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Development of General Purpose Liquid Chromatography Simulator for the Exploration of Novel Liquid Chromatographic StrategiesJeong, Lena N. 01 January 2017 (has links)
The method development process in liquid chromatography (LC) involves optimization of a variety of method parameters including stationary phase chemistry, column temperature, initial and final mobile phase compositions, and gradient time when gradient mobile phases are used. Here, a general simulation program to predict the results (i.e., retention time, peak width and peak shape) of LC separations, with the ability to study various complex chromatographic conditions is described. The simulation program is based on the Craig distribution model where the column is divided into discrete distance (Δz) and time (Δt) segments in a grid and is based on parameterization with either the linear solvent strength or Neue-Kuss models for chromatographic retention. This algorithm is relatively simple to understand and produces results that agree well with closed form theory when available. The set of simulation programs allows for the use of any eluent composition profile (linear and nonlinear), any column temperature, any stationary phase composition (constant or non-constant), and any composition and shape of the injected sample profile. The latter addition to our program is particularly useful in characterizing the solvent mismatch effect in comprehensive two-dimensional liquid chromatography (2D-LC), in which there is a mismatch between the first dimension (1D) effluent and second dimension (2D) initial mobile phase composition. This solvent mismatch causes peak distortion and broadening. The use of simulations can provide a better understanding of this phenomenon and a guide for the method development for 2D-LC. Another development that is proposed to have a great impact on the enhancement of 2D-LC methods is the use of continuous stationary phase gradients. When using rapid mobile phase gradients in the second dimension separation with diode array detection (DAD), refractive index changes cause large backgrounds such as an injection ridge (from solvent mismatch) and sloping baselines which can be problematic for achieving accurate quantitation. Use of a stationary phase gradient may enable the use of an isocratic mobile phase in the 2D, thus minimizing these background signals. Finally, our simulator can be used as an educational tool. Unlike commercially available simulators, our program can capture the evolution of the chromatogram in the form of movies and/or snapshots of the analyte distribution over time and/or distance to facilitate a better understanding of the separation process under complicated circumstances. We plan to make this simulation program publically available to all chromatographers and educators to aid in more efficient method development and chromatographic training.
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Étude de l'échange d'ions modulé électriquement : application du couplage échange d'ions-électrodialyse à la séparation de biomolécules / Study of electrical swing ion exchange : application of coupling of ion exchange-electrodialysis to biomolecules separationLu, Wei 21 June 2010 (has links)
Le présent travail vise à étudier le couplage de l’échange d’ions et de l’électrodialyse. Cette étude est appliquée à la séparation de biomolécules. Un des objectifs est de diminuer la génération d’effluents salins produits par les étapes d’échange d’ions utilisées de façon classique dans les bioséparations. Une première approche a conduit à la conception d’une architecture avec un mode de fonctionnement cyclique en 3 étapes qui permet de purifier certaines familles de peptides sans utiliser de tampon de pH ni générer d’effluents. Le dispositif expérimental est constitué d’une cellule d’électrodialyse dans laquelle sont introduites des résines échangeuses d’anions. Les trois étapes sont les suivantes : fixation des biomolécules sur la résine initialement sous forme carbonate, élution par une solution de dioxyde de carbone dissous dans l’eau, électrorégénération de la résine sous sa forme initiale, conduisant simultanément à la régénération de la solution d’acide carbonique. L’étape d’électrorégénération a été modélisée et les simulations permettent d’améliorer la compréhension des processus couplés mis en jeu comme les équilibres d’échange d’ions, les équilibres en solution, l’électromigration. Une deuxième approche a ensuite consisté à étudier les possibilités de contrôle du pH par voie électrochimique, afin de limiter l’utilisation de solutions tampons. La dissociation de l’eau, conduisant à la formation de protons et d’ions hydroxyles, a été plus particulièrement étudiée en mettant à profit les propriétés des contacts dits « bipolaires » sous l’effet d’un champ électrique. Il s’est alors avéré que les choix du type de résine et de la densité de courant permettent de jouer sur le pH Toutefois ce travail doit être poursuivi par la recherche d’architectures et de modes opératoires qui permettent d’obtenir un pouvoir tampon adéquat / The present work aims to study the coupling of ion exchange and electrodialysis. This study is applied to the separation of biomolecules. One objective is to reduce the generation of saline wastewater produced by the ion exchange steps used conventionally in bioseparations. One approach has led to the design of architecture with a cyclic mode in 3 steps to purify some families of peptides without using a buffer pH or generate wastes. The experimental device consists of an electrodialysis cell in which are introduced anion exchange resins. The three steps are: loading of biomolecules on the resin initially in the carbonate form, elution with a solution of carbon dioxide dissolved in water, electroregeneration of the resin in its original form leading simultaneously to the regeneration of the carbonic acid solution. Using a modelling of the electroregeneration step, simulations can improve the understanding of coupled processes as the ion exchange equilibria, the equilibria in solution, the electromigration. A second approach has then been to study the possibilities of controlling the pH by electrochemical means to limit the use of buffers. The dissociation of water, leading to the formation of protons and hydroxyl ions, has been particularly studied by accounting the properties of contacts called « bipolar » as a result of an electric field. It was established that the choice of resin type and the current density can modify the pH. However this work must be pursued through research of architectures and operating procedures that deliver appropriate buffer capacity
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