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Davies, Ilona Lynn. "Analysis of polycyclic aromatic compounds by multidimensional chromatography." Thesis, University of Leeds, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328575.
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Dixon, Antony. "Multidimensional chromatography of the soybean proteome following genetic modification." Thesis, University of Leeds, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.406209.
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Johnson, Kevin J. "Strategies for chemometric analysis of gas chromatographic data /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/8513.
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Van, der Westhuizen Katriena Elizabet. "Comprehensive multidimensional gas chromatography for the analysis of Fischer-Tropsch products." Thesis, Stellenbosch : Stellenbosch University, 2011. http://hdl.handle.net/10019.1/18006.
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Thesis (PhD)--University of Stellenbosch, 2011.ENGLISH ABSTRACT: The analysis of Fischer–Tropsch–derived (FT–derived) synthetic crude and derived products is very challenging because of the highly complex nature of these products. In this study, the use of comprehensive multidimensional gas chromatography (GCxGC) with time-of-flight mass spectrometry (TOF-MS) and flame ionisation detection (FID) was investigated for the analysis of these products and the technique was found to be invaluable for the analysis of these complex mixtures. The compositions of FT synthetic crude, produced at low temperature (LT–FT) and high temperature (HT–FT) processes were compared and the effect that changes in FT reaction temperature has on product formation was investigated. Results for conventional onedimensional GC (1D-GC) and GCxGC were compared. It was found that conventional 1D–GC does not have sufficient peak capacity to separate the thousands of compounds in the HT FT products. GCxGC provides a huge peak capacity of tens-of-thousands to separate highly complex mixtures. Structured chromatograms, where groups of compounds with similar properties are grouped together, aid in peak identification. Moreover, sensitivity at low microgram per milliliter levels is obtained. These attributes enabled accurate analysis of various complex feed and product streams in the FT refinery, and also various final fuel products. The use of GCxGC alone was demonstrated, and also combined with high performance liquid chromatography (HPLC), supercritical fluid chromatography (SFC) and nuclear magnetic resonance (NMR) when even more separation power was needed. HPLC–GCxGC enabled the separation of alkene and cyclic alkane compound classes in oligomerisation products. These compound classes have similar mass spectra, elute in adjacent regions and co–elute even to some extent on the GCxGC contour plot, making differentiation difficult. SFC is a good replacement for HPLC for these applications because it does not use solvents as mobile phases. CO2 is easily evaporated after the separation and does not interfere with the GCxGC separation of the analytes. SFC is also a very good technique to separate the compound classes of alkanes, alkenes, aromatics and oxygenates, and is therefore highly complementary to GCxGC. The combination of GCxGC with NMR data was also found to be very valuable for the identification of branched alkane isomers in LT–FT diesels. GCxGC provides excellent separation of individual compounds but the identification of isomers (except for mono–methyl branching) is difficult because the mass spectra of most of these isomers are similar and not all compounds are in the mass spectral libraries. NMR, on the other hand, is able to distinguish between the individual types of branched isomers but has limited separation power for the complex mixtures. By combining the two techniques, the best of both was obtained. The study found GCxGC to be invaluable for the analysis of the highly complex FT–derived products, while its combination with other techniques such as HPLC, SFC and NMR provided even more separation power.
AFRIKAANSE OPSOMMING: Die hoogs komplekse samestelling van sintetiese ru–olie en afgeleide produkte, afkomstig van Fischer–Tropsch (FT) sintese, bied groot uitdagings aan die analis. Die studie het die gebruik van GCxGC met ’n TOF-MS en FID bestudeer vir die analise van FT produkte en het bevind dat die tegniek van onskatbare waarde is vir die analise van die hoogs komplekse mengsels. Die samestellings van produkte van lae- en hoë-temperatuur FT prossesse is vergelyk en die effek van ’n verhoging in die reaksie–temperatuur op die produk samestelling is ondersoek. Resultate vir 1D–GC and GCxGC is vergelyk en dit was duidelik dat 1D-GC nie naastenby voldoende piekkapasiteit het om al die komponente van die produkte wat tydens die hoëtemperatuur prosses gevorm word, te kan skei nie. Die GCxGC se piekkapasiteit daarteenoor is in die orde van tienduisende wat die skeiding van hoogs komplekse mensels moontlik maak terwyl die tegniek hoogs gestruktureerde kontoerplotte verskaf wat help met identfikasie van komponente. Die tegniek is verder ook baie sensitief en kan komponente op lae μg/mL vlakke waarneem. Hierdie eienskappe het akkurate analise van verskeie FT produkstrome moontlik gemaak. Die kombinasie van GCxGC met HPLC, SFC en KMR het selfs meer skeidingskrag verskaf waar nodig. HPLC–GCxGC het die skeiding van alkene en sikliese alkane moontlik gemaak. Hierdie komponent klasse se massaspektra is feitlik dieselfde en terselfdertyd elueer die twee groepe reg langs mekaar, en oorvleuel soms selfs tot ’n mate, op die GCxGC kontoerplot, sodat dit moeilik is om daartussen te onderskei. SFC is ’n goeie alternatief vir HPLC in meeste toepassings aangesien die tegniek net CO2 gebruik, wat maklik verdamp by kamertemperatuur en nie oplosmiddels gebruik wat se pieke steur met die van die laekookpunt komponente op die GCxGC kontoerplot nie. Skeidings van die komponentgroepe alkane, alkene, aromate en oksigenate is moontlik met SFC en daarom komplimenteer dit die GCxGC skeiding goed aan. Die kombinasie van GCxGC met kern–magnetiese resonansie (KMR) is van waarde gevind om die verskillende tipes vertakkings in ’n lae-temperatuur FT diesel te identifiseer. GCxGC verskaf uitstekende skeiding van individuele komponente maar die identifikasie van die verskilende isomere, behalwe vir die mono-metiel vertakkings, is moeilik aangesien die massaspektra van baie van die komponente soortgelyk is en die komponente nie in die massa spektrum–biblioteke voorkom nie. KMR, aan die ander kant, kan tussen die individuele vertakkings onderskei maar het beperkte skeidingskrag vir komplekse mensels. Deur die twee tegnieke te kombineer is die beste van albei tegnieke bekom. Die studie het bevind dat GCxGC van onskatbare waarde is vir die analise van die komplekse sintetiese FT produkte terwyl die kombinasie met ander tegnieke soos HPLC, SFC and KMR selfs meer skeidingskrag verskaf.
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Adusumilli, Harika. "Separation and identification of peptides by integrated multidimensional liquid chromatography-mass spectrometry (IMDLC-MS)." Diss., Columbia, Mo. : University of Missouri-Columbia, 2007. http://hdl.handle.net/10355/6028.
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Thesis (M.S.)--University of Missouri-Columbia, 2007.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on April 15, 2008) Vita. Includes bibliographical references.
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Zhao, Yun, and 赵赟. "Fully automatable multidimensional liquid chromatography with online tandem mass spectrometry for proteomics and glycoproteomics." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2015. http://hdl.handle.net/10722/208554.
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Maiko, Khumo Gwendoline. "Multidimensional separation of complex polymers according to microstructure." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/86227.
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Thesis (PhD)--Stellenbosch University, 2014.ENGLISH ABSTRACT: Complex polymer systems have multiple distributions with regard to molecular parameters such as molar mass, functionality, chemical composition, molecular architecture and microstructure. These distributions affect the properties of the polymers making it necessary to develop separation methods to be able to correlate structure to property. A single onedimensional chromatographic method is usually not sufficient to separate these complex polymers with respect to all the distributions. Hence, multidimensional liquid chromatography is necessary for the complete analysis of complex polymers using two or more chromatographic techniques before detection. In this work, two novel liquid chromatographic methods were developed to separate complex polymers according to microstructure. Comprehensive two-dimensional liquid chromatography (LC x LC) was carried out to observe the correlation between microstructure and molar mass. The separation according to microstructure was coupled to NMR (LC-NMR) to observe, identify and quantify the different microstructural components during chromatographic elution. The first chromatographic method separated hydrogenated and deuterated polystyrene homopolymers with respect to the isotope effect. For the LC x LC experiments, liquid chromatography at critical conditions (LCCC) was employed as the first dimension separating according to the isotope effect and size exclusion chromatography (SEC) as the second dimension separating according to molar mass. The LC x LC results of the blends showed that there was an improvement in isotopic separation with an increase in molar mass. The LCNMR coupling using both 1H and 2H NMR detection allowed for the identification of low molar mass blend components which were not sufficiently separated by liquid chromatography. The second chromatographic method separated stereoregular poly(methyl methacrylate)s (PMMAs) with respect to tacticity. The LC x LC experiments of stereoregular PMMAs utilised solvent gradient liquid chromatography as the first dimension to separate according to tacticity and size exclusion chromatography (SEC) as the second dimension to separate according to molar mass. The LC x LC results showed a change in the triad composition with elution of the stereoregular PMMAs with a slight influence of molar mass. The LC-NMR coupling allowed the observation of the triad composition during chromatographic elution.
AFRIKAANSE OPSOMMING: Komplekse polimeriese sisteme het meervoudige verspreidings ten opsigte van molekulêre parameters, soos byvoorbeeld, molêre massa, funksionaliteit, chemiese samestelling, molekulêre argitektuur en mikrostruktuur. Hierdie verspreidings beïnvloed die eienskappe van die polimere en dus is dit nodig om skeidingsmetodes te ontwikkel ten einde polimeerstruktuur met polimeereienskappe te kan korreleer. ‘n Enkele een-dimensionele chromatografiese metode is gewoonlik nie voldoende om hierdie komplekse polimere te skei met betrekking tot al die verspreidings nie. Multidimensionele vloeistofchromatografie, met die insluiting van twee of meer chromatografiese tegnieke, is dus nodig om polimere te skei voor waarneming kan plaasvind. Twee nuwe chromatografiese metodes is ontwikkel om komplekse polimere volgens mikrostruktuur te skei. Twee-dimensionele vloeistofchromatografie (LC x LC) is uitgevoer ten einde die korrelasie tussen mikrostruktuur en molêre massa te ondersoek. Daarna is die skeiding wat op mikrostruktuur gebasseer is, gekoppel aan KMR (LC-KMR) om die verskillende mikrostrukturele komponente gedurende chromatografiese eluering waar te neem, te identifiseer en te kwantifiseer. Die eerste chromatografiese metode het die gehidrogeneerde en gedeutereerde polistireen geskei met betrekking tot die isotoopeffek. Hier het die LC x LC skeiding bestaan uit vloeistofchromatografie onder kritiese kondisies (LCCC) as die eerste dimensie, wat skeiding bewerkstellig het gebasseer op die isotoopeffek, en grootte-uitsluitingschromatografie (SEC) as die tweede dimensie, wat skeiding bewerkstellig het gebasseer op die molêre massa. Die LC x LC resultate van die vermengings het ‘n verbetering in isotopiese skeiding met ‘n toename in molêre massa getoon. Deur gebruik te maak van die LC-KMR koppeling, waar beide 1H en 2H KMR waarneming gebruik is, was dit moontlik om die lae-molêre-massakomponente van vermengings wat nie volledig d.m.v. LC geskei kon word nie, te identifiseer. Die tweede chromatografiese metode het stereoreëlmatige polimetielmetakrilate (PMMAs) m.b.t. taktisiteit geskei. Die LC x LC skeiding van stereoreëlmatige PMMAs het bestaan uit oplosmiddel -gradiënt-LC as eerste dimensie om volgens taktisiteit te skei, en SEC as tweede dimensie om volgens molêre massa te skei. Die LC x LC resultate het ‘n molêre massa afhanklikheid van stereoreëlmatige PMMAs op taktisiteit getoon. Die LC-KMR koppeling het dit moontlik gemaak om die triade-samestelling gedurende chromatografiese eluering waar te neem.
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Lam, Pui-yu, and 林沛瑜. "Multidimensional liquid chromatography for the analyses of hydrophilicand hydrophobic components in mass spectrometry-based proteomics." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B45960392.
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Kong, Pak-wing, and 江柏榮. "Development of fully automatable multidimensional liquid chromatography (MDLC) with online tandem mass spectrometry for shotgunproteomics." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2011. http://hub.hku.hk/bib/B48199278.
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Proteomics is the systematic study of the proteome: the total protein expression of a cell or tissue under specified conditions. The multiplicity and complexity of proteins in cells requires sensitive, selective, and comprehensive methodologies for their distinction and characterization. Multidimensional liquid chromatography (MDLC) coupled with biological tandem mass spectrometry (MS/MS) is uniquely suited to fulfill those requirements and has become an indispensable tool in MS-based proteomics. Our laboratory has developed an online high-/low-pH reversed-phase/reversed-phase (RP–RP) LC system exhibiting fully automatable and reproducible performance. It is a promising alternative to the strong cation exchange/reversed-phase (SCX–RP) system commonly used in high-throughput comprehensive proteomics analyses. The first part of this Thesis (Chapter 2) describes the development of a variant of the high-/low-pH RP–RP platform—RP–SCX–RP—that integrates an additional SCX trap column between the two RP columns to enhance sample recovery. This new system allows the detection of larger numbers of hydrophilic peptides. Indeed, in the analyses of a lysate of Arabidopsis chloroplast proteins, it identified approximately 25% more non-redundant proteins than those identified using the previous version of the RP–RP system. The modified platform has been extended for the online removal of sodium dodecyl sulfate and other excess interference chemicals used in Isobaric Tags for Relative and Absolute Quantification (iTRAQ) reactions, thereby avoiding the need for time-consuming offline SCX clean-up prior to RP–RP separation in the quantitative proteomics analyses of crude biological samples at low-microgram levels. A novel online three-dimensional liquid chromatography (3DLC) system was derived from the RP–SCX–RP design, exhibiting remarkably enhanced orthogonality, resolution, and peak capacity. Peptides were separated in the first-dimension high-pH RP column based on their hydrophobicity, followed by sub-fractionation in the second-dimension SCX column, primarily based on charge; the third dimension was a typical low-pH RP separation, prior to MS analysis. The overall performance of the system was evaluated through analysis of a cell lysate of mouse embryonic fibroblasts. Relative to the two-dimensional high-/low-pH RP–RP system, the new 3D system yielded significant increases in the number of unique peptides and proteins identified, making it a good alternative to SCX–RP and high-/low-pH RP–RP as an efficient automated MDLC platform for high-throughput shotgun proteomics. An optimized and miniaturized variant of the three-dimensional LC platform was also developed. Its simplified setup and operation, by decreasing the number of six-port switching valves (from three to two) and the number of SCX fractionation steps, minimized both the potential sample loss and the total analysis time (by ca. 30%). Thus, a variety of novel, automatable, and robust RP–SCX–RP-based MDLC platforms have been developed for high-throughput qualitative and quantitative analysis. The performance of these systems complements conventional MDLC systems, with enhanced quality, quantity, reproducibility, and throughput of protein identification and quantification.published_or_final_version
Chemistry
Doctoral
Doctor of Philosophy
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Radebe, Nonhlanhla Mtandi. "Multidimensional fractionation of wood-based tannins." Thesis, Stellenbosch : University of Stellenbosch, 2011. http://hdl.handle.net/10019.1/6621.
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Thesis (MSc)--University of Stellenbosch, 2011.ENGLISH ABSTRACT: High molar mass tannin extracts are complex mixtures which are distributed in both molar mass and chemical composition. Condensed tannins from quebracho and mimosa and hydrolysable tannins of tara, chestnut wood and turkey gall were studied. Application of a single analytical technique is not sufficient to elucidate the complete structures present in the extracts. 13C Nuclear Magnetic Resonance (NMR) spectroscopy and Matrix Assisted Laser Desorption/Ionisation Time-of-Flight (MALDI-TOF) mass spectrometry were applied in order to determine the chemical composition and molar mass, respectively. A new mass spectrometric method that can uniquely determine the oligomer microstructure was developed using Collision Induced Dissociation (CID) experiments. Bulk analysis only showed the average composition of the extracts, in order to obtain specific information on the molar mass and chemical composition distributions. Hydrophilic Interaction Liquid Chromatography (HILIC) was used for analysis of the condensed tannins and for the hydrolysable tannins Normal Phase Liquid Chromatography (NP-LC) was utilised. The HILIC separation was up-scaled and the fractions were collected and analysed by MALDI-TOF, and this coupling revealed that separation occurs by molar and chemical composition. For separation of the molecules only by size, Size Exclusion Chromatography (SEC) analyses were carried out; this allowed for relative comparison of the tannin molecules. In conclusion, for characterisation of high molar mass tannins a multi-dimensional approach was necessary since the various distributions present in these extracts are superimposed.
AFRIKAANSE OPSOMMING: Hoë molekulêre massa tannienekstrakte is komplekse mengsels, in terme van beide molekulêre massa en chemiese samestelling. Gekondenseerde tanniene vanaf quebracho en mimosa, en hidroliseerbare tanniene vanaf tara, kastaaiinghout en Turksegal is bestudeer. Die gebruik van ‘n enkele analitiese tegniek is nie voldoende om die volledige struktuur van komponente teenwoordig in die ekstrakte te analiseer nie. 13C KMR-spektroskopie en MALDI-TOF-massaspektroskopie is gebruik om die chemiese samestelling en molekulêre massa, onderskeidelik, te bepaal. ‘n Nuwe metode is ontwikkel vir die bepaling van die oligomeer-mikrostruktuur deur gebruik te maak van botsings-geïnduseerde dissosiasie eksperimente. Grootmaat analise het net die gemiddelde samestelling van die ekstrak bepaal. Hidrofiliese-interaksie-vloeistofchromatografie (HILIC) is gebruik vir die analise van gekondenseerde tanniene en gewone fase-vloeistofchromatografie is gebruik vir die hidroliseerbare tanniene. Die HILIC-skeiding is op groter skaal uitgevoer en die fraksies is versamel en gebruik vir MALDI-TOF analise. Hierdie koppeling het getoon dat skeiding plaasvind op grond van molekulêre massa en chemiese samestelling. Grootte-uitsluitingschromatografie is gebruik vir die skeiding van molekules alleenlik op grootte. Hierdeur kon ‘n relatiewe vergelyking van die tannienmolekules gemaak word. Vir die karakterisering van hoë molekulêre massa tanniene is ‘n multi-dimensionele benadering nodig aangesien die verskeie verspreidings teenwoording in hierdie ekstrakte supergeponeerd is.
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Luo, Zhaohui. "GC/FT-ICR Mass Spectral Analysis of Complex Mixtures: A Multidimensional Approach for Online Gas Phase Basicity Measurements." Fogler Library, University of Maine, 2006. http://www.library.umaine.edu/theses/pdf/LuoZX2006.pdf.
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Chappuis, Thomas. "Prélèvement et analyse des composés organiques volatils dans l’air expiré : apport des microtechnologies et de la chromatographie multidimensionnelle." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLET035.
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L’air expiré présente un intérêt pour des applications médicales comme le dépistage, le suivi de pathologies ou d’expositions. En effet, cet échantillon contient des marqueurs volatils endogènes ou exogènes et son prélèvement est non invasif. Même si le prélèvement est simple, la complexité et la variabilité de l’air expiré expliquent le peu de tests autorisés par les autorités sanitaires.Cette thèse s’est intéressée à deux outils analytiques pour l’analyse de l’air expiré : une puce de préconcentration et la chromatographie en phase gazeuse intégralement bidimensionnelle. Ces deux techniques, peu explorées jusqu’à présents dans ce domaine, peuvent présenter un intérêt en simplifiant le prélèvement et en permettant une analyse plus exhaustive des marqueursLe travail effectué sur la puce de préconcentration a montré que les micropréconcentrateurs fabriqués au laboratoire prélèvent et injectent des mélanges de gaz modèles et des échantillons d’air expiré avec des variabilités proches des systèmes de laboratoires. De plus, nos travaux ont montré que ces micropréconcentrateurs présentent deux avantages majeurs en réduisant les volumes d’échantillon nécessaires et en s’intégrant dans des systèmes simples, portables et fonctionnant sur batterie. Afin d’illustrer leur intérêt sur un cas réel simple, nous avons utilisé ces micropréconcentrateurs pour étudier trois marqueurs du tabagisme dans l’air expiré de trois fumeurs et de trois non-fumeurs et suivre les cinétiques de ces composés dans l’air expiré d’une personne. Finalement, nous avons effectué un travail préliminaire d’intégration dans des échantillonneurs dédiés afin d’exploiter les avantages des micropréconcentrateurs pour le prélèvement de l’air expiré et tenter d’obtenir un prélèvement sur une expiration unique.Nous avons ensuite choisi et reproduit une architecture de modulateur fluidique simple, pertinente pour la miniaturisation, basée sur un Dean’s switch. Nous avons montré que ce modulateur décrit en 2016 était compatible avec une injection par thermodésorption et comparé ses performances à la GC simple pour l’analyse d’un même échantillon d’air expiré. Ceci a montré que cette architecture présente un intérêt en modulant des composés exhalés très volatils ce qui permet de nombreuses levées de coélution. Finalement, nous avons montré, grâce à des plans d’expériences, que l’amélioration des performances de ce modulateur nécessitait un contrôle minutieux des paramètres.Enfin, nous avons confronté nos outils à des échantillons d’une malade atteinte d’une maladie rare, la phénylcétonurie. Des échantillons d’espace de tête d’urine et d’air expiré de la patiente ont été prélevés. Les résultats, incomplets à ce stade, sont discutés dans le manuscritBreath is of interest for medical applications such as screening, monitoring pathologies or exposures. Indeed, this sample contains endogenous or exogenous volatile markers and its sampling is non-invasive. Although the sampling is simple, the complexity and variability of breath explain the few tests authorized by the health authorities.This thesis focused on two analytical tools for the analysis of breath: a preconcentration chip and two-dimensional gas chromatography. These two techniques, little explored so far in this area, may be of interest by simplifying sampling and allowing a more comprehensive analysis of markersWork on the preconcentration chip has shown that micropreconcentrators manufactured in the laboratory sample and inject model gas mixtures and expired air samples with variability close to laboratory systems. In addition, our work has shown that these microproconcentrators have two major advantages in reducing the necessary sample volumes and integrating into simple, portable and battery-powered systems. In order to illustrate their interest in a simple real-world case, we used these microproconcentrators to study three smoking markers in the exhaled breath of three smokers and three non-smokers, and to track the kinetics of these compounds in a person’s breath. Finally, we performed preliminary integration work in dedicated samplers in order to exploit the benefits of micropreconcentrators for the collection of breath and attempt to obtain a single expiratory sampling.We then chose and reproduced a simple fluidic modulator architecture, relevant for miniaturization, based on a Dean's switch. We showed that this modulator described in 2016 was compatible with a thermodesorption injection and compared its performance to GC for the analysis of the same breath sample. This has shown that this architecture is of interest in modulating very volatile exhaled compounds which allows many coelution lifts. Finally, we showed, thanks to experimental designs, that the improvement of the performances of this modulator required a meticulous control of the parameters.Finally, we confronted our tools with samples of a patient suffering from a rare disease, phenylketonuria. Samples of urine head space and exhaled air from the patient were taken. The results, incomplete at this stage, are discussed in the manuscript
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Evans, Charles Robert Jorgenson James W. "Multidimensional liquid chromatography coupled to mass spectrometry for the analysis of complex mixtures of proteins." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2007. http://dc.lib.unc.edu/u?/etd,1468.
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Thesis (Ph. D.)--University of North Carolina at Chapel Hill, 2007.Title from electronic title page (viewed Apr. 25, 2008). " ... in partial fulfillment of the requirements for the degree of Doctor of Philosophy in the Department of Chemistry." Discipline: Chemistry; Department/School: Chemistry.
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Nestola, Marco [Verfasser], and Torsten Claus [Akademischer Betreuer] Schmidt. "Multidimensional high-performance liquid chromatography–gas chromatography (HPLC-GC) hyphenation techniques for food analysis in routine environments / Marco Nestola ; Betreuer: Torsten Claus Schmidt." Duisburg, 2016. http://d-nb.info/1115654659/34.
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Pretorius, Nadine Odette. "Multidimensional analytical techniques for the characterization of aliphatic polyesters." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/80127.
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Thesis (PhD)--Stellenbosch University, 2013.ENGLISH ABSTRACT: Complex polymers are defined by their distributive properties with respect to molecular weight, chemical composition, functionality and molecular topology. As a result, polymer properties are very frequently determined not only by one of these entities but by the correlation of two or more distributions. Aliphatic polyesters are industrially implemented in high performance coatings, paints and varnishes. However, it is typically difficult to correlate the resulting properties with the synthesis parameters as these polymers vary in reactivity and application properties. Copolyester synthesis by direct polyesterification is often assumed to produce randomized products due to the mechanisms involved in stepwise polymerization. The formation of cyclic products by intramolecular reactions of hydroxyl (OH) and carboxylic (COOH) functional groups, sidereactions such as transesterification, alcoholysis, and ester-ester interchange allow even further randomization, enabling a highly complex system. Therefore, in addition to molecular weight distribution, polyesters exhibit chemical composition, functionality type as well as branching distributions, classifying them as complex polymeric systems. The different methods of polymer chromatography in combination with sophisticated spectrometry techniques are useful tools for enabling the full description of the molecular heterogeneity of these complex polyesters. The present study entails method development of different modes of chromatography and mass spectrometry along with their combination, to facilitate the analysis of the various distributions of two model polyester systems, phthalic and maleic anhydride, respectively, in combination with propylene glycol. Gradient HPLC analysis enabled an oligomeric separation based on chemical composition of the respective anhydride/propylene glycol samples. Its off-line coupling to MALDITOF MS and ESI-QTOF MS revealed the presence of several distributions of varying endgroup functionality type and molecular weight distributions at different intervals throughout the polymerization. In addition, online gradient HPLC x size exclusion chromatography (2D-LC) was conducted to obtain the dual chemical composition-molecular weight (CCD-MWD) distribution. The combination of the different coupling techniques provided the opportunity to a more in-depth analysis of the structure-property relationships.
AFRIKAANSE OPSOMMING: Komplekse polimere word gedefinieer deur hul verdelings eienskappe ten opsigte van molekulêre massa, chemiese samestelling, funksionaliteit en molekulêre topologie. Gevolglik, word hul eienskappe dikwels bepaal deur nie net een van hierdie entiteite nie, maar ‘n korrelasie van twee of meer verdelings. Alifatiese poliësters word industrieel geϊmplimenteer in hoë werkverrigting bestrykings, verwe en politoere, dog is dit tipies moeilik om die uiteinde eienskappe met die verwante sintese parameters te korrelleer, aangesien die polimere varieer in reaktiviteit en toepassingseienskappe. Ko-poliëster sintese vanaf direkte poliësterivering word dikwels aanvaar om willekeurige produkte op te lewer as gevolg van die meganismes wat betrokke is tydens trapgroei polimerisasie. Die produsering van sikliese produkte weens intra-molekulêre reaksies van hidroksiel(OH) en karboksiel (COOH) verwante funksionele groepe, newereaksies soos transverestering, alkoholise en ester-ester verwisseling, het verdere ewekansigmaking tot gevolg wat ‘n hoog gekomplekseerde sisteem tot gevolg het. Benewens die molekulere massa verdeling, vertoon poliësters dus chemiese samestelling, funksionaliteit tipe so wel as vertakkings verdeling wat hul as komplekse polimeer sisteme klassifiseer. Die verskillende metodes van polimeer chromatografie in kombinasie met gesofistikeerde spektrometriese tegnieke dien as nuttige bronne vir die volledige beskrywing wat betref die molekulêre heterogeniteit van komplekse poliesters. Die huidige studie stel metode ontwikkeling van verskillende modus van chromatografie, massa spektrometrie sowel as hul aaneenvoeging bekend, om die die verskillende verdelings van twee model poliester sisteme, ftaal- en maleϊensuuranhidried onderskeidelik in kombinasie met propileenglikol, suksesvol te analiseer. Gradiënt hoë-druk vloeistof chromatografie (HPLC) analise het ‘n oligomeriese skeiding, gebaseer op die chemiese samestelling van die verskeie anhidried /propileenglikol monsters, opgelewer. Die nie-gekoppelde skakeling met matriks-assisteerdelaser/ desorpsie-ionisasie tyd-van-vlug (MALDI-TOF) en elektron-sproei-ionisasie kwadrupool-tyd-van-vlug (ESI-QTOF) massa spektrometrie het die teenwoordigheid van verskeie verdelings van varieërende endgroep funksionaliteit tipe en molekulêre verdelings by verskillende intervalle tydens die polimerisasie aan die lig gebring. Gekoppelde skakeling van gradient HPLC en grootte uitsluitings chromatografie is ook uitgevoer om die tweedelige chemiese samestelling-molekulere massa verdeling te bepaal. Aaneenvoeging van die verskeie skakelings tegnieke het die geleentheid gebied om ‘n deeglike studie van die struktuureienskappe verhoudinge suksesvol uit te voer.
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Cheruthazhekatt, Sadiqali. "Novel multidimensional fractionation techniques for the compositional analysis of impact polypropylene copolymers." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/80118.
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Thesis (PhD)--Stellenbosch University, 2013.ENGLISH ABSTRACT: Impact Polypropylene Copolymers (IPCs) are extremely complex materials, consisting of a mixture of polypropylene homopolymer and copolymers having different comonomer (ethylene) contents and chemical composition distributions. IPC can only be effectively analysed by multidimensional analytical approaches. For this, initially, the individual components have to be separated according to any of their molecular characteristics, either by chemical composition distribution (CCD) or molar mass distribution (MMD), followed by further analysis of these separated fractions with conventional analytical techniques. The combination of preparative temperature rising elution fractionation (TREF) with several other analytical techniques have been reported for the thorough characterization of this material. However, even the combinations of these methods were of limited value due to the complex nature of this polymer. Therefore, novel analytical approaches are needed for a more detailed compositional analysis of IPCs. This work describes a number of multidimensional analytical techniques that are based on the combination of fractionation and hyphenated techniques. Firstly, preparative TREF was combined with high temperature size exclusion chromatography-FTIR (HT SEC-FTIR), HT SEC-HPer DSC (High Performance Differential Scanning Calorimetry) and high temperature two-dimensional liquid chromatography (HT 2D-LC) for the comprehensive analysis of a typical impact polypropylene copolymer and one of its midelution temperature TREF fractions. HT SEC-FTIR analysis provided information regarding the chemical composition and crystallinity as a function of molar mass. Thermal analysis of selected SEC fractions using a novel DSC method - High Speed or High Performance Differential Scanning Calorimetry (HPer DSC) - that allows measuring of minute amounts of material down to micrograms, yielded the melting and crystallization behaviour of these fractions which is related to the chemical heterogeneity of this complex copolymer. High temperature 2D-LC analysis provided the complete separation of this TREF fraction according to the chemical composition of each component along with its molar mass distribution. In a second step, the compositional characterization by advanced thermal analysis (HPer DSC, Flash DSC 1, and solution DSC) of the TREF-SEC fractions was extended to all semi-crystalline and higher temperature TREF fractions. By applying HPer DSC at scan rates of 5−200°C/min and Flash DSC 1 at scan rates of 10−1000°C/s, the metastability of one of the fractions was studied in detail. DSC measurements of TREF-SEC cross-fractions at high scan rates in p-xylene successfully connected reversely to the slow scan rate in TREF elution, if corrected for recrystallization. Finally, the exact chemical structure of all HT HPLC separated components was determined by coupling of HT HPLC with FTIR spectroscopy via an LCTransform interface. This novel approach revealed the capability of this hyphenated technique to determine the exact chemical composition of the individual components in the complex TREF fractions of IPCs. The HT HPLC–FTIR results confirmed the separation mechanism in HPLC using a solvent gradient of 1-decanol/TCB and a graphitic stationary phase at 160°C. FTIR analysis provided information on the ethylene and propylene contents of the fractions as well as on the ethylene and propylene crystallinities.
AFRIKAANSE OPSOMMING: Impak Polipropileen Kopolimere (IPKe) is uiters komplekse materiale, bestaande uit 'n mengsel van polipropileen homopolimeer en kopolimere met verskillende komonomeer (etileen) inhoud en chemiese samestelling verspreiding. IPKe kan slegs doeltreffend ontleed word deur multidimensionele analitiese benaderings te volg. Hiervoor moet die individuele komponente aanvanklik eers geskei word volgens enige van hul molekulêre eienskappe, hetsy deur die chemiese samestelling verspreiding (CSV) of molêre massa verspreiding (MMV), gevolg deur 'n verdere ontleding van hierdie geskeide fraksies met konvensionele analitiese tegnieke. Die kombinasie van voorbereidings temperatuur-verhogings eluasie fraksionering (TVEF) met verskeie ander analitiese tegnieke is gerapporteer vir die deeglike karakterisering van hierdie materiaal. Maar selfs die kombinasies van hierdie metodes was van beperkte waarde as gevolg van die komplekse aard van hierdie polimeer. Daarom word nuwe analitiese benaderings benodig vir 'n meer gedetailleerde komposisionele ontleding van IPKe. Hierdie studie beskryf 'n aantal multidimensionele analitiese tegnieke wat gebaseer is op die kombinasie van fraksionering en gekoppelde tegnieke. Eerstens is voorbereidings TVEF gekombineer met hoë temperatuur grootte-uitsluitingschromatografie-FTIR (HT GUC-FTIR), HT GUC-HPer DSK en hoë temperatuur twee-dimensionele vloeistof chromatografie (HT 2D-VC) vir die omvattende ontleding van 'n tipiese impak polipropileen kopolimeer en een van sy mid-eluasie temperatuur TVEF fraksies. HT GUC-FTIR analiese het inligting verskaf met betrekking tot die chemiese samestelling en kristalliniteit as 'n funksie van molêre massa. Termiese analiese van geselekteerde GUC fraksies deur gebruik te maak van 'n nuwe-DSK metode - Hoë Spoed of Hoë Prestasie Differensïele skandeer kalorimetrie (HPer DSK) - wat die meting van klein hoeveelhede materiaal tot by mikrogram hoeveelhede toelaat, het die smelt en kristallisasie gedrag van hierdie fraksies bepaal wat verwant is aan die chemiese heterogeniteit van hierdie komplekse kopolimeer. Hoë temperatuur 2D-LC analiese het die volledige skeiding van hierdie TVEF fraksie volgens die chemiese samestelling van elke komponent saam met die molêre massa verspreiding moontlik gemaak. In 'n tweede stap, is die komposisionele karakterisering deur gevorderde termiese analiese (HPer DSK, Flash DSK 1 en oplossing DSK) van die TVEF-GUC fraksies uitgebrei na alle semi-kristallyne en hoër temperatuur TVEF fraksies. Deur die gebruik van HPer DSK, teen ’n skandeerspoed van 5-200°C / min, en Flash DSK 1, teen ’n skandeerspoed van 10-1000°C / s, is die meta-stabiliteit van een van die fraksies in detail bestudeer. DSK metings van TVEF-GUC kruis-fraksies by 'n hoë skandeeerspoed in p-xyleen het suksesvol omgekeerd verbind aan die stadige skandeerspoed in TVEF eluasie, wanneer gekorrigeer vir dekristallisatie. Ten slotte is die presiese chemiese struktuur van al die HT HPVC geskeide komponente bepaal deur die koppeling van HT HPVC met FTIR spektroskopie deur middel van 'n LC-transform-koppelvlak. Hierdie nuwe benadering het die vermoë van die gekoppelde tegniek om die presiese chemiese samestelling van die individuele komponente in die komplekse TVEF fraksies of IPKe te bepaal aan die lig gebring. Die HT HPVC-FTIR resultate het die skeidingsmeganisme in HPVC bevestig deur die gebruik van ’n oplosmiddelgradiënt van 1-dekanol/TCB en 'n graphitiese stasionêre fase by 160°C. FTIR analiese verskaf inligting in verband met die etileen en propileen inhoud van die fraksies sowel as die etileen en propileen krystalliniteit.
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Mohammad, Ahmed Trifa. "Determination of OPAHs and PAHs in Particulate Matter from Ambient Air and Engine Emissions : Multidimensional Chromatography." Doctoral thesis, Stockholms universitet, Institutionen för miljövetenskap och analytisk kemi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-122046.
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Particulate matter (PM) is an air pollutant that seriously impacts human health. Epidemiological studies have shown associations between human exposure to urban air PM and lung cancer, respiratory and cardiovascular diseases. Polycyclic aromatic hydrocarbons (PAHs) and oxygenated polycyclic aromatic hydrocarbons (OPAHs) are two groups of compounds associated with PM in ambient air. These compounds are generated from the incomplete combustion of organic material of both natural and anthropogenic origin. PAHs are thought to play an important role in the adverse health outcomes from exposure to PM in air. OPAHs contain one or more carbonyl groups and could be more toxic to humans compared to their corresponding parent PAH. Measurement of these compounds at trace levels in complex matrices requires analytical methods with high selectivity and precision and low quantification limits. This thesis describes the development and application of analytical methods for the determination of PAHs and OPAHs in ambient air and engine exhaust PM. Extraction was performed using pressurized liquid extraction, and two different setups for liquid chromatography–gas chromatography (LC-GC) were employed for automated sample clean-up, separation and detection. The developed methods were validated using standard reference materials issued by the National Institute of Standards and Technology. The first methodology developed used off-line solid-phase extraction and on-line LC-GC/mass spectrometry (LC-GC/MS). This method provided low limits of quantification and high selectivity and was successfully applied to the determination of OPAHs and PAHs in PM from the urban atmosphere of Sulaymaniyah city in the Kurdistan region of Iraq. The concentration of benzo[a]pyrene in Sulaymaniyah city was three times higher than the legislated EU target value (1 ng/m3). Furthermore the analytical method was applied on exhaust PM of vehicles fuelled with various gasoline/ethanol blends. The emissions factors for PAHs and OPAHs were highest when using70% ethanol/gasoline blends at -7 °C. The second method developed provided fully automated clean-up, separation and detection of PAHs in PM extracts using a multidimensional 2D-LC/2D-GC system. Polar, mono/di-aromatic and alkane compounds were successively removed by the two-dimensional LC part of the system. Heart-cutting segments from the first GC column (first dimension) to the second GC column (second dimension) increased the resolution of poorly separated or co-eluted PAHs. The results were in good agreement with the certified values from NIST (±25%).At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Manuscript.
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Wenner, Brett Romain. "METHODS DEVELOPMENT AND APPLICATION OF TWO DIMENSIONAL CHROMATOGRAPHY AND TANDEM MASS SPECTROMETRY IN PROTEOMICS." UKnowledge, 2004. http://uknowledge.uky.edu/gradschool_diss/281.
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Although molybdenum blue solutions have been known for more than twocenturies, an understanding of their chemical nature is only beginning to emerge.This dissertation aimed at elucidating the structural nature of the polydisperse,nanoscopic components in the solution phases and the solid states of partiallyreduced polyoxomolybdate (Mo-POM). The study offered at least fourcontributions to the area: (1) a rational protocol for the molecular recognition ofMo-POM with de novo organic hosts. (2) demonstration of kinetic precipitation ofa dynamic mixture of polyoxomolybdates and application of the technique to thestudy of the dynamic mixture by TEM (3) characterization of the Mo-POMnanostructures by an unusual combination of complementary analyticaltechniques. (4) a general approach for the synthesis of crown-ethers-containingtripodal molecules.The molecular recognition of Mo-POM with designer tripodal hexaminetris-crown ethers opened a window to the solution phase structures of Mo-POMnanoscopic components. Studies with a series of structurally analogous hostsprobed the relationship between the structure of the molecular host and theformation of nanostructures.An unusual combination of complementary analytical protocols: flow fieldflowfractionation, electron microscopy (transmission and scanning), andinductively coupled plasma – emission spectroscopy, was used to monitor thesolution-phase evolution of Mo-POM nanostructures. The crystallization – drivenformation of keplerate Mo-POM and solution-phase evolution of structurallyrelated nanoscopic species were apparent in the self-assembling process ofpartially reduced Mo-POM.
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Van, der Westhuizen Rina. "The use of multidimensional GC techniques for the analysis of complex petrochemical products." Thesis, Stellenbosch: University of Stellenbosch, 2005. http://hdl.handle.net/10019.1/4639.
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90 leaves on CD format, preliminary i-ix pages and numbered pages 1-81. Includes bibliography, list of figures in color to pdf format (OCR).Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2005.
ENGLISH ABSTRACT: The composition of petrochemical products obtained from Fischer Tropsch (FT) technologies is of the highest complexity possible and may contain thousands of components. Chemicals produced from FT feedstocks often contain trace level contaminants that can poison catalysts or that affect product performance in down-line processes. Single dimension GC analysis of these mixtures provides incomplete information because of lack of separation power. This study evaluates the separation power of heart-cut GC-GC, comprehensive GCxGC and sequential GC-GC for three selected challenging petrochemical applications. The fundamental theoretical aspects of the techniques are discussed. Oxygenates are removed as far as possible in C10 – C13 alkylation feedstocks, used in the production of linear alkyl benzenes, because the oxygenates may have deactivating effects on some expensive alkylation catalysts. Residual oxygenates may still be present and can consist of hundreds of components. Detection of individual components at ng/g levels is required. Heart-cut GC-GC is used to illustrate the separation and enrichment power for oxygenates in an alkylation feedstock. The stationary phase in the first dimension column was selected to provide separation of the oxygenates from the hydrocarbons in a relatively narrow window. The oxygenate fraction is then enriched by repeated injections and collection on the cryotrap. After sufficient enrichment, the trap is heated and the oxygenates are analysed on the second dimension column. Comprehensive GCxGC and Sequential GC-GC are compared for the separation and analysis of the oxygenated chemical component classes in the alkylation feedstock, before removal of oxygenates. Cyclic alcohols can occur in detergent alcohols produced from FT feedstocks. These cyclics are regarded as impurities because they affect the physical properties of the detergents. The cyclic and noncyclic alcohols in a narrow C12 – C13 detergent alcohol distillation cut have similar boiling points and polarities, and separation of individual components is thus difficult to achieve. Comprehensive GCxGC and sequential GC-GC are evaluated for the separation of the alcohol component classes. The study shows that both approaches provide component class separation but the high resolving power of the second column and the optimal chromatographic operating conditions of sequential GC-GC provide better separation of the individual components. The study illustrates the immense power of the three multidimensional GC techniques namely heart-cut GC-GC, comprehensive GCxGC and sequential GC-GC. The three multidimensional GC techniques each have their own advantages, disadvantages and unique applications and should be used as complementary rather than as competitive analytical tools.
AFRIKAANSE OPSOMMING: Fischer Tropsch (FT) petrochemiese produkte is van baie hoë kompleksiteit en kan uit duisende komponente bestaan. Chemikalië afkomstig van dié voerstrome bevat soms spoorhoeveelhede onsuiwerhede wat deaktiverend op kataliste kan inwerk of wat die werkverrrigting van finale produkte kan beïnvloed. Enkeldimensie GC analises van die komplekse mengsels is meesal onakkuraat as gevolg van geweldige piekoorvleueling. Die studie evalueer die skeidingsvermoë van drie multidimensionele tegnieke, Heart-cut GC-GC, Comprehensive GCxGC en Sequential GC-GC vir geselekteerde petrochemiese toepassings. Die fundamentele teoretiese aspekte van die tegnieke word bespreek en drie analitiese toepassings word beskryf. Oksigenate word so ver moontlik verwyder uit C10 – C13 paraffien-voerstrome, wat gebruik word in die vervaardiging van liniêre alkielbenzene, aangesien dit deaktiverend kan inwerk op alkileringskataliste. Die oorblywende oksigenate kan uit honderde komponente bestaan sodat analise van individuele komponente tot op lae ng/g vlakke nodig is. Heart-cut GC-GC word gebruik om die skeiding en verryking van die oksigenate in die alkileringsvoerstroom te illustreer. Die stationêre fase in die eerste-dimensie kolom is so gekies dat skeiding tussen oksigenate en koolwaterstowwe verkry word. Met herhaalde inspuitings verhoog die oksigenaat-konsentrasie op die cryo val en - na voldoende verryking - word die val verhit en die oksigenate geanaliseer op die tweede dimensie kolom. Die skeiding en analises verkry met Comprehensive GCxGC en Sequential GC-GC word vergelyk vir die chemiese klasse-skeiding van die alkileringsvoer (voor verwydering van oksigenate). Sikliese alkohole kan voorkom in detergent-alkohole vervaardig vanaf FT voerstrome. Dit word as onsuiwerhede beskou aangesien dit die fisiese eienskappe van die finale produkte beïnvloed. Die sikliese en nie-sikliese alkohole se kookpunte en polariteite is baie naby aanmekaar sodat skeiding van individuele komponente moeilik verkry word. Comprehensive GCxGC en Sequential GC-GC word evalueer vir die skeiding van die alkohol. Die studie toon aan dat albei die tegnieke skeiding gee van die chemiese komponent-klasse maar dat die hoë-resolusie tweede-dimensie kolom en die optimisering van die experimentele kondisies van die Sequential GC-GC sisteem beter skeiding van individuele komponente gee. Die uitsonderlike skeidingsvermoë van die drie multidimensionele tegnieke, Heart-cut GC-GC, Comprehensive GCxGC en Sequential GC-GC word geïllustreer in die studie. Elke tegniek het sy eie voordele, nadele en unieke toepassings en die drie tegnieke behoort as komplementêre eerder as kompeterende tegnieke gebruik te word.
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Mohler, Rachel E. "Discovery based yeast metabolomic analysis using comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry and chemometrics /." Thesis, Connect to this title online; UW restricted, 2007. http://hdl.handle.net/1773/11578.
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Thekkudan, Dennis. "Multidimensional Methods: Applications in Drug-Enzyme Intrinsic Clearance Determination and Comprehensive Two-Dimensional Liquid Chromatography Peak Volume Determination." VCU Scholars Compass, 2009. http://scholarscompass.vcu.edu/etd/2005.
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The goal of the first project was to evaluate strategies for determining the in vitro intrinsic clearance (CLint) of dextrorphan (DR) as metabolized by the UGT2B7 enzyme to obtain dextrorphan glucuronide (DR-G). A direct injection liquid chromatography-mass spectrometry (LC-MS) method was used to monitor products using the pseudo-first-order (PFO) model. Standard enzymatic incubations were also quantified using LC-MS. These data were fit utilizing both PFO and Michaelis-Menten (MM) models to determine estimates of kinetic parameters. The CLint was determined to be 0.28 (± 0.08) µL/min/mg protein for a baculovirus insect cell-expressed UGT2B7 enzyme. This is the first confirmation that dextrorphan is specifically metabolized by UGT2B7 and the first report of these kinetic parameters. Simulated chromatographic data were used to determine the precision and accuracy in the estimation of peak volumes in comprehensive two-dimensional liquid chromatography (2D-LC). Volumes were determined both by summing the areas in the second dimension chromatograms via the moments method and by fitting the second dimension areas to a Gaussian peak. When only two second dimension signals are substantially above baseline, the accuracy and precision are poor because the solution to the Gaussian fitting algorithm is indeterminate. The fit of a Gaussian peak to the areas of the second dimension peaks is better at predicting the peak volume when there are at least three second dimension injections above the limit of detection. Based on simulations where the sampling interval and sampling phase were varied, we conclude for well-resolved peaks that the optimum precision in peak volumes in 2D separations will be obtained when the sampling ratio is approximately two. This provides an RSD of approximately 2 % for the signal-to-noise (S/N) used in this work. The precision of peak volume estimation for experimental data was also assessed, and RSD values were in the 4-5 % range. We conclude that the poorer precision found in the 2D-LC experimental data as compared to 1D-LC is due to a combination of factors, including variations in the first dimension peak shape related to undersampling and loss in S/N due to the injection of multiple smaller peaks onto the second dimension column.
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Venter, Andre. "Comprehensive two-dimensional supercritical fluid and gas chromatography (SFCxGC)." Thesis, Pretoria : [s.n.], 2003. http://upetd.up.ac.za/thesis/available/etd-03132003-161136.
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Batista, Lilian Ribeiro. "Desenvolvimento e validação de método para determinação de etanol em xaropes utilizando headspace e cromatografia gasosa multidimensional acoplada a espectrometria de massas (HS - MDGC - MS)." Universidade Federal de Goiás, 2015. http://repositorio.bc.ufg.br/tede/handle/tede/4855.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Despite the efforts of many pharmaceutical companies to replace or reduce the content, many liquid medications still contains ethanol, which needs to have its contents regulated and monitored by quality control. Ethanol analyzes are generally carried out using one-dimensional gas chromatograph, however this technique does not always have adequate separation for the analysis of complex samples. The multidimensional chromatography has emerged as an innovative alternative because it allows the combination of two or more independent separation steps, significantly increasing the power of separation of the corresponding one-dimensional techniques. In this way, towards doing ethanol analysis in syrups for child and adult audience, a method by multidimensional gas chromatography-mass spectrometry was developed and validated for quality control purposes in the pharmaceutical industry. The analytical method developed led to a gain in selectivity by using the headspace extraction phase of ethanol in miniaturized and automated sample preparation. The use of HS-MDGC / GCMS provided a better separation of syrup components allowing to evidence that some commercial syrup have ethanol content above the maximum levels recommended by ANVISA. The method was validated according to standards established by ANVISA. The method was validated according ANVISA standards, presenting LOD 0.03% (v / v) and the LOQ of 0.06% (v / v) ethanol. The recovery values were 96.71% to 101.38%. Commercial samples of syrup in selected pharmacies in Goiânia/GO were analyzed by the proposed method and the content of ethanol in some samples was higher than maximum value allowed for this medicines.
Apesar dos esforços de muitas empresas farmacêuticas em substituir ou reduzir o teor alcoólico, muitos medicamentos líquidos ainda contém etanol, o qual precisa ter seu teor regulado e monitorado por técnicas específicas e precisas de controle da qualidade. Análises de etanol são geralmente realizadas utilizando cromatografia gasosa unidimensional, porém esta técnica nem sempre apresenta adequada separação para a análise de amostras complexas. A cromatografia multidimensional surgiu como uma alternativa inovadora, pois permite a combinação de duas ou mais etapas de separação independentes, aumentando significativamente o poder de separação das técnicas unidimensionais correspondentes. Assim, visando efetuar a análise de etanol em xaropes destinados ao público infantil e adulto, um método via cromatografia gasosa multidimensional acoplada à espectrometria de massas foi desenvolvido e validado para fins de controle de qualidade na indústria farmacêutica. O método analítico desenvolvido proporcionou ganho de seletividade pela utilização do headspace como fase extratora de etanol em sistema miniaturizado e automatizado de preparo de amostra. O uso de HS-MDGC-MS proporcionou a separação mais adequada dos componentes do xarope, permitindo evidenciar que alguns xaropes comerciais apresentam teor de etanol acima dos teores máximos preconizados pela Anvisa. O método foi validado segundo as normas estabelecidas pela Anvisa apresentando LD de 0,03% (v/v) e o LQ de 0,06% (v/v) de etanol. Os valores de recuperação foram de 96,71% a 101,38%. Amostras comerciais de xarope selecionados em farmácias de Goiânia/GO foram analisadas pelo método proposto, sendo que em algumas dessas amostras a concentração de etanol obtida foi superior aos limites máximos permitidos nestes medicamentos.
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Neto, Álvaro José dos Santos. "Cromatografia líquida multidimensional e espectrometria de massas em tandem para análise direta de fármacos em fluidos biológicos: da escala convencional à miniaturizada." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/75/75132/tde-15012008-114604/.
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A análise de fármacos e outras moléculas relacionadas em fluidos biológicos é essencial no âmbito farmacêutico. Atualmente, a demanda por análises rápidas e mais complexas impulsiona a química analítica para o desenvolvimento de soluções inovadoras. A cromatografia líquida multidimensional com acoplamento de colunas para injeção direta de fluidos biológicos tem ganhado atenção nos últimos anos. Ao mesmo tempo, o acoplamento entre cromatografia líquida e espectrometria de massas proporcionou marcante desenvolvimento científico na área biomédica e bioquímica. Esta tese apresenta os diversos estágios na redução da escala em sistemas de column switching utilizando colunas RAM, para a análise de fármacos em fluidos biológicos. Na escala convencional, com colunas de 4,6 mm de diâmetro interno, desenvolveu-se um sistema para a análise de fluoxetina em plasma. A metodologia desenvolvida foi adequadamente validada para aplicação na monitorização terapêutica, com tempo de análise de 20 minutos (incluído o preparo de amostras) e consumo de apenas 100 µL de amostra. Avaliou-se a escala microbore (2,1 mm), a qual apresentou excelente potencialidade para o acoplamento com a espectrometria de massas utilizando ionização por electrospray. Na primeira etapa em escala capilar, com colunas de 520 µm de diâmetro interno, desenvolveu-se um sistema para análise de fluoxetina em plasma. Esse sistema proporcionou análises em 25 minutos, também aplicáveis à monitorização terapêutica, consumindo poucos microlitros de amostra. Finalmente, foi desenvolvido um sistema de column switching capilar com colunas na ordem de 200 µm. Esse sistema foi acoplado à espectrometria de massas em tandem proporcionando, inovadoramente, análises altamente sensíveis e simultâneas, com baixo consumo de amostras. Um grupo de cinco antidepressivos e o albendazol, com seus produtos de biotransformação, tiveram suas análises validadas em menos de 8 minutos, consumindo menos de um microlitro de amostra. Esse sistema capilar contrasta com os sistemas convencionais comumente utilizados, os quais consomem entre centenas e milhares de vezes mais amostra para atingir a mesma detectabilidade.Analysis of drugs and other related molecules in biofluids is essential in the pharmaceutical field. Nowadays, the development of innovative solutions in analytical chemistry has been pushed by the needs for speed and more complex analysis. Lately, multidimensional liquid chromatography using column switching for direct injection of biofluids has gained attention. At the same time, liquid chromatography hyphenated with mass spectrometry provided remarkable scientific development in biomedical and biochemical area. This thesis presents the scale reduction steps in RAM column switching, for drug analysis in biofluids. In the conventional scale, using 4.6 mm i.d. columns, a system was developed, providing fluoxetine analysis in plasma. The developed method resulted in a 20 min long run, including the sample preparation step, which consumed 100 µL of sample. The method was adequately validated, being applicable to therapeutic drug monitoring. The microbore scale (2.1 mm) was evaluated, presenting great potentiality for coupling with electrospray-mass spectrometry. In the first capillary scale step, using 520 µm columns, a system was developed for fluoxetine analysis. Fluoxetine analysis was achieved in 25 min, within the application range for therapeutic drug monitoring, and consuming few microliters of sample. Finally, a RAM capillary column switching system employing columns on the order of 200 µm was developed, in an innovative way. This system was coupled with a tandem mass spectrometer, rendering sensitive and simultaneous analysis with reduced sample volume. The analysis of one group containing five antidepressants, as well as the analysis of albendazol and its metabolites was validated. These analyses took only 8 minutes and consumed less than one microliter of sample. In contrast with conventional systems, this system consumes about hundreds or thousands times less sample, with the same detectability.
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Song, Shin Miin, and shinmiin@singnet com sg. "Comprehensive two-dimensional gas chromatography (GCxGC ) for drug analysis." RMIT University. Applied Sciences, 2006. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080627.114511.
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Separation technologies have occupied a central role in the current practices of analytical methods used for drug analysis today. As the emphasis in contemporary drug analysis shifts towards ultra-trace concentrations, the contribution from unwanted matrix interferences takes on greater significance. In order to single out a trace substance with confidence from a rapidly expanding list of drug compounds (and their metabolites) in real complex specimens, analytical technologies must evolve to keep up with such trends. Today, the task of unambiguous identification in forensic toxicology still relies heavily upon chromatographic methods based on mass spectrometric detection, in particular GC-MS in electron ionisation (EI) mode. Although the combined informing power of (EI) GC-MS has served faithfully in a myriad of drug application studies to date, we may ask if (EI) GC-MS will remain competitive in meeting the impending needs of ultra-trace drug analysis in the fut ure? To what extent of reliability can sample clean-up strategies be used in ultra-trace analysis without risking the loss of important analytes of interest? The increasing use of tandem mass spectrometry with one-dimensional (1D) chromatographic techniques (e.g. GC-MS/MS) at its simplest, considers that single-column chromatographic analysis with mass spectrometry alone is not sufficient in providing unambiguous confirmation of the identity of any given peak, particularly when there are peak-overlap. Where the mass spectra of the individual overlapping peaks are highly similar, confounding interpretation of their identities may arise. By introducing an additional resolution element in the chromatographic domain of a 1D chromatographic system, the informing power of the analytical system can also be effectively raised by the boost in resolving power from two chromatographic elements. Thus this thesis sets out to address the analytical challenges of modern drug analysis through the application of high resolut ion comprehensive two-dimensional gas chromatography (GCeGC) to a series of representative drug studies of relevance to forensic sciences.
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Barqawi, Haitham [Verfasser], Wolfgang H. [Akademischer Betreuer] Binder, and Manfred [Akademischer Betreuer] Schmidt. "Multidimensional liquid chromatography coupled to soft ionization techniques : analysis of telechelic polymers ; [kumulative Dissertation] / Haitham Barqawi. Betreuer: Wolfgang H. Binder ; Manfred Schmidt." Halle, Saale : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2015. http://d-nb.info/1066645000/34.
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Leonhardt, Juri [Verfasser], and Torsten Claus [Akademischer Betreuer] Schmidt. "Development and optimization of multidimensional methods based on online comprehensive microscale liquid chromatography and mass spectrometry / Juri Leonhardt ; Betreuer: Torsten Claus Schmidt." Duisburg, 2017. http://d-nb.info/1123491194/34.
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Alawani, Nadrah. "Structural Characterization of Synthetic Polymers and Copolymers Using Multidimensional Mass Spectrometry Interfaced with Thermal Degradation, Liquid Chromatography and/or Ion Mobility Separation." University of Akron / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=akron1386591497.
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Wagner, Knut. "Development of a comprehensive on-line multidimensional high performance column liquid chromatography system for protein and peptide mapping with integrated size selective sample fractionation." [S.l.] : [s.n.], 2001. http://ArchiMeD.uni-mainz.de/pub/2001/0143/diss.pdf.
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Paudel, Liladhar. "High Field 1H Nuclear Magnetic Resonance (NMR) Spectroscopy Based Metabolomics and Complex Mixture Analysis by Multidimensional NMR and Liquid Chromatography-Mass Spectrometry (LC-MS)." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1343403647.
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Burgess, Karl. "Multidimensional liquid chromatographic separations for proteomics." Thesis, University of Glasgow, 2008. http://theses.gla.ac.uk/322/.
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Sample complexity is one of the key challenges facing contemporary proteomic analysis. A variety of methods is commonly employed to reduce this complexity, both at an intact protein and digested peptide level. For complex lysates containing many thousands of proteins, orthogonal (mutually independent), multidimensional separation methods must be employed to provide sufficient resolution to characterize the appropriate number of different species. The most common of these methods are two dimensional gel electrophoresis (2DGE) of proteins and multidimensional liquid chromatographic separation (MuDPIT) of peptides, which rely on isoelectric focusing followed by mass separation in the former, and ion exchange followed by reversed phase separation in the latter. These methods have significant drawbacks in terms of sample bias, sample preparation and reproducibility, and therefore a new methodology that combines the positive aspects of both separation technologies in an automatable, reproducible form is highly desirable. New developments in column technology have allowed rapid improved-resolution separation of intact proteins in complex samples, coupled to improved methodology for peptide and protein identification. The separation of complex protein mixtures using both on- and off-line 2D liquid chromatography using derivitized polystyrene-divinylbenzene (PS-DVB) pellicular ion-exchange resins and PS-DVB monolithic reversed-phase columns is described. Proteolytic digestion of the fractions followed by rapid liquid chromatography - tandem mass spectrometry was used to complete the analysis. An alternative methodology, relying on direct analysis of the second dimension eluents by top-down (mass spectrometric analysis of intact proteins) methodology, using an Apex IV 12 T Fourier-transform ion cyclotron resonance mass spectrometer (Bruker Daltonics) and an HCT ion trap (Bruker Daltonics) equipped with electron transfer dissociation has allowed in-depth analysis of intact proteins. Sample types investigated to establish the utility of the methodology include bacterial lysates (Bordetella parapertusis, and Escherichia coli), a eukaryotic parasite (Leishmania donovani), and transformed human cell lines. These developments lead to a multidimensional intact protein separation methodology suitable for small-sample proteomics (minimum effective protein load of 200 μg) and good reproducibility (1.5% variation in the ion exchange dimension, 0.5% variation in the reversed phase dimension). Analysis of the digested fractions gave good coverage of the proteome as well as a high predicted dynamic range, capable of detecting proteins with codon adaptation index scores ranging from 0.22 to 0.99, out of a logarithmic scale from 0 to 1. Proteins representing low (8 kDa) and high (500 kDa) molecular mass and extremes of predicted pI were identified, as well as a number of membrane proteins. Resolution of the overall protein separation was such that single protein species often occurred in one or two fractions for both the ion-exchange and reversed phase separations, with the fractions varying in complexity. Separation of modified proteins in the ion-exchange dimension demonstrated separation of isoforms. Most analyses coupled anion-exchange chromatography in the first dimension to monolithic reversed phase separation in the second dimension. To provide alternative first dimension methodologies for specific sample types, external gradient chromatofocussing (based on separation by isoelectric point) and high-pH ion-pair reversed phase were evaluated as additional techniques. In particular the pISEP (CryoBioPhysica) technique for chromatofocussing constituted an effective orthogonal separation methodology for separation, and its use in a proteomics context was compared to that of the original anion-exchange, reversed phase technology. To rapidly analyse the large number of fractions generated by the technique, bottom-up protocols required improvements in the throughput of peptide separations. PS-DVB monoliths were employed for rapid peptide separations and conditions for analysis were evaluated and optimized. The implementation of a parallel 200 μm monolith system for tryptic peptide separations ensured minimal sample loss and improved sample throughput with little loss of sensitivity. For simple mixtures, reversed-phase separation times could be reduced to a few minutes without significantly affecting data content, although rapid scanning capability is essential due to the very narrow peak widths. Quantitation is of paramount importance to any proteomic technique, and liquid chromatographic separation of intact proteins provides flexibility for differential analysis of complex samples. Three categories of quantitative analysis were evaluated for two dimensional intact protein separation by liquid chromatography: ultraviolet-absorbance maps, isotopic labeling and label-free computational analyses. UV-absorbance maps of wild-type and pentamidine resistant Leishmania donovani were compared using standard two dimensional gel electrophoresis analysis software and resulted in the identification of a small number of quantitiative differences. Modifications to the isotope coded affinity tag (ICAT) and isotope tags for relative and absolute quantitation (ITRAQ) protocols were developed to allow protein labeling prior to separation, and the related methodologies ExacTag, isotope coded protein label (ICPL) and stable isotope labels for amino acids in culture (SILAC) were evaluated. Finally, label-free techniques have been employed for protein quantitation by liquid chromatography (LC)/Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR-MS). A particular niche for liquid chromatographic separation of intact proteins is in top-down analysis, in which mass spectrometric analysis of intact proteins is performed. The separation technology was directly coupled to high-resolution FT-ICR MS for analysis of standards, mixtures, and cellular lysates, leading to the identification of an intact Leishmania protein and post-translational modification (PTM) mapping of histone H4. In addition, the recently developed electron transfer dissociation (ETD) fragmentation methods coupled with proton transfer reaction (PTR) for charge reduction allowed analysis of standards and isotopically labeled cellular lysates using an ion trap instrument. In summary, we have developed a general proteomic methodology with unique flexibility as well as applicability to top-down analysis. It has been applied to multiple complex samples in a variety of analysis conditions including quantitation methodologies and state-of-the-art mass spectrometric techniques. In general, the method equals other separation methods in terms of protein identification rates, is substantially more reproducible and automated, but is more time-consuming. Currently, two dimensional intact protein separation by liquid chromatography using polystyrene-divinylbenzene-based columns is particularly applicable to top-down analysis of heavily modified proteins. However, there is considerable remaining room for optimization and improvement of methodologies, and further development will enhance the technique for general use.
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Chappell, Colin Graham. "Multidimensional liquid and gas chromatographic methods for veterinary drug analysis." Thesis, University of East Anglia, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357971.
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Feely, Stephen Joseph. "Multidimensional chromatographic/mass spectrometric techniques for the trace determination of steroids." Thesis, Nottingham Trent University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.388946.
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Research has centred on multidimensional chromatographic techniques which utilise the high specificity of immunoaffinity chromatography for extraction of analytes from complex biological matrices. On-line immunoaffinity chromatography-high performance liquid chromatography-mass spectrometry (IAC-HPLC-MS) systems (IAC and HPLC coupled via a loop interface) were developed for the confirmatory analysis of the corticosteroids dexamethasone and flumethasone with MS detection. Utilising an atmospheric pressure chemical ionisation (APCI) LC-MS interface, dexamethasone was confirmed in both spiked and post administration equine urine samples, with a detection limit of 0.1 ug 1-l. Detection by quadrupole ion trap mass spectrometry (ITMS) using a particle beam (PB) interface was performed for dexamethasone and flumethasone in post administration equine urine samples with high precision (6.9-7.4 %) with limits of detection in the range 3-4 ug 1-l. Studies were also conducted in this work into the antibody crossreactivity and non-specific binding of corticosteroids on a HEMA bound anti-dexamethasone lAC column. On-line IAC-HPLC and IAC-HPLC-GC have been developed and assessed for the determination of testosterone in equine urine. A novel approach to interfacing lAC with HPLC being achieved using a porous graphitic carbon (PGC) column. The IAC-HPLC system developed was used for sample pre-treatment for combustion isotope ratio mass spectrometry analysis. The IAC-HPLC and IAC-HPLC-GC systems finally being coupled with mass spectrometry to enable confirmation of the endogenous steroid at 0.5 ug 1-l and 1 ug 1-l respectively in stripped equine urine.
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Bergström, Sara. "Integrated Micro-Analytical Tools for Life Science." Doctoral thesis, Uppsala University, Analytical Chemistry, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-6049.
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Advances in life science require knowledge of active molecules in complex biological systems. These molecules are often only present for a certain time and at limited concentrations. Integrated micro-analytical tools for sampling, separation and mass spectrometric (MS) detection would meet these requests and are therefore continuously gaining interest. An on-line coupling of analytical functions provides shorter analysis time and less manual sample handling. In this thesis, improved compatibility of microdialysis sampling and multidimensional separations coupled to MS detection are developed and discussed.
Microdialysis was used in vitro for determination of the non-protein bound fraction of the drug ropivacaine. The sampling unit was coupled on-line to capillary column liquid chromatography (LC) followed by ultraviolet or MS detection. For MS detection, the system was extended with a desalting step and an addition of internal standard. A method for MS screening of microdialysates, collected in vivo, was also developed. The method involved sampling and measurements of the chemical pattern of molecules that generally are ignored in clinical investigations. Chemometric tools were used to extract the relevant information and to compare samples from stimulated and control tissues.
Complex samples often require separation in more than one dimension. On-line interfaces for sample transfer between LC and capillary electrophoresis (CE) were developed in soft poly(dimethylsiloxane) (PDMS). MS detection in the LC-CE system was optimised on frequent sampling of the CE peak or on high resolution in mass spectra using time-of-flight (TOF)MS or Fourier transform ion cyclotron resonance (FTICR)MS, respectively. Aspects on electrode positioning in the LC-CE interface led to development of an on-column CE electrode. A successful method for deactivation of the PDMS surface using a polyamine polymer was also developed. The systems were evaluated using peptides and proteins, molecules that are gaining increased attention in bioscience, and consequently also in chemical analysis.
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Delmotte, Nathanaël. "Development of multidimensional liquid chromatographic methods hyphenated to mass spectrometry : Preparation and analysis of complex biological samples." Université Louis Pasteur (Strasbourg) (1971-2008), 2007. https://publication-theses.unistra.fr/public/theses_doctorat/2007/DELMOTTE_Nathanael_2007.pdf.
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Des immunoadsorbeurs ont été développés à partir de disques CIM monolithiques pour l’analyse de biomarqueurs impliqués dans des maladies cardio-vasculaires. Les colonnes développées ont permis d’isoler sélectivement la myoglobine et le NT-proBNP du sérum humain. Les colonnes anti-NT-proBNP ont permis l’isolation quantitative du NT-proBNP (R2 = 0,998) à des concentrations jusqu’à 750 amol/μL de sérum. Six matériaux à accès restreints ont été évalués en fonction de leur aptitude à exclure l’hémoglobine d’hémolysats sanguins. Des injections à différents pH ont montré que la rétention de l’hémoglobine est drastiquement restreinte à pH 10,7. En raison d’une bonne stabilité à pH basique, la colonne polymérique Biotrap 500 MS RAM a été retenue pour l’extraction d’antibiotiques d’hémolysats sanguins. Des extractions quantitatives d’analytes à faibles concentrations (200 pg/μL) ont été réalisées sans effet mémoire d’hémoglobine sur la colonne. Un nouveau système 2D-HPLC-ESI-MS/MS pour l’analyse protéomique a été développé. Le système est composé d’une séparation par RP-HPLC à pH 10,0, suivie d’une séparation par IP-RP-HPLC à pH 2,1. Ce nouveau système a été comparé à un système conventionnel SCX x IP-RP-HPLC. L’orthogonalité des méthodes de séparation est plus élevée dans l’approche SCX x IP-RP-HPLC que dans le schéma RP x IP-RP-HPLC. Cependant, en raison d’une meilleure distribution des peptides et d’une meilleure efficacité de séparation, le système RP x IP-RP-HPLC permet d’identifier significativement plus de peptides. Les deux approches sont complémentaires et une combinaison des deux systèmes permet d’identifier plus de peptides que des analyses répétées par un système uniqueImmunoadsorbers based on monolithic epoxy-activated CIM disks have been developed in order to target biomarkers of heart diseases. The developed immunoadsorbers permitted to selectively isolate myoglobin and NT-proBNP from human serum. Anti-NT-proBNP-CIM disks permitted a quantitative isolation of NT-proBNP at concentrations down to 750 amol/μL in serum (R2 = 0. 998). Six different restricted access materials have been evaluated with respect to their ability to remove hemoglobin from hemolysates. Experiments at different pH revealed that the retention of hemoglobin can be drastically diminished at pH 10. 7. Because of better chemical stability at high pH, the polymeric Biotrap 500 MS RAM column was optimized for the analysis of hemolysates. The setup permits to quantitatively extract antibiotics from whole blood hemolysates at biologically relevant concentrations (200 pg/μL), and without carry-over of hemoglobin. A new 2D-HPLC-ESI-MS/MS setup for proteome analysis was developed. It consisted of a peptide separation by RP-HPLC at pH 10. 0, followed by IP-RP-HPLC at pH 2. 1. This new setup was compared with a classical SCX x IP-RP-HPLC setup. Separation repeatability is similar with both setups. The orthogonality between methods of separation is higher in the SCX x IP-RP-HPLC approach than in the RP x IP-RP-HPLC scheme. However, the better peptide distribution and separation efficiency achieved with the RP x IP-RP-HPLC setup permitted to identify significantly more peptides than with the classical SCX x IP-RP-HPLC setup. Both approaches are complementary and a combination of both setups permits to identify more peptides than replicate injections performed with a single setup
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Hantao, Leandro Wang 1986. "Aplicação de métodos quimiométricos na investigação do metaboloma de eucalipto por técnicas cromatográficas multidimensionais e hifenadas à espectrometria de massas." [s.n.], 2014. http://repositorio.unicamp.br/jspui/handle/REPOSIP/250199.
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Orientador: Fabio AugustoTese (doutorado) - Universidade Estadual de Campinas, Instituto de Química
Made available in DSpace on 2018-08-26T03:33:38Z (GMT). No. of bitstreams: 1 Hantao_LeandroWang_D.pdf: 43243215 bytes, checksum: 64816c43abccdd0dc00de5b11a91371c (MD5) Previous issue date: 2014
Resumo: O presente trabalho é dedicado à aplicação de técnicas cromatográficas multidimensionais à problemas complexos de separação. No primeiro conjunto de estudos foram desenvolvidos métodos analíticos para investigação do metaboloma de plantas de interesse comercial. Para isso, foram utilizadas a cromatografia gasosa bidimensional abrangente (GC×GC-MS) e a cromatografia líquida de ultra eficiência (UHPLC-MS) acopladas à espectrometria de massas para aquisição do perfil metabólico de folhas de eucalipto. Logo, foram desenvolvidos modelos quimiométricos para interpretação dos dados e determinação de marcadores biológicos associados ao estresse biótico e ao fenômeno de resistência. Estes estudos permitiram aprimorar o entendimento do mecanismo de defesa de eucaliptos contra fitopatógenos. Em segundo plano, foram desenvolvidas fases estacionárias derivadas de líquidos iônicos (IL) para separação de compostos apolares por GC×GC. Para isso, foram sintetizados diversos IL derivados de fosfônio e imidazólio. A partir destes materiais foram preparadas colunas capilares pelo método estático de revestimento. Estas colunas de GC foram utilizadas na separação de analitos modelo (i.e., hidrocarbonetos alifáticos) por GC×GC. Estes ensaios visaram aprimorar o entendimento da relação entre as características estruturais dos IL e os mecanismos que governam a retenção de compostos apolares pelas fases derivadas de IL
Abstract: In the present dissertation, we discuss the application of multidimensional chromatographic techniques to solve complex problems. In the first chapter it is presented the development of chemometric strategies for data processing of metabolic data ¿ the current bottleneck of a metabolomics workflow. The case studies examined investigate the metabolome of eucalyptus leaves to address several growing concern in plant pathology, namely, prospection of orthogonal methods for early diagnosis diseases and selection of hybrids with specific phenotypes in genetic enhancement programs. To accomplish these goals, comprehensive two-dimensional gas chromatography coupled to mass spectrometry (GC×GC-MS) and ultra-high performance liquid chromatography-mass spectrometry (UHPLC-MS) were examined to generate unbiased and reliable metabolic profiles. From these experiments, it was possible to improve our understanding of the defense mechanism of plants. The second chapter addresses the limited availability of stationary phases for multidimensional gas chromatography. In this work, we evaluated ionic liquids as stationary phases for gas-liquid chromatography. The model analytes were nonpolar aliphatic hydrocarbons due to the aggravated lack of highly selective and thermally stable GC columns for their separation. From these experiments, we ascertained the structure-selectivity relationship of ILs and were able to improve our understanding on the retention of nonpolar analytes by IL-based GC columns
Doutorado
Quimica Analitica
Doutor em Ciências
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Najafi, Ali. "Application of Polymeric Ionic Liquid Solid-Phase Microextraction Sorbent Coatings and Ionic Liquid Stationary Phases for Liquid and Multidimensional Gas Chromatographic Techniques." University of Toledo / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1449846148.
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Slabizki, Petra [Verfasser], and Hans-Georg [Akademischer Betreuer] Schmarr. "Identification and quantification of cork off-flavor compounds in natural cork stoppers by multidimensional gas chromatographic methods / Petra Slabizki. Betreuer: Hans-Georg Schmarr." Duisburg, 2016. http://d-nb.info/1101343516/34.
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Delmotte, Nathanaël Van Dorsselaer Alain Huber Christian. "Développement de méthodes chromatographiques liquides multidimensionnelles couplées à la spectrométrie de masse, préparation et analyse d'échantillons biologiques complexes Development of multidimensional liquid chromatographic methods hyphenated to mass spectrometry, preparation and analysis of complex biological samples /." Strasbourg : Université Louis Pasteur, 2007. http://eprints-scd-ulp.u-strasbg.fr:8080/804/01/Delmotte_Thèse.pdf.
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Thèse de doctorat : Chimie : Strasbourg 1 : 2007. Dissertation : Naturwissenschaften der Naturwissenschaftlich-Technischen : Universität des Saarlandes : 2007.Thèse soutenue en co-tutelle. Titre provenant de l'écran-titre. Bibliogr. p. 180-88.
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Hesse, Anne-Marie. "Etude du peptidome du stratum corneum humain par une approche protéomique." Paris 6, 2009. http://www.theses.fr/2009PA066649.
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L’épiderme a pour fonction majeure de garantir à l’organisme une couche protectrice contre les agressions extérieures, via notamment la production du stratum corneum. Pour assurer cette fonction correctement, il existe un équilibre finement régulé entre les kératinocytes qui entrent en différenciation et les cornéocytes qui desquament à la surface de l’épiderme. Le phénomène de desquamation fait intervenir la dégradation des protéines des cornéodesmosomes, jonctions adhésives entre les cornéocytes. Afin de mieux comprendre ce phénomène et de caractériser les protéases impliquées, nous avons développé une approche sans a priori qui repose sur les outils de la protéomique pour l’étude des peptides endogènes. Pour cela, nous avons développé le couplage entre la chromatographie multidimensionnelle en phase liquide et la spectrométrie de masse en tandem à transformée de Fourier. Différentes approches ont été évaluées pour les analyses protéomiques. Nous avons ainsi pu mettre en évidence l’intérêt spécifique et la complémentarité de ces techniques analytiques dans l’étude de protéomes complexes. La découverte des peptides endogènes du stratum corneum a permis de montrer que les protéines des cornéodesmosomes étaient particulièrement dégradées par rapport aux autres protéines de ce tissu. Cette dégradation concerne des zones clefs pour l’adhésion des protéines entre elles. L’étude plus fine des sites de coupure observés a permis de mettre en évidence les protéases impliquées.
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Fairchild, Jacob N. "Multidimensional Liquid Chromatography Separations." 2010. http://trace.tennessee.edu/utk_graddiss/796.
Full textAbstract:
Many mixtures important to research consist of hundreds or even thousands of individual components of interest. These types of mixtures are far too complex to separate by a single chromatographic dimension in any reasonable amount of time. However, if a multidimensional approach is used, where a complex mixture is separated by an initial dimension, simpler fractions of that separation are collected and each of those fractions are analyzed individually, highly complex mixtures can be resolved in relatively short amounts of time. This dissertation serves as a guide to multidimensional chromatography, in particular, two-dimension liquid chromatography. There are many aspects of multidimensional separations that have been investigated to show its aspects, drawbacks and potential ability to separate highly complex mixtures. Measurements for the performance of multidimensional chromatography, the effects of the first and subsequent dimensions and the approaches to pairing dimensions are shown with experimental examples. Fundamental and practical features of multidimensional chromatography are explained as well as theoretical discussions on current and future multidimensional chromatography performance. Experimentally, very high peak capacities were obtained (ca. 7000) and an algorithm to predict how to best optimize a two-dimensional separation based on the time used and performance was created for designing experiments.
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Mostafa, Ahmed Mohamed. "Advances in Multidimensional Chromatography." Thesis, 2012. http://hdl.handle.net/10012/6825.
Full textAbstract:
Comprehensive two-dimensional gas chromatography (GC×GC) is among the most powerful methods used to separate complex samples. Two columns of different selectivities are coupled in series through a special interface (modulator). The main role of the modulator is to trap and/or sample the primary column effluent and inject it into the secondary column. This results in an enhanced sensitivity, increased peak capacity and structured chromatograms. Practically all thermal modulators in use today are equipped with two trapping stages to prevent problems related to analyte breakthrough, which makes their design more complicated.
In this work, The sensitivity of GC×GC coupled to two different detectors, time-of-flight mass spectrometer (GC×GC-TOFMS) and flame ionization detector (GC×GC-FID) was compared to the sensitivity of conventional one-dimensional gas chromatography (GC-TOFMS and GC-FID) by determining the limits of detection (LOD) for a series of different compounds such as n-alkanes and alcohols using both approaches. Different modulation periods were used for GC×GC ranging from 2 to 8 seconds. In addition, different types of inlet ferrules were used to study their effect on both systems. In general, the LODs in GC×GC were lower by at least an order of magnitude.
A new liquid nitrogen-based single-stage cryogenic modulator was developed and characterized. In addition, a new liquid nitrogen delivery system was developed. Band breakthrough was prevented using changes in the carrier gas viscosity with temperature to reduce the carrier gas flow during desorption. Injection band widths for n-alkanes of 30-40 ms at half height were obtained. Most importantly, even the solvent peak could be perfectly modulated, which is impossible with any commercially available thermal modulator. Moreover, the newly developed liquid nitrogen supply system reduced liquid nitrogen consumption to ~30 L per day versus 50-100 L per day for commercially available modulators. Evaluation of the newly developed system for the GC×GC separation of some real samples such as regular gasoline and diesel fuel showed that the analytical performance of this single-stage modulator rivals that of the more complicated dual-stage designs.
The technique was tested in various applications. Headspace solid phase microextraction in combination with GC×GC coupled to time-of-flight mass spectrometry (HS-SPME-GC×GC-TOFMS) were used for the detailed investigation of the impact of malolactic fermentation (MLF) using three commercial Oenococcus oeni strains on the volatile composition of Pinotage wines. The technique was also applied for the characterization of Pinotage wine volatiles and blue honeysuckle berries volatiles.
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Jacobs, MR. "Resistive heating for multidimensional gas chromatography." Thesis, 2016. https://eprints.utas.edu.au/23033/1/Jacobs_whole_thesis.pdf.
Full textAbstract:
Gas chromatography is a critical technique used for the separation of volatile and
semi-volatile samples prior to analyte detection for qualitative identification and
quantitation. The separation of samples prior to detection provides useful information
on the physical properties of analytes based on their retention within the
chromatographic system, and separating sample components prior to their detection
vastly simplifies the identification and quantitation of each component due to the
reduction in sample complexity at the point of signal transduction.
The optimisation of GC methods is crucial for ensuring high quality, timely and
repeatable separations. Often a goal of method optimisation is to minimise the time
required for an analysis while ensuring that adequate separation of target analytes is
obtained. Such optimisations are achieved through the selection of column dimensions,
stationary phase coating, carrier gas flow rate, and column temperature. While changing
the column dimensions and stationary phase properties are very effective methods for
adjusting separations, they are not programmable and require changes in hardware
configuration. The carrier gas flow rate can be manipulated via pressure control of the
carrier gas; unfortunately high carrier gas flow rates are detrimental to separation
efficiency, without offering proportional gains in the speed for analysis. Another control
parameter that is potentially very useful for high speed GC is the temperature of
analysis. Changing the temperature of analysis can vastly increase the speed of analysis
while maintaining separation efficiency.
Temperature control of GC columns has been achieved using convection ovens for
over 50 years. Convection ovens are simple to operate, safe and provide accurate control
of column temperature during moderate temperature programming rates compared to
classical alternatives such as liquid bath heating. Convection ovens simplified the
installation of injectors, GC columns and detectors due to the connectivity provided by
the heated oven cavity, which minimised solute condensation in the analyte flow path.
The main limitation of convection ovens is their large thermal mass, which can cause
thermal hysteresis during fast temperature programming. Secondly large amounts of
electrical power are required to facilitate fast temperature programming, which can be
detrimental in applications such as portable analysis. The separation column is normally
the only component that needs to be temperature-programmed during GC analysis,
while the injector and detector components are held at high isothermal temperatures to
prevent solute condensation; therefore convection ovens present a source of instrument
inefficiency.
The resistive heating of capillary columns is an alternative to convection oven based
heating that is significantly faster since only the mass of the capillary columns and
associated heating elements need be heated. There are a number of commercially
available GC instruments that offer the option of resistively heated capillary columns
however these instruments still maintain the legacy convection oven for column to
injector and detector connectivity. Commercial GC instrumentation is almost entirely
limited to bench-top laboratory analysis, with few options for portable GC analysis
systems. Portable analysis offers significant benefits over laboratory-based analysis.
Performing an analysis at the point of sampling abolishes the need for transporting
samples back to a laboratory-based facility, eliminating the time delay between
sampling and analysis. Removing the sample transport step also minimises the risk of
sample degradation or cross contamination arising from the analyte storage procedure,
time, or sample preparation steps back at the laboratory. This allows portable analysis
to provide greater confidence in the quality of measurements made compared to
laboratory analysis. Portable analysers must be robust, repeatable, simple to use, and
relatively low in cost to facilitate their deployment in the field.
The Falcon Calidus™ GC was selected as the analytical platform in this research due
to its use of resistive column heating for fast GC analysis, excellent power efficiency,
small form factor and low cost that would make it ideal for deployment in the field for
portable GC analysis.
Since the separation of complex mixtures using one-dimensional GC is generally
unfeasible due to instrument and time constraints, multi-dimensional (MD) separation
techniques were investigated as a strategy for maximising the separation capabilities of
the Calidus™ GC instrument. Specifically comprehensive two-dimensional gas
chromatography (GC × GC) was investigated due to its potential to separate a large
numbers of components without substantially increasing the time of analysis.
Resistively heated thermal modulation and flow modulation strategies using PMDs were
explored as a means to incorporate MD GC analysis techniques into the Calidus™ GC.
The Calidus™ GC instrument was evaluated and found to be capable of providing
comprehensive two-dimensional GC × GC analyses for the characterisation of a range of
complex samples, while maintaining the capability of portable analysis unlike
conventional bench top GC instruments. Additionally a novel single-stage thermal
modulator was characterised, optimised and applied for GC × GC and found to be very
effective at modulating a range of solutes without the need for the cryogenic focusing
common in commercial GC × GC modulators. PMDs were also investigated as a low cost
means of controlling injection bandwidths and providing effluent modulation in the
Calidus™ system and were found to be similarly effective compared to thermal focusing
strategies.
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Rojas, Cardona A. "Resolving dissolved organic matter : new multidimensional chromatographic approaches." Thesis, 2018. https://eprints.utas.edu.au/30225/3/Rojas_Cardona_whole_thesis_ex_pub_mat.pdf.
Full textAbstract:
This thesis focuses on the study of dissolved organic matter (DOM) as one of the earth’s largest carbon reservoirs and one of the most complex naturally occurring mixtures of organic material. DOM is a critical component on biogeochemical processes which relevance, origin, fate and chemical composition, which are still relatively poorly understood. In chapter 2, a detailed review on the on the extraction, fractionation and chemical characterization of dissolved organic matter (DOM) from seawater and freshwater sources for the rapid and effective processing of this complex sample prior to mass spectrometry (MS) and nuclear magnetic resonance (NMR) analysis is presented.
This thesis also explores new single- and multidimensional chromatographic approaches to the fractionation of DOM. Within chapter 3, a relatively new chromatographic method, high-performance counter-current chromatography (HPCCC), was applied to the study of DOM. A HPCCC method was developed for the quantification of solid phase pre-extracted low molecular weight dissolved organic matter (DOM) from natural water sources. The method was applied to the determination of the concentration of DOM in seawater and compared with traditional quantification, demonstrating a clear advantage for the determination of the amount of DOM in water by using small volumes of samples.
Detailed within chapter 4, a new separation technique based on Eleven Onyx monolithic C18 columns connected in series was developed in order to obtain a high capacity reversed- phase HPLC column providing 110,000 theoretical plates for the fractionation of the components of DOM. The method was complemented by coupling the main fractionation with a second dimension of reversed-phase HPLC and high-resolution mass spectrometry (HRMS) detection. Successful fractionation of the major compositional materials within DOM (i.e. carboxylic-rich alicyclic molecules, CRAM) in order of decreasing polarity was confirmed.
This research also seeks to provide improve pathways to the characterization of DOM by addressing the extraction of DOM from fresh and marine waters by using three different solid phase extraction (SPE) adsorbents, the selectivity of, phenyl-hexyl functionalised silica gel, a novel in house prepared adsorbent, and the commercially available polystyrene di- vinyl-benzene (PS-DVB), and octadecyl-silica gel (C-18) based adsorbents was described in chapter 5. Compositional differences between DOM extracted using the three different types of adsorbents could clearly be seen. DOM obtained from phenyl-hexyl functionalised silica proved to be richer in aromatics, aldehydes and aliphatics molecules than the other adsorbents.
Finally, within chapter 6, for the first time, the characterization of dissolved organic matter (DOM) from seafoam samples extracted via solid phase extraction SPE using C18 and PPL functionalised adsorbents was performed. The results highlight the different selectivity of the examined adsorbents and underlining the potential to isolate specific classes of compounds within complex mixtures such as seafoam. Furthermore, NMR and HRMS analysis of the seafoam samples, confirmed the presence of the following classes of compounds: aliphatics, unsaturated, aromatics, aldehydes, peptides and carbohydrates in high concentrations within DOM.
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Fornells, Vernet E. "Flow-through evaporative solvent removal and applications with chromatography." Thesis, 2018. https://eprints.utas.edu.au/30160/1/Fornells_whole_thesis.pdf.
Full textAbstract:
This thesis describes the development of a device to address solvent issues in analysis techniques and improve automation. These include the removal of solvent for preconcentration or selective removal of organic solvent in mixtures to address solvent incompatibilities.
In chapter I, a review of preconcentration techniques and applications by solvent removal is presented. Preconcentration is typically the first part of analytical method development covering the need to improve detection sensitivity. This review gathers presented strategies to accomplish preconcentration by solvent removal. Evaporation and partitioning in an immiscible fluid has been reported in a variety of forms with good control of the interfaces and accurate results. A comprehensive comparison of different approaches is presented, as well as an indication on the research needs in this area. In addition, an overview on solvent incompatibility problems for instrumental coupling is provided, which can potentially be addressed by similar solvent removal techniques.
In chapter II, the development of a temperature controlled membrane evaporation concentrator for continuous flow conditions is described. An exponential relationship was observed between temperature and concentration factor and a theoretical model was described to better understand the performance of the concentrator. Caffeine was the analyte used to construct the model which was employed to predict the concentration performance of three target analytes at different conditions. Experimentally, a 30-fold concentration can be attained in less than 60 min whilst maintaining solute integrity under different sub-ambient pressure conditions and mild temperatures. While using the model it was determined that a 10-fold concentration (±0.5) can be performed at 56.72 ± 0.07°C and at a flow rate of 10 μL min\(^{-1}\). Altogether, the model provides a better understanding of the process and its applicability to analytical methods. This work demonstrates that it is possible to obtain high concentration factors with a continuously flowing fluid when temperature is precisely controlled and in times that are reasonable compared to existing evaporation concentration procedures.
Chapter III describes a further development of the membrane evaporator as an evaporative membrane modulator (EMM) to address solvent incompatibilities in two-dimensional liquid chromatography. A feedback control mechanism was used to precisely control evaporation, adjusting temperature automatically in real time to address the need for high temperature precision described in Chapter II. In addition, the automated interface can keep evaporation constant regardless of the changing solvent content in the feed. It reduces the volume after \(^1\)D elution by a pre-determined factor, regardless of the separation solvent gradient. This volume reduction ensures that the injection volume in the \(^2\)D is appropriate for the second column, avoiding the detrimental effects of overloading. In addition, the fraction solvent composition is constant over the length of the separation increasing reproducibility of \(^2\)D separations. The evaporative membrane modulator was demonstrated with a 10-fold reduction, reducing the fraction injection volume from 50 to 5 μL. A consequence of the EMM device is a reduction in the capacity of the first dimension, which is decreased by a factor of 2.4, but the peak width at half maximum was reduced by up to 22% in the second dimension. When band broadening is considered, the corrected peak capacity with the modulator was only 10% lower than that without the modulator, but with a gain in peak height of 2-3. Also a decrease in retention time between subsequent peak-slices reduced from 4 s to be negligible. Avoiding loss of performance in the second dimension when coupling two-dimensional liquid chromatography systems shows potential to facilitate peak identification and quantitation in more complex applications.
In chapter IV, the evaporation process across the membrane is fully characterized with water/solvent mixtures showing organic solvent removal capabilities. The system allowed continuous methanol, ethanol and acetonitrile removal from samples containing up to 80% organic solvent. The use of the device is then demonstrated for on-line sample reconstitution after solvent extractions. Removal of organic solvent from sample extracts is required before analysis by RPLC to preserve chromatographic performance and allow for bigger injection volumes, boosting sensitivity. An automated on-line extraction evaporation procedure is integrated with HPLC analysis, applied to analysis of the antibiotic chloramphenicol in milk samples. Sample reconstitution and HPLC injection is performed in less than 10 min and can be executed simultaneously to HPLC analysis of the previous sample in a routine workflow, thus having minimal impact on the total sample analysis time when run in a sequence.
The developed device shows great potential to aid automation and address instrumental coupling issues arise from solvent incompatibilities. Advantages and further development options for this technology are discussed.
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George, Olivia Kaye. "Utilization of a derivatization method with multidimensional liquid chromatography-mass spectrometry for the detection of neurotransmitters." Thesis, 2020. https://hdl.handle.net/2144/42148.
Full textAbstract:
Neurotransmitters are endogenous compounds located in the brain and can occur in other parts of the body at low concentrations. They are a challenging group of compounds when it comes to analysis. Compounds with amine functionality such as dopamine and serotonin are sensitive to high pH and light and can spontaneously oxidize and degrade. Since neurotransmitters exist at low levels, it can be difficult to achieve sufficient spectrometry data and clean chromatography. In order to improve data acquisition, derivatization and the use of multidimensional liquid chromatography (2D-LC) was evaluated. Dopamine, L-3,4-dihydroxyphenylalanine (L-DOPA), serotonin, tyrosine, tryptophan, and noradrenaline were the compounds of interest with tyramine included as an internal standard. Data was collected before and after derivatization to compare the resulting chromatography. Chromatography was completed using a 6x6 grid of methods with variables of organic solvent, elution pH, loading pH, and trapping column chemistry utilizing different elution column chemistries. Derivatization was examined with Dabsyl-Cl and Dansyl-Cl at pH 8.5, 9.5, 10.5, and 14. A final method was chosen with Dabsyl at pH 8.5 for the Multiple Reaction Monitoring (MRM) scans. Before derivatization, the chromatography had poor peak shapes such as tailing, fronting, or shouldering or too much distortion to be able to distinguish a peak for all of the examined methods. Resulting chromatography after derivatization showed overall improvement in peak shape and intensity for a majority of the methods. Derivatization aided in increasing the mass and stability of the compounds which allowed for more sensitive detection. Multidimensional liquid chromatography improved the separation of structurally similar compounds and increased sensitivity. By combining the two, better analysis of neurotransmitters was possible.
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Ranjbar, Shourabi L. "Multidimensional separation approaches for complex sample analysis : two-dimensional ion chromatography ✕ capillary electrophoresis." Thesis, 2017. https://eprints.utas.edu.au/23920/1/Ranjbar_Shourabi_whole_thesis.pdf.
Full textAbstract:
The work presented in this thesis describes development, evaluation and implementation of an online interfacing/modulation technique for comprehensive two-dimensional ion chromatography ✕ capillary electrophoresis (IC ✕ CE) separation of low-molecular-mass ionic or ionogenic compounds.
Chapter 1 provides an insight into the evolution of multidimensional liquid-phase separations combining both chromatography and electrophoresis from inception in 1948 to present. As noted in this chapter, column-based multidimensional electrophoretic and chromatographic separations have shown to be powerful complementary techniques to the traditional two-dimensional gel-electrophoresis approaches; especially for the analysis of lower molecular-mass-molecules in addition to proteins and peptides. However, complexities in instrumentation and online
interfacing technologies are known to have hindered development of such techniques.
Chapter 2 introduces a non-focusing interfacing technology for online hyphenation of ion chromatography with capillary electrophoresis. The system compromised of an in-house sequential-injection capillary instrument which, through the use of a two-position six-port injection valve, allowed comprehensive sampling of the IC effluent for quantitative analysis of inorganic anions and haloacetic acids in water.
In addition to instrumental developments, the second section of this thesis focuses on alternative method development approaches for screening/optimisation of IC ✕ CE separations.
Chapter 3 demonstrates the impact of background electrolyte pH on sample dimensionality and peak capacity for IC ✕ CE separation of multi-valent lowmolecular-mass organic acids. In this chapter, a simplified screening approach based on calculation and maximising of Euclidean distance between the two-dimensional peaks was used to predict the optimal background electrolyte pH in CE as well as the eluent profile in IC. However, due to lack of overall two-dimensional selectivity, further investigations were necessary to make full resolution of the analytes possible.
In Chapter 4, based on a ground set by the findings presented in Chapter 3, a universal framework is proposed for simultaneous screening of separation selectivity in both dimensions as a preceding step in method development/optimisation of twodimensional separations. In this chapter, through the introduction of the concept of
two-dimensional selectivity mapping, effect of stationary phase in IC and background electrolyte pH in CE on the overall two-dimensional separation selectivity was studied to enable full resolution of the organic acids.
Finally, Chapter 5 of this thesis discusses the limitations of IC ✕ CE and provides further insight and direction for future research.
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Benvenuto, Kayla. "Analysis of synthetic cannabinoids in urine, plasma, and edibles utilizing multidimensional liquid chromatography tandem mass spectrometry." Thesis, 2017. https://hdl.handle.net/2144/26594.
Full textAbstract:
Synthetic cannabinoids (SCs), present a multitude of problems in terms of maintaining up-to-date, reliable, specific, and sensitive methods of detection. Synthetic cannabinoids are novel psychoactive substances originally synthesized for medical use and research purposes. Abuse of these compounds, however, has demonstrated a variety of effects ranging from euphoria to aggressive behavior and loss of consciousness. The most dangerous reported result of synthetic cannabinoids use has been death. The number of synthetic cannabinoid compounds detected drastically increased from two to over 80 compounds within six years. The marketing of these compounds, similar naming, and described pharmacological interactions, create the dangerous and very false perception that SCs are similar to, or the same as, tetrahydrocannabinol in cannabis products.
This research focused on the development of a method to detect and quantify seven synthetic cannabinoids in urine, plasma, and gummy bears. The seven synthetic cannabinoids studied include XLR-11, AB-PINACA 5-pentanoic acid metabolite, UR-144 5-pentanoic acid metabolite, 5F-PB-22, AM-2201 4-hydroxypentyl metabolite, JWH-018, and JWH-018 5-hydroxypentyl metabolite. Sample preparation methods and a two dimensional liquid chromatography tandem mass spectrometry method were optimized and developed for analysis of the seven SCs in each matrix. The method was successfully applied to 17 authentic urine case samples previously screened positive for synthetic cannabinoids and a calibration curve for each matrix was generated from spiked samples at varying concentrations. Utilizing two-dimensional (2D) chromatography for the analysis of synthetic cannabinoids allowed for a novel approach to be employed. With this method, 100% organic samples were analyzed with improved resolution and increased sensitivity.
The sample preparation method for the urine and plasma samples included a protein precipitation technique with acid followed by solid phase extraction (SPE) on a mixed-mode reversed phase strong anion exchange sorbent. The spiked gummy bear samples were prepared in 50% methanol in water, dissolved by heating, and extracted with SPE on the same sorbent used for the urine and plasma samples. A 200µL injection of the 100% MeOH extracts was injected into 2D-LC-MS/MS for analysis with a loading and diluting solvent consisting of water and 2% ammonium hydroxide and elution solvents containing water or methanol with 0.5% formic acid. These conditions were optimized with an automated method development protocol assessing various conditions such as mobile phase solvents, pH additives, and trap column chemistries. The final chromatography method utilized an ACQUITY ultra performance liquid chromatography (UPLC) ethylene bridged hybrid (BEH) C8 2.1 x 30mm, 10µm trap column and an ACQUITY UPLC high strength silica with tri-functional C18 bonding (HSS T3) analytical column 2.1 x 150mm, 1.7µm.
The urine calibration curve produced had a linear dynamic range (LDR) of 0.05-2.5ng/mL for UR-144 5-COOH and AB-PINACA 5-COOH and 0.05-5ng/mL for the other five synthetic cannabinoids. R2 values included 0.992 and 0.993 for UR-144 5-COOH and AB-PINACA 5-COOH, respectively and 0.995 or above for the other five compounds. Synthetic cannabinoids were detected at varying concentrations in all 17 urine case samples. Analysis of plasma and gummy bear samples was also successfully carried out. Plasma calibration curves had a LDR 0.05-10ng/mL with all R2 values above 0.995. Gummy bear calibration curves produced a LDR of 0.05-10ng/mL or 0.05-2.5ng/mL with R2 values over 0.995. All extraction recovery values were greater than 80% with the exception of 63% recovery for AB-PINACA 5-COOH in the gummy bear matrix. Suppression effects of 8%, 19%, and 6.6% were observed for urine, plasma, and gummy bears, respectively. Relatively low recovery values, reduced linear dynamic ranges, and suppression matrix effects for the carboxylic acid analytes assessed in this research suggested an alternative approach may be more successful for the analysis of these particular compound types in all three matrices. Overall, a sensitive, specific, and reliable method was developed with low limits of detection and quantification for efficient and rapid analysis of compounds at trace levels utilizing 2D-LC-MS/MS.
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Raust, Jacques-Antoine. "Development of multidimensional Chromatography for complex (METH)Acrylate-based Copolymers used in cosmetic Applications." Phd thesis, 2008. http://tuprints.ulb.tu-darmstadt.de/1223/2/PhD_thesis_Raust.pdf.
Full textAbstract:
The fast growing cosmetic market and the need for innovative products with new or combined properties lead to the development of a large variety of new complex polymer materials. The variations which can be achieved by modifying the monomer composition or the method of synthesis are very useful to produce (co)polymers with peculiar properties. The demand in characterization is then very important to understand the molecular structure of these new products in order to relate them with the observed properties aiming at the establishment of structure-property relationships. Such knowledge allows for optimization of the parameters of the synthesis and consequently the final application properties. The aim of this work was to develop analytical methods and tools to comprehensively characterise the heterogeneities of acrylate- and methacrylate-based copolymers. The focus of the method development was on multidimensional chromatographic techniques that allow the different parameters of molecular heterogeneity (e.g. molar mass distribution, MMD, chemical composition distribution, CCD) to be described quantitatively.
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MAIMONE, MARIAROSA. "Development of sample-tailored gas chromatography strategies involving one, two and three analytical dimensions." Doctoral thesis, 2017. http://hdl.handle.net/11570/3104258.
Full textAbstract:
The scope of modern gas chromatography (GC) analysis is to qualitatively and
quantitatively characterize the profiles of complex samples, such as foods,
fragrances, petrochemicals, etc. If the objective is connected to sensory analyis,
then the purpose is to recognize and prioritise target organoleptically-interesting
molecules, and distinguish them from other volatiles that may not have
relevance to the overall odour of a sample.
The research work carried out during the three years of the PhD course in
Chemistry Sciences can be placed within such contexts. In such a broad field of
science separation, I have dealt with a number of innovative techniques, such as
preparative (heart-cutting) multidimensional chromatography for the isolation
and identification of highly-pure compounds; use of flow-modulated
comprehensive two-dimensional gas chromatography (FM GC×GC) with
different detectors as a powerful tool for the characterization of complex
samples.
Finally, during the last year of PhD course, I approached sensorial analysis,
exploring the use of gas chromatography-olfactometry (GC-O) for the
determination of odour-active compounds in food samples.
With regard to preparative chromatography, a lab-constructed system composed
of one liquid and three GC systems was used for the isolation of the most
important sesquiterpenes belonging to sandalwood essential oil [1].
With regard to FM GC×GC, the studies are related to fragrances [2], bio-diesel
[3], and an essential oil [4].
Finally, GC-O was exploited for the determination of the odour-active
compounds belonging to Heracleum transcaucasicum [5].
As can be derived from the brief description, during the three-year research
period one-, two-, and three-dimensional GC methods have been developed
with fine tuning for various analytical scopes.