• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 11
  • 7
  • 2
  • 2
  • 1
  • Tagged with
  • 24
  • 24
  • 24
  • 7
  • 6
  • 5
  • 5
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 3
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Novel Technology for Crystal Engineering of Pharmaceutical Solids

Jadav, Niten B. January 2018 (has links)
The research work described in this thesis, the environmentally friendly novel "Microwave Assisted Sub-Critical water (MASCW)" technology for particle engineering of active pharmaceutical ingredients and excipients was developed. The present novel technology MASCW process is described as green technology as water is used as the solvent medium and microwave energy as external source of heat energy for generation of a particle with different morphological and chemical properties. In MASCW process supersaturated solution of APIs is prepared by dissolving solute in water at high temperature and pressure conditions. Upon rapid and controlled cooling, based on the aqueous solubility of solute, solute/solvent concentration and dielectric constant of water rapid precipitation of API with narrow particle size distribution occurs. Using paracetamol (pca) as API moiety understanding of the mechanism of MASCW crystallisation process was investigated. The effect of different process and experimental parameters on crystallisation pathway and end product attributes were analysed. Correlation between the degree of supersaturation concentration of pca solution against temperature and pressure parameters was explained by generating binary phase diagram. Determination of polymorphic transformation pathway of pca from form I (stable) to form II metastable polymorphs in solution was analysed using Raman spectroscopy. The difference between conventional heating and subcritical treatment was explored by determining the change in the solvent dielectric constant and solubility of hydrophobic API molecule. Based on the process understanding results, this technology was further implemented to explore its application in generating phase pure stable and metastable cocrystal phase. Based on the solubility of API and cocrystal former congruent (CBZ/SAC, SMT/SAC, SMZ/SAC) and incongruent (CAF/4HBA) cocrystal pairs were selected. For the first time generation of anhydrous phase of CAF: 4HBA cocrystal in 1:1 stoichiometric ration was reported and generation of metastable cocrystal phase of CA CBZ: SAC form II was reported. The application of this technology was explored in generating phase pure metastable polymorph of paracetamol which retain higher compressibility and dissolution rate. The potential of MASCW micronisation process, theophylline is used as the model component to produce micro sized particles for pulmonary drug delivery system via dry powder inhaler (Foradil inhaler). The results demonstrate that the THF particles generated using MASCW process displayed greater aerodynamic performance compared to conventional spray-dried THF sample. In the final chapter, synthesis of inorganic biomaterial (nano crystalline hydroxyapatite) was reported for the first time and the prospects of combining API like ibuprofen (IBU) with a biologically active component like nano-crystalline hydroxyapatite (HA) through hydrogen bonding was mechanistically explained using X-ray diffractometer and spectroscopic techniques.
12

Charakterizace interakcí fluorované stacionární fáze Rtx-200MS s analyty metodou inverzní plynové chromatografie / Characterization of interactions between Rtx-200MS fluorinated stationary phase and analytes by inverse gas chromatography

Vrzal, Tomáš January 2014 (has links)
Fluorinated stationary phase in Rtx-200MS column have been characterized by determination of system constants of Abraham equation. Retention on this phase is driven by dispersive and orientation/induction forces. Significant interaction contribution of lone pair electrons or π- electrons provides unique selectivity for analytes with excess of electron density. Unusual behavior of this phase have been determined by study of separation mechanism of polar and nonpolar analytes, in comparison of their separation on polar and nonpolar phases. This behavior is due to medium polarity of the phase (system constant s), which is not so pronounced to cancel separation of nonpolar analytes due to induction forces. In some cases contribution of lone pair electrons or π-electrons can contribute to this separations. Key words fluorinated stationary phase Rtx-200MS, inverse gas chromatography, LFER method, Abraham's equation
13

Approaches to understanding the milling outcomes of pharmaceutical polymorphs, salts and cocrystals : the effect of different milling techniques (ball and jet) on the physical nature and surface energetics of different forms of indomethacin and sulfathiazole to include computational insights

Robinson, Fiona January 2011 (has links)
The process of milling drugs to obtain samples with a desirable particle size range has been widely used in the pharmaceutical industry, especially for the production of drugs for inhalation. However by subjecting materials to milling techniques surfaces may become thermodynamically activated which may in turn lead to formation of amorphous material. Polymorphic conversions have also been noted after milling of certain materials. Salt and cocrystal formation is a good way of enhancing the properties of an API but little or no work has been published which investigates the stability of these entities when subjected to milling. Different milling techniques (ball and jet) and temperatures (ambient and cryogenic) were used to investigate the milling behaviour of polymorphs, salts and cocrystals. All materials were analysed by XRPD and DSC to investigate any physical changes, i.e. changes in melting point and by inverse gas chromatography (IGC) to investigate whether any changes in the surface energetics occurred as a result of milling. Another aim of this thesis was to see if it was possible to predict the milling behaviour of polymorphs by calculating the attachment energies of the different crystal facets using Materials Studio 4.0. These results were compared to the IGC data to see if the predicted surface changes had occurred. The data collected in this study showed that different milling techniques can have a different effect on the same material. For example ball milling at ambient temperature and jet micronisation of the SFZ tosylate salt caused a notable increase in the melting point of the material whereas ball milling at cryogenic temperatures did not cause this to happen. The IGC data collected for this form also showed a contrast between cryomilling and the other two techniques. The study also showed that the formation of salts and cocrystals does not necessarily offer any increased stability in terms of physical properties or surface energetics. Changes in melting point were observed for the SFZ tosylate salt and the IMC:Benzamide cocrystal. Changes in the specific surface energies were also observed indicating that the nature of the surfaces was also changing. The materials which appeared to be affected the least were the two stable polymorphs, gamma IMC and SFZ III. The computational approach used has many limitations. The software does not allow for conversion to the amorphous form or polymorphic conversions. Such conversions were seen to occur, particularly for the metastable polymorphs used, meaning that this computational approach may only be suitable for stable polymorphs.
14

Caractérisation de solides organiques par chromatographie gazeuse inverse : potentialités, confrontation à d’autres techniques / Characterization of organic solids by inverse gas chromatography : potential, confrontation with other techniques

Cares Pacheco, María Graciela 28 November 2014 (has links)
Le polymorphisme revêt un grand intérêt dans le domaine pharmaceutique puisqu’il concerne plus de 80% des principes actifs (PA). Les différences de propriétés physicochimiques entre deux polymorphes peuvent influer sur la mise en forme galénique de la molécule active, sa biodisponibilité, sa stabilité lors du stockage voire même sur son activité. D'un point de vue industriel, l'hétérogénéité de surface d'un solide pharmaceutique semble jouer un rôle fondamental, lors de sa mise en forme mais aussi lors de son stockage. Néanmoins, les interactions de surface avec l’environnement de ce type de solides sont des phénomènes de faible amplitude et donc très difficiles à quantifier. Les techniques de mouillabilité, les plus utilisées, relient le travail d’adhésion à l’énergie de surface par la mesure de l’angle de contact entre le solide et un liquide. La valeur de l’énergie de surface obtenue, n’a qu’un caractère statistique qui caractérise un comportement macroscopique global du solide d’étude. Cette notion perd toute signification à l’échelle microscopique et donc ne répond pas aux besoins actuels de l’industrie pharmaceutique. L’objectif de cette étude est donc de quantifier l’anisotrope énergétique de surface des solides d’intérêt pharmaceutique. La Chromatographie Gazeuse Inverse (CGI) apparaît alors comme une méthode de choix pour caractériser les propriétés de surface de solides divisés. L’étude de l’énergie de surface par CGI à dilution infinie, au travers d’une étude rigoureuse du domaine de Henry, nous a permis de distinguer, en surface, les formes polymorphes α, β et δ du D-mannitol. De plus, elle nous a permis de faire un lien entre la composante dispersive de l’énergie de surface et des procédés de génération et de mise en forme, tels que l’atomisation et le cryobroyage. Les augmentations d’énergie de surface à la suite de ces procédés ont été attribués aux changements intrinsèques de la particule, telles que sa taille et sa morphologie. / The polymorphism phenomenon is of great interest in the pharmaceutical field since it concerns more than 80% of the active pharmaceutical ingredients (API). Differences in physicochemical properties between polymorphs are known to influence the formatting dosage of the active molecule (compression during tableting), bioavailability, toxicity and stability under storage conditions. From an industrial point of view, the surface heterogeneity of pharmaceutical solids seems to play a fundamental role in formatting but also during storage. However, organic solid’s surface interactions are small amplitude phenomenon and therefore very difficult to quantify. Wettability techniques, the most commonly used, relate the work of adhesion to the surface energy by measuring the contact angle between the solid and a liquid. The value of the surface energy obtained has a statistical nature that characterizes a global macroscopic behavior of the solid. This concept becomes meaningless at microscopic level and therefore does not respond to the existing and growing needs of the pharmaceutical industry. The objective of this study is to quantify the anisotropic surface energy of pharmaceutical solids. The inverse gas chromatography (IGC) will appear as the technique of choice for characterizing divided solid surface properties. The study of the surface energy using IGC at infinite dilution, through a rigorous study of Henry’s domain, allowed us to distinguish the polymorphic forms α, β and δ of D-mannitol. In addition, we were able to make a connection between the dispersive component of the solid’s surface energy and the generation and forming processes, such as spray drying (SD) and cryo-milling (CM). Surface energy increments after SD and CM were attributed to changes of the intrinsic characteristics of the particles such as size and morphology.
15

Approaches to Understanding the Milling Outcomes of Pharmaceutical Polymorphs, Salts and Cocrystals. The Effect of Different Milling Techniques (Ball and Jet) on the Physical Nature and Surface Energetics of Different Forms of Indomethacin and Sulfathiazole to Include Computational Insights.

Robinson, Fiona January 2011 (has links)
The process of milling drugs to obtain samples with a desirable particle size range has been widely used in the pharmaceutical industry, especially for the production of drugs for inhalation. However by subjecting materials to milling techniques surfaces may become thermodynamically activated which may in turn lead to formation of amorphous material. Polymorphic conversions have also been noted after milling of certain materials. Salt and cocrystal formation is a good way of enhancing the properties of an API but little or no work has been published which investigates the stability of these entities when subjected to milling. Different milling techniques (ball and jet) and temperatures (ambient and cryogenic) were used to investigate the milling behaviour of polymorphs, salts and cocrystals. All materials were analysed by XRPD and DSC to investigate any physical changes, i.e. changes in melting point and by inverse gas chromatography (IGC) to investigate whether any changes in the surface energetics occurred as a result of milling. Another aim of this thesis was to see if it was possible to predict the milling behaviour of polymorphs by calculating the attachment energies of the different crystal facets using Materials Studio 4.0. These results were compared to the IGC data to see if the predicted surface changes had occurred. The data collected in this study showed that different milling techniques can have a different effect on the same material. For example ball milling at ambient temperature and jet micronisation of the SFZ tosylate salt caused a notable increase in the melting point of the material whereas ball milling at cryogenic temperatures did not cause this to happen. The IGC data collected for this form also showed a contrast between cryomilling and the other two techniques. The study also showed that the formation of salts and cocrystals does not necessarily offer any increased stability in terms of physical properties or surface energetics. Changes in melting point were observed for the SFZ tosylate salt and the IMC:Benzamide cocrystal. Changes in the specific surface energies were also observed indicating that the nature of the surfaces was also changing. The materials which appeared to be affected the least were the two stable polymorphs, gamma IMC and SFZ III. The computational approach used has many limitations. The software does not allow for conversion to the amorphous form or polymorphic conversions. Such conversions were seen to occur, particularly for the metastable polymorphs used, meaning that this computational approach may only be suitable for stable polymorphs.
16

Physico-chimie de l’interface fibres/matrice : applications aux composites Carbone/Carbone / Physico-chemical interface of fibers/matrix : carbone/Carbone Composites applications

Fradet, Guillaume 11 December 2013 (has links)
Ces travaux de thèse portent sur la physico-chimie de l'interface fibre/matrice appliquée aux composites Carbone/Carbone. La surface des fibres de carbone est modifiée par divers traitements de surface (voie gazeuse et voie humide). L'impact de ces différents procédés sur l'état de surface des fibres a été évalué par chromatographie gazeuse en phase inverse à dilution infinie, MEB, AFM, MET, RAMAN… Suite à ces caractérisations, des traitements de surface ont été retenus pour la réalisation de composite C/C. Les propriétés notamment mécaniques des matériaux composites à interfaces modulées (force de la liaison fibre/matrice) ont pu être évaluées. Finalement, il a pu être établi une relation entre modifications de surface des fibres de carbone et comportement macroscopique des composites C/C. / This work focuses on the physical chemistry of the fiber/matrix interface applied to composites carbon/carbon. The surface of carbon fibers was modified by various surface treatments. The carbon fibers surface variation was evaluated by inverse gas chromatography at infinite dilution, SEM, AFM, TEM, Raman... After these characterizations, surface treatments were selected for the realization of C/C composites. The mechanical properties of composites at modulated interfaces (fibers/matrix bonding) were evaluated. Finally, a correlation between surface modification of carbon fibers and macroscopic behavior of composite C/C was established.
17

Physikochemische Untersuchung der Analyt – HKUST-1 Wechselwirkung unter Verwendung der inversen Gaschromatographie / Physicochemical investigation of the Analyt – HKUST-1 interaction using the inverse gas chromatography

Münch, Alexander 15 November 2013 (has links) (PDF)
Die vorliegende Arbeit hat neben der Untersuchung der Synthese über den Controlled SBU-Approach von HKUST-1, ein poröses Kupfertrimesat, die Abscheidung dieses Metal-Organic Frameworks in dünnen Quarzglaskapillaren mit einer Länge von 10 bis 30 m und Innendurchmessern zwischen 0,53 und 0,25 mm zum Thema. Diese Säulen werden zur gaschromatographischen Trennung wie auch zur Bestimmung physikochemischer Kenngrößen, die den Adsorptionsvorgang verschiedener Analyten auf der HKUST-1 Oberfläche beschreiben, verwendet. Zu den untersuchten Stoffen gehören neben unpolaren n-Alkanen, unterschiedlich substituierte Phenylaromaten und starke Lewisbasen, wie Alkoxyalkane. Bei diesen kann der Einfluss der Gestalt und Länge der an den Sauerstoffatomen befindlichen Alkylgruppen auf die Adsorption an HKUST-1 in Form von spezifischen und unspezifischen Wechselwirkungsenthalpien, bestimmt aus gaschromatographischen Messungen, und infrarotspektroskopischen Auswertungen untersucht werden. Abschließend wird eine quantitative Aussage über das Verhältnis von Acidität und Basizität der HKUST-1 Oberfläche getroffen.
18

Interactions entre morphologies, acidités et diffusion dans les zéolithes beta : éléments de réponse par spectroscopie infrarouge, réactions modèles et chromatographie à flux inversés / Interactions between morphologies, acidities and diffusion in beta zeolites : highlighted parameters using infrared spectroscopy, model reactions and reversed-flow inverse gas chromatography

Benghalem, Mohammed Amine 07 December 2017 (has links)
Dans le but d'étudier l'impact de la taille et de la morphologie de cristaux zéolitiques sur les propriétés texturales, chimiques et diffusionnelles, une série de zéolithe beta a été étudiée.L'augmentation logique des surfaces et des volumes poreux avec la diminution de la taille des cristaux est constatée. En outre, cela implique également une baisse de l'acidité globale ainsi que de la force des sites. Toutefois, la compréhension de l'acidité complexe de ces matériaux nécessite des techniques poussées de caractérisation.L'adsorption de molécules sondes (pyridine, CO, éthylène) suivie par infrarouge ainsi que la thermodésorption d'ammoniac ont été corrélées à des réactions modèles de transformation de l'éthanol et de craquage du n-hexane. Lors de celui-ci, la morphologie des cristaux a peu d'influence et les performances sont dictées par les sites de Brønsted. La présence d'aluminiums extra-réseaux permet d'exalter la force acide des sites protoniques. Avec la transformation de l'éthanol, de meilleures activités et stabilités sont observées dans le cas de zéolithes hiérarchisées.L'étude de la diffusion par chromatographie en phase gaz à flux inversées (RF-IGC) a permis de montrer que, si les coefficients de diffusion augmentent à l'opposé de la taille des cristaux, la porosité secondaire réduit le chemin diffusionnel. De plus, les sites faibles majoritairement présents sur les matériaux hiérarchisés facilitent la désorption des molécules et sont impliqués dans les interactions latérales mesurées par RF-IGC.Ce travail apporte donc des éléments de réponse à la stabilité et aux comportements catalytiques complexes observés sur la zéolithe beta. / In order to study the impact of the size and morphology of zeolite crystals on the textural, chemical and diffusion properties, a series of beta zeolites was studied.The logical increase of the porous surfaces and volumes with the decrease in crystal size is observed. In addition, this also implies a decrease in the overall acidity as well as strength of the adsorption sites. However, understanding the complex acidity of these materials requires advanced characterization techniques.The adsorption of probe molecules (pyridine, CO, ethylene) followed by infrared as well as ammonia thermodesorption were correlated to model reactions of ethanol conversion and n-hexane cracking. In this case, the morphology of the crystals has little influence and performance is mainly dictated by the Brønsted sites. The presence of extra-framework aluminums makes it possible to exalt the acid strength of the protonic sites. With the transformation of ethanol, better activities and stabilities are observed in the case of hierarchical zeolites.The study of diffusion by the reversed-flow gas chromatography (RF-IGC) showed that if the diffusion coefficients increase as opposed to crystal size, the secondary porosity reduces the diffusion path. Moreover, the weak sites predominantly present on the hierarchized materials facilitate the desorption of the molecules and are involved in the lateral interactions measured by RF-IGC.This work thus provides elements of response to the stability and the complex catalytic behaviors observed on the beta zeolite.
19

Modélisation moléculaire et expérimentation en réacteur solide/gaz pour la compréhension de la sélectivité de la lipase B de Candida antarctica / Molecular modeling and experimentation in solid/gas reactor for understanding the selectivity of lipase B from Candida antarctica

Marton, Zsuzsanna 22 July 2010 (has links)
L’objectif de cette thèse était de mieux comprendre les paramètres structuraux et environnementaux gouvernant l’énantiosélectivité de la lipase B de Candida antarctica (CALB), lors de la résolution des alcools secondaires linéaires chiraux. Ces composés sont notamment utilisés comme synthons chiraux dans l’industrie pharmaceutique. Dans un premier temps, une étude systématique des orientations du butan-2-ol et du pentan-2-ol au sein du site actif a été réalisée par modélisation moléculaire. Les résultats suggèrent l’existence de modes d’arrimages supplémentaires à ceux mentionnés dans la littérature. La comparaison selon l’énergie potentielle du substrat des structures les plus stables, combinée à la prise en compte de modes de fixation non productifs, nous a permis d’expliquer qualitativement l’énantiopréférence de la CALB pour la forme R. A l’aide du réacteur solide/gaz, nous avons montré que les résidus hydrophobes formant le canal d’accès du substrat au site actif (Ile189, Leu278 et Ala282), jouaient un rôle significatif dans l’énantiosélectivité de la CALB vis-à-vis des alcools secondaires. L’influence de la partie alkoxy du donneur d’acyle sur le ratio énantiomérique a également pu être mise en évidence. Par ailleurs, nous avons montré que des mutations isostériques de la poche stéréosélective conduisaient à des variations des paramètres thermodynamiques d’activation de l’acylation du pentan-2-ol, probablement suite à des modifications du réseau de liaisons hydrogène formé entre les résidus de la poche. Les études d’adsorption de l'eau et des substrats sur l’enzyme immobilisée nous ont permis de relier l'état d'hydratation de la CALB avec les effets particuliers de l'eau sur l’activité et la sélectivité de l’enzyme. / The aim of this thesis was to understand more precisely the structural and environmental parameters governing the enantioselectivity of lipase B from Candida antarctica (CALB), involved in the discrimination of chiral secondary alcohols enantiomers. These compounds are used in particular for the synthesis of enantiomerically pure pharmaceutical molecules. Initially a systematic study of the orientation of butan-2-ol and pentan-2-ol in the active site was performed by molecular modeling. The results suggest the existence of additional binding modes to those mentioned in the literature. The potential energy comparison of the most stable conformations of the substrate, combined with the existence of non productive binding modes, allowed us to explain qualitatively the enantiopreference of CALB for the R form. Using the solid/gas reactor, we have shown that hydrophobic residues forming the access channel of substrate to the active site (Ile189, Leu278 and Ala282), played a significant role in the enantioselectivity of CALB towards secondary alcohols. The influence of the alkoxy part of the acyl donor on the enatiomeric ratio E has also been highlighted. Furthermore, we showed that isosteric mutations of the stereoselective pocket led to changes in pentan-2-ol activation thermodynamic parameters of acylation, probably due to changes in the hydrogen bonds network formed between residues of the pocket. Studies of water and substrates adsorption on the immobilized enzyme allowed us to relate the hydration status of CALB with specific effects of water on the enzyme activity and selectivity.
20

Charakterizace poly(1,4-diethynylbenzen)u metodou IGC / Characterization of poly(1,4-diethynylbenzene) by IGC method

Petrášová, Sabina January 2011 (has links)
Poly(1,4-diethynylbenzene) ( -conjugated polymer) was prepared as an insoluble polymer network via chain coordination polymerization of 1,4-diethynylbezene catalyzed with [Rh(NBD)acac] complex. Thermodynamic properties and acid-base characteristics of the prepared poly(1,4-diethynylbenzene) were studied by means of Inverse Gas Chromatography (IGC) in the temperature range 80-100 řC. Retention data of selected testing substances were used to determine the Gibbs energy of sorption, the sorption enthalpy and their acid-base and disperse parts as well as the disperse contribution to the surface energy and parameters of KA, KD, ANHPS and DNHPS quantifying the acid-base character of the studied polymer. The results showed that poly(1,4-diethynylbenzene) interacted more efficiently with Lewis bases than with Lewis acids. The values of experimental sorption enthalpy were used for the determination of the parameters KA and KD. Values of these parameters classify poly(1,4-diethynylbenzene) as the material with a slightly acid character. This conclusion is further supported by the results of H. P. Schreiber method based on the application of ANHPS and DNHPS parameters for the evaluation of the acid-base properties of the material. The infrared spectroscopy proved that poly(1,4-diethynylbenzene) contained...

Page generated in 0.1157 seconds