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1
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.
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Power, Gillian Mary. "The study of chromatographic interactions using model reversed-phase chromatography surfaces." Thesis, University of Nottingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285643.
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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.
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Shalliker, Ross Andrew, and mikewood@deakin edu au. "Studies on the behaviour of polystyrene in reversed phase chromatography." Deakin University. School of Sciences, 1992. http://tux.lib.deakin.edu.au./adt-VDU/public/adt-VDU20051125.112118.
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Polystyrene behaviour in reversed phase high performance liquid chromatography was influenced mainly by the solvent system, but secondary affects were observed depending on the stationary phase. A variety of reversed phase columns were investigated using mobile phase combinations of dichlorom ethane-methanol, dichloromethane-acetonitrile, ethyl acetate-methanol and ethyl acetate-acetonitrile. Several different modes of behaviour were observed depending on the polymer solubility in the solvent system.
In the dichloromethane-methanol solvent system, polymer-stationary phase interactions only occurred when the molecules had pore access. Retention of excluded polystyrene depended on the kinetics of precipitation and redissolution of the polymer. Peak splitting and band broadening occurred when the kinetics were slow and molecular weight separations were limited !o oligomers and polystyrenes lower than 5-10(4) dalton.
Excellent molecular weight separations of polystyrenes were obtained using gradient elution reversed phase chromatography with a dichloromethane-acetonitrile mobile phase on C18 columns. The retention was based on polymer-stationary phase interactions regardless of the column pore size. Separations were obtained on large diameter pellicular adsorbents that were almost as good as those obtained on porous adsorbents, showing that pore access was not essential for the retention of high molecular weight polystyrenes. In the best example, the separation ranged from the monomer to 10(6) dalton in a single analysis. Very little adsorption of excluded polymers was observed on C8 or phenyl columns.
Polystyrene molecular weight separations to 7-10(5) dalton were obtained in an ethyl acetate-acetonitrile solvent system on C18 columns. Adsorption was responsible for retention. When an ethyl acetate-methanol solvent system was used, no molecular weight separations were obtained because of complex peak splitting.
Reversed phase chromatography was compared to size exclusion chromatography for the analysis of polydisperse polystyrenes. Similar results were obtained using both methods. However, the reversed phase method was less sensitive to concentration effects and gave better resolution.
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Torrellas-Hidalgo, Luzmila. "EFFECTS OF ETHANOL/WATER MOBILE PHASES ON REVERSED-PHASE LIQUID CHROMATOGRAPHY." Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/275466.
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El-Rjoob, Abdul-Wahab. "Dynamic stationary phase modification in reversed-phase high performance liquid chromatography /." free to MU campus, to others for purchase, 1996. http://wwwlib.umi.com/cr/mo/fullcit?p9720536.
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Sabharwal, Arvind. "Preparative reversed-phase high performance liquid chromatography of proteins." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.361678.
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Watson, Richard Charles. "Studies of reversed phase high performance liquid chromatography (RP-HPLC) stationary phases." Thesis, University of Nottingham, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.338492.
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Grossman, Shau. "Methylammonium Formate as a Mobile Phase Modifier for Reversed Phase Liquid Chromatography." Miami University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=miami1217890628.
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Sexton, Danessa Leann. "Determination of lactose by reversed-phase high performance liquid chromatography." [Johnson City, Tenn. : East Tennessee State University], 2004. http://etd-submit.etsu.edu/etd/theses/available/etd-0328104-212023/unrestricted/SextonD041504f.pdf.
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Thesis (M.S.)--East Tennessee State University, 2004.Title from electronic submission form. ETSU ETD database URN: etd-0328104-212023. Includes bibliographical references. Also available via Internet at the UMI web site.
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Liu, Kun. "Polymeric Monolithic Stationary Phases for Capillary Reversed-phase Liquid Chromatography of Small Molecules." BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/3843.
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Highly cross-linked monoliths prepared from single cross-linking monomers were found to increase surface area and stability. Therefore, seven cross-linking monomers, i.e., 1,3-butanediol dimethacrylate (1,3-BDDMA), 1,4-butanediol dimethacrylate (1,4-BDDMA), neopentyl glycol dimethacrylate (NPGDMA), 1,5-pentanediol dimethacrylate (1,5-PDDMA), 1,6-hexanediol dimethacrylate (1,6-HDDMA), 1,10-decanediol dimethacrylate (1,10-DDDMA), and 1,12-dodecanediol dimethacrylate (1,12-DoDDMA), were used to synthesize highly cross-linked monolithic columns in 75-µm i.d. capillaries by one-step UV-initiated polymerization using dodecanol and methanol as porogens for reversed-phase liquid chromatography (RPLC) of small molecules. Selection of porogen type and concentration was investigated in detail. Isocratic elution of alkylbenzenes at a flow rate of 300 nL/min was conducted for all of the monoliths. Gradient elution of alkylbenzenes and alkylparabens provided high resolution separations. Several of the monoliths demonstrated column efficiencies in excess of 50,000 plates/m. Monoliths with longer alkyl-bridging chains showed very little shrinking or swelling in solvents of different polarities. In addition, highly cross-linked monolithic capillary columns poly(1,6-HDDMA), poly(cyclohexanediol dimethacrylate) [poly(CHDDMA)] and poly(1,4-phenylene diacrylate) [poly(PHDA)], were synthesized and compared for RPLC of small molecules. Isocratic elution of alkylbenzenes was performed using 1,6-HDDMA and CHDDMA monolithic columns. Gradient elution of alkylbenzenes using all three monolithic columns showed good separations. Monolithic columns formed from 1,6-HDDMA, which had a linear alkyl-bridging chain structure, exhibited the highest column efficiencies (86,000 plates/m). Optimized columns showed high permeability and high run-to-run and column-to-column reproducibilities. Monoliths prepared from controlled/living polymerization was demonstrated exhibiting narrower molecular weight distribution and more homogeneous cross-linked structures due to the reversible character of this polymerization method. Thus, monolithic columns were developed from three cross-linking monomers, i.e., 1, 12-DoDDMA, trimethylolpropane trimethacrylate (TMPTMA) and pentaerythritol tetraacrylate (PETA) using organotellurium-mediated living radical polymerization (TERP) in 150-µm i.d. capillaries for RPLC of small molecules. Selection of the polymerization conditions for the 1,12-DoDDMA monolirh was investigated in detail. Isocratic elution of alkylbenzenes was achieved with good efficiency (47,700 to 64,200 plates/m for uracil) using all monolithic columns prepared using TERP.
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Barnes, Karen Wink. "The synthesis and characterization of reversed phase stationary phases for high performance liquid chromatography." Gainesville, FL, 1986. http://www.archive.org/details/synthesischaract00barn.
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Liao, Zhaohui. "Investigation and Control of Alkylsilane Stationary Phase Structure in Reversed Phase Liquid Chromatography." Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/193834.
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Investigation and control of alkylsilane stationary phase structure in reversed phase liquid chromatography is presented. Raman spectroscopy is used to probe the alkyl chain conformational order and interchain coupling as a function of various chromatographic conditions. A new method is further developed to fabricate alkylsilane stationary phases with controlled surface coverage. The alkyl chain conformational order and interchain coupling of a series of high-density docosylsilane (C22) bonded stationary phases is shown as a function of temperature, surface coverage, polymerization method, common solvents and solutes. The conformational order of C22 stationary phases is compared to that of octadecylsilane (C18) stationary phases to understand the chain length effect on stationary phase structure. The conformational order information as indicated by Raman spectral order indicators for a C22 phase are correlated with the capacity factor and separation efficiency for each solute studied to gain insight into the retention mechanism. These studies help to understand the origin of stationary phase shape selectivity and the separation process in general. Based on these results, the molecular pictures at the stationary phase/solvent interface are proposed. The effect of pressurized solvent environments on two C18 phases is studied to obtain direct evidence for changes in stationary phase structure due to pressure. These changes are compared to effects of solvation relative to air in the same solvents. In addition, Raman spectral order indicators are identified for perdeuterated alkyl-containing system. This study provides a foundation for studying stationary phase structure in complex systems comprised of long alkyl-containing solutes.A further development of a new method is presented as well for synthesizing alkylsilane stationary phases with precisely controlled surface coverage by using a displaceable surface template monolayer of n-alcohol. A mechanism for this process is proposed based on the studies of n-alcohol concentration and chain length effect on the stationary phase surface coverage. The utility of these new stationary phases as chromatographic support is demonstrated. The shape selectivity for these new phases is comparable to or better than similar phases prepared by conventional methods.
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Murphy, Kellyann M. "Analysis of Biodiesel Quality Using Reversed Phase High-Performance Liquid Chromatography." Scholarship @ Claremont, 2012. http://scholarship.claremont.edu/pomona_theses/45.
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The alternative fuel biodiesel is produced from the transesterification of vegetable oils or animal fat to fatty acid methyl esters. Pomona has a reactor on campus that can be used to run this reaction and produce biodiesel. The use of biodiesel has been found to lower air pollutant and greenhouse gas emissions, but can be potentially harmful to the engines if it contains impurities. This paper proposes a method using high-performance liquid chromatography to test the quality of biodiesel. This method utilizes instrumentation and materials that are available in Pomona College's Chemistry Department, requires very little sample preparation, and is relatively safe, as long as general lab safety practices are followed. This method can also be used to optimize the procedure used to make the biodiesel. An optimized production procedure and a test method to assess the final product will ensure high quality fuel that can be used with confidence in diesel engines. This will likely add strength to proposals to increase the use of the on-campus reactor and produce biodiesel for campus grounds equipment from waste vegetable oil.
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fadhil, ali abd al-karim alkarim. "Reversed-phase and surfactant modified reversed-phase high and ultra-high performance liquid chromatography of phenolic and aliphatic carboxylic acids." Miami University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=miami1574428923192499.
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McCrossen, Sean David. "The role of mobile phase additives on the retention characteristics of solutes in reversed-phase chromatography." Thesis, Birkbeck (University of London), 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.297212.
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Quast, Arthur D. "Investigating a Model Reversed-Phase Liquid Chromatography Stationary Phase with Vibrationally Resonant Sum Frequency Generation Spectroscopy." BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/2764.
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Reversed-phase liquid chromatography (RPLC) is a widely used technique for analytical separations but routinely requires empirical optimization. Gaining a better understanding of the molecular reasons for retention may mean more efficient separations with fewer trial and error runs to obtain optimized separations. Vibrationally resonant sum frequency generation (VR-SFG) is a surface specific technique that has allowed for in situ examination of model RPLC stationary phases under various solvent and pressure conditions. In order to improve on past work with model RPLC stationary phases two challenges had to be overcome. First, improved vibrational mode assignments of the C18 stationary phase were needed for proper understanding of this model system. Second, the synthesis of back-surface reference mirrors used in these VR-SFG experiments allowed us to better correct the relative intensities of the various spectral peaks present in typical spectra. After examination of model RPLC systems under various conditions, we have found that these model substrates have a significant amount of interference from nonresonant signal. This interference of resonant and nonresonant signals on fused silica surfaces has not been previously examined and further studies of the model RPLC stationary phase must properly deal with the non-negligible nonresonant interference that is present. We have seen changes in the VR-SFG spectra of these model systems under a variety of conditions including elevated pressure, however the changes are mostly due to nonresonant interference. These spectral changes, although apparently not solely from structural changes, need to be investigated further to better understand the molecular basis of retention in model RPLC systems.
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Lao, Ying. "Chromatographic Behavior of Peptides Containing Oxidized Methionine in Reversed-phase Chromatography: Application to Cyclolinopeptides in Flaxseed Oil and Linear Tryptic Peptides." Elsevier, 2012. http://hdl.handle.net/1993/30202.
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The thesis consists of two parts targeting the characterization of chromatographic behavior of linear tryptic and cyclic peptides containing oxidized methionine (Met) in reversed-phased chromatography. The retention order of methionine-containing peptide analogues was observed to be the same in both studies: Met oxide < Met dioxide < Met. For linear tryptic peptides, the magnitude of the retention time shift may vary dramatically: from –9 % to +0.36 % acetonitrile. Particularly, large negative retention time shifts are found mostly associated with methionine being in the hydrophobic face of an amphipathic helix. Contrary to previously reported observations, I demonstrate for the first time that methionine oxidation may increase peptide hydrophobicity, this occurs only when methionine is in the N3 position of the N-capping stabilization motif preceding an amphipathic helix. In the second study, the effect of peak splitting was observed for some Met oxide-containing cyclolinopeptides, which most likely appear due to diastereomerization.
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Essaka, David Christian. "Reversed-Phase HPLC Determination of Cholesterol in Food Items." Digital Commons @ East Tennessee State University, 2007. https://dc.etsu.edu/etd/2034.
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Cholesterol is a fat-like molecule found among lipids in animal (including human) tissues. It is needed for maintaining good health. However, health issues have been raised because of the strong correlation between high levels of cholesterol in the body and cardiovascular disease. An HPLC method for quantitative determination of cholesterol in foods is presented. This involves a C-18 stationary phase using a 70:30 methanol: 2-propanol mobile phase with an UV detector set at 212 nm. The method showed linearity in the range 5.0 to 100.0 μg/mL and also good reproducibility with relative standard deviation of 4.22%, 2.71%, 4.8%, and 3.7% for the different samples analyzed. The mean recovery of the butter sample was 106.5%. The samples under investigation were common food items such as butter, lard, and two different types of cheese.
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Trujillo, Rebollo Andres. "ROLE OF BRILLIANT GREEN ON THE DETECTION AND SEPARATION OF NON-CHROMOPHORIC ANALYTES BY REVERSED-PHASE LIQUID CHROMATOGRAPHY (DIMERIZATION)." Thesis, The University of Arizona, 1985. http://hdl.handle.net/10150/275434.
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Quach, Van. "Evaluation of polar-embedded reversed-phase liquid chromatography columns and the temperature dependence of the phase ratio." Tallahassee, Fla. : Florida State University, 2009. http://etd.lib.fsu.edu/theses/available/etd-09012009-164008/.
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Thesis (Ph. D.)--Florida State University, 2009.Advisor: John G. Dorsey, Florida State University, College of Arts and Sciences, Dept. of Chemistry and Biochemistry. Title and description from dissertation home page (viewed Mar. 5, 2010). Document formatted into pages; contains x, 99 pages. Includes bibliographical references.
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Zhou, Feng. "Protein characterization by capillary isoelectric focusing electrophoresis, reversed phase liquid chromatography and mass spectrometry." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 103 p, 2008. http://proquest.umi.com/pqdweb?did=1456289241&sid=4&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Patel, Hasmukh B. "Reversed-phase high-performance liquid chromatography : some basic studies and application in microbial transformation." Thesis, University of Bath, 1987. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379158.
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Alabbas, Alhumaidi. "Reversed-phase Ion-Pairing Ultra Performance Liquid Chromatography-Mass Spectrometry in Characterization of Glycosaminoglycans." VCU Scholars Compass, 2014. http://scholarscompass.vcu.edu/etd/3547.
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Glycosaminoglycans (GAGs) are a family of linear bio-polysaccharides, which are heterogeneously modified with negatively charged sulfate and carboxylate groups. They are located on every cell surface, extracellular matrix or intracellular space in the body. GAGs are composed of alternating units of an amino sugars (glucosamine or galactosamine) and hexuronic acid/hexose (iduronic acid, glucoronic acid/ or galactose), which are linked by glycosidic bonds with different geometries. In recent years, GAGs have attracted considerable interest. GAGs play vital roles in fundamental biological processes, such as hemostasis, angiogenesis, cell signaling, growth and differentiation. Thus, GAGs contribute to a number of diseases such as thrombosis, cancer, inflammation, osteoarthritis and degenerative diseases. One of the most studied GAGs is heparin, which is widely used as an anticoagulant and is also implicated in other biological processes. Despite its extensive clinical use, heparin continues to suffer from major problems, such as life threatening hemorrhagic complications and heparin-induced thrombocytopenia. These activities originate from the large number of glycan sequences generated during its biosynthesis. Many different enzymes act in a non-template fashion to produce heparin chains with various chain lengths, sulfation and acetylation patterns. Their inherent heterogeneity, complexity and highly anionic nature have seriously limited the development of tools for rapid identification of sequences critical for many biological activities. A RPIP-UPLC MS protocol was developed to separate and characterize structures of heparin oligosaccharides prepared through enzymatic cleavage process and chemoenzymatic synthesis. In designing such protocol, several UPLC and MS parameters were considered. An efficient separation of each oligosaccharide mixture was achieved with different ion-pairing reagents. Yet, the structural elucidation of the multiple chromatographic peaks was hindered by the heterogeneity inherent in these mixtures even with supposedly defined standards. In order to elucidate the structures of these complex molecules, we utilized a strategy, which exploits the ease with which sulfate groups can be fragmented during MS ionization. A systematic increment of the MS cone voltage was employed starting from a minimum dissociation voltage, where the intact molecule is preserved, to a high enough dissociation voltage, where the only core oligosaccharide backbone was retained. This allowed identifying the number of sulfate groups and the core structures. However, positions of substituents were difficult to pinpoint because of the phenomenal number of possibilities. Such analysis would require tandem MS/MS–based approaches.
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Chilton, Anthony Stephen. "Reversed-phase extraction coupled with capillary gas chromatography : development of a fully automated technique for bioanalysis." Thesis, University of Hertfordshire, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358283.
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Su, Xiaodan. "Characterization of histones and their post-translational modifications using reversed-phase high performance liquid chromatography and mass spectrometry." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1155687874.
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Liang, Hongxi. "An investigation into the use of #beta#-cyclodextrins as additives to effect enantiometric separation by reversed phase HPLC." Thesis, Robert Gordon University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.260042.
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Bailes, Sophie. "Retention mechanism for reversed phase and hydrophilic interaction liquid chromatography : development and characterisation of modified silica particles." Thesis, Open University, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.602375.
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Silanophilic interaction chromatography columns can give rise to complementary selectivity compared to the more commonly used hydrophobic interaction based HPLC columns. However, the former types of phase have historically caused issues of tailing and irreversible retention with polar or basic analytes. An investigation was therefore undertaken into the fundamental nature of their electrostatic, dipole-dipole and hydrogen bonding interactions. This was particularly focussed on interactions that are induced by the presence of residual silanols on the surface of HPLC phases, in order to fully understand the retention mechanism and the practical limitations of commercial stationary phases. Manufacturer's literature for these types of phase often contains specific applications and claims, however full independent testing of a range of acid, basic, phenolic, and polar compounds had not previously been demonstrated . Research in this area will aid in the development of new industrial applications by highlighting the stationary phase type with the most suitable mechanism to separate any combination of polar and non-polar compounds. Initial investigations evaluated silanophilic interactions present in a set of Extended Polar Selectivity (EPS) phases utilising a set of known characterisation probes. Structural elucidation of these phases confirmed the intensity of these interactions is due to the accessibility of the silanols and the purity of the base silica. Shorter chains and sparsely bonded hydrocarbon ligands were shown to reduce hindrance and increase the degree of interaction. Endcapping was shown to decrease the accessibility of residual silanols and mask silanophilic interactions. High purity base silica was shown to reduce silanophilic interactions compared to similar phases bonded to a TVPE-A silica. The control and restriction of silanophilic interactions is of great importance for the analysis of basic and polar molecules. Commercial TVPE-C™ phases are claimed to minimise silanophilic interactions through the " silanization" process. This converts the surface silanols to silica hydride prior to derivatisation with a functionalised ligand.
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Muchena, John Kailemia. "Studies of Capsaicinoids Contents of Locally Grown and Commercial Chilies Using Reversed-Phase High Performance Liquid Chromatography." Digital Commons @ East Tennessee State University, 2009. https://dc.etsu.edu/etd/1800.
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Capsaicinoids are a class of compounds responsible for the "heat" of hot peppers. Capsaicin and dihydrocapsaicin have the highest burning effect. The aim of this work is to separate and quantify the two major capsaicinoids in fruits harvested at different stages of development and at different seasons. Simple and rapid HPLC method involves 73:27% methanol water mobile phase with C18 stationary phase and UV-Vis detector set at 210 nm. The method showed good reproducibility with 1.74% - 4.72% relative standard deviations, a linear response within 0.65–45.5 and 0.25-17.5 μg/mL for capsaicin and dihydrocapsaicin, respectively. The method achieved average recovery of 106% for capsaicin and 102% dihydrocapsaicin. Determination of capsaicinoids in four naturally grown chili and commercial source habanero were analyzed. The amount in the sample ranged from 1184-8156 μg/g for capsaicin and 430-3299 μg/g for dihydrocapsaicin.
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Thévenon, Géraldine. "Mecanismes de retention en chromatographie liquide a polarite de phases inversee en milieu non aqueux : etude de la retention des triglycerides." Paris 6, 1986. http://www.theses.fr/1986PA066353.
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Goodwin, Wayne E. "Preconcentration neutron activation analysis of trace elements with 1-(2-thiazolylazo)-2-naphthol using reversed-phase extraction chromatography." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq24741.pdf.
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Wang, Zhenyu. "Supercritical Fluid Extraction Directly Coupled with Reversed Phase Liquid Chromatography for Quantitative Analysis of Analytes in Complex Matrices." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/30073.
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The purpose of this research was to design a simple, novel interface for on-line coupling of Supercritical Fluid Extraction (SFE) with High Performance Reversed Phase Liquid Chromatography (HP-RPLC), and to explore its ability for quantitative analysis of analytes in different matrices. First, a simple interface was developed via a single one six-port injection valve to connect the SFE and LC systems. A water displacement method was utilized to eliminate decompressed CO2 gas in the solid phase SFE trap and connection tubes. To evalute this novel hyphenated system, spiked polynuclear aromatic hydrocarbons (PAHs) in a sand matrix were used as target analytes with the achievement of quantitative results. Also PAHs in naturally contaminated soil were successfully extracted and quantitatively determined by this hyphenated system. Compared to the EPA method (Soxhlet extraction followed by GC-MS), on-line SFE-LC gave precise (4-10% RSD) and accurate results in a much shorter time.
Based on this hyphenated technique, a method for the extraction and analysis of hyperforin in St. John's Wort was developed under air/light free conditions. Hyperforin is a major active constituent in the antidepression herbal medicine-Hypericum Perforatum (St. John's Wort). Hyperforin is very sensitive to oxygen and light. There is no way to date to determine whether any degradation occurs during the sample-processing step in the analytical laboratory. On-line coupling of SFE-LC with UV absorbance/ electrospray ionization mass spectrometry (SFE-LC-UV/ESI-MS) provided an air/light free extraction-separation-detection system, which addressed this issue. Mass spectral data on the extract confirmed the presence of the major degradation compounds of hyperforin (i.e. furohyperforin and two of its analogues). Thus, the degradation process must have occurred during plant drying or storage. The feasibility of quantitative extraction and analysis of hyperforin by on-line SFE-LC was made possible by optimizing the extraction pressure, temperature, and modifier content. High SFE recovery (~90%) relative to liquid-solid extraction was achieved under optimized conditions.
We then extended the interface's application to an aqueous sample by using a liquid-fluid extraction vessel. Quantitative extraction and transfer were achieved for the target analytes (progesterone, phenanthrene, and pyrene) spiked in water, as well as in real samples (urine and environmental water). During each extraction, no restrictor plugging was realized. Extraction temperature and pressure were optimized. Different amounts of salt were added to the aqueous matrix to enhance ionic strength and thus extraction efficiency. Methanol and 2-propanol were used as CO2 modifiers. Two modifier modes were compared, e.g. dynamically mixing modifier with the CO2 extraction fluid, and pre-spiking modifier in the extraction vessel. Surprisingly, we found pre-spiking the same amount of modifier in the vessel enhanced the recovery from ~70% to ~100% for progesterone, phenanthrene, and pyrene due to a "co-extraction effect".
The last phase of our work explored the disadvantages/limitations of this hyphenated technique through the analysis of more highly polar phenolic compounds in grape seeds. Five types of SFE trapping adsorbent materials were evaluated in an effort to enhance the collection efficiency for the polar components. Pure supercritical CO2 was used first to remove the less polar oil in the seeds. Then methanol-modified CO2 was used to remove the polar components (e.g. phenolic compounds). Catechin and epicatechin (90%) were exhaustively extracted out of the de-oiled seed after 240 minutes with 40% methanol as modifier. Both singly linked (B-type) and doubly linked (A-type) procyanidins were identified by LC-ESI-MS, as well as their galloylated derivatives. Compared to the off-line SFE-LC approach, much less sample was required for extraction in the on-line method, since all the extracted components could be transferred to the LC column. Also, no extract processing/concentration step was needed in the on-line method. However, in the on-line mode, some polar compounds were lost (1) during the collection step (e.g. lower trapping efficiency on a single solid SFE trap when a high percentage modifier was used) and (2) during the water rinsing step (e.g. less retention of polar compounds on C18 trap). Therefore, this hyphenated technique is less desirable for the analysis of highly polar compounds.Ph. D.
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Collins, Matthew P. "Reversed Phase Liquid Chromatography Using the Ionic Liquid Isopropylammonium Formate and Comparison of Indirect Spectrophotometric Methods for Phosphate." Miami University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=miami1312342055.
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Kipruto, Eric Wekesa. "APPLICATION OF POLARITY MODELS TO CHARACTERIZING THE REVERSED-PHASE LIQUID CHROMATOGRAPHY SEPARATION OF CHIRAL STEROID ISOMER PAIRS EMPLOYING VARIOUS TERNARY MOBILE PHASES." Cleveland State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=csu1631533233544729.
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AL-Shaer, Mahmoud. "Reversed-Phase HPLC Determination of Citral in Locally Grown Lemon Grass Harvested at Different Season." Digital Commons @ East Tennessee State University, 2006. https://dc.etsu.edu/etd/2229.
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A simple HPLC procedure for the quantitative determination of citral, the major fragrant component in the lemon grass, has been developed. The procedure involves a C-8 stationary phase using a 90:10 methanol: water pH 5 mobile phase containing 0.25% 1-octanesulfonic acid and an UV detector (set at 233 nm). The lemon grass leaves were harvested fresh at different times of the year and were soaked in methanol for 48 hours without any mechanical assistance to extract the citral and other methanol soluble components. The method showed good reproducibility with relative standard deviation of 2.8% and 10.8% for two different sets of samples. The method showed linearity in the range of 0.89 - 35.52 μg/mL. The average recovery was 104.8%. The amount of citral found as a percentage of the dried leaves are, 0.093, 0.27, 0.10, 0.13, 0.16, and 0.066 for fall, winter, three summer, and 1 commercial store samples, respectively.
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Fields, Patrice R. "Methods for the Characterization of Electrostatic Interactions on Surface-Confined Ionic Liquid Stationary Phases for High Pressure Liquid Chromatography." University of Cincinnati / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1307044073.
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Zhang, Liwen. "Characterization of histone post-translational modification using reversed-phase high performance liquid chromatography and fourier transform ion cyclotron resonance mass spectrometry." Connect to this title online, 2003. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1054660495.
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Thesis (Ph. D.)--Ohio State University, 2003.Title from first page of PDF file. Document formatted into pages; contains xv, 219 p.; also includes graphics (some col.) Includes bibliographical references (p. 147-173). Available online via OhioLINK's ETD Center
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Wiest, Landon A. "Formation, Functionalization, Characterization, and Applications of a Mixed-Mode, Carbon/Diamond-Based, Core-Shell Phase for High Performance Liquid Chromatography." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/4239.
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My work has focused on a variety of different types of diamond-based, core-shell particles. These particles are formed with inert cores and poly(allylamine)/nanodiamond shells. Their intended purpose is to form an LC stationary phase that is stable from pH 1 – 14 and at elevated temperatures. At the beginning of my studies, the particles that had been made in the Linford laboratory were pH stable, but irregular and had poor mechanical stability. Since that time, I have worked to improve the particles by using more spherical zirconia and carbon cores, and I have improved their mechanical stability via chemical crosslinking with epoxides. I have performed van Deemter and van’t Hoff analyses to understand the properties of these columns. Efficiencies greater than 100,000 N/m are routinely achieved with these carbon/nanodiamond-based phases. In addition I contributed to two patents that show innovations in diamond functionalization. My contributions involved reduction of an oxidized diamond surface with LiAlH4 prior to functionalization with isocyanates. I also wrote some application notes for the Flare mixed-mode column, which was recently introduced to the market and contains particles comprised of a carbon core and a polymer/nanodiamond shell. These application notes show the gradient separations of four essential oils (lavender, melaleuca, peppermint and eucalyptus), and the isocratic separations of various triazine herbicides and a mixture of β2-agonists and amphetamines.This dissertation contains the following sections. Chapter 1 is a review of liquid chromatographic history and theory. It also includes a history of the use of diamonds in liquid chromatography. Chapter 2 is a study on a glassy carbon core - polymer/nanodiamond shell particle made in our laboratory. Stability studies at pH 11.3 and 13 were performed and different analytes were retained and/or separated on the column. Chapter 3 is a study performed on the Flare mixed-mode column. Separations of tricyclic antidepressants, β2-andrenergic receptor agonists, and linear chain alkylbenzenes were demonstrated with this phase. Van Deemter and van’t Hoff studies were also performed to probe the efficiency and selectivity of this column with different classes of analytes. Chapter 4 chronicles, via SEM and van Deemter analysis, the improvements that have taken place in our column after many iterations of improved synthetic methods and new materials. These include better particle uniformity, particle stability, and column efficiency. Three different carbon cores were analyzed, each better than the previous one. Appendices 1 – 6 are application notes published by Diamond Analytics of β2-andrenergic receptor agonists and amphetamines, triazine herbicides, and lavender, melaleuca, eucalyptus and peppermint essential oils. Appendices 7 and 8 are patents that contain ideas and research contributed by the author.
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Li, Yuanyuan. "Polymeric Monolithic Stationary Phases for Capillary Hydrophobic Interaction Chromatography." BYU ScholarsArchive, 2010. https://scholarsarchive.byu.edu/etd/2796.
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Rigid poly[hydroxyethyl acrylate-co-poly(ethylene glycol) diacrylate] (Poly(HEA-co-PEGDA) monoliths were synthesized inside 75-µm i.d. capillaries by one-step UV-initiated copolymerization using methanol and ethyl ether as porogens. The optimized monolithic column was evaluated for hydrophobic interaction chromatography (HIC) of standard proteins. Six proteins were separated within 20 min with high resolution using a 20 min elution gradient, resulting in a peak capacity of 54. The performance of this monolithic column for HIC was comparable or superior to the performance of columns packed with small particles. Monoliths synthesized solely from PEGDA were also found to show excellent performance in HIC of proteins. Continuing efforts showed that rigid monoliths could be synthesized from PEGDA or poly(ethylene glycol) dimethacrylates (PEGDMA) containing different ethylene glycol chain lengths for HIC of proteins. Effects of PEG chain length, bi-porogen ratio and reaction temperature on monolith morphology and back pressure were investigated. Monoliths prepared from PEGDA 258 were found to provide the best chromatographic performance with respect to peak capacity and resolution. An optimized PEGDA 258 monolithic column was able to separate proteins using a 20-min elution gradient with a peak capacity of 62. The preparation of these in situ polymerized single-monomer monolithic columns was highly reproducible. The single-monomer synthesis approach clearly improves column-to-column reproducibility.The highly crosslinked monolith networks resulting from single crosslinking monomers were found to enhance the surface area of the monolith and concentrations of mesopores. Thus, monolithic columns were developed from four additional crosslinking monomers, i.e., bisphenol A dimethacrylate (BADMA), bisphenol A ethoxylate diacrylate (BAEDA, EO/phenol = 2 or 4) and pentaerythritol diacrylate monostearate (PDAM) for RPLC of small molecules. Gradient elution of alkyl benzenes and alkyl parabens was achieved with high resolution using all monolithic columns. Porogen selection for the BADMA and PDAM was investigated in detail with the intention of obtaining data that could possiblly lead to a rational method for porogen selection.
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Peterson, Anthony D. "Nonlinear Spectroscopic Investigation of Adsorption to C-18 Model Stationary Phase." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3888.
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Reversed-phase liquid chromatography (RPLC) is a commonly used separation technique in chemistry. Nevertheless, the mechanistic interactions at the molecular level among the eluent, analyte, and the stationary phase are not fully understood. Because of this limited understanding, optimization of the separation must be done experimentally. Learning more about molecular interactions should aid in improving separations. We are currently using second-harmonic generation (SHG) spectroscopy to investigate how analytes adsorb to the surface. SHG is a spectroscopic technique that produces signal only at places of non-isotropic symmetry; this typically occurs at surfaces. SHG can be used to produce surface isotherms of test analytes adsorbed to a model C18 stationary phase surface. Fitting these isotherms with a Langmuir model produces an adsorption equilibrium constant. However, the equilibrium constant can only be accurately determined if the true bulk concentration is known; this thesis describes an approach to ensure this. The equilibrium constant relates to Gibbs free energy and is the start to obtaining other thermodynamic information. The long equilibration times of analytes with the stationary phase observed in this study emphasize the importance of both thermodynamic information and kinetic values for understanding retention. Once equilibrium constants and other parameters are accurately obtained, this information can be used to improve predictions and calculations from numerical models.
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Mouline, Ghita. "Apport de la chromatographie gazeuse inverse dans l'étude des mécanismes et cinétiques de réticulation des matériaux composites." Pau, 1988. http://www.theses.fr/1988PAUU3017.
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Dubuis, Alexis. "Déformulation de matrices complexes : vers une méthodologie raisonnée adaptée aux matrices issues des procédés de valorisation de la biomasse." Thesis, Lyon, 2019. http://www.theses.fr/2019LYSE1228/document.
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La conversion de la biomasse lignocellulosique en biocarburants et molécules biosourcées produit des matrices liquides complexes thermosensibles qui couvrent une large gamme de polarités et de masses moléculaires. Les outils analytiques développés dans la littérature donnent une description partielle de ces matrices oxygénées. Pour en comprendre la réactivité et mieux guider le développement des procédés de conversion, une meilleure caractérisation est nécessaire. L’objectif de cette thèse est de démontrer l’apport d’une dimension de fractionnement pertinente en amont de techniques séparatives pour accéder à la caractérisation à l’échelle moléculaire d’échantillons ex-biomasse. Une déformulation complète et structurée par familles chimiques est visée, sans perte ni modification des composés. Deux voies de fractionnement ont été investiguées : (1) fractionnement par solubilité à l’aide de l’extraction liquide-liquide (LLE) et de la chromatographie de partage centrifuge (CPC) et (2) fractionnement par taille avec la chromatographie d’exclusion stérique (SEC). Ces techniques se veulent complémentaires à une analyse par chromatographie liquide à polarité de phase inversée avec détection par spectroscopie ultraviolet-visible et spectrométrie de masse haute résolution (RPLC-UV/HRMS). Des méthodes de fractionnement LLE, CPC et SEC ont été développées sur molécules modèles afin d’identifier les mécanismes et la sélectivité chimique mis en jeu. Des cartographies 2D inédites ont ainsi été obtenues, assurant un gain important en pouvoir résolutif et une structuration nouvelle des chromatogrammes en comparaison à l’approche RPLC-UV/HRMS. Dans un second temps, le potentiel des couplages SECxRPLC-UV/HRMS et CPCxRPLC-UV/HRMS pour la description de matrices complexes a été illustré via l’étude de deux échantillons issus d’expérimentations en unités pilotes et de compositions chimiques très différentes, représentant deux voies possibles de transformation (biochimique et thermochimique) de biomasse lignocellulosique. La complémentarité entre les approches de séparation mises au point a ainsi permis de doubler le nombre de pics détectés tout en bénéficiant de l’organisation chimique des composés. Cette aide précieuse à l’identification a été renforcée par les informations structurales délivrées via les différents modes de détection, en particulier l’HRMS. La compréhension de la structuration des cartographies 2D a été présentée et discutée afin de proposer la stratégie la plus adaptée pour déformuler complètement un échantillon en s’appuyant sur la mesure de descripteurs pertinents. Enfin, l’une des approches développée dans cette thèse a été mise en œuvre pour l’isolement sélectif et l’élucidation structurale de molécules clefs au sein d’une matrice complexe à l’aide d’expériences en fragmentation MS et spectroscopie de résonance magnétique nucléaire (RMN)The conversion of lignocellulosic biomass into biofuels and biosourced molecules produces complex thermosensitive liquid matrices which cover a wide range of polarity and molecular weight. Analytical tools developed in the literature only give a partial description of these oxygenated matrices. To understand the reactivity of these samples and optimize the development of conversion processes, a better characterization is required. The objective of this thesis is to demonstrate the interest of a relevant fractionation step prior to separation techniques to help the molecular characterization of biomass samples. The reverse engineering proposed for the sample is desired complete and chemically controlled (without loss or sample modification). Two fractionation pathways were investigated: (1) solubility fractionation with liquid-liquid extraction (LLE) and centrifugal partition chromatography (CPC) and (2) size fractionation with size exclusion chromatography (SEC). These techniques intend to be complementary to reversed-phase liquid chromatography hyphenated to ultraviolet-visible spectroscopy detection and high resolution mass spectrometry (RPLC-UV/HRMS). LLE, CPC and SEC methods were developed on model molecules to understand mechanisms involved and control the chemical selectivity. 2D contour plots were obtained, improving the resolving power and structuring chromatograms in comparison with RPLC-UV/HRMS. Then, SECxRPLC-UV/MS and CPCxRPLC-UV/MS hyphenations were applied to describe two complex samples from different substrates produced on experimental pilot units from two possible conversion pathways of lignocellulosic biomass (biochemical and thermochemical). The complementarity of separation modes allows to double the number of peaks detected, benefiting from the chemical organization of compounds. This constitute a support to identification also enhanced by multi-detection which provide additional structural information on compound detected, especially HRMS. Chemical organization in 2D contour plots were presented and discussed to propose the most adapted strategy to fully fractionate a sample based on the measurement of relevant descriptors. Finally, one of the fractionation approach developed in this thesis was used to isolate and structurally elucidate key molecules of a complex sample through MS fragmentation experiments and nuclear magnetic resonance spectroscopy (NMR)
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DUMAS, HERBIN CHRISTINE. "Chromatographie en phase liquide et synthese organique, exemple d'un produit industriel : la cylcododecanone oxime." Paris 6, 1987. http://www.theses.fr/1987PA066104.
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Les techniques de la chromatographie en phase liquide ont permis de mettre au point une separation optimisee des impuretes de la cyclododecanone oxime. La methode la plus performante est la chromatographie de partage a polarite de phases inversee sur un gel de silice greffee octadecyle avec une phase mobile ayant la composition suivante : methanol-acetonitrile-tetrahydrofurane-eau 33:24:3,5:39,5 (v/v). Une trentaine d'impuretes sont ainsi mises en evidence grace a l'emploi d'une colonne de petit calibre de 1 metre de long et de 1 millimetre de diametre interieur. Cette colonne contient 30000 plateaux theoriques. La duree de la separation est de 3,5 heures. L'identification d'un certain nombre de ces impuretes a ete effectuee par la conjonction de differentes methodes : couplage en ligne avec la spectrometrie de masse et chromatographie semi-preparative permettant d'isoler des quantites notables de certaines impuretes identifiees par la spectrometrie de masse differee de meme on a pu appliquer a ces impuretes la spectrometrie infrarouge par transformee de fourier
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Ramos, Alex Martins 1981. "Separação de piperonal contido em uma solução de síntese a partir do óleo essencial de Piper hispidinervum C. CD. por cromatografia líquida de alta eficiência com injeção empilhada." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266015.
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Orientador: Marco Aurélio CremascoTese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
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Resumo: O piperonal é uma molécula de grande valor econômico, pois é utilizado como matéria-prima nas indústrias de cosméticos e de fármacos. Uma das formas de obtenção do piperonal é por meio de síntese cujo substrato é o safrol. O safrol é o principal constituinte químico do óleo essencial de pimenta-longa (Piper hispidinervum, C. DC), espécie que é abundante na região Amazônica. Após os processos de síntese aplicados diretamente no óleo de pimenta longa, obtém-se o piperonal, como produto principal, e os coprodutos safrol, isosafrol glicol, cis-isosafrol, trans-isosafrol e terpinoleno. O rendimento dessa rota sintética é cerca de 84% de piperonal. Por este motivo, e considerando o alto valor agregado ao piperonal é que se propôs separá-lo por cromatografia líquida de alta eficiência (CLAE) com injeção empilhada. Nesse tipo de separação são essenciais as definições de tempo de ciclo e tempo de coleta. Para isso, foram empregadas duas abordagens: a abordagem experimental, na qual o tempo de ciclo e o tempo de coleta foram obtidos diretamente do cromatograma e a abordagem teórica que surgiu em decorrência do modelo proposto nesta Tese, onde os tempos de ciclo e coleta foram obtidos a partir dos parâmetros da curva gaussiana. Para essa última abordagem, são necessárias as constantes de equilíbrio e os parâmetros de transferência de massa (Dp, Def, Ds e Eb), que foram obtidos experimentalmente. Foram empregados três sistemas cromatográficos de separação: o primeiro e segundo foi constituido de fase móvel acetonitrila/água ¿ 70/30 (v/v) a 25 e 35 oC e o terceiro, de fase móvel etanol/água ¿ 70/30 (v/v) a 35 oC, com detecção em 245 nm para todos os sistemas. Utilizou-se coluna analítica de 25 x 0,46 cm e coluna semipreparativa de 25 x 1,0 cm recheadas com fase estacionária C18 cujo tamanho médio de partícula foi 20 ?m. Na coluna analítica foram determinadas a porosidade total e as constantes de equilíbrio do piperonal, safrol, isosafrol e terpinoleno, nas vazões de 0,6 ¿ 1,4 mL.min-1. Na coluna semipreparativa foram determinadas a porosidade total bem como os parâmetros de transferência de massa, nas vazões de 4,0 ¿ 6,0 mL.min-1. Para realização da abordagem teórica, foi preparado uma solução na qual a concentração foi de 0,2 g.L-1. Já na abordagem experimental, preparou-se uma solução de 9,50 g.L-1. Os resultados quanto aos parâmetros cromatográficos e às constantes de equilíbrio mostraram que os componentes têm a seguinte ordem crescente de eluição: piperonal, safrol, isosafrol e terpinoleno. O piperonal tem a menor afinidade com a fase estacionária C18 enquanto o terpinoleno possui a maior. Quanto aos parâmetros de transferência de massa, todos os valores foram próximos àqueles previsto na literatura, sendo o coeficiente de difusão efetivo da ordem de 10-6 cm2.s-1 e o coeficiente de dispersão axial da ordem de 10-3 cm2.s-1. Em relação à abordagem experimental, o piperonal apresentou pureza e recuperação superiores a 98% e 97%, respectivamente, em que a fase móvel acetonitrila/água à 25 oC, constitui-se como o melhor sistema de separação. O mesmo resultado foi obtido para a abordagem teórica quanto ao sistema de separação, sendo a pureza e recuperação de aproximadamente 100% de piperonal. A CLAE semipreparativa com injeção empilhada mostrou-se bastante eficiente em termos de produção de piperonal com elevado grau de pureza. Os resultados indicaram também que uma quantidade maior de amostra pode ser injetada e as informações operacionais bem como os parâmetros determinados neste estudo podem ser facilmente implementados em cromatografia preparativa, tanto em batelada quanto contínua, para obter grandes quantidades de piperonal puro
Abstract: Piperonal is a molecule of great economic value because it is used as raw material in the cosmetic and pharmaceutical industries. One way of obtaining piperonal is through synthesis which substrate is safrole. Safrole is main constituents of the essential oil of long pepper (Piper hispidinervum, C. DC), specie that is abundant in Amazon region. After synthesis processes applied directly to the long pepper oil, piperonal is obtained as the main product and coproducts safrole, isosafrole glycol, isosafrole cis, trans-terpinolene, and isosafrole. The throughput for this synthetic route is about 84% of piperonal. For this reason, and considering the high added value at the piperonal is proposed that separate it by High Performance Liquid Chromatography with stacked injection. For this, two approaches were used: the experimental approach, in which the cycle time and the time of collection were obtained directly from the chromatogram in concentrated solution and the theoretical approach that arose due to proposed model in the thesis on condition of infinite dilution, where cycle times and collection were obtained from the parameters of the gaussian curve. In this last approach, the equilibrium constants and parameters of mass transfer (Dp, Def, Ds and Eb), which were obtained experimentally are needed. Três chromatographic separation systems were used: the first and second, consisted of mobile phase acetonitrile/water ¿ 70/30(v/v) at 25 and 35 oC and the third, ethanol/water ¿ 70/30 (v/v) at 35 oC, with detection in 245 nm all systems. It was used analytical column of 25 x 0,45 cm and semipreparative column of 25 x 1,0 filled with stationary phase C18 which size particle is 20 ?m. In analytical column were determined the total porosity and equilibrium constants of piperonal, safrole, isosafrole and, terpinoleno, in flow rate of 0.6 ¿ 1.4 mL.min-1. In semipreparative column were determined the total porosity as well as the parameters of mass transfer, in flow rates 4.0 ¿ 6.0 mL.min-1. For the performance of theoretical approach, was prepared a solution in which the concentration 9.50 g.L-1. The results regarding to chromatographic parameters and equilibrium constants showed that the components has a followed ascending order of elution: piperonal, safrole, isosafrole, terpinolene. The piperonal has a lowest affinity in respect to stationary phase C18 while terpinoleno has the greatest. Regarding mass transfer parameters, all values are close to those predicted in the literature, the effective diffusion coefficient of about 10-6 cm2.s-1 and the axial dispersion coefficient of the order of 10-3 cm2.s-1. With respect to experimental approach, piperonal presented purity and recovery greater than 98% and 97%, respectively, in which mobile phase acetonitrile/water at 25 ° C, was established as the best separation system. The same result was obtained to theoretical approach regarding to separation system, being purity and recovery about 100% of piperonal. The semipreparative HPLC with stacked injection proved to be very efficient in terms of producing piperonal with high purity. The results also indicate that a greater amount of sample may be injected, and the operational information¿s and the parameters determined in this study may be easily implemented in preparative chromatography, either batch or continuous, to obtain large quantities of pure piperonal
Doutorado
Engenharia de Processos
Doutor em Engenharia Química
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Van, Meter David S. III. "Synthesis and Characterization of Surface-Confined Ionic Liquid Stationary Phases for High Performance Liquid Chromatography." University of Cincinnati / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1227275073.
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Tlili, Nawal. "Procédés de séparation multi colonnes continus : extension à la chromatographie à gradient de solvant." Thesis, Université de Lorraine, 2013. http://www.theses.fr/2013LORR0190/document.
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Les procédés multi-colonnes de chromatographie ont connu depuis quelques années un développement tel qu'ils sont devenus des standards industriels à toutes échelles, depuis celle des produits pharmaceutiques à haute valeur ajoutée jusqu'à celle des grands intermédiaires chimiques. La spécificité du présent travail consiste à étudier, pour ces procédés, l'influence d'un gradient d'élution. Il s'agit de faire varier au cours du temps la force éluante de la phase mobile. L'objectif est d'augmenter la productivité et le taux de récupération d'un produit à haute valeur ajoutée, tout en répondant à des contraintes de pureté. L'utilisation d'un gradient de solvant, courante en chromatographie analytique, fait l'objet d'un intérêt plus récent en chromatographie préparative. Les applications visées concernent des séparations de mélanges complexes où l'espèce cible a une affinité intermédiaire pour le support solide par rapport à celle des autres espèces, ce qui est souvent le cas lors de la purification de biomolécules issues de matières premières naturelles ou issues des biotechnologies. Dans ce cas, la séparation conduit à trois fractions, des impuretés faiblement retenues, la fraction intermédiaire et des impuretés fortement retenues. Pour notre étude, un mélange modèle, peu coûteux et non toxique, de cinq acides aminés a été choisi. Ces acides aminés ont été choisis en tenant compte de leur caractère apolaire et hydrophobe. Les séparations ont été réalisées par chromatographie en phase inverse. Dans un premier temps, une étude expérimentale, réalisée à l'aide d'une chaîne HPLC, a permis de déterminer les paramètres des isothermes d'adsorption de chaque acide aminé pour différentes teneurs en solvant organique de l'éluant. Une loi empirique a permis de relier le facteur de rétention k à la composition de la phase mobile (K = f (xméthanol)). Un travail de modélisation/simulation, reposant sur l'approche d'une cascade de mélangeurs, a ensuite permis de simuler les séparations obtenues dans le cas d'une seule colonne, puis dans le cas d'un système multi-colonnes. L'utilisation des lois reliant les facteurs de rétention k à la concentration en modifieur a alors permis de réaliser des simulations pour différents gradients de solvants. Dans le cas d'une seule colonne, le gradient a été optimisé en minimisant la durée de la séparation et en respectant une contrainte sur la résolution des pics des 2 espèces les plus difficiles à séparer. Une bonne adéquation a été observée entre les simulations et les résultats expérimentaux obtenus avec un gradient sur une seule colonne. Des expérimentations numériques ont alors été réalisées dans le cas du système multi-colonnes. Les paramètres opératoires optimaux ont été déterminés dans le cas du mélange étudié. Ces réglages seront ainsi utilisés lors de la validation expérimentale qui sera réalisée sur l'unité pilote. Cette unité comporte trois colonnes. Il s'agit d'un procédé séquentiel cyclique. Pour le mode opératoire retenu, chaque cycle comporte 8 étapes. A chaque étape les alimentations et soutirages des différentes colonnes sont modifiées. Pour le soutirage qui correspond à la fraction de l'espèce cible, les critères étudiés seront la pureté et le taux de récupérationMulti-column chromatographic processes have known, for a few years, a development on all scales, from high added value pharmaceutical products to major chemical intermediates. The specificity of the present work is to study the influence of a gradient elution for these processes. It consists in varying the eluent strength of the mobile phase over the time. The aim is to increase the productivity and the recovery ratio of a high added value product, while satisfying the constraints of purity. Solvent gradient is currently used in analytical chromatography and presents a recent interest in preparative chromatography. The applications concern separations of complex mixtures where the target species has an intermediate affinity for the solid phase compared to other species, which is often the case during the purification of biomolecules extracted from natural raw materials or resulting from biotechnologies. In this case, separation leads to three fractions, impurities weakly retained, an intermediate fraction and impurities strongly retained. For our study, a model mixture, inexpensive and nontoxic, of five amino acids was selected considering their nonpolar and hydrophobic character. The separations were carried out by reversed phase chromatography. An experimental study using a HPLC system was first carried out with single-element solution of each amino acid in isocratic mode. This enabled to determine adsorption isotherm parameters. An empirical law giving the retention factor as a function of eluent composition was determined (K = f (xmethanol)). A work of modeling / simulation, assuming linear isotherm and based on the mixed cells approach, permitted to simulate the separations obtained in the case of a one-column process, then in the case of a multi-column system. The use of retention factors laws allowed to carry out simulations for different solvent gradients. In the case of a single column, a simple methodology was developed to calculate the optimal solvent gradient. The gradient was optimized by minimizing the separation time and by respecting a constraint on the peaks resolution of the two species which are the most difficult to separate. A really good adequacy was observed between simulations and the experimental results. Numerical experimentations, executed in the case of the multi-columns process, made it possible, yet, to find the optimal operating parameters in the case of the studied mixture. These settings will be applied in the experimental validation which will be realized on the pilot unit. This unit has three columns. It is a cyclic sequential process. For the selected operating mode, each cycle contains eight steps. At each step, inlets ant outlets streams of different columns are switched. The criteria for the target species fraction are purity and recovery
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Edström, Lena. "Adsorption Studies with Liquid Chromatography : Experimental Preparations for Thorough Determination of Adsorption Data." Doctoral thesis, Uppsala universitet, Analytisk kemi, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-216235.
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Analytical chemistry is a field with a vast variety of applications. A robust companion in the field is liquid chromatography, the method used in this thesis, which is an established workhorse and a versatile tool in many different disciplines. It can be used for identification and quantification of interesting compounds generally present in low concentrations, called analytical scale chromatography. It can also be used for isolation and purification of high value compounds, called preparative chromatography. The latter is usually conducted in large scale with high concentrations. With high concentrations it is also possible to determine something called adsorption isotherms. Determination of adsorption isotherms is a useful tool for quite a wide variety of reasons. It can be used for characterisation of chromatographic separation systems, and then gives information on the retention mechanism as well as provides the possibility to study column-column and batch-batch reproducibility. If a protein is immobilised on a solid support, adsorption isotherms can be used for pharmacological characterisation of drug-protein interactions. Moreover, they can be used for the study of unexpected chromatographic phenomena. If the adsorption isotherm is known it is also possible to simulate chromatograms, and subsequently optimise the separation process numerically. The gain of a numerically optimised separation process is higher purity or yield of valuable compounds such as pharmaceuticals or antioxidants, as well as reducing the solvent usage. Taken all together, it saves time, money and the environment. However, the process of the adsorption isotherm determination requires a number of careful experimental considerations and preparations, and these are the main focus of the thesis. Important steps along the way include the choice of separation system and of suitable analytes, preparation of mobile phases and sample solutions, calibration, determination of injection profiles and column void, and of course the adsorption isotherm determination method itself. It is also important to keep track of parameters such as temperature and pH. These issues are discussed in this thesis. At the end, a description of useful methods for processing of the raw adsorption isotherm data is presented, as well as a brief passage on methods for numerical optimisation.
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Begnini, Fernanda Ribeiro. "Preparação e caracterização de fase estacionária reversa fenil-propil-metil-siloxano, imobilizada por micro-ondas, para cromatografia líquida de alta eficiência." [s.n.], 2011. http://repositorio.unicamp.br/jspui/handle/REPOSIP/250515.
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Orientador: Isabel Cristina Sales Fontes JardimDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química
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Resumo: Novas fases estacionárias (FE) para Cromatografia Líquida de Alta Eficiência em fase reversa (CLAE-FR) foram preparadas a partir da sorção e imobilização por micro-ondas do copolímero poli(2- fenilpropil)metilsiloxano (PFPMS) sobre suporte de sílica Kromasil (tipo B, esférica, 5 mm). A FE preparada com carga do copolímero de 50%, imobilizada a 540 W por 80 minutos e extraída com clorofórmio (3 horas) e metanol (2 horas) após 8 dias de imobilização, apresentou desempenho cromatográfico satisfatório, com eficiências acima de 60000 pratos/m e parâmetros cromatográficos na faixa aceita pela literatura. Através da caracterização físico-química da FE preparada, pelas técnicas de RMN Si e C, e espectroscopia de absorção no infravermelho, entre outras, foi possível sugerir que o PFPMS encontra-se fisicamente sorvido e quimicamente ligado à sílica. A caracterização cromatográfica mostrou que a FE possui seletividade hidrofóbica, seletividade estérica, pouca interação com analitos polares e grupos silanóis residuais, sendo características apropriadas para uma FR. A FE preparada apresenta grande potencial na separação de agrotóxicos, fármacos e hidrocarbonetos policíclicos aromáticos, além de possuir estabilidade em meio ácido
Abstract: A new stationary phase for reversed-phase high-performance liquid chromatography (RP-HPLC) was prepared by sorption and microwave immobilization of the copolymer poly(2- phenylpropyl)methylsiloxane (PPPMS) onto a silica support (Kromasil®, type B, 5 mm). The stationary phase prepared with copolymeric content of 50%, immobilized at 540 W for 80 min and extracted with chloroform (3 hours) and methanol (2 hours) eight days after immobilization, showed satisfactory chromatographic performance, with efficiency above 60000 plates/m and symmetrical peaks. The physical¿chemical characterization of the new microwave immobilized stationary phase using solid-state NMR spectroscopy and infrared spectroscopy suggested that the copolymer is physically sorbed and chemically bonded onto the silica support. The chromatographic characterization showed that the stationary phase has hydrophobic selectivity, steric selectivity, low interaction with polar analytes and residual silanols, suggesting that the stationary phase prepared is promising to be used in RP-HPLC. The microwave immobilized stationary phase presented chemical stability and potential applicability to separation of pesticides, pharmaceutical drugs and polycyclic aromatic hydrocarbons
Mestrado
Quimica Analitica
Mestre em Química
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Mautjana, Nare Alpheus. "Determination of platinum, palladium and rhodium, in aqueous media by means of reversed phase-high performance liquid chromatography (RP-HPLC) after complexation with N,N-dialkyl-N'-acylthioureas." Master's thesis, University of Cape Town, 2000. http://hdl.handle.net/11427/11809.
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Includes bibliographical references.The complexes were successfully separated using conventional Reversed Phase-High Performance Liquid Chromatography (RP-HPLC) and a UV detector. A simple method of complexation of platinum(II) and palladium(II) in acidic, aqueous samples was developed. This method involves the mixing of excess ligand (HL") in acetonitrile with aqueous solutions containing traces of platinum(II) and palladium(II) at room temperature followed by salt-induced phase separation prior to RP-HPLC analysis. In the case of rhodium(III), however, complexation was extremely slow and it has not been possible to include this metal in the complexation procedure for platinum(ll) and palladium(II).
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Delrieu, Pascal. "Utilisation d'acides perfluores en clhp de phase inverse : application a la purification semi-preparative de peptides et d'antibiotiques." Toulouse 3, 1988. http://www.theses.fr/1988TOU30039.
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