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See detailDetermination of flurbiprofen enantiomers in plasma using a single-isomer amino cyclodextrin derivative in nonaqueous capillary electrophoresis.
Rousseau, Anne ULg; Pedrini, Matteo; Chiap, Patrice ULg et al

in Electrophoresis (2008), 29(17), 3641-8

A nonaqueous capillary electrophoresis (NACE) assay was developed for the separation and determination of flurbiprofen enantiomers in plasma samples using 6-monodeoxy-6-mono(3-hydroxy)propylamino-beta ... [more ▼]

A nonaqueous capillary electrophoresis (NACE) assay was developed for the separation and determination of flurbiprofen enantiomers in plasma samples using 6-monodeoxy-6-mono(3-hydroxy)propylamino-beta-cyclodextrin as chiral selector. The nonaqueous background electrolyte was made up of 40 mM ammonium acetate in methanol (MeOH), and flufenamic acid was employed as internal standard. Solid-phase extraction was used for sample cleanup prior to the NACE separation.The NACE method reproducibility was optimized by evaluating different capillary washing sequences between runs. After having tested various conditions, trifluoroacetic acid (1 M) in MeOH was finally selected. Concerning the solid-phase extraction procedure, good and reproducible analyte recoveries were obtained using MeOH for protein denaturation and a polymeric phase combining hydrophobic interactions with anion exchange properties (Oasis) MAX) was selected as extraction sorbent. The method selectivity was not only demonstrated toward a blank plasma sample but also toward other non-steroidal anti-inflammatory drugs. The method was then successfully validated with respect to response function, trueness, precision, accuracy, linearity and limit of quantification. [less ▲]

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See detailDETERMINATION OF GLUCOSINOLATES IN RAPESEED
Wathelet, Jean-Paul ULg; Mabon, N.; Marlier, M.

Poster (1999)

The official ISO protocol (similar to U.E. recommendations established in 1987 by six european laboratories) for determination of individual glucosinolate content in rapeseed using HPLC was published for ... [more ▼]

The official ISO protocol (similar to U.E. recommendations established in 1987 by six european laboratories) for determination of individual glucosinolate content in rapeseed using HPLC was published for the first time in 1992 (ISO 9167-1). Numerous laboratories, all over the world, use now this method, especially in order to control the 00 varieties. The goals of our research were to considerably reduce the analysis time without loosing precision. A single extraction is now suggested (200 mg of ground seeds stirred in 10 ml of 75°C methanol/water 70/30 with an internal standard for 10 min). Then 1-6 ml of the crude extract is directly put on DEAE A-25 resin prepared according to the ISO method. Glucosinolates are desulfated by addition of 100 µl of concentrated Helix pomatia sulfatase (H1, EC 3.1.6.1) quickly prepared by ethanol precipitation. The desulfatation process can be reduced to 1 hour without any problems with all kind of glucosinolate (alcenyl, benzyl, indolyl, methylthio, methylsulfinyl, methylsulfonyl...). Elution of the desulfo-glucosinolates is realised with 4 x 0.5 ml of distilled water. Desulfo-glucosinolates are separated by HPLC using an Inertsil 3 ODS-3 column (100 x 3 mm, 3 µm) with a water/acetonitrile gradient (from 2 to 25% in 35 min). Resolution is very nice and the limited flow (0.4 ml/min) reduce the solvent costs and the elimination of wastes. The suggested fast method has been compared with the official ISO method analysing the three certified reference materials prepared by BCR (now IRMM) and recommended by U.E. and ISO (CRMs 366, 190 and 367). The recovery of indolyl desulfo-glucosinolates, specially 4-OH glucobrassicin, is higher with the quicker method. Results obtained with the two methods are very close for other desulfo-glucosinolates. [less ▲]

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See detailDetermination of inhibitory potency of argatroban toward thrombin by electrophoretically mediated microanalysis
Pochet, Lionel; Servais, Anne-Catherine ULg; Farcas, Elena ULg et al

in Talanta (2013), 116

Developing an EMMA method for enzymatic assay remains a challenge, particularly using UV detection. Indeed, it is necessary to optimize the separation conditions while allowing the enzymatic reaction to ... [more ▼]

Developing an EMMA method for enzymatic assay remains a challenge, particularly using UV detection. Indeed, it is necessary to optimize the separation conditions while allowing the enzymatic reaction to occur within the capillary respecting kinetic constraints and achieving enough sensitivity. In this work, such EMMA methodology was set up to evaluate the inhibitory potency of drugs toward thrombin, a serine protease implicated in the coagulation cascade. To achieve our goal, the separation buffer, the injection sequence, the internal standard and the chromogenic substrate were investigated. The newly developed system was then assessed determining the kinetic Km constant for the selected substrate and compared with the results obtained with a continuous spectrophotometer cell assay. Secondly, the Ki inhibitory constant of the thrombin inhibitor argatroban was determined and found in agreement with the published value. [less ▲]

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See detailDetermination of isotopic fractionation delta13C of methane from ground-based FTIR observations performed at the Jungfraujoch
Duchatelet, Pierre ULg; Mahieu, Emmanuel ULg; Sussmann, Ralf et al

Poster (2009, April)

Atmospheric methane (CH4) is a strong greenhouse gas that has important chemical impacts on both the troposphere and the stratosphere. In the troposphere, oxidation of methane is a major regulator of OH ... [more ▼]

Atmospheric methane (CH4) is a strong greenhouse gas that has important chemical impacts on both the troposphere and the stratosphere. In the troposphere, oxidation of methane is a major regulator of OH and is a source of formaldehyde, carbon monoxide and hydrogen. In the stratosphere, CH4 plays a central role (i), due to its contribution to the stratospheric water vapor budget, and (ii), as a sink for chlorine atoms which reduces the rate of stratospheric ozone depletion. Because the different sources of methane (natural and anthropogenic like wetlands, rice paddies, termites, natural gas escape, biomass burning, etc) have distinct 13C/12C ratios (usually reported in “delta” notation δ13C), measurements of atmospheric 13CH4 content, in addition to those of the main isotopologue (12CH4), can be used to investigate individual source strengths as well as their spatial and temporal distributions. Characterization of the isotopic fractionation of methane is therefore important, for example, to help models constrain estimates of the global methane budget. However, experimental data for the 13C/12C isotope ratio are sparse. The currently accepted average value of δ13C in atmospheric methane is about -47‰ (Platt et al., 2004). The first goal of this work is to develop and to characterize (in terms of information content and error budget) an original retrieval approach to derive 13CH4 columns from ground-based Fourier transform infrared (FTIR) spectra recorded at the International Scientific Station of the Jungfraujoch (ISSJ; 46.5°N, 8.0°E, 3580m a.s.l., Swiss Alps). The retrieval strategy is based on a Tikhonov L1 approach which has been originally developed for 12CH4 by Sussmann et al. (2008) [see also contributions by Sussmann et al. to this conference (EGU2009-7869)]. In order to validate our 13CH4 products, comparisons with satellite ACE-FTS (Atmospheric Chemistry Experiment - Fourier Transform Spectrometer) measurements are performed. Then, atmospheric δ13C ratios derived from the FTIR measurements will be compared to values published in the literature and critically discussed. References: Platt, U., W. Allan and D. Lowe, Hemispheric average Cl atom concentration from 13C/12C ratios in atmospheric methane, Atmos. Chem. Phys., 4, 2393-2399, 2004. Sussmann, R., Forster, F., Borsdorff, T., et al.: Satellite validation of column-averaged methane on global scale: ground-based data from 15 FTIR stations versus last generation ENVISAT/SCIAMACHY retrievals, IGAC 10th International Conference, Annecy, France, 7-12 Sep 2008. [less ▲]

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See detailDetermination of ITM Key Parameters By the Ionospheric Connection Explorer (ICON)
Immel, T. J.; England, S.; Mende, S. B. et al

Conference (2014)

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See detailDetermination of kinetics and the crystal structure of a novel type 2 isopentenyl diphosphate: dimethylallyl diphosphate isomerase from Streptococcus pneumoniae.
de Ruyck, Jerome; Janczak, Matthew W.; Neti, Syam Sundar et al

in Chembiochem : a European journal of chemical biology (2014), 15(10), 1452-1458

Isopentenyl diphosphate isomerase (IDI) is a key enzyme in the isoprenoid biosynthetic pathway and is required for all organisms that synthesize isoprenoid metabolites from mevalonate. Type 1 IDI (IDI-1 ... [more ▼]

Isopentenyl diphosphate isomerase (IDI) is a key enzyme in the isoprenoid biosynthetic pathway and is required for all organisms that synthesize isoprenoid metabolites from mevalonate. Type 1 IDI (IDI-1) is a metalloprotein that is found in eukaryotes, whereas the type 2 isoform (IDI-2) is a flavoenzyme found in bacteria that is completely absent from human. IDI-2 from the pathogenic bacterium Streptococcus pneumoniae was recombinantly expressed in Escherichia coli. Steady-state kinetic studies of the enzyme indicated that FMNH2 (KM =0.3 muM) bound before isopentenyl diphosphate (KM =40 muM) in an ordered binding mechanism. An X-ray crystal structure at 1.4 A resolution was obtained for the holoenzyme in the closed conformation with a reduced flavin cofactor and two sulfate ions in the active site. These results helped to further approach the enzymatic mechanism of IDI-2 and, thus, open new possibilities for the rational design of antibacterial compounds against sequence-similar and structure-related pathogens such as Enterococcus faecalis or Staphylococcus aureus. [less ▲]

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See detailDetermination of lidocaine and its two N-desethylated metabolites in dog and horse plasma by high-performance liquid chromatography combined with electrospray ionization tandem mass spectrometry
Maes, A.; Weiland, L.; Sandersen, Charlotte ULg et al

in Journal of Chromatography. B : Analytical Technologies in the Biomedical & Life Sciences (2007), 852(1-2), 180-187

A sensitive method for the quantification of lidocaine and its metabolites, monoethylglycinexylidide (MEGX) and glycinexylidide (GX), in animal plasma using high-performance liquid chromatography combined ... [more ▼]

A sensitive method for the quantification of lidocaine and its metabolites, monoethylglycinexylidide (MEGX) and glycinexylidide (GX), in animal plasma using high-performance liquid chromatography combined with electrospray ionization mass spectrometry is described. The sample preparation includes a liquid-liquid extraction with methyl tert-butylmethyl ether after addition of 2 M sodium hydroxide. Ethyl methylglycinexylidide (EMGX) is used as an internal standard. For chromatographic separation, an ODS Hypersil column was used. Isocratic elution was achieved with 0.0 1 M ammonium acetate and acetonitrile as mobile phases. Good linearity was observed in the range of 2.5-1000 ng ml(-1) for lidocame in both dog and horse plasma. For MEGX, linear calibration curves were obtained in the range of 5-1000 ng ml(-1) and 20-1000 ng ml(-1) for dog and horse plasma, respectively. In dog and horse plasma good linearity was observed in the range of 200-1500 ng ml(-1) for GX. The limit of quantification (LOQ) in dog plasma for lidocaine, MEGX and GX was set at 2.5 ng ml(-1), 20 ng ml(-1) and 200 ng ml(-1), respectively. For horse plasma a limit of quantification of 2.5 ng ml(-1), 5 ng ml(-1) and 200 ng ml(-1) was achieved for lidocaine, MEGX and GX, respectively. In dog plasma, the limit of detection (LOD) was found to be 0.8 ng ml(-1), 2.3 ng ml(-1) and 55 ng ml(-1) for lidocaine, MEGX and GX, respectively. In horse plasma the LOD's found for lidocame, MEGX and GX, were 1.1 ng ml(-1), 0.5 ng ml(-1) and 13 ng ml(-1), respectively. The method was shown to be of use in pharmacokinetic studies after application of a transdermal patch in dogs and after an intravenous infusion in horses. (c) 2007 Elsevier B.V. All rights reserved. [less ▲]

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See detailDetermination of liquid hold-up and flow distribution inside modular catalytic structured packings
Viva, Aurora; Aferka, Saïd ULg; Toye, Dominique ULg et al

in Chemical Engineering Research & Design : Transactions of the Institution of Chemical Engineers Part A (2011), 89

This paper presents the results of a study carried out to examine liquid hold-up and flow distribution in a 0.1m internal diameter column filled with catalytic structured packing Katapak-SP. Information ... [more ▼]

This paper presents the results of a study carried out to examine liquid hold-up and flow distribution in a 0.1m internal diameter column filled with catalytic structured packing Katapak-SP. Information has been gathered at local scale by means of a non-intrusive high energy X-ray tomograph. Measurements have been carried out in a large number of packing cross sections situated at different heights between the top and bottom of the packed column, giving access to the evolution of axial profiles of liquid hold-up in the open channels (separation zone) and in the catalytic baskets (reaction zone) as a function of the liquid load. The total hold-up, evaluated by averaging local tomographic values over the packed volume, was compared with global hold-up data obtained by traditional methods, like draining and RTD measurements. A method was also proposed to deduce the distribution of liquid flowrate, between the reaction and the separation zones, from hold-up distribution measured by tomography. The methodology was validated by comparison with experimental data obtained by collecting separately the liquid flowing out of the two zones at the bottom of the packed bed. The obtained results are invaluable to improve the description of hydrodynamics in rate based performance models. [less ▲]

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See detailDetermination of mass-loss rates from early-type stars on the basis of 'log(W1)-log(W1 0)' diagrams
Surdej, Jean ULg

in Astronomy and Astrophysics (1983), 127

Using realistic expressions for the velocity and opacity distributions in rapidly expanding atmospheres, the author presents numerical results for the first order moment W[SUB]1[/SUB] of a P Cygni line ... [more ▼]

Using realistic expressions for the velocity and opacity distributions in rapidly expanding atmospheres, the author presents numerical results for the first order moment W[SUB]1[/SUB] of a P Cygni line profile calculated as a function of the parameter W[SUB]1[/SUB][SUP]0[/SUP] â Mn(level), where Mrepresents the mass-loss rate and n(level) the average fractional abundance of the relevant ion. The calculations clearly show that the resulting "log(W[SUB]1[/SUB]) - log(W[SUB]1[/SUB][SUP]0[/SUP])" curves depend almost essentially on the opacity distribution and that for unsaturated P Cygni line profiles the relation W[SUB]1[/SUB] â Mn(level) holds irrespective of the both distributions. For W[SUB]1[/SUB] ⪠0.24, the line profiles become saturated and the first order moment W[SUB]1[/SUB] does not provide anymore accurate information on the mass-loss rate. This technique of mass-loss determination and that which consists in fitting observed line profiles with theoretical ones are compared. [less ▲]

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See detailDetermination of mass-loss rates from the first order moment W1 of unsaturated Cygni line profiles
Surdej, Jean ULg

in Astrophysics & Space Science (1982), 88

The relationship between the first order moment and the mass loss rate is investigated within the framework of the Sobolev approximation (1947, 1957, 1958) under various physical and geometrical ... [more ▼]

The relationship between the first order moment and the mass loss rate is investigated within the framework of the Sobolev approximation (1947, 1957, 1958) under various physical and geometrical conditions. By assuming that the size of the expanding envelope from which the observed P Cygni profiles arise is large with respect to the central stellar core, a general expression for the n-th order moment is obtained for the case of a point-like source in terms of the usual parameters inherent to Sobolev-type theories. It is then shown how the first result is altered when considering separately the effects due to collisions and rotation, the presence of the underlying photospheric absorption line, the finite size of the central core, and the limb-darkening of the stellar core. It is concluded that the total uncertainty of the mass loss rate determination made with the approach proposed here should be less than 60 percent. [less ▲]

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See detailDetermination of mass-loss rates of planetary nebulae nuclei using the first order moment of P Cygni line profiles.
Hutsemekers, Damien ULg; Surdej, Jean ULg

in Comptes rendus sur les Journées de Strasbourg, 8ème réunion - Les Nébuleuses Planétaires (1986)

The authors conclude that the mass-loss rates of planetary nebulae nuclei derived by Cerruti-Sola, Perinotto (1985) have been systematically underestimated by one or nearly two orders of magnitude.

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See detailDetermination of Meprobamate in Pharmaceutical Dosage Forms Also Containing Carbromal by Liquid Chromatography and Indirect Photometric Detection
Bechet, I.; Ceccato, Attilio ULg; Hubert, Philippe ULg et al

in Journal of Pharmaceutical & Biomedical Analysis (1992), 10(10-12, Oct-Dec), 995-9

In a pharmaceutical form also containing carbromal, meprobamate could not be quantified selectively by classical methods described in pharmacopoeias due to a significant interference from carbromal ... [more ▼]

In a pharmaceutical form also containing carbromal, meprobamate could not be quantified selectively by classical methods described in pharmacopoeias due to a significant interference from carbromal. Consequently, reversed-phase HPLC methods have been developed to separate the two active ingredients using indirect photometric detection to visualize and determine meprobamate which has very poor chromophoric properties. Different parameters influencing the sensitivity of the indirect response, such as the nature of the highly absorbing compound added to the mobile phase (the marker) as well as the methanol content and the pH of this phase, have been studied. Two chromatographic systems containing benzoic acid or cinnamic acid as the marker, have been optimized and validated. Good linearity and reproducibility have been obtained with both systems but the cinnamic acid method has the advantage that meprobamate and carbromal can be determined simultaneously at 273 nm. [less ▲]

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See detailDetermination of methionine requirement of growing double-muscled Belgian Blue bull.
Froidmont, Eric; Beckers, Yves ULg; Thewis, André ULg

in Book of abstract of the VIIIth International Symposium on Protein Metabolism and Nutrition. (1999)

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See detailDetermination of minimal serum estradiol for prevention of postmenopausal bone loss
Sarlet, N; Reginster, Jean-Yves ULg; GASPARD, Ulysse ULg et al

in Calcified Tissue International (1989), 44

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See detailDetermination of minimum effective doses of luteinizing hormone and human chorionic gonadotropin for intrafollicular treatment to induce ovulation in dairy heifers.
Mala, J; Beckers, Jean-François ULg; Melo de Sousa, Noelita ULg et al

in Acta Veterinaria BRNO (2013), 82

The aim of this study was to determine the minimum effective intrafollicular doses of luteinizing hormone and human chorionic gonadotropin in order to induce ovulation in cycling dairy heifers that have ... [more ▼]

The aim of this study was to determine the minimum effective intrafollicular doses of luteinizing hormone and human chorionic gonadotropin in order to induce ovulation in cycling dairy heifers that have not yet been adequately established. Application of 10, 5, 1, 0.5, 0.1, 0.01 and 0.001 µg luteinizing hormone as well as 10, 1, 0.1, 0.01 and 0.001 international units (IU) of human chorionic gonadotropin in dominant follicles was performed on day 7 of the oestrous cycle. Control animals were given luteinizing hormone (12.5 mg and 25 mg) or human chorionic gonadotropin (2000 IU) intravenously. Accessory corpus luteum on day 14 of the oestrous cycle was considered as an evidence of ovulation. Ovulation was observed in 2 out of 3 heifers in each treatment group (n = 3) after administration of 10–0.1 µg luteinizing hormone (except for 0.5 µg – ovulation in 3 of 3 heifers), in all heifers after administration of 10–0.01 IU human chorionic gonadotropin as well as in all control heifers. Administration of 0.01 µg and 0.001 µg luteinizing hormone as well as of 0.001 IU human chorionic gonadotropin did not result in ovulation. Higher progesterone concentration on day 14 vs. day 7 of the oestrous cycle was found after all treatments. Nevertheless, the differences were signicant (P < 0.05) only after intrafollicular treatments with 5, 1 and 0.001 µg luteinizing hormone as well as 10, 1 and 0.01 IU human chorionic gonadotropin. In conclusion, minimum efcient doses for intrafollicular treatment of the dominant follicles in cycling heifers capable of inducing ovulation were 0.1 µg of luteinizing hormone and 0.01 IU of human chorionic gonadotropin. This is the rst study describing the intrafollicular luteinizing hormone administration in cycling dairy heifers. [less ▲]

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