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Monitoring complex reactions using tandem mass spectrometric methodsTing, Michelle Yan Chi 01 May 2019 (has links)
Suzuki-Miyaura cross-coupling is a well-known method for making biaryls. With bifunctional monomers, Suzuki polycondensation (SPC) can be used to make polyaryls. Given the complexity of the reacting solution, studying the mechanism of SPC is extremely tough. To solve this problem, we used tandem mass spectrometric (MS/MS) methods to observe the dynamic behaviour of catalytically relevant species in real time.
Catalysis involves a complex soup of reactants, intermediates and products. We used an ESI-MS with a triple quadrupole mass analyzer to monitor the SPC in positive ion mode using pressurized sample infusion (PSI) in real time. Full scan, selected ion recording (SIR), product ion scan, neutral loss scan (NLS) and multiple reaction monitoring (MRM) MS/MS methods were applied. Tetrakistriphenylphosphine palladium(0) was the catalyst of this reaction and a positively charged phosphonium aryl iodide tag (m/z 478) was implemented into the first catalytic cycle, enabling us to track all the intermediate oligomers up to the 4th addition. Product ion scan revealed all the intermediate oligomers lose a triphenylphosphine fragment (m/z 262) which would either come from the complex or the charged tag. Three significant intermediate types were observed in each stage of the catalysis, oxidative addition, transmetallation and reductive elimination and their behavior was studied in a chronogram, normalized to the total ion current. As expected, the use of selected ion recording, and neutral loss scan dramatically improved the signal-to-noise ratio. Ultimately, multiple reaction monitoring showed the best chronogram data due to the fact that this scan acts as a “double filter” in a soup of reactive species and contaminants.
Real time reaction monitoring has proven to provide detailed insights regarding a reaction. MS/MS methods are promising for improving data quality, selectivity and sensitivity in reaction monitoring. The principle is broadly applicable to other systems, from an intricate catalytic reaction with short-lived ionic intermediates to a reaction with only a single product generated. Reaction dynamics for an exceptionally complex reaction can be made simple and easy by utilizing tandem mass spectrometry methods in time resolved reaction monitoring. / Graduate
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Discovery of stress biomarkers in biological matrices using novel sample collection techniques, inorganic and organic mass spectrometry and multivariate analysisPatel, Pareen January 2013 (has links)
New methodologies for the collection and analysis of biological samples from psychological, physical and emotional stress are described. Currently, there is little research relating to the elemental, VOC and small molecule changes in biological samples as a consequence of stress on the human body, with much of the current research indicating physical symptoms. This research sought to measure chemical changes in three different categories of stress. The first uses an existing PASAT intervention to induce psychological stress and a further two new methodologies using exercise to induce physical stress and a trapped human in a simulation of a collapsed building to induce emotion stress. Psychological, physical and emotional stress elemental profiles are compared against their respective chemical baseline profiles. Skin samples are collected from the foreheads of participants who endured emotional stress while drool saliva, urine, plasma and forehead skin samples were obtained from physically stressed participants. Furthermore, drool saliva is also obtained from the individual who experienced emotional stress.
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A Novel Experimental Scheme to Fully Separate Permethylated Glycans and Allow Online RP-LC-MS with Simplified ESI-MS AnalysisHines, Jesse, Tao, Shujuan, Orlando, Ron, Brown, Stacy D. 01 March 2012 (has links)
Abstract available for download.
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Electrochemical Aspects of Miniaturized Analytical PlatformsKlett, Oliver January 2003 (has links)
<p>This thesis ties some electrochemical aspects of development and fabrication of an analytical system on a microchip together. These aspects develop through the fundamentals of amperometric detection in microsystems and microfabrication via the interaction of electrochemical detection and electrophoretic separation finally to the interfacing of a microsystem to the macro world.</p><p>Paper <b>I</b> deals with amperometric detection in microscale systems and describes the fabrication of the necessary on-chip microelectrodes together with fluidic channels in silicon. It was furthermore studied, if the interelectrode distance of some μm could be used to improve the sensitivity in amperometric detection by employing redox cycling. </p><p>Papers <b>II</b>, <b>III</b> and <b>IV</b> deal with the effect of a high voltage field on amperometric detection. In analytical microdevices typically an electrophoretic separation step (e.g. capillary electrophoresis, CE) precedes the detection. The interference of the CE high voltage with the amperometric detection potential is often considered one of the main hindrances for an effective combination of these techniques. In paper <b>II</b> one reason for the observed disturbing potential shift was elucidated. It was shown that positioning of working electrode and reference electrode on an equipotiental surface eliminates this problem. Paper <b>III</b> reports an application of this technique. In paper <b>IV</b> it could be shown that this approach could further be used to significantly reduce the instrumental requirements for amperometric detection in CE.</p><p>Papers <b>V</b>, <b>VI</b>, <b>VII</b>, finally discuss the interfacing of low volumetric flows that typically occur on microanalytical devices to other techniques. Both, interfacing from liquid to liquid phase (μLC to CE in paper <b>V</b>) and from liquid to gas phase (CE to MS in paper <b>VI</b> and <b>VII</b>) were discussed. Electrochemical methods are used in this context to evaluate the stability and, in paper <b>VI</b> and <b>VII</b>, to increase the understanding of underlying processes of corrosion.</p>
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Palladium-Catalyzed Carbonylation and Arylation ReactionsSävmarker, Jonas January 2012 (has links)
Palladium-catalyzed reactions have found widespread use in contemporary organic chemistry due to their impressive range of functional group tolerance and high chemo- and regioselectivity. The pioneering contributions to the development of the Pd-catalyzed C-C bond forming cross-coupling reaction were rewarded with the Nobel Prize in Chemistry in 2010. Today, this is a rapidly growing field, and the development of novel methods, as well as the theoretical understanding of the various processes involved are of immense importance for continued progress in this field. The aim of the work presented in this thesis was to develop novel palladium(0)- and palladium(II)-catalyzed reactions. The work involved in achieving this aim led to the development of a Mo(CO)6-mediated carbonylative Stille cross coupling reaction for the preparation of various deoxybenzoins. The protocol utilized convenient gas-free conditions to facilitate the carbonylative coupling of benzyl bromides and chlorides with aryl and heteroaryl stannanes. Mo(CO)6-assisted conditions were then used in the development of a general protocol suitable for the aminocarbonylation of aryl triflates. Both electron-poor and electron-rich triflates were coupled with primary, secondary and aryl amines. In addition, DMAP was found to be a beneficial additive when using sterically hindered or poorly nucleophilic amines. An efficient and convenient method for the synthesis of styrenes from arylboranes was developed, employing the relatively inexpensive vinyl acetate as the ethene source under Pd(II)-catalyzed conditions. The reaction mechanism was studied using ESI-MS, and a plausible catalytic cycle was proposed. A method for the oxidative Heck reaction employing aryltrifluoroborates and aryl MIDA boronates was also developed. Electron-rich and electron-poor olefins were regioselectively arylated under microwave-assisted conditions. Various arylboron species were identified in an ongoing reaction using ESI-MS. Further investigations led to the development of a direct method for the synthesis of arylamidines from aryltrifluoroborates and cyanamides. Under Pd(II)-catalyzed conditions it was possible to insert the aryl into primary, secondary and tertiary cyanamides. Finally, a desulfitative method for the synthesis of aryl ketones was developed. A variety of aryl sulfinates were effectively inserted into alkyl- and aryl nitriles. The mechanism was further investigated using ESI-MS and a plausible catalytic cycle was proposed.
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Resin acids in commercial products and the work environment of Swedish wood pellets production : Analytical methodology, occurrence and exposureAxelsson, Sara January 2012 (has links)
The aims of the work this thesis is based upon were to develop convenient analytical procedures for determining resin acids in biological and environmental matrices, and apply them to enhance understanding of the occurrence, exposure to and uptake by exposed individuals of resin acids. Particular focus has been on the workplace environment of the Swedish wood pellets industry. Sample extraction procedures and high-performance liquid chromatography/electrospray ionisation-mass spectrometry (HPLC/ESI-MS) methodologies were developed for measuring resin acids in dust, skin and urine samples. Chromatographic separation of abietic (AA) and pimaric acid was achieved by using a polar-embedded C12 stationary phase. The HPLC/ESI-MS method avoids undesirable oxidation of AA, which was found to occur during the derivatisation step in the standard MDHS 83/2 gas chromatography/flame ionisation detection (GC/FID) methodology, leading to false observations of both AA and the oxidation product 7-oxodehydroabietic acid (7-OXO). Personal exposures to resin acids in the Swedish wood pellet production industry were found to be lower, on average, than the British Occupational Exposure Limit for rosin (50 µg/m3). The oxidised resin acid 7-OXO, was detected in both dust and skin samples indicating the presence of allergenic resin acids. A correlation between air and post-shift urinary concentrations of dehydroabietic acid (DHAA), and a trend towards an increase in urinary 7-OXO during work shifts, were also observed. Whether the increase in 7-OXO was due to direct uptake or metabolism of other resin acids cannot be concluded from the results. An efficient HPLC/UV methodology with diode-array detection was developed for screening commercial products for rosin that could be used in laboratories lacking mass spectrometers. Very high concentrations of free resin acids were detected in depilatory wax strips using the method. / At the time of doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Submitted.
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Methods for structural studies of an antibody, screening metabolites in rat urine and analysis of spent cell cultivation media using LC/ESI-MS and chemometricsZamani, Leila January 2009 (has links)
This thesis describes bioanalytical methods for generating fingerprints of biological systems for extracting relevant information with (protein) drugs in focus. Similarities and differences between samples can reveal the hidden relevant information, which can be used to optimize the production and facilitate the quality control of such protein drugs during their development and manufacture. Metabolic fingerprinting and multivariate data analysis (MVDA) can also facilitate early diagnosis of diseases and the effects and toxicity of drugs. Currently, several protein drugs are available on the global market. Nevertheless, despite, the success of such biotherapeutics significant challenges remain to be overcome in maintaining their stability and efficacity throughout their production cycle and long-term storage. The native structure and functional activity of therapeutic proteins is affected by many variables from production to delivery, incl. variables assoc. with conditions in bioreactors, purification, storage and delivery. Thus, part of the work underlying this thesis focused on structural analysis of a protein drug using chemical labeling, peptide mapping, and evaluation of the charge state distributions of the whole protein generated by ESI. The other part focuses on non-targeted metabolomics with a view to optimizing the cell cultivation process and assessment of the drug’s toxicity. A combination of appropriate analytical methods and MVDA is needed to find markers that can facilitate optimization of the cultivation system and expression of the target proteins in early stages of process development. Rapid methods for characterizing the protein drugs in different stages of the process are also required for quality control. In order to obtain high quality fingerprints analytical separation techniques with high resolution (such as HPLC or UHPLC) and sensitive analytical detection techniques (such as ESI, quadrupole or TOF MS) have been used, singly or in combination. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript.
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Isolation of Lead-Amino Acid and Mercury-Amino Acid Complexes with Characterization in the Solid State, the Solution State, and the Gas PhaseSaunders, Cheryl D.L. 11 August 2009 (has links)
Although some physiological effects of toxic metal poisoning have been known for centuries, the specific chemical interactions between biological molecules and mercury(I), mercury(II) or lead(II) are not well understood. To date, only thirteen crystal structures of inorganic mercury-amino acid complexes and six crystal structures of lead-amino acid complexes have been reported with varying degrees of characterization. In order to improve our understanding of the coordination chemistry of mercury and lead in biological environments, a systematic method for the isolation of inorganic metal-amino acid complexes from acidic aqueous solutions has been developed. With this method we have prepared five new lead-amino acid complexes (with L-valine, L-isoleucine, L-phenylalanine, and L-arginine) and four new mercury-amino acid complexes (with L-alanine, D-alanine, L-proline, and N-methyl-L-alanine). These metal-amino acid complexes have been comprehensively characterized in the solid state, solution state and gas phase. The development of this isolation technique in conjunction with the exploration of a number of characterization techniques for studying metal-amino acid interactions greatly enhances the known methods by which metal-biological molecule systems are studied.
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Fabrication of Integrated Nebulizer Nozzle Plate Utlizing Micro-molding for FD- ESI Mass SpectrometryChang, Chien-chung 01 July 2005 (has links)
This study presents a novel concept to integrated nebulizer nozzle plate for FD-ESI (Fused-droplet Electrospary Ionization Mass Spectrometry) using modified LIGA process. This fabrication technique can reduce the production cost of current nozzle plate. It comprises of multi-exposure and single develop (MESD) process, the extra-hard Ni-Co (Nickel-Cobalt) electroforming and thin-wall plastic microinjection molding. The template of nozzle plate is patterned using dry film and MESD process. Later, the template is transferred into metal Ni-Co mold by electroplating. In this study, the technique of extra-hard Ni-Co alloy electroplating process with Hardness of Vickers over (HV) 550 is developed. Then with the stiffness of Ni-Co mold, it can withstand high injection speed. Thin-wall microinjection molding process with short cycle time to fabricate nozzle plate can be finished. Liquid crystal polymer (LCP) is used for thin-wall microinjection molding process. In order to make efficiently atomization, we used ANSYS to optimize PZT actuator. Besides, the work of nebulizer with FD-ESI was demonstrated in this study. a novel design of nozzle plate.
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Analysis of biological fluids proteins by high-performance liquid chromatography / electrospray ionization mass spectrometry¡]HPLC/ESI/MS¡^Haung, Zong-Chih 26 July 2005 (has links)
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