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  • 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.
1

Denatūrantų nustatymas hidrofilinės sąveikos chromatografijos metodu / Determination of denaturants by hydrophilic interaction chromatography

Juknaitė, Ina 13 June 2006 (has links)
A hydrophilic interaction chromatography (HILIC) technique has been developed and validated for determination of common denaturants (denatonium benzoate, crystal violet and methylene blue) in denaturated alcohol formulations. Among the three different polar stationary phases (i.e., aminopropyl, cyanoethyl and silica) studied the cyanoethyl phase provided much stronger retention for the organic cations. It was shown that high efficiencies were reached only with anionic ion-pairing reagent that reduces the interactions with the silanol groups. The anion ion-pairing strength under HILIC conditions was: acetate < formate << trifluoroacetate < perchlorate. This study also investigated the effect of various experimental factors on the retention of the cyanoethyl stationary phase, such as acetonitrile content, pH, ionic strength, and ion-pairing anion concentration in the mobile phase. The separation of three denaturants was achieved in about 8 min with a mobile phase containing 60% (v/v) acetonitrile and 10 mmol/l HClO4. The proposed method was validated and applied to the determination of danaturating agents in various Lithuanian denaturated alcohol formulations.
2

Investigations of the retention mechanisms in hydrophilic interaction chromatography

Dinh, Ngoc Phuoc January 2013 (has links)
Hydrophilic interaction chromatography is well known as a powerful technique separation of polar and ionizable compound nowadays. However the retention mechanism of the technique is still under debate. Understanding retention mechanism would facilitate the method development using the technique and its future improvement. This was inspiring and became the goal of this thesis. This work involves the characterization of the water enriched layer regarding to water and buffer salt accumulation. Twelve HILIC stationary phase with a diverse surface chemistry regarding to function groups and modification type were studied. Effect of water and salt on regarding to the retention mechanism was investigated by correlating the adsorption data to the retention of selected solutes This also involved the characterization of interactions involve in the separation of 21 HILIC columns. Interactions was probe by retention ratio of pair solutes which are characteristic for each specific interaction. The data was evaluate using principle component analysis – a multivariable data analysis method. The model was comprehensive and its outcomes were confirmed by the studies on adsorptions of water and salts.
3

Développement d'une méthode de séparation chromatographique couplée aux spectrométries de masse à source d'ionisation électrospray (ESI-MS) et à source plasma à couplage inductif (ICP-MS) : application à l'analyse de spéciation des lanthanides / Development of a chromatographic separation method hyphenated to electrospray ionization mass spectrometry (ESI-MS) and inductively coupled plasma mass spectrometry (ICP-MS) : application to the lanthanides speciation analysis

Beuvier, Ludovic 12 October 2015 (has links)
Ces travaux de thèse concernent les développements d'une méthode de séparation chromatographique couplée simultanément à l'ESI-MS et l'ICP-MS afin de réaliser l'analyse de spéciation exhaustive des lanthanides en phase aqueuse représentative des phases de désextraction des procédés de traitement du combustible usé. Cette méthode analytique permet de séparer, caractériser et quantifier des complexes de lanthanides à ligands polyaminocarboxyliques comme le DTPA et l'EDTA, utilisés comme agents complexants dans ces procédés. La méthode de séparation par chromatographie HILIC des complexes de lanthanides a été mise au point avec la phase stationnaire à fonctions amide. Un criblage d'une large gamme de compositions de phase mobile a permis de déterminer que le mécanisme d'adsorption est prédominant lors l'élution des complexes de lanthanides et d'obtenir des conditions de séparation optimisées. Des conditions d'analyse plus rapides obtenues avec une colonne à fonctions amide de granulométrie sub-2 µm et de longueur plus faible ont permis de réduire le temps d'analyse d'un facteur 2,5 et la consommation de solvant de 25 %. La caractérisation structurale et isotopique par HILIC ESI-MS a été réalisée ainsi que la mise au point d'une méthode d'étalonnage externe. Les performances analytiques de la méthode de quantification ont été déterminées. Enfin, le développement d'un système de couplage de l'HILIC à l'ESI-MS et l'ICP-MS a été réalisé. Une méthode de quantification simultanée par ESI-MS et par ICP-MS a permis de déterminer la distribution quantitative des espèces en solution ainsi que les performances analytiques associées. / This work focuses on the development of a chromatographic separation method coupled to both ESI-MS and ICP-MS in order to achieve the comprehensive speciation analysis of lanthanides in aqueous phase representative of back-extraction phases of advanced spent nuclear fuel treatment processes. This analytical method allowed the separation, the characterization and the quantitation of lanthanides complexes holding polyaminocarboxylic ligands, such as DTPA and ETDA, used as complexing agents in these processes. A HILIC separation method of lanthanides complexes has been developed with an amide bonded stationary phase. A screening of a wide range of mobile phase compositions demonstrated that the adsorption mechanism was predominant. This screening allowed also obtaining optimized separation conditions. Faster analysis conditions with shorter amide column packed with sub 2 µm particles reduced analysis time by 2.5 and 25% solvent consumption. Isotopic and structural characterization by HILIC ESI-MS was performed as well as the development of external calibration quantitation method. Analytical performances of quantitation method were determined. Finally, the development of the HILIC coupling to ESI-MS and ICP-MS was achieved. A simultaneous quantitation method by ESI-MS and ICP-MS was performed to determine the species quantitative distribution in solution. Analytical performances of quantitation method were also determined.
4

DEVELOPMENT OF NOVEL LIQUID CHROMATOGRAPHY STATIONARY PHASES FOR IMPROVED CHARACTERIZATION OF BIOPHARMACEUTICALS

Cameron C Schwartz (11209392) 30 July 2021 (has links)
Monoclonal antibodies are large, complex biomolecules that can be difficult to characterize. Characterization is important because of the various post translational modifications that can occur during manufacturing, processing, and storage. Some modifications can lead to efficacy and safety issues and therefore are heavily monitored. A leading way to monitor various modifications is by using liquid chromatography. The high sensitivity, reproducibility, and ability to quantitate analytes makes it very attractive for monoclonal antibody characterization. The large molecular size of monoclonal antibodies (150 kDa) makes them challenging to separate efficiently and with high enough resolution to be helpful. New column technologies that would help improve protein separation efficiencies and slectivities would greatly help in this challenging process. In this thesis, three novel bonded phases are developed for the separation of monoclonal antibodies including a weak anion and cation exchanger (WAX, CEX) for the separation of charged species as well as a novel hydrophilic interaction chromatography (HILIC) for the separation of glycoforms. Column develop is achieved by optimizing selectivity and improving efficiency of separations by altering particle surface chemistry.
5

Polyhydroxyl and Polyphosphorylcholine functionalized Silica for Hydrophilic interaction liquid Chromatography- Synthesis, characterization and application

Bui, Nhat Thi Hong January 2012 (has links)
This thesis focuses on the development of new stationary phases for use in hydrophilic interaction liquid chromatography using TRIS-based and phosphorylcholine typed monomers and porous silica particles as starting substrates. In this thesis, several ways of polymerizing highly hydrophilic mono­mers onto pore surfaces of silica supports are described, based on several “grafting from” schemes. “Controlled/living” radical polymerizations including atom transfer radical polymerization (ATRP) and iniferter-mediated polymerization in conjunction with conventional free radical polymerization are demonstrated to be successful tools for grafting different hydrophilic monomers (polyhydroxyl and phosphorylcholine [meth]acrylamide/acrylates) onto the silica surfaces. Reaction solvents are proven to play an essential role to achieve efficient graft polymerization of activated silica surfaces with these amphiphilic vinylic monomers, which is difficult because of their restricted access to the activated surface in solvents that can be used because of solubility constraints. Two tentacle TRIS-based polymer grafted silica, namely TRIS-WAX – TRIS functionality bonded to silica via a C–N–C imine bond and TRIS-Amide – TRIS bonded to silica via an amide bond, prove to be useful as stationary phases for hydrophilic interaction chromatography (HILIC).The TRIS-WAX exhibits a mixed mode hydrophilic partitioning and weak anion exchange (HILIC/WAX) retention mechanism while retention by hydrophilic partitioning is the dominant mechanism on the neutral TRIS-Amide phase which lacks weak anion exchange (WAX) properties. Interestingly, both these phases have selectivities that are radically different from most commercial HILIC stationary phases. Finally, a method is demonstrated for synthesizing a stratified (graft-copolymerized) silica material based on N,N′-methylenebisacrylamide and 2-methacryloyloxyethyl phosphorylcholine (MPC) using a “controlled/living” photoiniferter-mediated polymerization from the N,N-diethyldithiocarbamate iniferter moiety immobilized silica surfaces. This polymerization method proves to be successful for graft-blockcopolymerization of different highly hydrophilic monomers onto the activated surfaces of porous silica. In this way, silica surfaces are grafted with a cross-linked amide-based hydrogel, on top of which a tentacle zwitterionic phosphorylcholine-typed layer is synthesized. The resulted material proves to be useful for HILIC separations and possesses different selectivity for the tested organic acids compared to that of commercial ZIC-cHILIC stationary phase.
6

On the investigation of chemical parameters reflecting microbial activity linked to nutrient availability in forest soil

Olofsson, Madelen January 2015 (has links)
As agrarian society developed, the most fertile soils able to sustain the nutritional requirements needed for high crop yield were assigned to farming, while the more penurious soils were left to uphold the forest ecosystems. Some temperate forests are developed on acidic soils considered to be nutrient poor, as much of the inorganic nutrients are entrapped in poorly weatherable soil minerals and not easily accessed by plant roots. In an undisturbed ecosystem, the largest contribution of available nutrients comes from the recycling of organically bound nutrients via the decomposition of dead plant material. If biomass is removed, for instance with a more intensified exploitation of the forest ecosystems including whole tree harvesting, this source of nutrients is consequently decreased. The importance of soil mineral weathering as a source of nutrients, and especially that promoted by soil biota, is thereby emphasized. This thesis addresses biotic parameters associated with mineral weathering. Different aspects of soil solution sampling strategies and analysis of different organic ligands as well as biomarkers for the estimation of fungal biomass were investigated. These chemical parameters were also evaluated as indicators of microbial activity in relation to mineral nutrient availability in soil. With the assumption that the current nutrient status of a soil will affect the microbial interest of certain minerals as sources of inorganic nutrients, a mineral amendment trial was performed in a Swedish boreal forest soil. Overall, the amended soil presented good nutrient status, but with a possible shortage of iron. Due to this, it was hypothesized that the amended mineral with the highest iron content i.e. biotite would cause an elevation of microbial activity in its vicinity when compared to the bulk soil. The level of microbial activity in the vicinity of the amended minerals was evaluated via quantification of organic acids and siderophores, as well as estimation of fungal biomass and enzymatic activity. The highest microbial activity was measured for the O horizon of the investigated podzol, although nothing indicated an elevated association with the amended minerals. In the E horizon, however, elevation in microbial activity was observed in the vicinity of the biotite mineral when compared with bulk soil, although only a few of the investigated parameters differed significantly when evaluated separately.   To enable this study, a highly sensitive analytical method employing liquid chromatography and mass spectrometry was developed to quantify a number of hydroxamate siderophores. On-line pre-concentration enabled detection of these organic ligands in the pico-molar range – a necessity when analyzing natural samples. Furthermore, an analytical method was developed for the estimation of fungal biomass via quantification of chitin-derived glucosamine, which also employed liquid chromatography and tandem mass spectrometry. Unlike currently available methods, the one presented in this thesis did not involve analyte derivatization, which resulted in high sample throughput while simultaneously avoiding complications involved with the additional derivatization procedure. The distribution of a group of organic ligands known as aromatic low molecular mass organic acids was also studied in a boreal forest podzol soil. Different sampling and samples preparation techniques, namely tension-lysimeters, soil centrifugation and liquid-soil extraction, were compared when analyzing soil solution components. Significant differences in analyte amount and species type were found between these sampling techniques. Some of the differences could be accounted for by variation in soil composition at different depths of the investigated podzol, but others could be attributed to structural differences within the studied analyte group. This clearly illustrated the intricacy of sampling and analysis when working with a sample matrix as complex and diverse as soil. As previously, liquid chromatography and mass spectrometry was used to quantify the analytes of interest. A highly sensitive analytical method was developed that was able to detect eleven aromatic low molecular mass organic acids in the nano-molar range. High selectivity was ensured by applying multiple reaction monitoring enabled by collision induced fragmentation of the analytes. / FORE
7

Développement de méthodes analytiques de séparation des produits de digestion enzymatique des dérivés de cellulose

Farhat, Fatima 12 1900 (has links)
La cellulose et ses dérivés sont utilisés dans un vaste nombre d’applications incluant le domaine pharmaceutique pour la fabrication de médicaments en tant qu’excipient. Différents dérivés cellulosiques tels que le carboxyméthylcellulose (CMC) et l’hydroxyéthylcellulose (HEC) sont disponibles sur le commerce. Le degré de polymérisation et de modification diffèrent énormément d’un fournisseur à l’autre tout dépendamment de l’origine de la cellulose et de leur procédé de dérivation, leur conférant ainsi différentes propriétés physico-chimiques qui leurs sont propres, telles que la viscosité et la solubilité. Notre intérêt est de développer une méthode analytique permettant de distinguer la différence entre deux sources d’un produit CMC ou HEC. L’objectif spécifique de cette étude de maitrise était l’obtention d’un profil cartographique de ces biopolymères complexes et ce, par le développement d’une méthode de digestion enzymatique donnant les oligosaccharides de plus petites tailles et par la séparation de ces oligosaccharides par les méthodes chromatographiques simples. La digestion fut étudiée avec différents paramètres, tel que le milieu de l’hydrolyse, le pH, la température, le temps de digestion et le ratio substrat/enzyme. Une cellulase de Trichoderma reesei ATCC 26921 fut utilisée pour la digestion partielle de nos échantillons de cellulose. Les oligosaccharides ne possédant pas de groupements chromophores ou fluorophores, ils ne peuvent donc être détectés ni par absorbance UV-Vis, ni par fluorescence. Il a donc été question d’élaborer une méthode de marquage des oligosaccharides avec différents agents, tels que l’acide 8-aminopyrène-1,3,6-trisulfonique (APTS), le 3-acétylamino-6-aminoacridine (AA-Ac) et la phénylhydrazine (PHN). Enfin, l’utilisation de l’électrophorèse capillaire et la chromatographie liquide à haute performance a permis la séparation des produits de digestion enzymatique des dérivés de cellulose. Pour chacune de ces méthodes analytiques, plusieurs paramètres de séparation ont été étudiés. / Cellulose and its derivatives are used in a wide range of applications, including the pharmaceutical industry for the manufacturing of medicines as inactive additives. Various cellulosic derivatives such as carboxymethylcellulose (CMC) and hydroxyethylcellulose (HEC) are readily available for such use. The degree of polymerization and modification differs from one supplier to the other, according to the origin of the cellulose and its process of chemical modification, conferring on them different physico-chemical properties, such as viscosity and solubility. Our interest is to develop an analytical method that can distinguish between different sources of a given CMC or HEC product. The specific objective of this master’s study was to obtain a fingerprint of these complex biopolymers by developing an enzymatic digestion method to produce smaller oligosaccharides that could be separated by simple chromatographic methods. The digestion was studied as a function of various parameters, such as the composition of the hydrolysis solution, the pH, the temperature, the duration of digestion and the substrate/enzyme ratio. A cellulase enzyme from Trichoderma reesei ATCC 26921 was used for the partial digestion of our samples of cellulose. Since these oligosaccharides do not possess a chromophore or fluorophore, they can’t be detected either by absorbance or fluorescence. It was thus necessary to work out the labeling method for oligosaccharides using various agents, such as 8-aminopyrene-1,3,6-trisulfonic acid (APTS), 3-acetylamino-6-aminoacridine (AA-Ac) and phenylhydrazine (PHN). Finally, the use of capillary electrophoresis and high performance liquid chromatography allowed the separation of the enzymatic digestion products of the cellulose derivatives (CMC and HEC). For each of these analytical separation techniques, several parameters of the separation were studied.
8

Développement de méthodes analytiques de séparation des produits de digestion enzymatique des dérivés de cellulose

Farhat, Fatima 12 1900 (has links)
La cellulose et ses dérivés sont utilisés dans un vaste nombre d’applications incluant le domaine pharmaceutique pour la fabrication de médicaments en tant qu’excipient. Différents dérivés cellulosiques tels que le carboxyméthylcellulose (CMC) et l’hydroxyéthylcellulose (HEC) sont disponibles sur le commerce. Le degré de polymérisation et de modification diffèrent énormément d’un fournisseur à l’autre tout dépendamment de l’origine de la cellulose et de leur procédé de dérivation, leur conférant ainsi différentes propriétés physico-chimiques qui leurs sont propres, telles que la viscosité et la solubilité. Notre intérêt est de développer une méthode analytique permettant de distinguer la différence entre deux sources d’un produit CMC ou HEC. L’objectif spécifique de cette étude de maitrise était l’obtention d’un profil cartographique de ces biopolymères complexes et ce, par le développement d’une méthode de digestion enzymatique donnant les oligosaccharides de plus petites tailles et par la séparation de ces oligosaccharides par les méthodes chromatographiques simples. La digestion fut étudiée avec différents paramètres, tel que le milieu de l’hydrolyse, le pH, la température, le temps de digestion et le ratio substrat/enzyme. Une cellulase de Trichoderma reesei ATCC 26921 fut utilisée pour la digestion partielle de nos échantillons de cellulose. Les oligosaccharides ne possédant pas de groupements chromophores ou fluorophores, ils ne peuvent donc être détectés ni par absorbance UV-Vis, ni par fluorescence. Il a donc été question d’élaborer une méthode de marquage des oligosaccharides avec différents agents, tels que l’acide 8-aminopyrène-1,3,6-trisulfonique (APTS), le 3-acétylamino-6-aminoacridine (AA-Ac) et la phénylhydrazine (PHN). Enfin, l’utilisation de l’électrophorèse capillaire et la chromatographie liquide à haute performance a permis la séparation des produits de digestion enzymatique des dérivés de cellulose. Pour chacune de ces méthodes analytiques, plusieurs paramètres de séparation ont été étudiés. / Cellulose and its derivatives are used in a wide range of applications, including the pharmaceutical industry for the manufacturing of medicines as inactive additives. Various cellulosic derivatives such as carboxymethylcellulose (CMC) and hydroxyethylcellulose (HEC) are readily available for such use. The degree of polymerization and modification differs from one supplier to the other, according to the origin of the cellulose and its process of chemical modification, conferring on them different physico-chemical properties, such as viscosity and solubility. Our interest is to develop an analytical method that can distinguish between different sources of a given CMC or HEC product. The specific objective of this master’s study was to obtain a fingerprint of these complex biopolymers by developing an enzymatic digestion method to produce smaller oligosaccharides that could be separated by simple chromatographic methods. The digestion was studied as a function of various parameters, such as the composition of the hydrolysis solution, the pH, the temperature, the duration of digestion and the substrate/enzyme ratio. A cellulase enzyme from Trichoderma reesei ATCC 26921 was used for the partial digestion of our samples of cellulose. Since these oligosaccharides do not possess a chromophore or fluorophore, they can’t be detected either by absorbance or fluorescence. It was thus necessary to work out the labeling method for oligosaccharides using various agents, such as 8-aminopyrene-1,3,6-trisulfonic acid (APTS), 3-acetylamino-6-aminoacridine (AA-Ac) and phenylhydrazine (PHN). Finally, the use of capillary electrophoresis and high performance liquid chromatography allowed the separation of the enzymatic digestion products of the cellulose derivatives (CMC and HEC). For each of these analytical separation techniques, several parameters of the separation were studied.

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