rapport aux dimensions du système, ce qui amplifie encore l’impact de sa composition. C’est pourquoi il est capital d’avoir une bonne compréhension des phénomènes qui ont lieu entre l’injection de l’échantillon dans le système chromatographique et la détection par spectrométrie de masse, et particulièrement lors du développement de méthodes analytiques quantitatives. Dans cette étude, nous avons utilisé la planification expérimentale afin de mieux comprendre le comportement chromatographique des peptides, ainsi que les facteurs qui influencent la sensibilité de la méthode développée. Un mélange de peptides a été sélectionné, varié tant du point de vue du poids moléculaire que du point isoélectrique et de l’hydropathie. Un plan de criblage a permis de délimiter le domaine expérimental ainsi que les facteurs significatifs parmi la composition de la phase mobile (proportion et nature de l’agent de paire d’ions) et de l’échantillon en lui-même (nature de l’agent de paire d’ions et proportion de solvant organique). Ensuite, un plan d’expériences factoriel complet a été mis en œuvre afin d’observer plus finement le rôle de chaque facteur ainsi que les interactions éventuelles qui les lient. Certains facteurs ont montré un effet très marqué tant sur l’intensité de la réponse que sur la rétention. Entre autres, la composition de l’échantillon, facteur parfois négligé lors du développement de méthodes, a démontré son importance capitale, en particulier sur les phénomènes de rétention des peptides. Les données obtenues ont également permis de dégager des conditions optimales d’analyse en termes de rétention et de sensibilité. Enfin, une analyse en composantes principales a également été réalisée sur le grand nombre de données récoltées dans le but de mettre en évidence d’éventuels propriétés physicochimiques des peptides qui pourraient avoir un impact significatif sur les réponses étudiées. [less ▲]

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See detailFalsification des médicaments: mythe ou réalité ?
Marini Djang'Eing'A, Roland ULg; Fillet, Marianne ULg; Vancauwenberghe, Roy et al

Conference (2013, April 24)

La santé publique est de nos jours minée par la problématique des médicaments falsifiés ou de qualité inférieure, avec plusieurs conséquences sanitaires, économiques voire professionnelles. On estime à 7 ... [more ▼]

La santé publique est de nos jours minée par la problématique des médicaments falsifiés ou de qualité inférieure, avec plusieurs conséquences sanitaires, économiques voire professionnelles. On estime à 7% la part du marché pharmaceutique mondial que représenterait ce fléau; l’Afrique, l’Asie et de nombreux pays d'Amérique latine étant les régions les plus touchées avec plus de 30% de médicaments falsifiés. D’après l'OMS, plus de 50% des médicaments achetés à partir des sites internet illégaux sont contrefaits, annihilant très fortement les chances de succès thérapeutique. Ces médicaments viennent dans la plupart des cas des pays asiatiques et de l’Eurasie. Le trafic de faux médicaments est un crime contre l'humanité qui représente environ 50 milliards de dollars par an (10-15 % de plus que le marché de la drogue). Au travers de deux leçons, la situation de la falsification des médicaments sera présentée au grand public dans le but de le sensibiliser à ce fléau. La première leçon présentera la situation en Europe avec un accent sur la Belgique. La problématique du droit à la propriété intellectuelle et de l’encadrement législatif sera abordée, ainsi que la falsification des médicaments modernes et des phytomédicaments, ces derniers étant utilisés par plus de 40% de la population en Europe et aux Etats-Unis. Dans la seconde leçon sera abordée la situation vécue en Afrique. L’approvisionnement en médicaments de qualité par le partage de l’information sera présenté ainsi que les moyens analytiques à la disposition de ce continent pour combattre ce fléau. Des membres du Département de Pharmacie de l’Université de Liège, de l’Agence Fédérale des Médicaments et des Produits de Santé ainsi que du programme QUAMED (Quality Medicines for All) feront partager leur expérience sur cette question d’une brûlante actualité.  [less ▲]

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See detailUnusual Amino Acids and Monofluoroacetate from Dichapetalum michelsonii (Umutambasha), a Toxic Plant from Rwanda
Esters, Virginie ULg; Karangwa, Charles; Tits, Monique ULg et al

in Planta Medica (2013), 79

In the course of our investigations on Umutambasha in order to identify its convulsant principles, small quantities of monofluoroacetate were observed in stem bark, leaves, and fruits of this plant newly ... [more ▼]

In the course of our investigations on Umutambasha in order to identify its convulsant principles, small quantities of monofluoroacetate were observed in stem bark, leaves, and fruits of this plant newly identified as Dichapetalum michelsonii Hauman. Conclusive evidence for a monofluoroacetate presence came from its isolation from the freeze-dried extract of stem bark. Three free unusual amino acids, named N-methyl-α-alanine, N-methyl-β-alanine, and 2,7-diaminooctan-1,8-dioic acid, described for the first time in a plant, and known trigonelline were also isolated from the stem bark of D. michelsonii. Structure elucidations were mainly achieved by spectroscopic methods (1H-NMR, 2D-NMR, MS) and by comparison with authentic references. These unusual amino acids were detected by a fast, reliable TLC analysis in all our batches of Umutambasha, suggesting that they could be used for identification purposes in case of human or livestock intoxications. Finally, EEG recordings and behavioural observations performed in mice suggested that the convulsive patterns produced by Umutambasha are the consequence of monofluoroacetate presence in D. michelsonii. [less ▲]

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See detailA facile and efficient strategy to enhance hydrophilicity of zwitterionic sulfoalkylbetaine type monoliths.
Yuan, Guangxin; Peng, Yongbo; Liu, Zhenghua et al

in Journal of chromatography. A (2013), 1301

In order to prepare zwitterionic HILIC monolithic columns with high polarity, the highly hydrophilic monomer N,N-dimethyl-N-acryloyloxyethyl-N-(3-sulfopropyl)ammonium betaine (SPDA) and crosslinker N,N ... [more ▼]

In order to prepare zwitterionic HILIC monolithic columns with high polarity, the highly hydrophilic monomer N,N-dimethyl-N-acryloyloxyethyl-N-(3-sulfopropyl)ammonium betaine (SPDA) and crosslinker N,N'-methylenebisacrylamide (MBA) were employed for developing a novel sulfoalkylbetaine type stationary phase. The polymerization parameters were systematically optimized in order to obtain a satisfactory performance for column permeability, mechanical stability, hydrophilicity, efficiency and selectivity. Compared to the previously reported poly(N,N-dimethyl-N-methacryloxyethyl-N-(3-sulfopropyl)ammonium betaine-co-ethylene dimethacrylate) (poly(SPE-co-EDMA)) monolith and the poly(SPDA-co-EDMA) monolith that we developed, a significantly enhanced hydrophilicity was obtained on the poly(SPDA-co-MBA) monolithic column, illustrated by the lowered critical composition of the mobile phase corresponding to the transition from the HILIC to the RP mode. Excellent permeability, reproducibility and stability were achieved on this optimized poly(SPDA-co-MBA) monolith. A column efficiency of 70,000plates/m was obtained for the analysis of bases at a linear velocity of 1.95mm/s. As expected, by studying the influence of mobile phase pH and salt concentration on their retention, a weak electrostatic repulsion interaction for negatively charged analytes was also observed at low organic solvent content on the poly(SPDA-co-MBA) monolithic column. The final optimized poly(SPDA-co-MBA) monolith exhibited good selectivity for a series of polar compounds, such as phenols, bases, benzoic acid derivatives, small peptides, urea and allantoin. [less ▲]

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See detailUse of neutral capillaries for the enantioseparation of N-benzoylated amino acids by capillary electrophoresis with bromobalhimycin as chiral selector.
Peng, Yongbo; Zhang, Tingting; Wang, Tingting et al

in Journal of separation science (2013), 36(9-10), 1568-74

In this study, the partial filling technique on both polycationic polymer hexadimethrine bromide (HDB) modified capillary and eCAP neutral capillary were systematically compared in order to enhance the ... [more ▼]

In this study, the partial filling technique on both polycationic polymer hexadimethrine bromide (HDB) modified capillary and eCAP neutral capillary were systematically compared in order to enhance the enantioseparation ability of bromobalhimycin as CE additive. The separation conditions, such as pH, the plug length, and the concentration of bromobalhimycin, etc., were optimized in order to obtain satisfactory separations. As expected, for all tested 28 N-benzoylated amino acids, up to five times higher enantioresolutions were obtained on the eCAP neutral capillary compared to that on the polycationic polymer hexadimethrine bromide modified capillary. Moreover, 26 of 28 tested racemic compounds were almost baseline- resolved without observing any interference from the front of the plug of bromobalhimycin. Although the limitation of longer running time on the neutral capillary, it allows the use of higher content of bromobalhimycin in the running buffer without any interference on the detection of analytes when enantioseparations are more difficult to obtain. [less ▲]

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