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See detailCollaborative study of an liquid chromatographic method for the determination of R-timolol and other related substances in S-timolol maleate
Marini, R. D.; Matthijs, N.; Vanderheyden, Yvan et al

in Analytica Chimica Acta (2005), 546(2), 182-192

A collaborative study applying an enantiomeric liquid chromatographic (LC) method was carried out to determine the content of the enantiomeric impurity R-timolol and other related substances in three ... [more ▼]

A collaborative study applying an enantiomeric liquid chromatographic (LC) method was carried out to determine the content of the enantiomeric impurity R-timolol and other related substances in three different S-timolol maleate samples. Eight laboratories, all located in Europe, participated in the study. The quantitative results obtained were used to estimate the uncertainty on the content of the different impurities. For that purpose, a set-up was adapted from the ISO guidelines 5725-2, which allowed the estimation of the different variances, i.e. the between-laboratories (s(laboratories)(2)), the between-days (s(days)(2)) and the between-replicates (s(replicates)(2)), The variances of repeatability (s(r)(2)) and reproducibility (s(R)(2)) were then calculated using the equations s(r)(2) = s(replicates)(2) and s(R)(2) = s(replicates)(2) + s(days)(2) + s(laboratories)(2). For the timolol impurities, it was found that the estimated uncertainty seem to be concentration-dependent. Since the LC method which combines the compendial ones for enantiomeric purity and related substances testing was applied to evaluate uncertainty in this collaborative study, it was shown how a laboratory can evaluate the uncertainty of its results when applying the method in the future. (c) 2005 Elsevier B.V. All rights reserved. [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 detailAutomated method for the determination of a new matrix metalloproteinase inhibitor in ovine plasma and serum by coupling of restricted access material for on-line sample clean-up to liquid chromatography
Chiap, Patrice ULg; Piette, Marie ULg; Evrard, Brigitte ULg et al

in Journal of Chromatography. B : Analytical Technologies in the Biomedical & Life Sciences (2005), 817(1), 109-117

A fully automated liquid chromatographic method was developed for the determination of Ro 28-2653, a new synthetic inhibitor of matrix metalloproteinases (MMPs), in ovine serum and plasma. The method was ... [more ▼]

A fully automated liquid chromatographic method was developed for the determination of Ro 28-2653, a new synthetic inhibitor of matrix metalloproteinases (MMPs), in ovine serum and plasma. The method was based on the coupling of a pre-column packed with restricted access material, namely LiChrospher RP-8 ADS (alkyl diol silica), for sample clean-up to an analytical column containing octyl silica stationary phase. One hundred mul of biological sample, to which 2-propanol was automatically added, were injected onto the ADS pre-column, which was then washed with a washing liquid consisting of a mixture of 25 mM phosphate buffer (pH 7.0) and acetonitrile (90: 10; v/v) for 10 min. By rotation of the switching valve, the analyte was then eluted in the back-flush mode with the LC mobile phase composed of a mixture of acetonitrile and 25 mM phosphate buffer (pH 7.0) (57:43; v/v). The UV detection was performed at 395 nm. The main parameters likely to influence the sample preparation technique were investigated. The method was then validated over a concentration range from 17.5 to 1950 ng/mI, the first concentration level corresponding to the lower limit of quantitation. At this concentration level, the mean bias and the R.S.D. value for intermediate precision were -2.4% and 4.2%, respectively. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

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See detailUncertainty assessment from robustness testing applied on an LC assay for R-timolol and other related substances in S-timolol maleate
Marini Djang'Eing'A, Roland ULg; Boulanger, Bruno ULg; Vanderheyden, Yvan et al

in Analytica Chimica Acta (2005), 531(1), 131-140

The robustness testing of a normal-phase liquid chromatographic (LC) method for the determination of R-timolol and other related substances in S-timolol maleate was performed applying a two-level Plackett ... [more ▼]

The robustness testing of a normal-phase liquid chromatographic (LC) method for the determination of R-timolol and other related substances in S-timolol maleate was performed applying a two-level Plackett-Burman design. Two qualitative and five quantitative factors were examined. Two types of responses were considered, qualitative, i.e. chromatographic performance criteria, and quantitative ones. The latter were taken into account to determine if the analytical procedure was robust. The quantitative responses were the contents of R-timolol in two S-timolol maleate samples. Even though some significant factor effects were observed on the qualitative responses, the R-timolol contents were not significantly different from those observed at nominal conditions, which demonstrated the robustness of 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. It was shown that the robustness set-up allows estimating the reproducibility uncertainty without performing an interlaboratory study. (c) 2004 Elsevier B.V. All rights reserved. [less ▲]

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See detailDevelopment and validation of a fully automated LC method for the determination of cloxacillin in human plasma using anion exchancre restricted access material for sample clean-up
Rbeida, O.; Chiap, Patrice ULg; Lubda, D. et al

in Journal of Pharmaceutical & Biomedical Analysis (2005), 36(5), 961-968

In the framework of a preliminary investigation on the plasma profile of cloxacillin after oral administration, a simple and rapid LC method was developed for the direct determination of this compound in ... [more ▼]

In the framework of a preliminary investigation on the plasma profile of cloxacillin after oral administration, a simple and rapid LC method was developed for the direct determination of this compound in human plasma. The on-line sample clean-up was carried out using a weak anion exchanger (diethylaminoethyl groups) as restricted access material (RAM). The effects of the washing liquid pH, the ionic strength and the addition of organic modifier to the washing liquid were studied in order to obtain an efficient sample clean-up and a high recovery of cloxacillin. The separation was achieved on octadecylsilica stationary phase using a mobile phase consisting in a mixture of phosphate buffer (pH 4.0; 25 mM) and acetonitrile (72:28, v/v). The UV detection was performed at 215 nm. The most appropriate regression model of the response function as well as the limit of quantitation (LOQ) were first selected during the pre-validation step. These criteria were then assessed during the formal validation step. The LOQ was 50 ng/ml. The method was also validated with respect to analyte recovery, precision. trueness, accuracy and linearity. Finally, it was successfully applied for the analysis of the first plasma samples obtained from patients, having taken an oral dose of 500 mg cloxacillin. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

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See detailIntegrated on-line sample clean-up using cation exchange restricted access sorbent for the LC determination of atropine in human plasma coupled to UV detection
Rbeida, O.; Christiaens, B.; Hubert, Philippe ULg et al

in Journal of Pharmaceutical & Biomedical Analysis (2005), 36(5), 947-954

A new, simple and fully automated liquid chromatographic (LC) method with UV detection has been developed for the direct determination of atropine in plasma. Sample clean-up was based on the use of cation ... [more ▼]

A new, simple and fully automated liquid chromatographic (LC) method with UV detection has been developed for the direct determination of atropine in plasma. Sample clean-up was based on the use of cation exchange restricted access material (RAM) in a pre-column, coupled to LC by means of a column switching system. After direct injection of a 200 microl-volume of plasma sample, the biological matrix was washed out for 10 min using a washing liquid composed of 2 mM lithium perchlorate adjusted to pH 3.0 and methanol (97:3; v/v). By rotation of the switching valve, atropine was then eluted in the back-flush mode for 2 min and transferred to the analytical column packed with octadecyl silica by the LC mobile phase constituted of a mixture of acetonitrile and potassium phosphate buffer (pH 3.0; 50 mM) containing 2 mM sodium heptanesulfonate (16:84; v/v). The UV detection was performed at 220 nm. The method was validated according to a new approach based on accuracy profile over a concentration range from 25 ng/ml, corresponding to the limit of quantitation, to 1000 ng/ml. The method was then applied for the determination of atropine in plasma after intravenous administration to hospitalised patients. [less ▲]

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See detailbeta-carbolines induce apoptosis in cultured cerebellar granule neurons via the mitochondrial pathway
Hans, Grégory ULg; Malgrange, Brigitte ULg; Lallemend, François et al

in Neuropharmacology (2005), 48(1), 105-117

N-Butyl-beta-carboline-3-carboxylate (betaCCB) is, together with 2-methyl-norharmanium and 2,9-dimethylnorharmanium ions, an endogenously occurring beta-carboline. Due to their structural similarities ... [more ▼]

N-Butyl-beta-carboline-3-carboxylate (betaCCB) is, together with 2-methyl-norharmanium and 2,9-dimethylnorharmanium ions, an endogenously occurring beta-carboline. Due to their structural similarities with the synthetic neurotoxin 1-methy14-phenyl-1,2,3,6-tetrahydropyridine (MPTP), harman and norharman compounds have been proposed to be involved in the pathogenesis of Parkinson's disease. While also structurally related, betaCCB has received much less interest in that respect although we had previously demonstrated that it induces the apoptotic cell death of cultured cerebellar granule neurons (CGNs). Herein, we have investigated the molecular events leading to CGN apoptosis upon betaCCB treatment. We first demonstrated that betaCCB-induced apoptosis occurs in neurons only, most likely as a consequence of a specific neuronal uptake as shown using binding/uptake experiments. Then we observed that, in betaCCB-treated CGNs, caspases 9, 3 and 8 were successively activated, suegesing an activation of the mitochondrial pathway. Consistently, betaCCB also induced the release from the mitochondrial intermembrane space of two pro-apoptotic factors. i.e. cytochrome c and apotptosis inducing factor (AIF). Interestingly, no mitochondrial membrane depolarisation was associated with this release. suggesting a mitochondrial permeability transition pore-independent mechanism. The absence of any neuroprotective effect provided by two mPTP inhibitors. i.e. cyclosporine A and bongkrekic acid. further supported this hypothesis. Together. these results show that betaCCB is specifically taken up by neuronal cells where it triggers a specific permeabilization of the outer mitochondrial membrane and a subsequent apoptotic cell death. (C) 2004 Elsevier Ltd. All rights reserved. [less ▲]

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See detailUSING TOTAL ERROR AS DECISION CRITERION IN METHOD TRANSFER
Rozet, Eric ULg; Mertens, B.; Dewe, W. et al

Poster (2005)

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See detailThe Usefulness of Accuracy Profile to Validate Analytical Methods
Rozet, Eric ULg; Chiap, Patrice ULg; Dewe, W. et al

Conference (2005)

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See detailCollaborative study of an liquid chromatographic method for the determination of R-timolol and other related substances in S-timolol maleate
Marini Djang'Eing'A, Roland ULg; Matthijs, N.; Heyden, Y. V. et al

in Analytica Chimica Acta (2005), 546(2), 182-192

A collaborative study applying an enantiomeric liquid chromatographic (LC) method was carried out to determine the content of the enantiomeric impurity R-timolol and other related substances in three ... [more ▼]

A collaborative study applying an enantiomeric liquid chromatographic (LC) method was carried out to determine the content of the enantiomeric impurity R-timolol and other related substances in three different S-timolol maleate samples. Eight laboratories, all located in Europe, participated in the study. The quantitative results obtained were used to estimate the uncertainty on the content of the different impurities. For that purpose, a set-up was adapted from the ISO guidelines 5725-2, which allowed the estimation of the different variances, i.e. the between-laboratories (s(laboratories)(2)), the between-days (s(days)(2)) and the between-replicates (s(replicates)(2)), The variances of repeatability (s(r)(2)) and reproducibility (s(R)(2)) were then calculated using the equations s(r)(2) = s(replicates)(2) and s(R)(2) = s(replicates)(2) + s(days)(2) + s(laboratories)(2). For the timolol impurities, it was found that the estimated uncertainty seem to be concentration-dependent. Since the LC method which combines the compendial ones for enantiomeric purity and related substances testing was applied to evaluate uncertainty in this collaborative study, it was shown how a laboratory can evaluate the uncertainty of its results when applying the method in the future. (c) 2005 Elsevier B.V. All rights reserved. [less ▲]

Detailed reference viewed: 43 (2 ULg)