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See detailATR-IR and Raman spectroscopic study of interaction between major calixarene derivatives and oral anticoagulants
Tiuca, Ioana; Saponar, Alina; Bodoki, Andreea et al

in Farmacia (2013), 61(5), 874-882

In this study we analyzed by ATR-IR and Raman spectroscopy the interaction between six major calixarene derivatives and two anticoagulants: warfarin and acenocoumarol. The six calixarene derivatives were ... [more ▼]

In this study we analyzed by ATR-IR and Raman spectroscopy the interaction between six major calixarene derivatives and two anticoagulants: warfarin and acenocoumarol. The six calixarene derivatives were: p-tert-butyl-calix[4]arene (C4), p-tert- butyl-calix[6]arene (C6) and p-tert-butyl-calix[8]arene (C8) and their ethyl-ester- derivatives: tetraester-p-tert-butyl-calix[4]arene (C4Es4), hexaester-p-tert-butyl- calix[6]arene (C6Es6), octaester-p-tert-butyl-calix[8]arene (C8Es8). The results showed the most intense interaction in terms of complex formation for the C6-acenocoumarol couple and for the C6-warfarin couple, respectively. [less ▲]

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See detailApplication of a new optimization strategy for the separation of tertiary alkaloids extracted from Strychnos usambarensis leaves
Nistor, Iolanda ULg; Cao, Martine ULg; Debrus, Benjamin ULg et al

in Journal of Pharmaceutical & Biomedical Analysis (2011), 56

The HPLC separation of six alkaloids extracted from Strychnos usambarensis leaves has been developed and optimized by means of a powerful methodology for modelling chromatographic responses, based on ... [more ▼]

The HPLC separation of six alkaloids extracted from Strychnos usambarensis leaves has been developed and optimized by means of a powerful methodology for modelling chromatographic responses, based on three steps, i.e. design of experiments (DoE), independent component analysis (ICA) and design space (DS). This study was the first application of a new optimization strategy to a complex natural matrix. The compounds separated are the isomers isostrychnopentamine and strychnopentamine, 10-hydroxyusambarine and 11-hydroxyusambarine, also strychnophylline and strychnofoline. Three LC parameters have been optimized using a multifactorial design comprising 29 experiments that includes 2 center point replicates. The parameters were the percentage of organic modifiers used at the beginning of a gradient profile which consisted in different proportions of methanol (MeOH) and acetonitrile (MeCN), the gradient time to reach 70% of organic modifiers starting from the initial percentage and the percentage of MeCN found in the mobile phase. Subsequent to the experimental design application, predictive multilinear models were developed and used in order to provide optimal analytical conditions. The optimum assay conditions were: methanol/acetonitrile-sodium pentane sulfonate (pH 2.2; 7.5 mM) (33.4:66.6, v/v) at a mobile phase flow rate of 1mL/min during a 40.6 minutes gradient time. The initial organic phase contained 3.7% MeCN and 96.3% MeOH. The method showed good agreement between the experimental data and predictive value throughout the studied parameters space. Improvement of the analysis time and optimized separation for the compounds of interest was possible due to the original and powerful tools applied. Finally, this study permitted the acquisition of isomers profiles allowing the identification of the optimal collecting period of Strychnos usambarensis. [less ▲]

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See detailApplication of new methodologies based on design of experiments, independent component analysis and design space for robust optimization in liquid chromatography
Debrus, Benjamin ULg; Lebrun, Pierre ULg; Ceccato, Attilio ULg et al

in Analytica Chimica Acta (2011), 691

HPLC separations of an unknown sample mixture and a pharmaceutical formulation have been optimized using a recently developed chemometric methodology proposed by W. Dewé et al. in 2004 and improved by P ... [more ▼]

HPLC separations of an unknown sample mixture and a pharmaceutical formulation have been optimized using a recently developed chemometric methodology proposed by W. Dewé et al. in 2004 and improved by P. Lebrun et al. in 2008. This methodology is based on experimental designs which are used to model retention times of compounds of interest. Then, the prediction accuracy and the optimal separation robustness, including the uncertainty study, were evaluated. Finally, the design space (ICH Q8(R2) guideline) was computed as the probability for a criterion to lie in a selected range of acceptance. Furthermore, the chromatograms were automatically read. Peak detection and peak matching were carried out with a previously developed methodology using independent component analysis published by B. Debrus et al. in 2009. The present successful applications strengthen the high potential of these methodologies for the automated development of chromatographic methods. [less ▲]

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See detailRaman spectroscopic study of complex formation between major calixarene derivatives and three pharmaceutical substances
Tiuca, Ioana; Mantanus, Jérôme ULg; Iacob, Bogdan et al

Poster (2010, November)

Complex formation of six calix[n]arene derivatives – tert-butyl-calix[4]arene (C4), tert-butyl-calix[6]arene (C6), tert-butyl-calix[8]arene (C8) and their ethyl-acetic-ester derivatives (C4Es4, C6Es6 ... [more ▼]

Complex formation of six calix[n]arene derivatives – tert-butyl-calix[4]arene (C4), tert-butyl-calix[6]arene (C6), tert-butyl-calix[8]arene (C8) and their ethyl-acetic-ester derivatives (C4Es4, C6Es6, C8Es8) – has been the subject for our Raman spectroscopic study. Substances taken in study for complexation were the two widely used anticoagulants – warfarin and its 5-nitro- derivative, acenocoumarol – and their antidote, phytomenadione (also known as phylloquinone or vitamin K1). For each standard substance, Raman spectra were studied between 3620 and 90 cm-1. In order to obtain the complexes, a mixture of solutions of each calixarene and each analyte was prepared, in a stoichiometric ratio of 1:1 and then the solvents were evaporated. Spectra of solid residues obtained were compared with those of initial molecules. In all cases, there was observed a Raman band shifting or even the disappearance of some bands, indicating that calixarene derivatives interact with the studied molecules. In conclusion, the six calixarene derivatives taken in study seem to be able to form complexes with the molecules of warfarin, acenocoumarol and phylloquinone. [less ▲]

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See detailEffect of the nature of the single-isomer anionic CD and the BGE composition on the enantiomeric separation of beta-blockers in NACE.
Rousseau, Anne ULg; Chiap, Patrice ULg; Oprean, Radu et al

in Electrophoresis (2009), 30(16), 2862-8

The separation of ten beta-blockers has been investigated in NACE systems using heptakis(2,3-di-O-methyl-6-O-sulfo)-beta-CD (HDMS-beta-CD) and heptakis(2,3-di-O-acetyl-6-O-sulfo)-beta-CD (HDAS-beta-CD ... [more ▼]

The separation of ten beta-blockers has been investigated in NACE systems using heptakis(2,3-di-O-methyl-6-O-sulfo)-beta-CD (HDMS-beta-CD) and heptakis(2,3-di-O-acetyl-6-O-sulfo)-beta-CD (HDAS-beta-CD). The influence on enantioresolution, mobility difference and selectivity of the nature of both anionic CD and BGE anion as well as their concentrations were studied by means of a multivariate approach. A D-optimal design with 25 experimental points was applied. For all studied analytes, the enantiomeric resolution was shown to be significantly influenced by both CD nature and concentration. Except for two compounds, HDAS-beta-CD was found to give higher enantioresolution values than HDMS-beta-CD. The best enantioseparation for all compounds was achieved in the presence of a high chiral selector concentration and for most of them at a low BGE anion concentration. For each investigated compound, operating conditions leading to the best enantiomeric resolution were deduced. A generic NACE system was then recommended, namely 10 mM ammonium acetate and 40 mM HDAS-beta-CD in methanol acidified with 0.75 M formic acid. This generic system was able to completely resolve the enantiomers of all beta-blockers, with a R(s) value of at least 4. Finally, the optimal conditions obtained modelling resolution, mobility difference and selectivity were compared. [less ▲]

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See detailNouvelle méthodologie pour le développement automatisé de méthodes analytiques en chromatographie liquide pour l’analyse de mélanges de composés inconnus
Debrus, Benjamin ULg; Lebrun, Pierre ULg; Rozet, Eric ULg et al

in Spectra Analyse (2009), 268

Nowadays, many strategies to optimize chromatographic methods are available. However, the development of chromatographic methods remains the most limiting step in the process of synthesis or ... [more ▼]

Nowadays, many strategies to optimize chromatographic methods are available. However, the development of chromatographic methods remains the most limiting step in the process of synthesis or identification of new molecules that could lead to therapeutic agents or new biomarkers despite the availability of new technologies both in chemistry (chemical combinatorial, high throughput screening...) and in analytical biochemistr y (proteomics, metabolomics, herbal ... fingerprinting). Therefore, the aim of this study is to test a new methodology for developing automated chromatographic methods combining experimental planning, independent component analysis, analysis of predictive error propagation and multiple linear regression modeling. Finally, this automated methodology has enabled us to successfully separate the components of an unknown mixture. [less ▲]

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See detailAnalysis of recent pharmaceutical regulatory documents on analytical method validation.
Rozet, Eric ULg; Ceccato, Attilio ULg; Hubert, Cédric ULg et al

in Journal of Chromatography. A (2007), 1158(1-2), 111-25

All analysts face the same situations as method validation is the process of proving that an analytical method is acceptable for its intended purpose. In order to resolve this problem, the analyst refers ... [more ▼]

All analysts face the same situations as method validation is the process of proving that an analytical method is acceptable for its intended purpose. In order to resolve this problem, the analyst refers to regulatory or guidance documents, and therefore the validity of the analytical methods is dependent on the guidance, terminology and methodology, proposed in these documents. It is therefore of prime importance to have clear definitions of the different validation criteria used to assess this validity. It is also necessary to have methodologies in accordance with these definitions and consequently to use statistical methods which are relevant with these definitions, the objective of the validation and the objective of the analytical method. The main purpose of this paper is to outline the inconsistencies between some definitions of the criteria and the experimental procedures proposed to evaluate those criteria in recent documents dedicated to the validation of analytical methods in the pharmaceutical field, together with the risks and problems when trying to cope with contradictory, and sometimes scientifically irrelevant, requirements and definitions. [less ▲]

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