The ochratoxins, metabolites of certain Aspergillus and Penicillium species are the first group of mycotoxins discovered subsequent to the epoch-making discovery of the aflatoxins. Ochratoxin A (OTA) is a very important mycotoxin owing to its frequent occurrence in nature, its established role in Danish porcine nephropathy and in poultry mycotoxicoses and its implicated role in Balkan endemic nephropathy and urinary system tumors among population groups in North Africa. Chapters 2 and 3 highlight the importance of OTA and the research currently being done on mycotoxins. These efforts are focused on the molecular genetics of toxinogenic fungi; the mechanism of their action; species differences in metabolism and pharmacokinetics; quantification of mycotoxins; risk assessments on the exposure of man and animals to mycotoxins and regulations for the control of mycotoxin contamination. Methods developed to analyse OTA in different matrices by using reversed phase high performance-liquid chromatography with fluorescence detection and tandem liquid chromatography-mass spectrometry techniques are described in Chapter 10. Amino propyl solid phase extraction columns were used for the first time in cleanup steps of ochratoxin analysis. These techniques and methods were applied to the first survey on the levels of OTA in coffee on the South African retail market (Chapter 5). The results suggest that the levels of OT A in the coffee on the South African market are somewhat higher than the levels of OTA in coffees on the European market. The possibility to biologically produce different halogen-ochratoxins by supplementing the growth medium of Aspergillus ochraceus with halogen salts was investigated. Bromoochratoxin A was produced for the first time in this way. Supplementation of inoculated wheat with potassium iodide and -fluoride resulted in the poisoning of the yeast and no iodoor fluoro-ochratoxin B was produced. It was found that Aspergillus ochraceus produced OTA in higher yields at elevated levels of potassium chloride. This finding has important commercial applications in the production ofOTA (Chapter 4). The ochratoxins are hydrolyzed in vivo by carboxypeptidase A. The hydrolysis of the ochratoxins and analogues by carboxypeptidase A was measured in vitro in a structurefunction relation study by employing mass spectrometric techniques. The kinetic data of the ochratoxins were compared to the values of a number of synthesized structural analogues. It was found that the halogen containing analogues had lower turnovers than their des-halo analogues. There were no substantial differences in the kinetic data between the different halogen containing analogues (Chapter 8). The toxicokinetics of OTA in vervet monkeys were determined for the first time. The clearance of OTA from the plasma suggested a two-compartment model and the elimination half-life was determined to be 19-21 days. The half-life of OTA in humans was determined by allometric calculations to be 46 days. We came to the conclusion that the long term consumption of OT A contaminated foods will lead to potentially hazardous levels of the toxin in the body (Chapter 9). This hypothesis can be substantiated by the incidence of OTA in the blood of various population groups. Possible ways to decontaminate OT A contaminated foods by degrading the compound biologically with yeast; moulds or lipases to non-toxic compounds were investigated. Eight moulds, 323 yeasts and 23 lipases were screened for ochratoxin degradation. A lipase from Aspergillus niger is the first lipase that was proven to degrade OTA (Chapter 7). Four yeasts were found to degrade OT A of which one, Trichosporon mucoides degraded OTA substantially within 48 hours in a growing culture (Chapter 6). In addition to this first report of yeasts which have the ability to degrade OTA, the fungi Cochliobolus sativus, Penicillium islandicum and Metarhizium anispoliae also proved to degrade OT A. OT A was degraded in all instances to the non-toxic ochratoxin a and the amino acid phenylalanine. / Thesis (PhD (Chemistry))--Potchefstroom University for Christian Higher Education, 2000

Infrared multiple photon dissociation (IRMPD) spectroscopy has been coupled with electronic structure calculations in order to elucidate the structures of several small biological molecules including: uracil, 5-fluorouracil, 5-fluorocytosine, ferulic acid, and a number of their related analogs. IRMPD is a powerful technique, that when combined with electronic structure calculations can provide convincing evidence for the structural characterization of ions in the gas phase. Isomers of uracil and 5-fluorouracil (5-FU) have been characterized by calculations performed at the MP2(full)/aug-cc-pVTZ level of theory; however, infrared multiple photon dissociation spectroscopy experiments proved to be unsuccessful for these species. Geometry optimization and frequency calculations have isolated the dominant isomer(s) for neutral and deprotonated uracil and 5-fluorouracil, along with several cluster interactions involving water, methanol, ammonia, and methylamine. For both uracil and 5-FU, a single relevant neutral isomer was determined, with each isomer existing in the diketo, as opposed to the enol form. Following the deprotonation of this neutral isomer, both uracil and 5-FU were permitted to form anionic cluster ions with water, methanol, ammonia, or methylamine, and based on the relative Gibbs free energies (298 K) of the calculated isomers, relevant cluster interactions were determined. For each cluster, several sites of intramolecular interaction were found to exist; however, interaction at the site of deprotonation was the most favourable in every instance. Ionic hydrogen bond interactions have been found in several clusters formed by 5-fluorocytosine (5-FC). The chloride and trimethylammonium cluster ions, in addition to the cationic and anionic dimers have been characterized by infrared multiple photon dissociation (IRMPD) spectroscopy and electronic structure calculations performed at the B2PLYP/aug-cc-pVTZ//B3LYP/6-311+G(d,p) level of theory. IRMPD spectra in combination with calculated spectra and relative energetics have indicated, quite conclusively, that a single isomer for each 5-FC cluster that is likely being observed experimentally except in the case of the anionic dimer, in which a combination of isomers is probable. For the 5-FC-trimethylammonium cluster specifically, the calculated spectrum of the lowest energy isomer matches the experimental spectrum remarkably well. Interestingly, the cationic dimer of 5-FC was found to have a single energetically relevant isomer (Cationic-IV) in which a unique tridentate ionic hydrogen bond interaction is formed. The three sites of intramolecular ionic hydrogen bonds in this isomer interact very efficiently, leading to a significantly large calculated enthalpy of binding of 180 kJ/mol. The magnitude of the calculated binding energy for this species, in combination with the strong correlation between the simulated and IRMPD spectra, indicates that the tridentate-bound dimer is observed predominantly in experiment. Comparison of the calculated relative Gibbs free energies (298 K) for this species with several of the other isomers considered also supports the likelihood of the dominant protonated dimer existing as Cationic-IV. Protonated ferulic acid has been characterized using infrared multiple photon dissociation spectroscopy and electronic structure calculations at the B3LYP/6-311+G(d,p) level of theory. Neutral ferulic acid has been determined to undergo protonation on the carbonyl oxygen of the acid group, forming an ion of m/z 195. Due to its extensively conjugated structure, protonated ferulic acid (m/z 195) is observed to yield three stable fragment ions in IRMPD experiments. It is proposed that two parallel fragmentation pathways of protonated ferulic acid are being observed. First, proton transfer occurs from the carbonyl oxygen to the hydroxyl oxygen within the acid group, resulting in the loss of water and subsequently carbon monoxide, forming ions of m/z 177 and 149, respectively. The second proposed fragmentation pathway undergoes proton transfer from the phenolic group to the methoxy group resulting in loss of methanol and rearrangement to a five-membered ring of m/z 163. IRMPD spectra have been obtained for the ions m/z 195 and m/z 177, and anharmonic calculations have been performed on these species at the B3LYP/6-311+G(d,p) level of theory. The calculated anharmonic spectra for these ions match the experimental spectrum exceptionally well and strongly support the proposed fragmentation mechanisms.

Thesis (Ph.D.)--Ohio University, March, 2010. / Title from PDF t.p. Includes bibliographical references.

Mass spectrometry was used to study two disparate transformations: in an applied project, the supposed degradation of perfluorooctanesulfonate (PFOS); and in a fundamental study, the Suzuki-Miyaura (SM) reaction was investigated in detail. The first investigation revealed that published methods to degrade PFOS were ineffectual, with apparent decreases being associated with adsorption onto available surfaces. In the Suzuki-Miyaura reaction, a dynamic series of equilibria were observed, and there is no direct evidence of a single pathway. Instead, there appear to be two mechanisms which are active in different conditions (one fluoride, one aqueous). Studies were initiated into the related SM polycondensation reaction and the hydrolysis of aryltrifluoroborates, the former indicating a step-growth mechanism, and the latter indicating a dynamic series of equilibria which are very sensitive to experimental conditions. Processing and interpretation of mass spectrometric data was a significant part of all of these projects, so a python framework was developed to assist in these tasks and its features are also documented herein. / Graduate / 0488 / 0486 / larsy@uvic.ca

The goal of this project was to develop a rapid separation and detection method for analyzing organic compounds in smokeless powders and then test its applicability on gunshot residue (GSR) samples. In this project, a total of 20 common smokeless powder additives and their decomposition products were separated by ultra performance liquid chromatography (UPLC) and confirmed by tandem mass spectrometry (MS/MS) using multiple reaction monitoring mode (MRM). Some of the targeted compounds included diphenylamines, centralites, nitrotoluenes, nitroglycerin, and various phthalates. The compounds were ionized in the MS source using simultaneous positive and negative electrospray ionization (ESI) with negative atmospheric pressure chemical ionization (APCI) in order to detect all compounds in a single analysis. The developed UPLC/MS/MS method was applied to commercially available smokeless powders and gunshot residue samples recovered from the hands of shooters, spent cartridges, and smokeless powder retrieved from unfired cartridges. Distinct compositions were identified for smokeless powders from different manufacturers and from separate manufacturing lots. The procedure also produced specific chemical profiles when tested on gunshot residues from different manufacturers. Overall, this thesis represents the development of a rapid and reproducible procedure capable of simultaneously detecting the widest possible range of components present in organic gunshot residue.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第22775号 / 工博第4774号 / 新制||工||1747(附属図書館) / 京都大学大学院工学研究科材料工学専攻 / (主査)教授 邑瀬 邦明, 教授 杉村 博之, 教授 宇田 哲也 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Mass spectrometry (MS) has become a widely used technique for the characterization of a wide range of substances in diverse fields. The selection of appropriate ionization techniques, source parameters, charge carriers based on the analyte’s polarity is essential in MS as only the ions are detected. When using a soft ionization technique, single stage-MS at best provides only chemical composition; thus, tandem MS is needed to determine structural information and dissociation pathways. This dissertation focuses on the characterization of various small molecules and ions using different ionization techniques, charge carriers, and collision-induced dissociation (CID). In Chapter II, commercially available ionic liquid (IL) cations, specifically imidazolium-based IL cations with different side-chain chemistries, were characterized by CID-MS. The imidazolium-based IL cations have diverse dissociations pathways depending on the nature of the side chain (aliphatic or aromatic) or the functional groups (allyl, vinyl, alcohol, methoxy, nitro) present on the side chain. Additionally, it was observed that some IL cations undergo thermal degradation under normal operating temperatures of electrospray ~275 °C. A variety of experimental and complementary computational chemistry results are presented. In Chapter III, cis-3-hydroxyproline (c3hPro) and cis-4-hydroxyproline (c4hPro) isomers were differentiated upon lithiation using CID-MS. The CID-MS of [c4hPro+Li]+ produces three primary fragmentation pathways, namely the neutral losses of H2O, CO, and CO2; whereas CID-MS of [c3hPro+Li]+ produces only loss of CO2 in this same region. These observations may have analytical utility, and in this work, the experimental observations were explored with thermodynamic and transition state calculations to better understand the processes. In Chapter IV, the accurate mass of synthetic monomers including PAH perfluorocycloalkene monomers and their precursors were measured and reported with a publication-quality mass accuracy using atmospheric pressure chemical ionization (APCI)-MS. Additionally, the effect of solution flow rate, ionization mode, source parameters (such as vaporization temperature, dry gas temperature and dry gas flow rate, nebulizer gas pressure), acidification, and different solvent systems on APCI-MS signal intensity were studied.

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Desorption Electrospray Ionization Mass spectrometry Imaging (DESI-MSI) is an area of great interest and a promising tool in the field of chemical imaging. It is a powerful, label-free technique, which can determine, map and visualize different molecular compounds on a sample surface. The amount of information acquired in a single DESI-MSI experiment is enormous compared to other techniques, as it can simultaneously detect different compounds with their spatial distribution on the surface. The experiment can be used to produce two-dimensional and three-dimensional images. Chapter 2 focuses on the design and optimization of the setup for performing DESI-MS imaging on various substrates. The proposed setup was tested for its lateral spatial resolution. To provide proof-of-concept of the design, preliminary tests were performed to generate images from commercial thin layer chromatographic plates and photographic paper. Chapter 3 focuses on demonstrating the compatibility of novel microfabricated Thin Layer Chromatography plates (M-TLC plates) for detection with DESI-MSI.