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See detailDevelopment and validation of a high performance liquid chromatographic method for quantitative determination of aporphine alkaloids from different samples of Cassytha filiformis
Stevigny, C.; Wautier, M. C.; Jiwan, J. L. H. et al

in Planta Medica (2004), 70(8), 764-770

A sensitive and accurate procedure based on an alkaloid extraction coupled to an HPLC-UV-MS determination has been developed for the separation and quantification of the major aporphines in Cassytha ... [more ▼]

A sensitive and accurate procedure based on an alkaloid extraction coupled to an HPLC-UV-MS determination has been developed for the separation and quantification of the major aporphines in Cassytha filiformis. The extraction step and the liquid chromatography conditions were optimized in order to improve the selectivity of the method. The HPLC mobile phase consisted of a mixture of water containing 10 mM ammonium acetate adjusted to pH 3 with acetic acid-acetonitrile (90: 10, v/v) (A) and acetonitrile (B) used in a gradient mode (0 to 40%). The stationary phase was an RP-select B (5 mum) column. The method was completely validated using cassythine, one of the major aporphines in our samples, as reference standard and successfully applied to the determination of these pharmacologically interesting aporphines in seven different batches of C. filiformis. The detection and quantitation limits of cassythine were found to be 13 and 20 mug/mL, respectively. The results showed variations in the total alkaloid content in samples from 0.11 to 0.43%. [less ▲]

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See detailDevelopment and validation of a high-performance liquid chromatographic method for the determination of cyproterone acetate in human skin
Henry de Hassonville, Sandrine; Chiap, Patrice ULg; Liégeois, Jean-François ULg et al

in Journal of Pharmaceutical & Biomedical Analysis (2004), 36(1), 133-143

In the framework of a preliminary study on the transdermal penetration of cyproterone acetate (CPA), a simple and rapid procedure involving an extraction step coupled to a HPLC-UV determination has been ... [more ▼]

In the framework of a preliminary study on the transdermal penetration of cyproterone acetate (CPA), a simple and rapid procedure involving an extraction step coupled to a HPLC-UV determination has been developed for the separation and quantification of CPA in the two main skin layers-epidermis and dermis-after local application. The separation of epidermis and dermis layers was carefully carried out by means of a sharp spatula after skin immersion in heated water at 65 degrees C. The two skin layers were then treated separately according to the same process: (1) sample homogenization by vibration after freezing with liquid nitrogen in a Mikro-Dismembrator; (2) CPA extraction with methanol after addition of the internal standard (betamethasone dipropionate); (3) centrifugation; (4) evaporation of a supernatant aliquot; (5) dissolution of the dry residue in methanol and addition of water; (6) centrifugation; (7) injection of a supernatant aliquot into the HPLC system. The separation was achieved on octadecylsilica stationary phase using a mobile phase consisting in a mixture of acetonitrile and water (40:60 (v/v)). The method was then validated using a new approach based on accuracy profiles over a CPA concentration range from 33 to 667 ng/ml for each skin layer. Finally, the method was successfully applied to the determination of CPA to several skin samples after topical application of different gel formulations containing CPA. [less ▲]

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See detailDevelopment and validation of a LC method for the enantiomeric purity determination of S-ropivacaine in a pharmaceutical formulation using a recently commercialized cellulose-based chiral stationary phase and polar non-aqueous mobile phase.
Dossou, Katina Sourou Sylvestre ULg; CHIAP, Patrice ULg; Servais, Anne-Catherine ULg et al

in Journal of Pharmaceutical & Biomedical Analysis (2011), 54(4), 687-93

Ropivacaine is the first enantiomerically pure long-acting local anaesthetic used for surgical anaesthesia and post-operative pain relief. A liquid chromatographic (LC) method using acetonitrile as the ... [more ▼]

Ropivacaine is the first enantiomerically pure long-acting local anaesthetic used for surgical anaesthesia and post-operative pain relief. A liquid chromatographic (LC) method using acetonitrile as the main solvent and cellulose tris(4-chloro-3-methylphenylcarbamate) coated on silica as chiral stationary phase was successfully developed and applied for the enantiomeric purity determination of S-ropivacaine in a pharmaceutical formulation (Naropin((R))). The key role played by the acidic additive (trifluoroacetic acid or formic acid) in the enantioseparation of basic drugs in these LC systems was demonstrated by the reversal of ropivacaine enantiomers elution order observed when both acids were compared. In order to elute the enantiomeric impurity (R-ropivacaine) before S-ropivacaine, formic acid (FA) was selected. The temperature and the percentages of acidic additive and hexane in the mobile phase were found to significantly influence the retention and resolution of these enantiomers. The optimized mobile phase consisted of ACN/0.1% DEA/0.2% FA/5% hexane (v/v/v/v). The temperature was set at 35 degrees C to avoid the interference from a peak system related to the presence of water in the sample on ropivacaine enantiomers. The LC method was then fully validated applying the strategy based on total measurement error and accuracy profiles. The accuracy profile obtained by linear regression after square root transformation was selected, the acceptance limits being settled at +/-10% for the intended use of this analytical method. The relative bias was lower than 1.5%, while the RSD values for repeatability and intermediate precision were both below 1.0%. The limit of detection (LOD) and the limit of quantification (LOQ) were found to be about 0.2 and 1.0 mug/mL, respectively, corresponding to 0.02 and 0.1% of the enantiomeric impurity in S-ropivacaine. [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 detailDevelopment and Validation of a Markov Microsimulation Model for the Economic Evaluation of Treatments in Osteoporosis.
Hiligsmann, Mickaël ULg; Ethgen, Olivier ULg; Bruyère, Olivier ULg et al

in Value in Health (2009), 12(5), 687-696

ABSTRACT Objective: Markov models are increasingly used in economic evaluations of treatments for osteoporosis. Most of the existing evaluations are cohort-based Markov models missing comprehensive memory ... [more ▼]

ABSTRACT Objective: Markov models are increasingly used in economic evaluations of treatments for osteoporosis. Most of the existing evaluations are cohort-based Markov models missing comprehensive memory management and versatility. In this article, we describe and validate an original Markov microsimulation model to accurately assess the cost-effectiveness of prevention and treatment of osteoporosis. Methods: We developed a Markov microsimulation model with a lifetime horizon and a direct health-care cost perspective. The patient history was recorded and was used in calculations of transition probabilities, utilities, and costs. To test the internal consistency of the model, we carried out an example calculation for alendronate therapy. Then, external consistency was investigated by comparing absolute lifetime risk of fracture estimates with epidemiologic data. Results: For women at age 70 years, with a twofold increase in the fracture risk of the average population, the costs per quality-adjusted life-year gained for alendronate therapy versus no treatment were estimated at Euro 9105 and Euro 15,325, respectively, under full and realistic adherence assumptions. All the sensitivity analyses in terms of model parameters and modeling assumptions were coherent with expected conclusions and absolute lifetime risk of fracture estimates were within the range of previous estimates, which confirmed both internal and external consistency of the model. Conclusion: Microsimulation models present some major advantages over cohort-based models, increasing the reliability of the results and being largely compatible with the existing state of the art, evidence-based literature. The developed model appears to be a valid model for use in economic evaluations in osteoporosis. [less ▲]

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See detailDevelopment and validation of a multi-residue method for pesticide determination in honey using on-column liquid-liquid extraction and liquid chromatography-tandem mass spectrometry
PIRARD, Catherine ULg; Widart, Joëlle ULg; Nguyen, Bach Kim ULg et al

in Journal of Chromatography. A (2007), 1152(1-2), 116-123

We report on the development and validation under ISO 17025 criteria of a multi-residue confirmatory method to identify and quantify 17 widely chemically different pesticides (insecticides: Carbofuran ... [more ▼]

We report on the development and validation under ISO 17025 criteria of a multi-residue confirmatory method to identify and quantify 17 widely chemically different pesticides (insecticides: Carbofuran, Methiocarb, Pirimicarb, Dimethoate, Fipronil, Imidacloprid; herbicides: Amidosulfuron, Rimsulfuron, Atrazine, Simazine, Chloroturon, Linuron, Isoxaflutole, Metosulam; fungicides: Diethofencarb) and 2 metabolites (Methiocarb sulfoxide and 2-Hydroxytertbutylazine) in honey. This method is based on an on-column liquid liquid extraction (OCLLE) using diatomaceous earth as inert solid support and liquid chromatography (LC) coupled to mass spectrometry (MS) operating in tandem mode (MS/MS). Method specificity is ensured by checking retention time and theoretical ratio between two transitions from a single precursor ion. Linearity is demonstrated all along the range of concentration that was investigated, from 0.1 to 20 ng g(-1) raw honey, with correlation coefficients ranging from 0.921 to 0.999, depending on chemicals. Recovery rates obtained on home-made quality control samples are between 71 and 90%, well above the range defined by the EC/657/2002 document, but in the range we had fixed to ensure proper quantification, as levels found in real samples could not be corrected for recovery rates. Reproducibility is found to be between 8 and 27%. Calculated CC alpha and CC beta (0.0002-0.943 mg g(-1) for CC alpha, and 0.0002-1.232 ng g(-1) for CCP) show the good sensitivity attained by this rnulti-residue analytical method. The robustness of the method has been tested in analyzing more than 100 raw honey samples collected from different areas in Belgium, as well as some wax and bee samples, with a slightly adapted procedure. (C) 2007 Elsevier B.V. All rights reserved. [less ▲]

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See detailDevelopment and validation of a new Fourier transform infrared spectrometric method for the quantification of urea in creams and ointments
Otte, X; Evrard, Brigitte ULg; Delattre, Luc ULg et al

in Analytica Chimica Acta (2002), 451

A new Fourier transform infrared (FTIR) spectrometric method for the quantification of urea in creams and ointments was developed and validated. The sample was solubilized in a mixture of chloroform ... [more ▼]

A new Fourier transform infrared (FTIR) spectrometric method for the quantification of urea in creams and ointments was developed and validated. The sample was solubilized in a mixture of chloroform/acetonitrile (1/1 v/v) which allows to solubilize the vaseline or other fats as well as urea and water. The solution was examined in a transmission cell with a pathlength of 500 μm provided with NaCI windows. The urea spectrum was obtained by subtraction of the reference solvent mixture spectrum and the reference water spectrum from the sample spectrum. The absorbance of the peak at ±1688 cm-1 was compared to those of calibration standards to quantify urea. The detection limit and the quantification limit (three times and 10 times the noise, respectively) were estimated as 0.4 and 1.3 μg ml-1, respectively. Validation of the method was realized and application of this method to stability tests was done. [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 detailDevelopment and validation of a quantitative method for the selective determination of tin species in tin octoate by differential pulse polarography
Hubert, Cédric ULg; Ziemons, Eric ULg; Rozet, Eric ULg et al

in Talanta (2010), 80(3), 1413-1420

Tin octoate is used as a catalyst in the synthesis of polydimethylsiloxane (PDMS), a room temperature vulcanizing (RTV) silicone rubber. This rubber is largely used in the medical field due to its great ... [more ▼]

Tin octoate is used as a catalyst in the synthesis of polydimethylsiloxane (PDMS), a room temperature vulcanizing (RTV) silicone rubber. This rubber is largely used in the medical field due to its great biocompatibility. In this framework, a high-speed and costless analytical method for the determination of stannic ions, Sn(IV), in the presence of stannous ions, Sn(II), has been developed. The separation of these two ions was carried out using differential pulse polarography (DPP). For this purpose, the tin species contents in the catalyst is quantitatively extracted under inert condition to avoid any changes in the ratio Sn(IV)/Sn(II). Polarography showed well-shaped oxidation and reduction peaks respectively at −650 and −860 mV for stannous ions. The peak of the stannic ion was well separated and appeared at −1210 mV. Many parameters such as extraction process, extraction time, pH, chelating agents and polarographic conditions were optimized. We have also demonstrated that no oxidation of the stannous ions occurred during the sample preparation. The dosing range considered in this study extends between 10 and 40 μg/mL, corresponding to 6.8% and 27.2% of the degradation product (Sn(IV)) in the catalyst, regarding to the sampling. Finally this method was successfully validated using the total error concept. [less ▲]

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See detailDevelopment and validation of a questionnaire assessing volitional competencies to enhance the performance of physical activities in chronic low back pain patients.
Mathy, Céline ULg; Broonen, Jean-Paul ULg; Henrotin, Yves ULg et al

in BMC Musculoskeletal Disorders (2011), 12

BACKGROUND: Motivation has long been emphasized as the most important determinant of action. However, there is a substantial gap between people's goals and their attainment. Patients may be motivated and ... [more ▼]

BACKGROUND: Motivation has long been emphasized as the most important determinant of action. However, there is a substantial gap between people's goals and their attainment. Patients may be motivated and yet unable to take action if their volitional competencies are insufficient. One of the important tasks of volition is goal-maintenance. Research has stressed the importance of a volitional tool, the implementation intentions. Implementation intentions indicate where, when, and how the action leading to the goal will be performed. Forming implementation intentions favours the execution of goal-directed efforts, and reinforces the relationship between intentions and behaviours. Results from various studies clearly suggest that volitional competencies and implementation intentions could play a role in low back pain (LBP) patients. However, there is at present no questionnaire allowing assessing the capacity of implementation intentions of physical activities in LBP patients. METHODS/DESIGN: This study will develop such a questionnaire, using a 3-step approach. A first qualitative step to build categories and generate items; 30 patients suffering chronic LBP will be invited to participate in semi-structured interviews; verbatim and derived items will then be submitted to a panel of experts, using a Delphi method; a second quantitative step to examine the properties of items, and determine the factorial structure of the questionnaire; 100 patients suffering chronic LBP will be recruited to respond to this phase; and third, preliminary psychometric analyses (item-scale correlations, construct validity, reliability); 180 chronic LBP patients will be recruited for this phase of the study. The relationships between implementation intentions and variables affecting physical activity on chronic LBP patients, i.e. pain, physical capacities, fear-avoidance beliefs, kinesiophobia, work status, and level of physical activity will be considered. DISCUSSION: Developing a questionnaire to assess implementation intentions would allow investigating the role of these intentions in the transition from acute to chronic LBP. The results of this study should contribute to the understanding of the psychological processes at stake in the development of chronic LBP, and in particular to the identification of factors eventually favouring patients' participation in and adherence to active physical treatments. [less ▲]

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See detailDevelopment and validation of a radioimmunoassay for thyrotropin in cattle
Guyot, Hugues ULg; Sulon, Joseph ULg; Beckers, Jean-François ULg et al

in Journal of Veterinary Diagnostic Investigation (2007), 19(6), 643-651

In mammals, thyrotropin, or thyroid-stimulating hormone (TSH), assay is used for the diagnosis of primary hypothyroidism. Hypothyroidism is the most common type of thyroid disorder in cattle. The aim of ... [more ▼]

In mammals, thyrotropin, or thyroid-stimulating hormone (TSH), assay is used for the diagnosis of primary hypothyroidism. Hypothyroidism is the most common type of thyroid disorder in cattle. The aim of this study was to develop and validate, under physiologic and pathologic conditions, a radioimmunoassay (RIA) for bovine TSH (bTSH). Double RIA was performed with purified bTSH and specific bovine antiserum. Laboratory validation included research of minimal detection limit, accuracy, and reproducibility. The physiologic validation included a thyrotropin-releasing hormone (TRH) challenge performed on euthyroid cows and a follow-up of bTSH concentration over a 24-hour period. Furthermore, bTSH concentration was assayed in a large population of healthy dairy and beef cows to define reference interval. The pathologic validation was made by assaying bTSH and thyroid hormones on healthy and goitrous newborn calves. The minimum detection limit (MDL) for bTSH assay was 1.3 microU/ml. The recovery was 101% to 106%. The intra- and interassay coefficients of variation (CVs) ranged from 5% to 11% and 11% to 15%, respectively. The RIA covered the whole range of physiologic bTSH values, as shown by bTSH values induced by TRH-challenge. A pulsatile secretion of bTSH was observed, accompanied by a diurnal variation with lower night values than day values. Reference intervals of bTSH ranged from 1.3 to 13.0 microU/ml for beef and dairy breeds. Finally, bTSH easily discriminated goitrous newborn calves from healthy ones, leading to the definition of a cutoff value of 35 microU/ml. The bTSH assay positively reacted to physiologic and pathologic conditions. The accuracy and precision of the RIA were satisfying. [less ▲]

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See detailDevelopment and validation of a reference material for food microbiology using Bacillus cereus spores
Abel Massih, Marleen; Debast, Laurent; Planchon, Viviane et al

in Proceedings of the Thirteenth Conference on Food Microbiology (2008, September)

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