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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
11

Analysis of Small Biomolecules by Esi- and Maldi-Mass Spectrometry

Pilus, Rashidah 02 1900 (has links)
This thesis describes the use of mass spectrometric methods based upon electrospray ionization, ESI, and (matrix-assisted) laser desorption/ionization, (MA)LDI, for the quantitative analysis of small biomolecules. Structure analysis when required, was obtained through tandem mass spectrometry (MS/MS). The Girard type reagent, 4-hydrazino-4-oxobutyl tris(2,4,6 trimethoxy)phenyl phosphonium bromide, in combination with the solid phase derivatization technique, is used to selectively prepare a pre-ionized malondialdehyde derivative to be analyzed by MALDI or LDI. The in situ derivatization and isolation minimize interferences from other components in biological samples. The combination of pre-ionization and aromatic functionalities allows for laser induced ionization without the need of matrix. The combination of these techniques provides an avenue for development of automation to produce a high throughput method of analysis. Chapter 3 involves the study of the complexation of diols to the oxovanadium ion. The oxovanadium (IV) complex of ethylene glycol is used as a reference to study the complexation of other diols and amines with the vanadyl ion. The ES spectra of various diols studied produce intense signals for the mixed and the analyte complexes, indicating effective complexation of the analytes with the vanadyl ion. Oxovanadium (IV) is observed to be more selective for complexation to diols than amines. This eliminates the possibility of interference from N-containing ligands to the detection of diols by the reference complex. The electrospray spectrum is used for quantitation and the tandem mass spectrometry spectrum for structure confirmation. The MS/MS spectrum also assists the identification of the diols by the structural differences within their isomers. The equilibrium constant of a set of diols was determined and its calibration curve were constructed. This study produces an alternative method to detect and quantify diols in aqueous solutions and blood samples. / Thesis / Master of Science (MSc)
12

Characterization of Ionic Liquid As a Charge Carrier for the Detection of Neutral Organometallic Complexes Using Electrospray Ionization Mass Spectrometry

Joshi, Ubisha 08 1900 (has links)
A novel application of ionic liquid as a charge carrier for the analysis and detection of neutral organometallic complexes using a mass spectrometer has been presented. The mass spectrometer detects only charged compounds which raise a difficulty in analyzing a neutral molecule that lacks a basic site to associate with charge. Therefore, an effective way of providing charge has always been an area of keen interest in the field of mass spectrometry. Ionic liquids have a very fascinating property of forming a cation-? interaction with other molecules to give a charged complex. In order to take advantage of this, it is important to know the geometric structure of the complex. Advanced methodologies like hydrogen-deuterium exchange and computational calculations have been used assisting in better understanding of the structure of the ionic liquid complexes.
13

Development of Gas Chromatography/Electrospray Ionization Mass Spectrometry for the Characterization of Volatile Organic Mixture

Chen, Jiun-Chi 13 July 2010 (has links)
none
14

Identification and Quantification of selenium-containing compound in dietary supplement and arsenic-containing compound in seaweed by HPLC-ICP-MS and HPLC-ESI-MS

Hsieh, Yu-Jhe 20 July 2011 (has links)
none
15

Determination of Selenium Compounds in Dietary Supplements and Foods Using Ion-pair Reversed-phase and Anion-exchange Chromatography ICP-MS and ESI-MS

Lin, Yi-Chun 22 July 2012 (has links)
none
16

Development of Ambient Mass Spectrometry for The Detection of Drug and Small Biological Compound

Liu, Jia-jiun 11 July 2007 (has links)
none
17

Statkraft Hydro Power Plants – Oil Spills and Valuable Areas

Enzenhofer, Klaus January 2014 (has links)
Currently, Statkraft knows that they have oil spills from their hydraulic system, but the problem is that the amount of the oil spilled is not clear. Furthermore, Statkraft is missing a tool that can be used when decisions need to be made on what power plants that should be prioritized to be renovated next or which oil system that they should be switched to. In order to answer these points a look has been taken onto the environmental effects and the amount of oil spilled from hydropower plants, the general oil system inside a power plant, and in Kaplan turbines. Furthermore, two maps were developed: one presenting areas of interest for humans and environment around the hydropower plants and a second map about the river shorelines sensitivity to oil spills represented in form of an ESI ranked river shoreline. The maps give a general overview and can be used as a starting point to include environmental aspects into the planning and decision making process. The outcomes of the study are that more detailed information about the amount of oil spills released in small amounts from the turbines is needed. The catchment areas, where Statkraft Sverige AB has hydropower plants, which are most sensitive to oil spills, are Moälven and Nätraån. The hydropower plant with the most sensitive river shoreline is the Stennäs power plant due to a large wetland close by. Those areas should therefore be prioritized in projects about reducing the amount of oil inside Statkraft`s hydropower plants.
18

Mass spectrometric investigations into free radical polymerisation reaction mechanisms

Hart-Smith, Gene On, Chemistry, Faculty of Science, UNSW January 2009 (has links)
Contemporary mass spectrometry (MS) instrumentation featuring electrospray ionisation (ESI) or matrix-assisted laser desorption/ionisation (MALDI) ion sources were used to characterise the polymer distributions generated in various free radical polymerisations, allowing insights to be gained into the reaction mechanisms operating in these systems. In studying atom transfer radical polymerisation (ATRP) mediated star polymerisations of methyl acrylate (MA), ESI was found to be more effective in obtaining a comprehensive list of the distinct products present in the samples under investigation when compared to the employed MALDI technique. Furthermore, these studies showed that terminal Br losses observed at relatively high monomer to polymer conversions could be accounted for via mechanisms involving the acetone derived radicals (CH3)2??OH, ??H3 and ??H2COCH3. Through the use of ESI, it was found that for bulk polymerisations of MA and aqueous media polymerisations of N-isopropylacrylamide (NIPAAm) initiated using 60Co ??-irradiation and mediated via reversible addition-fragmentation chain transfer (RAFT), hydrogen radicals formed via the radiolysis of RAFT agent and/or monomer, and in the case of the NIPAAm system, water, are capable of initiating the polymerisations. In the NIPAAm polymerisations under scrutiny, it was also observed that hydroxyl radicals generated via the radiolysis of water may contribute towards the initiation process, and that propagating chains can potentially become terminated via trithiocarbonate cleavage reactions. By using ESI instruments to characterise oligomer samples produced via the free radical polymerisations of vinyl phosphonates, it was observed that chain propagations are initiated via activated monomer radicals, which likely form as a result of transfer reactions involving initiator fragments and vinyl phosphonate monomer units. Transfer to monomer reactions were suggested to limit chain growth in these systems, and evidence was also found for scission reactions involving alkoxy moieties which are formed via intramolecular methine carbon abstraction reactions. Characterisation of the polymer distributions generated in R-group approach RAFT MA star polymerisations using an ESI instrument allowed formation processes operating in acrylate star living/controlled radical polymerisations (CRPs) to be ascertained. Initiator fragment derived linear chains, ideal stars, star-star couples, and terminated star products formed as a result of disproportionation and combination reactions were detected. Evidence for mid-chain radical (MCR) derived reaction pathways was also observed; specifically, for termination reactions involving intermolecularly formed MCRs on both star arms and linear chains, and for re-propagation of intermolecularly formed MCRs on star arms.
19

Perfil Químico Associado ao Diferentes Estádios de Maturação do Abacaxi cv. Vitória Por ESI(-)-FT-ICR MS e Estudo de Suas Atividades Biológicas na Químioprevenção de Câncer

OGAWA, E. M. 23 March 2016 (has links)
Made available in DSpace on 2016-08-29T15:35:42Z (GMT). No. of bitstreams: 1 tese_9765_Elizângela Monteverde Ogawa.pdf: 2598194 bytes, checksum: 1787eb1dd5c33a454217a32f9cdaa732 (MD5) Previous issue date: 2016-03-23 / O abacaxi é o fruto do abacaxizeiro (Ananas comosus (L.) Merril), uma planta de clima tropical, perene, monocotiledônea, pertencente à família Bromeliaceae.1 O fruto é constituído por 100 a 200 frutilhos fundidos entre si sobre um eixo central. O sabor característico doce/azedo o torna amplamente apreciado pelos consumidores em todo o mundo. Além disso, ele também é usado por seus efeitos medicinais por apresentar a bromelina, uma enzima proteolítica com atividades farmacológicas, tais como anti-inflamatórias e inibição da agregação plaquetária. Além dessa protease, polissacarídeos são outras macromoléculas responsáveis pelos benefícios do abacaxi. A fibra da casca do fruto pode encurtar o tempo de trânsito gastrointestinal e melhorar o crescimento de pro-bióticos no intestino.2 Trata-se de uma fruta que possui elevado teor energético, devido à sua alta composição de carboidratos, e valor nutritivo pela presença de sais minerais (cálcio, potássio, fósforo, magnésio, sódio, cobre e iodo) e de vitaminas, principalmente ácido ascórbico, niacina, tiamina, riboflavina.1 O fruto é utilizado tanto para o consumo in natura quanto industrializado, em diferentes formas: pedaços em calda, suco, pedaços cristalizados e geleias.
20

Lipidome LC/MS Analysis in the Insect Adaptation and Development Studies / Lipidome LC/MS Analysis in the Insect Adaptation and Development Studies

TOMČALA, Aleš January 2009 (has links)
Insects represent very useful experimental model in various branches of biological research. The investigation is driven by economic importance of many insect species, and also by biological features of insects as model organisms such as short period of reproduction, easy breeding and manipulation and, in particular, the minimal regulatory requirements which are associated to the management of vertebrates. Here we report robust and efficient LC/MS/MS methodology for the determination of the physiologically important lipid molecular species in insects. The target metabolites represent polar glycerophos-phopholipids (GPL) and nonpolar lipids diacylglycerols (DG) and triacylglycerols (TG). Combination of the LC/MS data with the subsequent GC fatty acid analysis enables complete structural elucidation of particular lipid species including their fatty acid compositions. The developed methodology was applied to studies of the chill tolerance of the firebug Pyrhocorris appterus. Fields and laboratory experiments were conducted to separate the triggering effects of low temperature, desiccation and diapause progression on the physiological characteristics related to chill tolerance with emphasis on the restructuring of GPL composition. The same effect on the GPL composition was observed during acclimatization in the field and cold acclimation in laboratory. By contrast, the GPL changes related to desiccation and diapause progression were relatively small (Tomčala et al, 2006). In adults of Drosophila melanogaster it has been found that acclimation at 15, 20 and 25°C during preimaginal development affects thermal tolerance and composition of membrane GPLs. Low temperature acclimation was associated with increase in proportion of ethanolamine at the expense of choline in GPLS. Relatively small, but statistically significant changes in lipid molecular compositon were observed with decreasing acclimation temperature (Overgard et al, 2008). Hormonal treatment studies on insect model Locusta migratoria showed a heterogeneous distribution of individual DGs in haemolymph after the hormone application and revealed that mobilization of the DGs is molecular species-specific with the highest proportion of DG 16:0/18:1 and forming in summary about 20% of the total mobilized DG content. Additional analysis of fat body triacylglycerols revealed that the AKH mobilizes the DGs specifically with the preference of those possessing the unsaturated C18 fatty acids (FAs). The fat body FAs with more than 18 carbons did not participate on the mobilization (Tomcala et al, 2009). The LC/MS methodology was further applied to lipid composition studies of several samples with very diverse biological origin (fish, human blood etc.) and was proved to be universally applicable to the wide scope of biological samples.

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