No description available.

Zugl.: Kaiserslautern, Techn. Universiẗat, Diss., 2008.

No description available.

Les chirosciences étudient la préparation, les propriétés et les interactions des molécules chirales. La chromatographie chirale est une technique répandue pour analyser et produire des énantiomères. Son principe réside dans les interactions entre un sélecteur chiral et chaque énantiomère pour donner des complexes diastéréomères labiles avec différentes énergies et une rétention si différente.Cependant, les mécanismes de reconnaissance chirale ne sont pas bien connus, en particulier pour les sélecteurs chiraux les plus efficaces, qui sont à base de polysaccharides (en particulier de la cellulose et des carbamates d'amylose). Par exemple, le rôle du modificateur de phase mobile (co-solvant tel que l'alcool mélangé avec de l'heptane dans HPLC et avec du CO2 dans SFC) n'est pas expliqué dans la plupart des cas. Sur des phases stationnaires chirales à base de polysaccharide, l'effet du modificateur ne peut pas être restreint à la différence de polarité, ce qui entraîne une variation attendue des temps de rétention: plusieurs exemples ont rapporté la perte d'une énantioséparation ou même une inversion de l'ordre d'élution des énantiomères par changer le modificateur alcoolique.Notre travail vise à décrire les effets sur la rétention, l'ordre d'élution et l'enthalpie des complexes, lors de l'utilisation de mélanges de co-solvants dans la phase mobile. La description de ces comportements chromatographiques inhabituels peut aider à améliorer notre compréhension des mécanismes de reconnaissance chirale. / Chirosciences study the preparation, the properties and the interactions of chiral molecules. Chiral chromatography is a widespread technique to analyse and produces enantiomers. Its principle lies in the interactions between a chiral selector and each enantiomer to give labile diastereomeric complexes with different energies and so different retention.However, chiral recognition mechanisms are not well known, particularly for the most efficient chiral selectors, which are based on polysaccharides (especially cellulose and amylose carbamates). For instance, the role of the mobile phase modifier (co-solvent like the alcohol mixed with heptane in HPLC and with CO2 in SFC) is not explained in most case.On polysaccharide-based chiral stationary phases, the effect of the modifier can not be restricted to the difference of polarity, resulting in expected variation of retention times: several examples reported the loss of an enantioseparation or even a reversal of elution order of the enantiomers by changing the alcoholic modifier.Our work aims to describe the effects on retention, elution order and enthalpy of the complexes, when using mixtures of co-solvents in the mobile phase. The description of such unusual chromatographic behaviours may help to improve our understanding of the chiral recognition mechanisms.

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No / The kinetics of the dissociation is fundamental to the formation and the in vivo performance of cyclodextrin supramolecules. The individual determination of the apparent dissociation rate constant (kd,app) using high performance affinity chromatography (HPAC) is a tedious process requiring numerous separate studies and massive data fitting. In this study, the multianalyte approach was employed to simultaneously measure the kd,app values of three drugs through one injection based on the investigation of the dependence of drug-cyclodextrin interaction kinetics on the mobile phase composition. As a result, the kd,app values increased when decreasing the ion strength, increasing the ionization of drugs and adding extra organic solvents. The values of kd,app for acetaminophen, phenacetin and S-flurbiprofen estimated by the multianalyte approach were 8.54+/-1.81, 5.36+/-0.94 and 0.17+/-0.02s(-1), respectively, which were in good agreement with those determined separately (8.31+/-0.58, 5.01+/-0.42 and 0.15+/-0.01s(-1)). For both of the single and multiple flow rate peak profiling methods, the results of the multianalyte approach were statistically equivalent with that of the single compound analysis for all of the three drugs (p>0.05). The multianalyte approach can be employed for the efficient evaluation of the drug-cyclodextrin kinetics with less variance caused by cyclodextrin column bleeding.

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Dissertation thesis is a 5-publications' collection concerning characterization and application potential of cyclodextrins, polysaccharides and macrocyclic antibiotics based chiral stationary phases. The effects of stationary phase and mobile phase are studied. This approach ensures the complex insight into separation systems studied. Systems with different nature of chiral selector were studied by HPLC. Namely, macrocyclic antibiotics and derivatized polysaccharides were used for experiments. Former ones provided better results for enantioseparation of non-coded amino acids than latter ones. Dynamic coating procedure was used for preparation of a new chiral stationary phase. Characterization of new cationic cyclodextrin based chiral stationary phase was performed. Linear free energy relationship method was used for characterization of two different separation systems, i.e. newly prepared stationary phase and commercially available stationary phase. Based on results obtained, newly prepared stationary phase showed better results for separation of different achiral groups of analysts. New stationary phase prepared by dynamic coating was compared with chromatographic system, in which the chiral selector was used as a mobile phase additive. The chiral selector used for the two different approaches was...