References of "Servais, Anne-Catherine"
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See detailRobustness testing of a chiral NACE method for R-timolol determination in S-timolol maleate and uncertainty assessment from quantitative data.
Marini Djang'Eing'A, Roland ULg; Rozet, Eric ULg; Vanderheyden, Yvan et al

in Journal of Pharmaceutical & Biomedical Analysis (2007), 44(3), 640-51

A robustness test of a capillary electrophoresis method for the chiral separation of timolol in nonaqueous acidified media was performed. A two-level Plackett-Burman design was applied in which one ... [more ▼]

A robustness test of a capillary electrophoresis method for the chiral separation of timolol in nonaqueous acidified media was performed. A two-level Plackett-Burman design was applied in which one qualitative and six quantitative factors were examined. Resolution, migration times and relative migration times to pyridoxine (selected as internal standard) were examined as qualitative responses to evaluate electrophoretic performance. A quantitative response, the content of R-timolol in S-timolol maleate sample, was also considered. Even though some significant factor effects were observed on the qualitative responses, it was still possible to quantify the R-timolol in the S-timolol maleate samples properly. The quantitative response was not significantly affected by the selected factors, demonstrating the robustness of the procedure. However, the use of different HDMS-beta-CD batches seemed to affect both types of responses necessitating to introduce a warning in the procedure. Since the experiments of the Plackett-Burman design can be assimilated to laboratories in an interlaboratory study, uncertainty can be evaluated using the robustness test data. The robustness test was set-up in such a way that the required variances could be estimated. [less ▲]

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See detailEnantiomeric separation of acidic compounds using single-isomer amino cyclodextrin derivatives in nonaqueous capillary electrophoresis
Fradi, Inès; Servais, Anne-Catherine ULg; Pedrini, Matteo et al

in Electrophoresis (2006), 27(17), 3434-3442

The enantiomeric separation of a series of acidic pharmaceuticals (mostly nonsteroidal anti-inflammatory drugs) has been investigated in NACE systems using single-isomer amino beta-CD derivatives. The ... [more ▼]

The enantiomeric separation of a series of acidic pharmaceuticals (mostly nonsteroidal anti-inflammatory drugs) has been investigated in NACE systems using single-isomer amino beta-CD derivatives. The first part of this study consisted of the selection of the basic experimental conditions to separate efficiently the enantiomers of acidic drugs. Several parameters, such as the nature of the ionic BGE components, were studied and a methanolic solution of ammonium acetate containing the cationic CD was selected as BGE. A D-optimal design with 20 experimental points was then applied and the nature and concentration of the CD were found to have a significant effect on the enantiomeric resolution for all studied compounds. Resolution (R(s)) values were always higher with 6-monodeoxy-6-mono(3-hydroxy)propylamino-beta-CD (PA-beta-CD) compared to those obtained with 6-monodeoxy-6-mono(2-hydroxy)propylamino-beta-CD (IPA-beta-CD). However, the latter led to shorter migration times. Generic NACE conditions were then selected by means of the multivariate approach in order to obtain the highest R(s) values in a minimum amount of time. Finally, dependence of separation selectivity, resolution, as well as mobility difference on chiral selector concentration was discussed and binding constants with PA-beta-CD were estimated for the two enantiomers of one of the model compounds, suprofen in these NACE systems. [less ▲]

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See detailCapillary electrophoresis-mass spectrometry, an attractive tool for drug bioanalysis and biomarker discovery
Servais, Anne-Catherine ULg; Crommen, Jacques ULg; Fillet, Marianne ULg

in Electrophoresis (2006), 27(13), 2616-2629

The coupling of CE with MS detection, a relatively recent hyphenated technique, has gained increasing respect in the field of bioanalytical applications over the past few years. The first part of this ... [more ▼]

The coupling of CE with MS detection, a relatively recent hyphenated technique, has gained increasing respect in the field of bioanalytical applications over the past few years. The first part of this review presents CE-MS applications dealing with drug bioanalysis, including forensic analysis and metabolism studies. Practical considerations to achieve a robust and sensitive CE-MS coupling are also presented. It is indeed essential to strictly control some critical electrospray parameters, such as the sheath liquid composition and flow rate, the nebulizing gas pressure as well as the capillary outlet position. The second part of the review critically describes the applications of CE coupled on-line to MS for the identification of biomarkers in body fluids for diagnostic purposes. Since the sample preparation procedures strongly differ according to the intended use (drug bioanalysis or biomarker discovery), they are discussed separately, taking into account the particular properties of plasma and urine matrices. [less ▲]

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See detailOn-line coupling of cyclodextrin mediated nonaqueous capillary electrophoresis to mass spectrometry for the determination of salbutamol enantiomers in urine
Servais, Anne-Catherine ULg; Fillet, Marianne ULg; Mol, Roelof et al

in Journal of Pharmaceutical & Biomedical Analysis (2006), 40(3), 752-757

The usefulness of the on-line coupling of nonaqueous capillary electrophoresis (NACE) with electrospray ionization (ESI) mass spectrometry (MS) using heptakis(2,3-di-O-acetyl-6-O-sulfo)-beta-cyclodextrin ... [more ▼]

The usefulness of the on-line coupling of nonaqueous capillary electrophoresis (NACE) with electrospray ionization (ESI) mass spectrometry (MS) using heptakis(2,3-di-O-acetyl-6-O-sulfo)-beta-cyclodextrin (HDAS-beta-CD) was demonstrated for the enantioselective determination of low concentrations of salbutamol in human urine. After optimization of several parameters, such as sheath-liquid composition and flow rate, nebulizing gas pressure, CE counter-pressure and position of the CE capillary outlet, a limit of quantification of 18 and 20 ng/ml was obtained for salbutamol enantiomers. Moreover, the relative standard deviation values for repeatability at a concentration of 30 ng/ml were below 7% for both enantiomers. Typical regression lines obtained after application of a simple linear regression model revealed a pod relationship between peak area and analyte concentration (with 0.9988 and 0.9966 as coefficients of determination). This paper proposes an easy to use and sensitive NACE-MS method to determine enantiomers of a basic chiral drug in biological fluids preceded by solid-phase extraction as sample cleanup. (c) 2005 Elsevier B.V. All rights reserved. [less ▲]

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See detailInterlaboratory study of a NACE method for the determination of R-timolol content in S-timolol maleate: assessment of uncertainty.
Marini Djang'Eing'A, Roland ULg; Groom, Carl; Doucet, Francois R et al

in Electrophoresis (2006), 27(12), 2386-99

Analyses of statistical variance were applied to evaluate the precision and practicality of a CD-based NACE assay for R-timolol after enantiomeric separation of R- and S-timolol. Data were collected in an ... [more ▼]

Analyses of statistical variance were applied to evaluate the precision and practicality of a CD-based NACE assay for R-timolol after enantiomeric separation of R- and S-timolol. Data were collected in an interlaboratory study by 11 participating laboratories located in Europe and North America. General qualitative method performance was examined using suitability descriptors (i.e. resolution, selectivity, migration times and S/N), while precision was determined by quantification of variances in the determination of R-timolol at four different impurity levels in S-timolol maleate samples. The interlaboratory trials were designed in accordance with the ISO guideline 5725-2. This allowed estimating for each sample, the different variances, i.e. between-laboratory (s2(Laboratories)), between-day (s2(Days)) and between-replicate (s2(Replicates)). The variances of repeatability (s2r) and reproducibility (s2R) were then calculated. The estimated uncertainty, derived from the precision estimates, seems to be concentration-dependent above a given threshold. This example of R-timolol illustrates how a laboratory can evaluate uncertainty in general. [less ▲]

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See detailNonaqueous capillary electrophoresis method for the enantiomeric purity determination of S-timolol using heptakis(2,3-di-O-methyl-6-O-sulfo)-beta-cyclodextrin: validation using the accuracy profile strategy and estimation of uncertainty.
Marini Djang'Eing'A, Roland ULg; Servais, Anne-Catherine ULg; Rozet, Eric ULg et al

in Journal of Chromatography. A (2006), 1120(1-2), 102-11

Nonaqueous capillary electrophoresis (NACE) was successfully applied to the enantiomeric purity determination of S-timolol maleate using heptakis(2,3-di-O-methyl-6-O-sulfo)-beta-cyclodextrin (HDMS-beta-CD ... [more ▼]

Nonaqueous capillary electrophoresis (NACE) was successfully applied to the enantiomeric purity determination of S-timolol maleate using heptakis(2,3-di-O-methyl-6-O-sulfo)-beta-cyclodextrin (HDMS-beta-CD) as chiral selector. With a background electrolyte made up of a methanolic solution of 0.75 M formic acid, 30 mM potassium camphorsulfonate and containing 30 mM HDMS-beta-CD, the determination of 0.1% of R-timolol in S-timolol could be performed with an enantiomeric resolution of 8.5. Pyridoxine was selected as internal standard. The NACE method was then fully validated by applying a novel strategy using accuracy profiles. It is based on beta-expectation tolerance intervals for the total measurement error which includes trueness and intermediate precision. The uncertainty of measurements derived from beta-expectation tolerance intervals was estimated at each concentration level of the validation standards. To confirm the suitability of the developed and validated method, several real samples of S-timolol maleate containing R-timolol maleate at different concentrations were analysed and the results were compared to those obtained by liquid chromatography. [less ▲]

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See detailInfluence of the nature of the electrolyte on the chiral separation of basic compounds in nonaqueous capillary electrophoresis using heptakis(2,3-di-O-methyl-6-O-sulfo)-beta-cyclodextrin
Servais, Anne-Catherine ULg; Fillet, Marianne ULg; Chiap, Patrice ULg et al

in Journal of Chromatography. A (2005), 1068(1), 143-150

The influence on the enantiomeric resolution of the nature of the cationic BGE component (sodium, ammonium or potassium) and that of the anionic component (chloride, formate, methanesulfonate or ... [more ▼]

The influence on the enantiomeric resolution of the nature of the cationic BGE component (sodium, ammonium or potassium) and that of the anionic component (chloride, formate, methanesulfonate or camphorsulfonate) as well as the concentration of heptakis(2,3-di-O-methyl-6-O-sulfo)-beta-cyclodextrin (HDMS-beta-CD), the selected chiral selector, was studied in nonaqueous capillary electrophoresis (NACE). For this purpose, two D-optimal designs with 33 and 26 experimental points were applied. Three beta-blockers (atenolol, celiprolol and propranolol) and three local anesthetics (bupivacaine, mepivacaine and prilocaine) were selected as basic model compounds. Both cationic and anionic BGE components were found to have a deep impact on the enantiomeric resolution of the investigated analytes but it is the cationic component that has shown the strongest influence. Indeed, in some cases, the change of the latter led to a complete loss of enantioresolution. Based on the observed results, two NACE systems were recommended, namely ammonium formate and potassium camphorsulfonate in a methanolic solution containing HDMS-beta-CD and acidified with formic acid, in order to separate efficiently the enantiomers of basic drugs. (c) 2004 Elsevier B.V. All rights reserved. [less ▲]

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See detailSéparation et dosage de substances médicamenteuses par électrophorèse capillaire en milieu non aqueux : Influence de l’utilisation simultanée d’une cyclodextrine et d’un agent d’appariement d’ions
Servais, Anne-Catherine ULg

Doctoral thesis (2005)

The use of nonaqueous electrolyte solutions in capillary electrophoresis (CE) has made it possible to open up new horizons in the field of drug analysis. The achiral separation of four beta-blockers was ... [more ▼]

The use of nonaqueous electrolyte solutions in capillary electrophoresis (CE) has made it possible to open up new horizons in the field of drug analysis. The achiral separation of four beta-blockers was first investigated in nonaqueous CE (NACE) using the principle of ion-pair formation. Camphorsulfonate was selected as the counter-ion. The influence on resolution of parameters such as the nature and concentration of the counter-ion and the ionic components of the background electrolyte was studied by means of a univariate approach. Experimental designs were then applied to estimate possible quadratic effects and first-order interactions. Finally, the optimal conditions obtained by the univariate and the multivariate approaches were compared. The enantiomeric separation of basic pharmaceuticals was then investigated using an original combination in NACE, namely an ion-pairing reagent together with a cyclodextrin (CD). The simultaneous addition to the methanolic background electrolyte of (+)-S-camphorsulfonate or an alkanesulfonate and an anionic beta-CD derivative, namely heptakis(2,3-di-O-methyl-6-O-sulfo)-beta-CD (HDMS-beta-CD), led to partial or complete enantioresolution in all cases. The influence on the enantioseparation of the nature and concentration of the counter-ion and the anionic CD derivative was studied by means of a univariate approach. In order to understand the effects on the enantiomeric resolution of the simultaneous use of camphorsulfonate and HDMS-b-CD, experimental designs were applied. A fast method development strategy was finally recommended for the enantioseparation of basic drug compounds. The influence on the enantiomeric resolution of the nature of the cationic and anionic background electrolyte components was also studied in the presence of several HDMS-beta-CD concentrations. Both cationic and anionic background electrolyte components were found to have a deep impact on the enantioseparation but it is the cationic component that seems to have the strongest influence. Finally, NACE was successfully applied to the resolution and the determination of salbutamol enantiomers in urine samples using heptakis(2,3-di-O-acetyl-6-O-sulfo)-beta-CD. Solid phase extraction was used for sample clean-up prior to the CE separation. The method was then fully validated using a new approach based on accuracy profiles over a concentration range from 375 to 7500 ng/ml for each enantiomer. [less ▲]

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