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See detailDevelopment of a generic micellar electrokinetic chromatography method for the separation of 15 antimalarial drugs as a tool to detect medicine counterfeiting
Lamalle, Caroline ULg; Marini Djang'Eing'A, Roland ULg; Debrus, Benjamin ULg et al

in Electrophoresis (2012), 33

Since antimalarial drugs counterfeiting is dramatically present on the African market, the development of simple analytical methods for their quality control is of great importance. This work consists in ... [more ▼]

Since antimalarial drugs counterfeiting is dramatically present on the African market, the development of simple analytical methods for their quality control is of great importance. This work consists in the CE analysis of 15 antimalarials (artesunate, artemether, amodiaquine, chloroquine, piperaquine, primaquine, quinine, cinchonine, mefloquine, halofantrine, sulfadoxine, sulfalen, atovaquone, proguanil, and pyrimethamine). Since all these molecules cannot be ionized at the same pH, MEKC was preferred because it also allows separation of neutral compounds. Preliminary experiments were first carried out to select the most crucial factors affecting the antimalarials separation. Several conditions were tested and four parameters as well as their investigation domain were chosen: pH (5–10), SDS concentration (20–90 mM), ACN proportion (10–40%), and temperature (20–35°C). Then, the experimental design methodology was used and a central composite design was selected. Mathematical modeling of the migration times allowed the prediction of optimal conditions (29°C, pH 6.6, 29 mM SDS, 36% ACN) regarding analyte separation. The prediction at this optimum was verified experimentally and led to the separation of 13 compounds within 8 min. Finally, the method was successfully applied to the quality control of African antimalarial medicines for their qualitative and quantitative content. [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 detailChemo- and enantio-selective method for the analysis of amino acids by capillary electrophoresis with in-capillary derivatization.
Fradi, Ines ULg; Servais, Anne-Catherine ULg; Lamalle, Caroline ULg et al

in Journal of Chromatography. A (2012)

A novel dual chiral CE method was developed for the separation of l- and d-amino acids (AAs), using in-capillary derivatization with 9-fluoroenylmethyl chloroformate (FMOC). Firstly, using pre-column ... [more ▼]

A novel dual chiral CE method was developed for the separation of l- and d-amino acids (AAs), using in-capillary derivatization with 9-fluoroenylmethyl chloroformate (FMOC). Firstly, using pre-column derivatization, the enantioseparation of FMOC-AAs was optimized according to the nature of cyclodextrins (CD). A background electrolyte (BGE) composed of 30mM beta-CD, 30mM octakis(2,3-dihydroxy-6-O-sulfo)-gamma-CD (OS-gamma-CD), 40mM tetraborate and 15% isopropanol (IPA) was selected and led to 17 baseline resolved pairs (R(s)=1.7-5.8) and two partially resolved pairs (Lys, R(s)=0.5 and Arg, R(s)=1.2). Experimental conditions for in-capillary derivatization were then optimized. Several parameters, such as mixing voltage and time, concentration of labeling solution and the length of the spacer plug were studied. The optimal conditions for in-capillary derivatization procedure were obtained using successive hydrodynamic injections (30mbar) of AAs for 2s, borate buffer for 4s and 10mM FMOC solution for 6s, followed by a mixing at 3kV for 72s and wait time of 1min. Moreover, a particular attention was paid to improve separation chemoselectivity. The effect on stereoselectivity and chemoselectivity of different factors, such as decrease of pH and tetraborate concentration and the addition of sodium dodecyl sulfate (SDS), was investigated using the in-capillary derivatization procedure. The best separation of a standard mixture of ten AA racemates was observed using a BGE containing 30mM beta-CD, 30mM OS-gamma-CD, 25mM SDS, 40mM sodium tetraborate and 17% IPA. [less ▲]

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See detailContractile and electrophysiological properties of pulmonary artery smooth muscle are not altered in TASK-1 knockout mice.
Manoury, B.; Lamalle, Caroline ULg; Oliveira, R. et al

in Journal of Physiology (2011)

The acid-sensitive, two-pore domain K(+) channel, TASK-1, contributes to the background K(+) conductance and membrane potential (Em) of rat and human pulmonary artery (PA) smooth muscle cells (SMC), but ... [more ▼]

The acid-sensitive, two-pore domain K(+) channel, TASK-1, contributes to the background K(+) conductance and membrane potential (Em) of rat and human pulmonary artery (PA) smooth muscle cells (SMC), but its role in regulating tone remains elusive. This study aimed to clarify the role of TASK-1 by determining the functional properties of PA from mice in which the TASK-1 gene was deleted (TASK-1/3 KO), in comparison with wild type (WT) C57BL/6 controls. Small vessel wire myography was used to measure isometric tension developed by intact PA. Em and currents were recorded from freshly isolated PASMC using the perforated patch-clamp technique. Reverse-transcription polymerase chain reaction (RT-PCR) was used to estimate K(+) channel expression. We could find no difference between PA from WT and TASK-1/3 KO TASK KO mice. They showed similar constrictor responses to a range of agonists and K(+) concentrations, the K(+) channel blockers 4-aminopyridine, tetraethylammonuim ions and XE991. Treprostinil, proposed to dilate by activating TASK-1, was just as effective in TASK-1/3 KO arteries. Blocking Ca(2+) influx with nifedipine (1 muM) or levcromakalim (10 muM) had no effect on resting tone in either strain. The resting Em of PASMC and its responses to K(+) channel blockers were unchanged in TASK-1/3 KO mice as were voltage-activated K(+) currents, including the non-inactivating K(+) current (I(KN)) measured at 0 mV. The Em was, however, depolarised in comparison with other species. Mouse I(KN) was much smaller than in rat and showed no sensitivity to pH. The results imply that TASK-1 does not form a functional channel in mouse PASMC. [less ▲]

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See detailA DESIGN SPACE APPROACH TO DEVELOP A GENERIC CE METHOD FOR THE SEPARATION OF 19 ANTIMALARIAL DRUGS
Lamalle, Caroline ULg; Marini Djang'Eing'A, Roland ULg; Debrus, Benjamin ULg et al

Poster (2010, September)

This project consists in analysing different molecules used against malaria by capillary electrophoresis (CE). As qualitative and quantitative counterfeit is largely present in Africa, it is important to ... [more ▼]

This project consists in analysing different molecules used against malaria by capillary electrophoresis (CE). As qualitative and quantitative counterfeit is largely present in Africa, it is important to develop a simple method which can control the conformity of medicines from African market. For the moment no CE method has been developed to analyse simultaneously the most common antipaludics; but it can be very useful for the control of unknown tablets. The method development was performed on 4 preservatives (methylparaben, propylparaben, butylhydroxyanisol and butylhydroxytoluen) and 16 antipaludics (artesunate, artemether, amodiaquine hydrochloride, chloroquine diphosphate, piperaquine, primaquine diphosphate, quinine hydrochloride, cinchonine, mefloquine hydrochloride, lumefantrine, halofantrine, sulfadoxine, sulfalen, atovaquone, proguanil hydrochloride, pyrimethamine). Micellar electrokinetic chromatography (MEKC) was chosen because of the presence of neutral and charged compounds in the studied mixture. The first step of method development was to screen CE experimental conditions to select the most crucial factors. Several conditions were tested with antipaludics diluted in 100% methanol and in 70:30 (v/v) methanol/water in which resolution was better. Four parameters as well as their investigation domain were then chosen: pH (5-10), SDS concentration (20-90nM), acetonitrile proportion (10-40%) and temperature (20-35°C). Then, in order to predict the best condition for the method, an experimental design methodology using a face-centered central composite design (CCD) was realised. Twenty five experiments were defined by CCD. Molecules were separated in four groups and each molecule could be found in two groups. Four samples containing 10 molecules were therefore injected to reduce the number of runs. All the results were analysed and allowed the prediction of optimal conditions in terms of analyte separation. Finally, the condition giving the best separation was tested to verify the prediction. [less ▲]

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