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1
Li, Zhiguo. "High-performance liquid chromatography analysis of fatty acids and mathematical modeling of liquid chromatography". Ohio : Ohio University, 2001. http://www.ohiolink.edu/etd/view.cgi?ohiou1179157379.
Testo completo
2
Mekaoui, Nazim. "Contribution à l'étude de la chromatographie à contre-courant : partage de composés ionisables, nouvelles colonnes et purification séquentielles". Thesis, Lyon 1, 2012. http://www.theses.fr/2012LYO10249/document.
Testo completoAbstract (sommario):
La chromatographie à contre courant (CCC) est une technique de purification chimique préparative quitravaille avec un système biphasique liquide. Une phase est la phase mobile, l'autre phase est la phasestationnaire. Il n'y a aucun support solide: un champ de force centrifuge est utilisé pour maintenir en place laphase stationnaire. Ce travail est une contribution à l'étude de la purification préparative par CCC. Après uneimportante étude bibliographique des procédés de purification en continu tant en CCC qu'autres, il est montréque la méthode dite "multi-dual-mode", ou MDM, est une solution possible. Elle consiste à utiliser le fait queles deux phases liquides peuvent servir de phase stationnaire: il suffit d'inverser le sens de circulation et lanature de la phase mobile (méthode dual-mode). Le mélange est séparé de façon classique pendant untemps chronométré, puis on inverse le rôle des phases: la phase mobile devient stationnaire et vice versa eton inverse également le sens de circulation (ascendant devient descendant ou vice versa). On sort lescomposants du mélange soit d'un coté de la colonne CCC, soit de l'autre. La méthode est mise en oeuvrepour purifier le Bleu de Coomassie en le débarassant des ses composés polaires (d'un coté) et apolaire (del'autre coté de la colonne et en accumulant dans la colonne la fraction de polarité intermédiaire, fractiond'intérêt. Une nouvelle colonne hydrostatique de petit volume (30 mL) a également été testée: elle permetde tester un nouveau système liquide très rapidementCounter-current chromatography (CCC) is a preparative purification technique that works with the twoliquid phases of a biphasic liquid system. One phase is used as the mobile phase when the other phase isused as the stationary phase. There is no solid support: centrifugal fields are used to obtain a support-freeliquid stationary phase. This work contains an exhaustive bibliographic study of what can be found in theliterature concerning continuous chromatographic processes. The multi-dual-mode (MDM) process was foundto be the best one able to purify large amount of crude mixtures. The MDM method starts with a classicalseparation of the mixture followed by a switch of both the liquid phase nature and the flowing direction. Themobile phase flowing e.g. in a descending direction becomes the stationary phase. The previous stationaryphase becomes the mobile phase flowing in the ascending direction (or vice versa). The purified compoundsof the introduced mixture are eluted at one side of the column or the other according to their polarity. TheMDM method was used to purify a crude sample of Coomassie Blue: the polar part of the dye was eluted atthe column top (or head) and the apolar part at the column bottom (or tail) while the essential part of the dyewas trapped inside the CCC column. The work also presents a new small volume (30 mL) hydrostatic CCCcolumn. It is shown that this column could be used to test quickly the potential of a given biphasic liquidsystem
3
Jeong, Lena N. "Development of General Purpose Liquid Chromatography Simulator for the Exploration of Novel Liquid Chromatographic Strategies". VCU Scholars Compass, 2017. http://scholarscompass.vcu.edu/etd/5079.
Testo completoAbstract (sommario):
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.
4
Andersson, David. "Simulation Testbed for Liquid Chromatography". Thesis, Umeå universitet, Institutionen för fysik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-185024.
Testo completoAbstract (sommario):
The stlc package is proposed as a tool for simulation of liquid chromatography by implementing several lumped kinetic models which combine diffusive mass transport and adsorption isotherm equations. The purpose of the package is to provide computationally efficient approximations to the general rate model of chromatography. Orthogonal collocation is used to discretize the spatial domain and the resulting system of ordinary differential equations is evaluated by one of several solvers made available in the package. Comparisons between numerical and analytical Laplace domain solutions for values of mass transfer coefficient, k, ranging from 0 to 1000 and lumped dispersion constant values, DL,from 10-5 to 10-2 are presented. Analytical results were approximated to an L1 error in the range 10-5 to 10-3 with a maximum evaluation time of 0.27s for 100 grid points. The breakthrough curves of the analytical solution are accurately recreated indicating a correct implementation. Variations in accuracy can be partly attributed to oscillations induced by steep gradients in the solution. The oscillations are reduced by the addition further points to the spatial grid. The package is implemented in Python using minimal dependencies and can produce approximations with short evaluation times. The Python programming language is dynamically typed and uses automatic memory management, properties which can improve productivity and be beneficial to research applications. The addition of this package to the extensive Python ecosystem of libraries can potentially aid future developments in chromatography.
5
Waichigo, Martin M. "Alkylammonium Carboxylates as Mobile Phases for Reversed-Phase Liquid Chromatography". Miami University / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=miami1134142423.
Testo completo
6
Kirk, John Daniel. "Particle beam LC/MS with fast atom bombardment". Thesis, Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/27127.
Testo completo
7
Hemström, Petrus. "Hydrophilic Separation Materials for Liquid Chromatography". Doctoral thesis, Umeå universitet, Kemi, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1350.
Testo completoAbstract (sommario):
The main focus of this thesis is on hydrophilic interaction chromatography (HILIC) and the preparation of stationary phases for HILIC. The mechanism of HILIC is also discussed; a large part of the discussion has been adapted from a review written by me and professor Irgum for the Journal of Separation Science (ref 34). By reevaluating the literature we have revealed that the notion of HILIC as simply partitioning chromatography needed modification. However, our interest in the HILIC mechanism was mainly inspired by the need to understand how to construct the optimal HILIC stationary phase. The ultimate stationary phase for HILIC is still not found. My theory is that a non-charged stationary phase capable of retaining a full hydration layer even at extreme acetonitrile (> 85%) concentrations should give a HILIC stationary phase with a more pure partitioning retention behavior similar to that of a swollen C18 reversed phase. The preparation of a sorbitol methacrylate grafted silica stationary phase is one of our attempts at producing such a stationary phase. The preparation of such a grafted silica has been performed, but with huge difficulty and this work is still far from producing a column of commercial quality and reprodicibility. This thesis also discusses a new method for the initiation of atom transfer radical polymerization from chlorinated silica. This new grafting scheme theoretically results in a silica particle grafted with equally long polymer chains, anchored to the silica carrier by a hydrolytically stable silicon-carbon bond. The hydrolytic stability is especially important for HILIC stationary phases due to the high water concentration at the surface.
8
Hendriks, Margriet Megtilda Wilhelmina Bartholomea. "Nonlinear retention modeling in liquid chromatography". [S.l. : [Groningen] : s.n.] ; [University Library Groningen] [Host], 1996. http://irs.ub.rug.nl/ppn/148573207.
Testo completo
9
Hemström, Petrus. "Hydrophilic separation materials for liquid chromatography /". Umeå : Department of Chemistry, Umeå University, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-1350.
Testo completo
10
Hickling, Simon James. "Liquid crystal polymers for gas chromatography". Thesis, University of Bath, 1999. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760726.
Testo completo
11
Harvey-Doyle, Fiona. "Resistively heated columns for liquid chromatography". Thesis, Loughborough University, 2010. https://dspace.lboro.ac.uk/2134/6370.
Testo completoAbstract (sommario):
Interest in temperature as a modifier in HPLC separations has increased markedly recently due to miniaturisation, new stable hybrid stationary phases and the use of superheated water as an eluent. However, for decades temperature has generally been regarded as a parameter that should be kept constant in LC separations for retention reproducibility but there is now a mountain of journal papers supporting the use of this variable. Currently, the limit of implementation usually arises from the lack of LC ovens on the market capable of high temperature applications. This led to the development of a resistively heated LC oven which allowed rapid reproducible heating/cooling patterns of RP columns thus reducing equilibration times and realising high sample throughput. The main objective was to drive temperature programming to a new extreme by rapid column heating akin to GC rather than LC, the emphasis being to produce much sharper peaks very rapidly. It was hoped that temperature gradients could replace solvent gradients and extend the applicability of temperature-programming for hyphenation to other forms of detection. New column materials were sought and tested against high speed temperature gradients. This coupled with micro-column technology should reduce analysis time and appreciably limit the amount of solvent waste currently being generated by conventional LC techniques. The column heating was achieved by two system components, the oven and the eluent pre-heater unit both based on resistive heating. Post-column cooling prior to detection minimised baseline disturbances imposed by a temperature gradient and enabled the use of detection modes such as MS, RI and ELSD as well as UV spectroscopy.
12
Wilson, William Henry. "Packed capillary columns for liquid chromatography". Diss., Virginia Tech, 1990. http://hdl.handle.net/10919/37746.
Testo completo
13
Shih, Victor Chi-Yuan Tai Yu-Chong. "Temperature-controlled microchip liquid chromatography system /". Diss., Pasadena, Calif. : Caltech, 2006. http://resolver.caltech.edu/CaltechETD:etd-04182006-162552.
Testo completo
14
Sharma, Sonika. "Hand-portable Capillary Liquid Chromatography Instrumentation". BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/6164.
Testo completoAbstract (sommario):
This dissertation focuses on the development of hand-portable capillary liquid chromatography (LC) instrumentation. In this work, battery-operable nano-flow pumping systems (isocratic and gradient) were developed and integrated with portable UV-absorption detectors for capillary LC. The systems were reduced in size to acceptable weights and power usage for field operation. A major advantage of the pumps is that they do not employ a splitter, since they were specifically designed for capillary column use, thereby greatly reducing solvent consumption and waste generation. UV-absorption detectors were specifically designed and optimized for on-column detection to minimize extra-column band broadening. Initially, an isocratic nano-flow pumping system with a stop-flow injector was integrated with an on-column UV-absorption detector (254 nm). The pumping system gave excellent flow rate accuracy (<99.94%) and low percent injection carry-over (RSD 0.31%) suitable for quantitative analysis. Using sodium anthraquinone-2-sulfonate, the detector gave an LOD (S/N = 3) of 0.13 µM, which was 12 times lower than a commercial UV-absorption detector. Reversed-phase separations of a homologous series of alkyl benzenes was demonstrated. Further miniaturization of UV-absorption detection was accomplished using a 260 nm deep UV LED. The detector was small in size and weighed only 85 g (without electronics). No optical reference was included due to the low drift in the signal. Two ball lenses, one of which was integrated with the LED, were used to increase light throughput through the capillary column. Stray light was minimized by the use of a band-pass filter and an adjustable slit. Signals down to the ppb level (nM) were easily detected with a short-term noise level of 4.4 µAU, confirming a low limit of detection and low noise. The detection limit for adenosine-5'-monophosphate was 230 times lower than any previously reported values. Isocratic separations of phenolic compounds were performed using a poly(ethylene glycol) diacrylate monolithic capillary column. Finally, a novel nano-flow gradient generator integrated with a stop-flow injector was developed. Gradient performance was found to be excellent for gradient step accuracy (RSD < 1.2%, n = 4) and linear gradient reproducibility (RSD < 1.42%, n = 4). Separations of five phenols were demonstrated using the nano-flow gradient system. Efforts to develop a 405 nm laser diode-based UV-absorption detector for hemoglobin analysis were described.
15
Wong, Victor, University of Western Sydney, of Science Technology and Environment College e of Science Food and Horticulture School. "A fundamental study towards improving the performance of liquid chromatographic separation". THESIS_CSTE_SFH_Wong_V.xml, 2003. http://handle.uws.edu.au:8081/1959.7/467.
Testo completoAbstract (sommario):
The three factors of the resolution (Rs)equation(see Equation 1.1)were explored in this thesis. During the course of the research project, an important aim was to explore separation processes that would lead to an increase in productivity without sacrificing Rs. To that end, an increase in the retention factor (k)to enhance Rs was deemed detrimental to the cycle time, hence the production rate, particularly when preparative separations are involved. Consequently the primary objectives were to (i)prepare more efficient columns and (ii)investigate new strategies in manipulating selectivity. The significance of the work contained in this thesis is highlighted in 27th International Symposium on High Performance Liquid Phase Separations and Related Techniques (HPLC 2003)held in Nice, France between 15-19 June, 2003. Many of the papers presented significantly compared to chapters contained in this researchDoctor of Philosophy (PhD)
16
DONALD, GREGORY THOMAS. "Model Chiral Ionic Liquids for High Performance Liquid Chromatography Stationary Phases". University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1214325450.
Testo completo
17
McBrady, Adam Dewey. "Microfabricated chromatographic instrumentation for micro total analysis systems /". Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/8570.
Testo completo
18
Scullion, Simon Daniel. "The analysis of surfactants and their determination in surface water by liquid chromatography and liquid chromatography-mass spectrometry". Thesis, Sheffield Hallam University, 1997. http://shura.shu.ac.uk/20338/.
Testo completoAbstract (sommario):
Linear alkylbenzene sulphonates (LAS) and alkylphenol polyethoxylates (APEO), the surfactants most used in this country, are complex mixtures of oligomers and homologues. Due to their excellent surface active properties they are widely used as ingredients in many detergent formulations both in the home and more importantly in industry. For several years research has been carried out in order to understand the environmental impact of these widely used groups of compounds. However, some of the analytical techniques developed are not able to give reliable information concerning individual oligomer / homologue levels. As the toxicological profile of these compounds is dependent on the individual levels present this data is of great importance. Surfactants are most often introduced into the environment through wastewaters. In order to try and actively contribute to this area, laboratory investigations were undertaken to develop chromatographic techniques which would be able to determine individual oligomer / homologue levels in environmental surface water samples. Even if extensive sample clean up is used these samples are by nature, very 'complex'. Mass spectrometry lends itself to the analysis of environmental samples as it is able to give detailed structural data which aids in eliminating signal contributions from interfering compounds. To this end, work was carried out in order to develop liquid chromatography methods which are compatible with conventional mass spectrometers and could be used for the determination of the environmental levels of both LAS and APEO.
19
Bhattacharjee, Rathindra Chandra. "Development of a sensitive and stereoselective high performance liquid chromatographic assay method for propafenone enantiomers in human plasma". Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/27800.
Testo completoAbstract (sommario):
Propafenone is a new class 1C antiarrhythmic agent with additional calcium antagonistic and beta-blocking activities. Clinically it is effective in the treatment of supraventricular and ventricular tachycardia, atrial and ventricular fibrillation, ventricular premature contractions and for the management of Wolf-Parkinson-White syndrome. In North America it is still an investigational drug.
Propafenone is a chiral drug and is used clinically in the racemic form. The enantiomers of numerous chiral drugs have been shown to differ in their disposition kinetics in the body due to their stereoselective pharmacokinetics and/or pharmacodynamic properties. Two enantiomers are thus often considered as two different entities. The relative antiarrhythmic activities of individual enantiomers of propafenone have not been studied, nor their pharmacokinetic parameters have been elucidated. In order to study the possible enantioselective role of propafenone in the body, a stereoselective assay method would be required. The present study describes the development of a sensitive and stereoselective chromatographic assay method for the simultaneous determination of the two enantiomers of propafenone in human plasma.
Attempts for direct separation of the enantiomers of propafenone included several GLC and HPLC chiral stationary phases. The chiral stationary phases were a Chirasil-Valʳ GLC stationary phase, a Pirkle 2,4 dinitro-(D)-phenylglycine HPLC stationary phase and a β-cyclodextrin HPLC stationary phase. Unfortunately, these did not resolve the enantiomers of propafenone.
Formation of the diastereomers with R(+)-⍺-methyl benzyl isocyanate and racemic propafenone were partially resolved on a reverse phase HPLC using a 5 u, 25 x 0.45 cm i.d. ODS column and methanol/water (70:30) as the mobile phase. However, due to the long retention time (42 min), incomplete resolution (RS=1.15) and poor sensitivity for detection (500 ng of each enantiomer injected) this method was not deemed suitable for the pharmacokinetic studies planned, since the therapeutic plasma concentration range of propafenone is 64-1044 ng/mL.
The second chiral derivatizing reagent, 2,3,4,6-tetra-0-acetyl-β-D-glucopyranosylisothiocyanate (GITC), was synthesized in our laboratory. This reagent gave better resolution of the enantiomers (RS=1.4) within 15 minutes with enhanced sensitivity for detection (150 ng of each enantiomer injected).
To further optimize the limit of detection for future pharmacokinetic studies of propafenone, R(-)-1 -(naphthyl) ethylisocyanate, a chiral derivatizing agent, was employed. This reagent reacted with racemic propafenone and permitted the resolution of both enantiomers within 24 minutes (R5=l.25) and the minimum level of detection was 100 ng (at the detector) for each enantiomer of propafenone. Using this method, linearity was established over the concentration range, 125-1000 ng for each enantiomer (injected) with a coefficient of determination (r²) of greater than 0.99.
Reproducibility and precision of this assay method was obtained with an average coefficient of variability of 4.5% for the R(-) enantiomer and 7.2% for S(+) enantiomer at concentrations of 125-1000 ng/mL. Below the lower quantity, the NEIC-propafenone reaction virtually stopped at the conditions set for derivatization. A similar lack of reactivity at low concentrations was also observed with the GITC-propafenone reaction.
The absence of an autocatalysing effect of propafenone at lower nanogram levels, as well as two possible conformational forms of propafenone were also investigated. The existence of two conformational isomers of propafenone, due to intramolecular hydrogen bonding in aprotic solvents, was chromatographically verified. In addition, chromatographic separation of all the proposed conformers was obtained, indicating that enantiomeric separation and quantitation of propafenone enantiomers as their urea derivatives is substantially hindered.
To eliminate hydrogen bonding interactions, the carbonyl group of propafenone was blocked with dansylhydrazine and subsequently derivatized with the chiral R(-)NEIC reagent. The HPLC resolution (RS=1.35) of this dual derivative was better than that using the R(-) NEIC reagent alone, and the minimum level of detection was 2.5 ng for each enantiomer. Unfortunately, this procedure still did not provide adequate assay precision and accuracy at the lower levels required for single dose pharmacokinetic studies.Pharmaceutical Sciences, Faculty of
Graduate
20
Jedrzejewski, Paul T. "Investigation of mass spectrometric interfaces for supercritical fluid chromatography and liquid chromatography". Diss., This resource online, 1996. http://scholar.lib.vt.edu/theses/available/etd-08282003-155244/.
Testo completo
21
Yla-Maihaniemi, Pirre Paivikki. "A novel method for investigating solid-liquid interactions : inverse liquid chromatography". Thesis, Imperial College London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.429885.
Testo completo
22
Norcio, Lawrence P. "Stability studies of coal liquid products using high performance liquid chromatography". Morgantown, W. Va. : [West Virginia University Libraries], 1999. http://etd.wvu.edu/templates/showETD.cfm?recnum=984.
Testo completoAbstract (sommario):
Thesis (Ph. D.)--West Virginia University, 1999.Title from document title page. Document formatted into pages; contains xi, 152 p. : ill. (some col.) Vita. Includes abstract. Includes bibliographical references (p. 127-133).
23
Monser, Lotfi Ibrahim. "Modified porous graphitic carbon for liquid chromatography". Thesis, University of Hull, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.318379.
Testo completo
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Abid, F. M. "High performance liquid chromatography : theory and applications". Thesis, Swansea University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.635837.
Testo completoAbstract (sommario):
A detailed study was undertaken of both the individual and combined effects of pH, temperature and flow rate on the retention volumes of underivatised amino acids. The relative merits of 3-dimensional S-window diagrams to locate the optimum conditions for the separation of amino acids on a stationary phase comprising 5μ ODS has been successfully performed. The enthalpies of retention of transfer from stationary phase to mobile phase for the amino acids have been measured from the chromatographic data. An isocratic study of the separation of phenylthiohyddation (PTH) amino acids using a 3μ MOS Hypersil reverse phase column was performed by the pre-column derivatisation method. Subsequently, a more detailed investigation was made of the various factors which control the separation, viz. pH, temperature and eluent composition. The conditions for optimum separation were located by constructing, with the aid of a computer, a 3-dimensional S-window diagram. The enthalpy of transfer from stationary phase to mobile phase and the entropy of the process were evaluated from the chromatographic data. A new pre-column derivatisation method for the separation of amino acids by gradient elution was established using an ODS column; this was applied to the analysis of amino acids extracted from mammalian tissue. The retention behaviour of PTH-amino acids was studied on a mixed stationary phase comprising silica bonded to alkylcynanide and octyl silica in the ratio of 60:40, w/w. This factor has an important bearing on the solute retention selectivity of the column. It was found that the selectivity of the acidic and basic PTH-amino acids could be precisely controlled by adjusting the packing percentage and mobile phase composition, suggesting that the mixed phase technique could be profitably exploited for analytical purposes. HPLC group type analyses of oil samples, normally requiring more sophisticated and time consuming methods of analysis, were performed using normal and reverse phase columns of different materials. The separated fraction has been identified by mass spectrometry, and the results obtained have been of some assistance in an investigation relating to poorly combustable oil. Finally, an extended and modified LC theory has been proposed, and a new modified approach which relates the inverse corrected retention volume (1/VR) and volume fraction composition of polar solvent component (φB) has been established for a polar component variation of 0 to 100% . The results indicate good agreement between the theoretical and experimental values for all systems displaying a non-linear relationship between 1/VR and φB.
25
Cowen, Thomas. "Some studies in reversed phase liquid chromatography". Thesis, University of Salford, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.305175.
Testo completo
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Airiau, Christian Y. "Application of chemometrics to hyphenated liquid chromatography". Thesis, University of Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.392922.
Testo completo
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Ortman, Jerker. "Improvement of conductivity measurement in liquid chromatography". Thesis, Uppsala universitet, Institutionen för elektroteknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-448059.
Testo completoAbstract (sommario):
In liquid chromatography the ability to measure the conductivity is essential toreach a good result. This is done by applying a current through the electrolyte ofinterest and measuring the voltage drop over the electrolyte. The conductivity isthen calculated with the known current and the measured voltage. It is of highimportance that it is an AC-current to avoid polarization at the electrodes of thesensor. With the AC-current a frequency must be chosen to reach the most accurateresult. This is hypothetically done where the phase is as low as possible. An electricequivalent circuit and previous work was used as a starting point in the work offinding the best frequency algorithms that would give the lowest phase. Afterseveral measurements with different frequency algorithms it could be seen that thecurrent algorithm is plenty good and that at the moment it is not worth it to improveit further. The sensor in this thesis, chip LFS155 from IST AG, Switzerland, wassaid to have an linear cell constant between 0.1-200 mS/cm. So after multiplemeasurements on five different LFS155 sensors it could be seen that in the regions oflower conductivity as well as higher conductivity the cell constant could be adjustedfora better result. The adjustments were done by excels curve fitting function andimplemented witha good result. The demands on the accuracy for the sensor tomeasure conductivity could be improved. In the lower part of conductivity spectra(<0.1 mS/cm) the promised accuracy went from±0.02 mS/cm to±0.005 mS/cm.In the higher end of the conductivity spectra (>100 mS/cm) itwas changed from±4 % to±2 %
28
Leow, Pei Ling. "In-column electrochemical detection for liquid chromatography". Thesis, Imperial College London, 2009. http://hdl.handle.net/10044/1/5295.
Testo completoAbstract (sommario):
This research focuses on the development of whole column detection (WCD) for liquid chromatography (LC). The WCD uses electrochemical techniques for detecting the analytes passing through the separation column. Electrode array for in-column electrochemical detection (ICED) is fabricated along the separation column to enable whole column separation monitoring and allow better understanding on the affinity of particular analyte to the stationary and mobile phases. Numerical models were built to understand the feasibility and differences of electrochemical detection within an unpacked and packed column. From the simulated results, the surface area of the electrode was not hindered by the presence of the particles in flow condition. An electrochemical microfluidic device has been successfully fabricated on PET (polyethylene terephthalate) substrate using the reverse imprinting technique. The photolithographically produced gold metal electrode lines were imprinted into the PET substrate using a blank mould and produced an inlaid electrode array with overall step residue within 40 nm. The semi-cured thermoset polyester channel was irreversibly thermal bonded on the PET substrate. The devices were able to tolerate pressure in excess of 90 bars. The PET column was packed with 5 μm C18 silica beads to perform reverse phase chromatography separation. The array was electrochemically characterised using standard redox probes in both stagnant conditions and under flow. Both numerical modelling and experimental data show improved sensitivity under flow and a limiting current which scaled linearly with cubic root of volume flow rate. Isocratic and gradient mode chromatographic separations of neurotransmitters and metabolites: serotonin, dopamine, adrenaline, 5- HIAA and DOPAC were conducted in the fabricated device. Separation progress was electrochemically detected at multiple locations along the column. Whole column assessment on separation efficiency and column packing efficiency monitoring were conducted using the ICED.
29
Xiang, Yanqiao. "Capillary Liquid Chromatography Using Micro Size Particles". Diss., CLICK HERE for online access, 2004. http://contentdm.lib.byu.edu/ETD/image/etd531.pdf.
Testo completo
30
Dotlich, Erin Michele. "ALKYLAMMONIUM FORMATE IONIC LIQUIDS AS SOLVENTS FOR FLUORESCENCE AND LIQUID CHROMATOGRAPHY METHODS". Miami University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=miami1208983119.
Testo completo
31
Wong, Victor. "A fundamental study towards improving the performance of liquid chromatographic separation". Thesis, View thesis, 2003. http://handle.uws.edu.au:8081/1959.7/467.
Testo completoAbstract (sommario):
The three factors of the resolution (Rs)equation(see Equation 1.1)were explored in this thesis. During the course of the research project, an important aim was to explore separation processes that would lead to an increase in productivity without sacrificing Rs. To that end, an increase in the retention factor (k)to enhance Rs was deemed detrimental to the cycle time, hence the production rate, particularly when preparative separations are involved. Consequently the primary objectives were to (i)prepare more efficient columns and (ii)investigate new strategies in manipulating selectivity. The significance of the work contained in this thesis is highlighted in 27th International Symposium on High Performance Liquid Phase Separations and Related Techniques (HPLC 2003)held in Nice, France between 15-19 June, 2003. Many of the papers presented significantly compared to chapters contained in this research
32
Forssén, Patrik. "Adsorption Isotherm Parameter Estimation in Nonlinear Liquid Chromatography". Doctoral thesis, Uppsala universitet, Avdelningen för teknisk databehandling, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-5971.
Testo completoAbstract (sommario):
This thesis concerns the development and validation of methods for the industrially important area of adsorption isotherm parameter estimation in preparative, nonlinear high performance liquid chromatography (HPLC). Preparative chromatography is a powerful separation method to get pure compounds from more or less complex liquid mixtures, e.g., mixtures of mirror-image molecules. Computer simulations can be used to optimize preparative chromatography, but then competitive adsorption isotherm parameters are usually required. Here two methods to estimate adsorption isotherm parameters are treated: (i) the perturbation peak (PP) method and (ii) the inverse method (IM). A new theory for the PP method was derived and led to a new injection technique which was validated experimentally. This injection technique solved the severe problem with vanishing peaks and enabled us to use the PP method to estimate binary competitive adsorption isotherms valid over a broad concentration range. Also, the injection technique made it possible to estimate competitive adsorption isotherms for a quaternary mixture for the first time. Finally, an interesting perturbation peak phenomenon, known as the “Helfferich Paradox”, was experimentally verified for the first time. The IM is a relatively new method to determine adsorption isotherm parameters. It has the advantage of requiring very small samples, but also requires an advanced computer algorithm. An improved implementation of this computer algorithm was developed and tested experimentally. Also, a variant of the IM called “the inverse method on plateaus” was tested experimentally and the estimated adsorption isotherm parameters were shown to be valid over a broader concentration range than those estimated with the standard IM.
33
Rousu, T. (Timo). "Liquid chromatography–mass spectrometry in drug metabolism studies". Doctoral thesis, Oulun yliopisto, 2012. http://urn.fi/urn:isbn:9789514298172.
Testo completoAbstract (sommario):
Abstract Drug metabolite profiling and identification studies are nowadays regularly conducted with liquid chromatography (LC) coupled with mass spectrometry (MS) as an analytical tool. The speed, selectivity and sensitivity of modern LC–MS instruments have been significantly increased in recent years. Especially the use of ultra-high-performance LC (UHPLC) in combination with a modern high-resolution MS instrument offers high full scan detection sensitivity, mass accuracy and the detection of both expected and unexpected metabolites in a single LC–MS run. The present study showed that no single LC–MS conditions were suitable for the analysis of a large group of structurally diverse compounds. The testing of optimum conditions for each individual compound led to more high-quality data when chromatographic retention behavior and mass spectrometric ionization efficiency for in vitro metabolite profiling were considered. The developed LC–MS methods were applicable for measuring both the disappearance of the parent compound and the formation of metabolites. Tentative metabolite identification was based on the measured accurate mass time-of-flight (TOF) MS data. In the second part, a rapid and sensitive assay was designed and built for the trapping, screening and characterization of reactive metabolites in vitro. In total, 78 trapped reactive metabolite conjugates were detected and identified based on accurate mass data using 12 structurally different test compounds. The majority of the detected conjugates were reported for the first time. Amine-containing compounds, that formed methylated and cyanide-trapped products after CYP-mediated reaction steps in human liver microsomal (HLM) incubations, were studied further. The observed methylated cyano conjugates were shown to be experimental artifacts, i.e., metabonates. The study also describes the use of traditional high-performance LC (HPLC) and the more modern UHPLC coupled to time-of-flight, triple quadrupole and hybrid linear ion trap mass spectrometers in drug metabolism studies, and reviews on how to choose the most suitable LC–MS system for metabolite profiling purposes in drug discovery and early drug developmentTiivistelmä Nestekromatografia (LC) yhdistettynä massaspektrometriaan (MS) on nykyaikana yleisesti käytetty analyysimenetelmä lääkeaineiden aineenvaihduntatuotteiden (metaboliittien) havaitsemisessa ja tunnistamisessa. Modernien LC–MS -laitteiden nopeus, selektiivisyys ja herkkyys ovat merkittävästi parantuneet viime vuosina. Käytettäessä ultrakorkean suorituskyvyn nestekromatografia (UHPLC) yhdessä nykyaikaisen korkean massaresoluution MS-laitteen kanssa on mahdollista havaita kaikki sekä odotetut että odottamattomat metaboliitit yhdellä kertaa. Tutkimalla suurta joukkoa rakenteellisesti erilaisia yhdisteitä voitiin todeta, että yksittäiselle yhdisteelle optimoidut mittausolosuhteet johtivat korkealaatuisempaan dataan kuin yleiset ei-optimoidut olosuhteet, kun arvioitiin sekä kromatografista piikin profiilia ja pidättymistä että ionisaatiotehokkuutta. Yksikään yksittäinen analyysiolosuhde ei myöskään soveltunut kaikille yhdisteille. Tutkimuksessa kehitetyillä LC–MS -analyysimenetelmillä tutkittiin sekä kanta-aineen häviämistä että metaboliatuotteiden muodostumista in vitro -menetelmillä. Alustava metaboliatuotteiden tunnistus perustui tarkan massan mittaukseen lentoaikamassaspektrometrillä (TOFMS). Tutkimustyön seuraavassa vaiheessa kehitettiin nopea ja herkkä analyysimenetelmä reaktiivisten metaboliittien pyydystämiseen, havaitsemiseen ja tunnistamiseen ihmisen maksamikrosomivalmisteista in vitro -menetelmin. 12 testiyhdisteelle havaittiin kaikkiaan 78 erilaista reaktiivisen metaboliitin konjugaatiotuotetta, jotka tunnistettiin tarkan massan perusteella. Suurin osa tunnistetuista konjugaatiotuotteista raportoitiin ensimmäistä kertaa. Amiineja sisältäville testiyhdisteille havaittiin muodostuvan sytokromi P450 (CYP) entsyymien katalysoimien reaktioiden välityksellä metyloituneita ja syanidianionilla konjugoituneita metaboliatuotteita. Tarkempien tutkimusten jälkeen näiden todettiin olevan koejärjestelyistä johtuvia artefaktoja, toisin sanoen metabonaatteja, eivätkä todellisia reaktiivisten metaboliittien konjugaatiotuotteita. Tässä tutkimuksessa arvioitiin myös perinteiseen korkean suorituskyvyn nestekromatografiin (HPLC) sekä uudempaan UHPLC-laitteistoon kytkettyjen lentoaika-, kolmoiskvadrupoli- ja hybridimallisten ioniloukkumassaspektrometrien soveltuvuutta aikaisen lääkekehitysvaiheen metaboliatutkimuksiin
34
Tam, Chung Ming. "Use of liquid chromatography in membrane material characterization". Thesis, University of Ottawa (Canada), 1989. http://hdl.handle.net/10393/5701.
Testo completo
35
Forssén, Patrik. "Adsorption isotherm parameter estimation in nonlinear liquid chromatography /". Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-5971.
Testo completo
36
Fitzpatrick, Fiona Patricia. "Interactive liquid chromatography for the characterisation of polymers". [S.l. : Amsterdam : s.n.] ; Universiteit van Amsterdam [Host], 2004. http://dare.uva.nl/document/74455.
Testo completo
37
Enetoft, Daniel. "Automating analysis of two-dimensional liquid chromatography data". Thesis, Linköpings universitet, Institutionen för teknik och naturvetenskap, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-95339.
Testo completoAbstract (sommario):
A biomarker is a cellular or molecular indicator of exposure, disease, or susceptibility to disease. Ones a biomarker has been confirmed, it can be used to diagnose disease risk or to tailor treatment for it. A protein is a possible biomarker. These proteins can be found by several methods, where two-dimensional liquid chromatography (2DLC) is one of the newer approaches. This technique is capable of separating thousands of proteins. To find the proteins whose abundance differs in different groups, the data must be carefully analyzed. Due to the amount of proteins that can be found by the method and difficulties in preparation of the data, this is not a simple problem to solve. In this thesis a workflow for finding differences between groups of samples analyzed with 2DLC is presented. The workflow has been separated into three parts. The first part is background subtraction, to remove the parts of the signals that originate from noise. After that comes alignment of the signals. The difficulties to prepare the 2DLC data makes the signal unpredictably distorted in a non linear way. The last part is the essence of the analysis process. First determine that differences do exist between the groups of data being analyzed and then identify where it differs. Several methods for each part have been evaluated and are presented in this thesis.En biomarkör är en biologisk variabel som speglar en fysiologisk förändring till följd av sjukdom, läkemedelsbehandling eller annan yttre påverkan. När en biomarkör har blivit konfirmerad kan den användas för att diagnostisera riskerna för en sjukdom eller för att skräddarsy botemedel mot sjukdomen. Ett protein är en möjlig biomarkör. Dessa proteiner kan hittas med hjälp av ett flertal metoder, bland vilka tvådimensionell liquid chromatography (2DLC) är en av de nyaste infallsvinklarna. Denna teknik kan separera tusentals proteiner. För att hitta de proteiner vars mängd skiljer sig mellan olika grupper av 2DLC-prover måste data från experimentet analyseras noggrant. På grund av mängden proteiner som kan hittas av metoden och problem i framställningsprocessen av 2DLC-data, är detta inget lätt problem att lösa. I det här examensarbetet kommer ett arbetsflöde för att hitta skillnader mellan grupper av prover presenteras. Arbetsflödet har delats upp i tre delar. Den första delen är bakgrundsborttagning, att ta bort de delar av signalerna som inte korrelerar med mängden protein. Andra delen är linjering av signalerna. Problemet med att framställa 2DLC-data gör att signalerna blir oförutsägbart distorderade på ett olinjärt sätt. Den sista delen är själva kärnan i processen; först vill man säkerställa att det verkligen finns skillnader mellan de grupper av data som analyserats, sedan vill man veta var skillnaderna finns. Ett flertal metoder för varje av de ovanstående delarna har evaluerats och presenteras i det här examensarbetet.
38
Huft, Jens. "Microfluidic technologies for the integration of liquid chromatography". Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44898.
Testo completoAbstract (sommario):
The microfabrication technique of Multilayer Soft Lithography (MSL) has emerged as the dominant platform for the development of microfluidic devices in biomedical research. However, Multilayer Soft Lithography, as originally developed, has technological limitations that restrict its effectiveness and versatility in implementing laboratory operations on chip. This thesis solves two of these limitations, namely that channel routing is restricted to planar geometries and that no established methods exist for creating solid-phase columns needed to perform on-chip analytical and preparative separations.
The first technological advancement is the development of a new fabrication method using laser ablation that enables the automated fabrication of interlayer connections in MSL-based microfluidic devices. Real-time image recognition and computer control allow for robust wafer-scale registration of laser ablation features with moulded channel structures. This new functionality removes the constraint that all connected device features lie in a single plane, significantly enhancing achievable feature density and fluid handling complexity.
To further extend the range of accessible bioanalytical applications using MSL-based devices, this thesis also presents the development of a novel microfluidic column geometry that allows rapid packing of multiple microcolumns in parallel with near-perfect yield. These microcolumns are shown to be of high quality, with plate heights comparable to conventional high-performance capillary columns and superior to what has previously been reported for packed microfluidic columns.
Finally, this thesis shows how these new capabilities allow for the implementation of the first fully integrated microfluidic liquid chromatography system that exploits advantages of automation, small sample volume and parallel processing. All elements required for automated sample loading, programmable gradient generation, separation, fluorescent detection, and sample recovery are integrated on a single device.
The ability to reliably fabricate three-dimensional microfluidic devices and to integrate highly optimized solid-phase columns will open many new opportunities for on-chip integration, bringing the ultimate goal of complete lab-on-a-chip integration closer to reality.
39
Edwardson, P. A. D. "High Performance Liquid Chromatography of polynucleotides and proteins". Thesis, London School of Hygiene and Tropical Medicine (University of London), 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376534.
Testo completo
40
Zhu, Cuiru. "Elevated temperature liquid chromatography and peak shape analysis". Thesis, University of York, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413172.
Testo completo
41
Cooper, J. D. H. "Automated sample preparation for high pressure liquid chromatography". Thesis, De Montfort University, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292855.
Testo completo
42
Dias, H. "Gas and liquid chromatography on porous graphitic carbon". Thesis, University of Edinburgh, 1990. http://hdl.handle.net/1842/13643.
Testo completoAbstract (sommario):
A new hydrophobic support material, Porous Graphitic (or Graphitised) Carbon (PGC) has been studied using both Liquid (LC) and Gas Chromatography (GC). The heat of adsorbtion (AH) of typical LC solvents determined on PGC, using GC, showed that AH increased with the molecular area (Ax) of solvents for well graphitised carbons, but that AH/Ax values were similar for all solvents studied. By definition, AH/Ax is a measure of eluotropic strength. The results reveal that a strong eluotropic series does not exist on carbon. A strong eluotropic series does exist on silica. In this case, AH/Ax values of solvents were dependent upon their eluotropic strengths (Eo), determined by LC. GC work was carried out using alcohols, ketones and aliphatic hydrocarbons on PGC, modified with different amounts of Carbowax 1500. Symmetrical peaks were obtained with coated materials. The column efficiency (N), first increased and then dropped with increasing Carbowax content on the PGC surface. The retention of ketones and hydrocarbons decreased with increasing amount of Carbowax on PGC. In the case of alcohols, the retention decreased with the initial introduction of Carbowax on to PGC. Some alcohols displayed enhanced retention at 0.10% of Carbowax. All alcohols showed increased retention at the monolayer coverage of Carbowax. In the quest for a perfect material for adsorption GC, PGC samples were hydrogen treated at elevated temperatures (230-1030°C). All hydrogen treated samples failed to display signficantly improved chromatographic properties. PGC was then treated with toluene in a stream of either hydrogen (at 630°C) or nitrogen (at 630°C or 300°C) to eliminate any active sites present on the surface. Hexane was used us an alternative to toluene at 630°C in a stream of hydrogen. Such surface treatments yielded improved materials for adsorption GC. On heating the columns (beyond 230"C), containing these materials, with carrier gas running through the columns, the Chromatography deteriorated in the cases of toluene-treated PGC whilst the Chromatography of the hexane-treatcd PGC remained unaffected. LC work on some aromatic compounds using PGC, coated with surfactants such as Tween 80 or Span 80 showed that, analyte retention decreased with increasing surfactant concentration (up to 0.03% of Tween and 0.02% of Span) in the eluent. N dropped with the introduction of Tween to the PGC. Increasing the ratio of water to mcthanol in the eluent, at a constant eluent concentration of surfactant, resulted in diminishing N, increasing eluent polarity and analyte retention values. Ion pairing was carried out on PGC using cetyltrimethylammonium-bromide (CTAB) as the ion pairing agent, at an eluent pH of 12.5. The retention of solutes, that ionise under these conditions, increased whereas the retention of analytes, that do not ionise, decreased with increasing eluent concentration of CTAB. The coated or chemically modified PGC surfaces are useful in GC whilst the dynamically coated PGC surfaces are important in LC. Such surface treatments can alter the following properties of PGC; (a) Retention characteristics, (b) the selectivity and (c) chromatographic efficiency.
43
Wan, Quian-Hong. "Surface modification of porous graphite for liquid chromatography". Thesis, University of Edinburgh, 1992. http://hdl.handle.net/1842/13187.
Testo completoAbstract (sommario):
Surface modification of porous graphite has been studied in detail by liquid chromatography. The non-polar nature of the graphite provides the basis for adsorptive modification by which the graphite surface is either deactivated or functionized. While the elimination of geometric heterogeneity is achieved by adsorption of trace polyaromatic compounds, the specialist in selectivity is conferred to the graphite by a monolayer coating of modifiers. A number of strategies are used for different purposes. These include dynamic coating, insoluble coating and cross-linked coating. The chromatographic properties of the modified materials are evaluated in terms of efficiency, selectivity and stability. With the exception for cross-linked coating, the modified materials show performances better than those of the original graphite. Applications to adsorption, ion exchange, chiral and exclusion chromatography are demonstrated. These new packings are found particularly useful in the separation of inorganic anions, amino acid and hydroxy acid enantiomers. They give excellent peak symmetry and long term stability. The mechanisms of retention on the graphite based materials are characterised and discussed.
44
Dolci, Monica. "Liquid chromatography-mass spectrometry analysis of oligolactic acids". Thesis, Loughborough University, 2008. https://dspace.lboro.ac.uk/2134/35549.
Testo completoAbstract (sommario):
The project has demonstrated the application of liquid chromatography coupled to mass spectrometry (LC-MS) for the characterisation of oligolactic acids (OLAs), employed as pharmaceutical excipients in metered dose inhalers. OLAs proved to be difficult to characterise because of their complexity, which was ascribed. to the presence of repeated structural monomeric units and a nonrepeating moiety (the head group). Furthermore, during the course of method development the potential presence of degradation products and impurities had to be considered for quality control purposes. Various LC-MS methods were developed to target both oligomeric distribution and head group functionalities of OLAs. Liquid chromatography at critical conditions (LCCC), aimed at addressing the head group distribution of OLAs, led to the separation of the cyclic impurities from the parent linear molecules. However, to successfully achieve a complete characterisation of OLAs, a second separation targeting the oligomeric distribution was investigated. Hydrophobic and polar interactions and possible solvation effects, which regulate RP-HPLC separation mechanisms, proved to be able to offer the selectivity necessary to resolve OLAs in terms of their size and their head groups, leading to the simultaneous separation between the linear molecules and their cyclic impurities and the determination of oligomeric distribution.
45
Aggarwal, Pankaj. "High-Performance Polymer Monoliths for Capillary Liquid Chromatography". BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/4236.
Testo completoAbstract (sommario):
This dissertation focuses on improving the chromatographic efficiency of polymeric organic monoliths by characterizing and optimizing the bed morphology. In-situ characterization techniques such as capillary flow porometry (CFP), 3-dimensional scanning electron microscopy (3D SEM) and conductivity measurements were developed and implemented to quantitatively characterize the morphology of poly(ethylene glycol) diacrylate (PEGDA) monoliths. The CFP measurements for monoliths prepared by the same procedure in capillaries with different diameters (i.e., 75, 150, and 250 μm) clearly showed a change in average through-pore size with capillary diameter, thus, certifying the need for in-situ measurement techniques. Serial sectioning and imaging of PEGDA monoliths using 3D SEM gave quantitative information about the average pore size, porosity, radial heterogeneity and tortuosity of the monolith. Chromatographic efficiency was better for a monolith with smaller average pore size (i.e., 5.23 μm), porosity (i.e., 0.49), radial heterogeneity (i.e., 0.20) and tortuosity (i.e., 1.50) compared to another monolith with values of 5.90 μm, 0.59, 0.50 and 2.34, respectively. Other than providing information about monolith morphology, these techniques also aided in identifying factors governing morphological changes, such as capillary diameter, polymerization method, physical/chemical properties of the pre-polymer constituents and weight proportion of the same. A statistical model was developed for optimizing the weight proportion of pre-polymer constituents from their physical/chemical properties for improved chromatographic efficiency. Fabricated PEGDA columns were used for liquid chromatography of small molecules such as phenols, hydroxyl benzoic acids, and alkyl parabens. The chromatographic retention mechanism was determined to be principally reversed-phase (RP) with additional hydrogen bonding between the polar groups of the analytes and the ethylene oxide groups embedded in the monolith structure. The chromatographic efficiency measured for a non-retained compound (uracil) was 186,000 plates/m when corrected for injector dead volume. High resolution gradient separations of selected pharmaceutical compounds and phenylurea herbicides were achieved in less than 18 min. Column preparation was highly reproducible, with relative standard deviation (RSD) values less than 2.1%, based on retention times of the phenol standards (3 different columns). A further improvement in chromatographic performance was achieved for monoliths fabricated using a different polymerization method, i.e., living free-radical polymerization (LFRP). The columns gave an unprecedented column performance of 238, 000 plates/m for a non-retained compound under RP conditions.
46
Matos, Ana Karollyna Alves de [UNESP]. "Influência da vinhaça e da palhada de cana-de-açúcar na sorção de herbicidas aplicados em diferentes solos". Universidade Estadual Paulista (UNESP), 2014. http://hdl.handle.net/11449/110931.
Testo completoAbstract (sommario):
Made available in DSpace on 2014-12-02T11:16:45Z (GMT). No. of bitstreams: 0
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000800265.pdf: 1317086 bytes, checksum: 617587c5dc929a7726bd7a48f2571ce3 (MD5)O sistema de produção com ou sem a pres ença de palhada, bem como, a aplicação de vinhaça nos canaviais, podem levar a alterações nas propriedades do solo e influenciar a disponibilidade dos herbicidas na solução do solo. Diante disto, o presente trabalho teve por objetivo avaliar a influência d a água, água após passar pela palha de cana - de - açúcar e vinhaça na disponibilidade na solução do solo dos herbicidas amicarbazone, clomazone, diuron, hexazinone, imazapic, sulfentrazone e tebuthiuron em diferentes solos. Adotou - se o esquema fatorial 3 x 31, com delineamento em blocos inteiramente casualizados com três repetições, sendo utilizadas 31 amostras de solos distintos quanto às características físicas e químicas e três tratamentos (água, água de lavagem de palha e vinhaça). As amostras de solo foram dispostas em bandejas e submetidas à aplicação dos herbicidas, em seguida foram acondicionadas em cartuchos plásticos e saturadas com água deionizada, água de lavagem de palha e vinhaça, permanecendo em repouso durante 18 horas sob refrigeração (8 ± 3 ° C) . Posteriormente, fez - se duas extrações, na primeira quantificou - se os herbicidas presentes na solução do solo e na segunda foi realizada a extração total do herbicida remanescente no solo para determinação da porcentagem de recuperação de cada herbicida t estado. Para as quantificações utilizou - se um sistema LC - MS/MS, composto por um Cromatógrafo Líquido de Alta Performance (HPLC) acoplado ao espectrômetro de massas. O amicarbazone e o imazapic foram mais 2 disponibilizados na solução dos solos com a aplicaçã o de água e água de lavagem de palha na maioria das amostras. Todavia, a adição de vinhaça promoveu uma maior disponibilização do diuron e tebuthiuron em todos os solos. O clomazone, hexazinone e sulfentrazone não apresentaram diferença significativa entre os ...
The pr oduction system with or without the straw as how the sugarcane vinasse application may cause some changes in the soil properties and may influence the avaiability of the herbicides in the soil solution. Based on that, the objective of this study was to eva luate the water influence after passing throught the sugarcane straw and the vinasse, both correlated with the availability of the herbicides a micarbazone, clomazone, diuron, hexazinone, imazapc, sufentrazone and tebuthiuron in the soil solution in differ ent kinds of soils. The factorial 3 x 31 with complete randomized block design, with three replications, was used with 31 physical and chemical different soil samples and three treatments (water, wash water straw and vinasse). The soil samples were arrange d on trays and submitted to the herbicides application, then they were placed in plastic cartridges and satured with deionized water, wash water straw and vinasse, and remained resting for 18 hours under refrigeration (8 ± 3 o C) . After that, two extrations were made: the first one quantifying the presence of the herbicides in the soil solution and in the second one the total extraction of herbicide remaining in the soil was taken to determine the recovery percentage of each herbicide tested. For quantificat ions it was used a LC - MS/MS system, compound of a High Performance Liquid Chromatograph (HPLC) coupled with mass spectrometer. The amicarbazone and imazapic herbicides, in most samples, were more available in the soil solution with the water application an d in the wash water straw. However, vinasse had promoted an increase availability of diuron and tebuthiuron in all soils. Clomazone, hexazinone and sulfentrazone showed no significative difference between the treatments. The herbicides with the highest fre quency of availability of herbicides in soils were imazapic, hexazinone, amicarbazone and tebuthiuron. However, about 6% of ...
47
Matos, Ana Karollyna Alves de 1991. "Influência da vinhaça e da palhada de cana-de-açúcar na sorção de herbicidas aplicados em diferentes solos /". Botucatu :, 2014. http://hdl.handle.net/11449/110931.
Testo completoAbstract (sommario):
Orientador: Caio Antonio CarbonariCoorientador: Edivaldo Domingues Velini
Banca: Carlos Gilberto Raetano
Banca: Fernando Tadeu de Carvalho
Resumo: O sistema de produção com ou sem a pres ença de palhada, bem como, a aplicação de vinhaça nos canaviais, podem levar a alterações nas propriedades do solo e influenciar a disponibilidade dos herbicidas na solução do solo. Diante disto, o presente trabalho teve por objetivo avaliar a influência d a água, água após passar pela palha de cana - de - açúcar e vinhaça na disponibilidade na solução do solo dos herbicidas amicarbazone, clomazone, diuron, hexazinone, imazapic, sulfentrazone e tebuthiuron em diferentes solos. Adotou - se o esquema fatorial 3 x 31, com delineamento em blocos inteiramente casualizados com três repetições, sendo utilizadas 31 amostras de solos distintos quanto às características físicas e químicas e três tratamentos (água, água de lavagem de palha e vinhaça). As amostras de solo foram dispostas em bandejas e submetidas à aplicação dos herbicidas, em seguida foram acondicionadas em cartuchos plásticos e saturadas com água deionizada, água de lavagem de palha e vinhaça, permanecendo em repouso durante 18 horas sob refrigeração (8 ± 3 ° C) . Posteriormente, fez - se duas extrações, na primeira quantificou - se os herbicidas presentes na solução do solo e na segunda foi realizada a extração total do herbicida remanescente no solo para determinação da porcentagem de recuperação de cada herbicida t estado. Para as quantificações utilizou - se um sistema LC - MS/MS, composto por um Cromatógrafo Líquido de Alta Performance (HPLC) acoplado ao espectrômetro de massas. O amicarbazone e o imazapic foram mais 2 disponibilizados na solução dos solos com a aplicaçã o de água e água de lavagem de palha na maioria das amostras. Todavia, a adição de vinhaça promoveu uma maior disponibilização do diuron e tebuthiuron em todos os solos. O clomazone, hexazinone e sulfentrazone não apresentaram diferença significativa entre os ...
Abstract: The pr oduction system with or without the straw as how the sugarcane vinasse application may cause some changes in the soil properties and may influence the avaiability of the herbicides in the soil solution. Based on that, the objective of this study was to eva luate the water influence after passing throught the sugarcane straw and the vinasse, both correlated with the availability of the herbicides a micarbazone, clomazone, diuron, hexazinone, imazapc, sufentrazone and tebuthiuron in the soil solution in differ ent kinds of soils. The factorial 3 x 31 with complete randomized block design, with three replications, was used with 31 physical and chemical different soil samples and three treatments (water, wash water straw and vinasse). The soil samples were arrange d on trays and submitted to the herbicides application, then they were placed in plastic cartridges and satured with deionized water, wash water straw and vinasse, and remained resting for 18 hours under refrigeration (8 ± 3 o C) . After that, two extrations were made: the first one quantifying the presence of the herbicides in the soil solution and in the second one the total extraction of herbicide remaining in the soil was taken to determine the recovery percentage of each herbicide tested. For quantificat ions it was used a LC - MS/MS system, compound of a High Performance Liquid Chromatograph (HPLC) coupled with mass spectrometer. The amicarbazone and imazapic herbicides, in most samples, were more available in the soil solution with the water application an d in the wash water straw. However, vinasse had promoted an increase availability of diuron and tebuthiuron in all soils. Clomazone, hexazinone and sulfentrazone showed no significative difference between the treatments. The herbicides with the highest fre quency of availability of herbicides in soils were imazapic, hexazinone, amicarbazone and tebuthiuron. However, about 6% of ...
Mestre
48
Embree, Leanne. "Development of a high-performance liquid chromatographic assay for human chorionic gonadotropin as an alternative to the official United States pharmacopeial animal assay". Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/24637.
Testo completoAbstract (sommario):
Human chorionic gonadotropin (HCG), a glycoprotein hormone with two nonidentical subunits, is produced by chorionic tissue in pregnant women and by neoplastic tissue containing chorionic elements. It is used in the treatment of male hypogonadism and female sub-fertility.
Quantitation of HCG is used to monitor therapy, diagnose various disease states and diagnose and monitor pregnancy. Low levels of HCG in the early and late stages of pregnancy and in various disease states has prompted the development of extremely sensitive assay procedures. Clinically, radioimmunoassay methods are most frequently used due to their precision, sensitivity and cost. However, problems with specificity have been noted.
Commercial preparations of HCG must meet the standards outlined in the United States Pharmacopeia (USP). The assay procedure involves a rat uterine weight bioassay. This protocol is lengthy to perform (5 days), requires the sacrifice of a large number of animals (minimum of 60 female rats per assay) and may need to be repeated if the results do not meet the statistical requirements of the assay. Due to the use of animals and the animal care facilities required, this is an expensive assay. In addition, the bioassay is not specific for HCG. Therefore, this thesis reports the analysis of two commercial preparations of HCG, as well as USP Reference Standard HCG and commercially available purified intact HCG and purified individual subunits. Various HPLC assay procedures were evaluated to determine if HPLC would be a viable alternative to the official USP bioassay.
Size exclusion HPLC, using one Protein Pak 125 sw column and two Protein Pak 300 sw columns individually and in various combinations, was used to assess all the samples of HCG. Attempts to increase resolution of HCG from interfering components found in these preparations included using both 208 nm and 278 nm for ultraviolet detection, evaluation of 32 buffers as mobile phases with the Protein Pak 300 sw column, fluorescamine derivatization of HCG followed by fluorescence detection, connection of two size exclusion columns in series, and recycling on a Protein Pak 300 sw column. Further attempts to isolate HCG from its protein contaminants involved using ion exchange HPLC with a Protein Pak DEAE 5 pw column with 20 different buffers as mobile phases as well as reversed-phase HPLC with an Ultrasphere ODS column. The greatest resolution was obtained with one Protein Pak 300 sw column with a phosphate buffer (0.15 M, pH 7.0) for the mobile phase and ultraviolet detection.
Latex agglutination inhibition slide tests and electrophoresis techniques were used to evaluate commercial samples of HCG and chromatographic peak eluates.
Commercial HCG samples appear to contain the individual subunits of HCG and intact HCG along with impurities. The USP Reference Standard HCG contains intact HCG but also contains other ultraviolet absorbing components that were partially separated by HPLC. Electrophoresis also indicated that this HCG sample contained impurities. In addition, the purified intact HCG and purified subunit samples contained impurities, as shown by HPLC.
The size exclusion HPLC assay developed using one Protein Pak 300 sw column was unable to resolve intact HCG from the beta-subunit. This assay would be useful for a qualitative assay for purity of HCG preparations. However, at present, HPLC is not a viable alternative to the USP bioassay.Pharmaceutical Sciences, Faculty of
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Smith, Anita Mohler. "Objective judgement of cheese varieties by multivariate analysis of HPLC profiles". Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/26535.
Testo completoAbstract (sommario):
An objective analytical method was developed to characterize the taste profiles of five cheese varieties. Nonvolatile water extracts of Cheddar, Edam, Gouda, Swiss, and Parmesan cheeses were analyzed by high performance liquid chromatography (HPLC) with a reversed phase column. The HPLC operating conditions were determined with Mapping Super-Simplex followed by Centroid Mapping Optimization. A ternary gradient elution system was used with an Adsorbosphere C8 column to resolve a maximum number of components. The optimum solvent volume ratio was 96.8 : 1.2 : 2.0 for trifluoroacetic acid (0.1%), acetonitrile, and methanol, with a flow rate of 1.0 mL/min. Over 50.3 min this ratio was changed to 56.3 : 30.3 : 13.4.
Multivariate statistical analyses including principal component and discriminant analyses were applied to 55 peak areas from 106 cheese chromatograms. Principal component analysis reduced the dimensionality of the "data from 55 to 17 principal components, which are-combinations of the original variables, with a 26% loss of explained sample variation. Discriminant analysis on data from a single HPLC column was able to correctly classify cheeses by variety at a greater than 90% success rate. This grouping rate dropped to 64% when data from all four HPLC columns was combined, implicating large between column variations. A semi-trained sensory panel correctly classified cheeses by variety at a 63% rate. This objective method provides a lasting fingerprint of cheese products.Land and Food Systems, Faculty of
Graduate
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Shekhawat, Lalita Kanwar. "Modeling of liquid chromatography empirical and mechanistic modeling approaches". Thesis, IIT Delhi, 2019. http://eprint.iitd.ac.in:80//handle/2074/8051.
Testo completo