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171	Liquid Chromatography Coupled to Mass Spectrometry : Implementation of Chemometric Optimization and Selected Applications Moberg, My January 2006 (has links) Liquid chromatography (LC) coupled to mass spectrometry (MS) offers highly selective and sensitive analysis of a wide variety of compounds. However, the use of hyphenated experimental set-ups implies that many parameters may have an effect on the studied response. Therefore, in order to determine optimized experimental conditions it is of vital importance to incorporate systematic procedures during method development. In this thesis, a generic stepwise optimization strategy is proposed that aims at high chromatographic quality, as well as high mass spectrometric response. The procedure comprises (i) screening experiments to identify the most important parameters, (ii) LC studies to ensure sufficient chromatographic separation, (iii) extended infusion experiments in order to maximize precursor signal(s), and in the case of tandem MS (iv) extended infusion experiments to determine optimal conditions for collision induced dissociation and when applicable also ion trap settings. Experimental design and response surface methodology is used throughout the procedure. Further, the general applicability of LC-MS is demonstrated in this thesis. Specifically, a novel quantitative column-switched LC-MS method for ferrichrome, ferrichrysin and ferricrocin determination is presented. Using the method it was shown how the siderophore content varies with depth in podzolic soil profiles in the north and south of Sweden. The parallel approach using LC coupled to both inductively coupled plasma (ICP) mass spectrometry, and electrospray ionization (ESI) tandem MS is also evaluated as a tool to identify unknown siderophores in a sample. Additionally, different trypsin digestion schemes used for LC-ESI-MS peptide mapping were compared. By multivariate data analysis, it was clearly shown that the procedures tested induce differences that are detectable using LC-ESI-MS. Finally, the glutathione S-transferase catalyzed bioactivation of the prodrug azathioprine was verified using LC-MS. Analytical chemistry liquid chromatography mass spectrometry tandem mass spectrometry electrospray ionization inductively coupled plasma chemometrics optimization multivariate data analysis design of experiments response surface model siderophore azathioprine peptide Analytisk kemi
172	Analysis of Complex Biological Samples using Liquid Chromatography-Fourier Transform Ion Cyclotron Resonance Mass Spectrometry Ramström, Margareta January 2005 (has links) Studies of protein and peptide expression are vital in order to understand complex biological systems. As demonstrated in this thesis, on-line packed capillary liquid chromatography-Fourier transform ion cyclotron resonance mass spectrometry (LC-FTICR MS) is a useful analytical tool for such studies. A proteomics method, based on global tryptic digestion and subsequent separation and detection of the peptides by LC-FTICR MS, was developed for qualitative analysis of body fluids. Initial experiments on cerebrospinal fluid (CSF) provided results that were comparable or superior to those achieved by more time- and sample-consuming techniques. The method was also successfully applied on plasma and amniotic fluid. One of the major challenges in proteomics is the broad dynamic range of proteins in biological matrices. The advantages of removing high-abundant components from CSF and plasma prior to MS were demonstrated. In order to search for potential biomarkers, mass chromatograms of CSF from patients suffering from amyotrophic lateral sclerosis (ALS) and controls were compared using an in-house constructed pattern recognition program. ALS-specific patterns were observed, and four out of five unknown samples were correctly assigned. Alternative strategies to quantitatively compare two pools of samples rely on differential chemical labeling. The performance of one such method, quantification-using-enhanced-signal-tags, was investigated in complex sample analysis. The experimental intensity ratios were proven to be consistent with the prepared concentration ratios of abundant proteins in CSF. Finally, the thesis reports on the first experiments where electron capture dissociation (ECD) was successfully incorporated in on-line LC-MS experiments. ECD and nozzle-skimmer fragmentation were applied to a sample of endocrine peptides extracted from mouse pancreatic islets. The two fragmentation methods provided complementary information. However, the method needs further optimization before it can be applied in the analysis of more complex samples, such as body fluids. Analytical chemistry mass spectrometry liquid chromatography protein proteomics peptide cerebrospinal fluid amyotrophic lateral sclerosis electrospray ionization electron capture dissociation Analytisk kemi Analytical chemistry Analytisk kemi
173	Microscale Tools for Sample Preparation, Separation and Detection of Neuropeptides / Mikroskaliga verktyg för provpreparering, separation och detektion av neuropeptider Dahlin, Andreas January 2005 (has links) The analysis of low abundant biological molecules is often challenging due to their chemical properties, low concentration and limited sample volumes. Neuropeptides are one group of molecules that fits these criteria. Neuropeptides also play an important role in biological functions, which makes them extra interesting to analyze. A classic chemical analysis involves sampling, sample preparation, separation and detection. In this thesis, an enhanced solid supported microdialysis method was developed and used as a combined sampling- and preparation technique. In general, significantly increased extraction efficiency was obtained for all studied peptides. To be able to control the small sample volumes and to minimize the loss of neuropeptides because of unwanted adsorption onto surfaces, the subsequent analysis steps were miniaturized to a micro total analysis system (µ-TAS), which allowed sample pre-treatment, injection, separation, manipulation and detection. In order to incorporate these analysis functions to a microchip, a novel microfabrication protocol was developed. This method facilitated three-dimensional structures to be fabricated without the need of clean room facilities. The sample pre-treatment step was carried out by solid phase extraction from beads packed in the microchip. Femtomole levels of neuropeptides were detected from samples possessing the same properties as microdialysates. The developed injection system made it possible to conduct injections from a liquid chromatographic separation into a capillary electrophoresis channel, which facilitated for advanced multidimensional separations. An electrochemical sample manipulation system was also developed. In the last part, different electrospray emitter tip designs made directly from the edge of the microchip substrate were developed and evaluated. The emitters were proven to be comparable with conventional, capillary based emitters in stability, durability and dynamic flow range. Although additional developments remain, the analysis steps described in this thesis open a door to an integrated, on-line µ-TAS for neuropeptides analysis in complex biological samples. Analytical chemistry Neuropeptides Microchip Enhanced microdialysis Poly(dimethylsiloxane) (PDMS) Electrospray ionization (ESI) Multidimensional separation Electrochemical manipulation Mass spectrometry (MS) Capillary electrophoresis (CE) Microdevice Microfabrication Micro total analysis system (μ-TAS) Analytisk kemi Analytical chemistry Analytisk kemi
174	Analysis of Clinically Important Compounds Using Electrophoretic Separation Techniques Coupled to Time-of-Flight Mass Spectrometry Peterson, Zlatuse Durda 16 April 2004 (has links) Capillary electrophoretic (CE) separations were successfully coupled to time-of-flight mass spectrometric (TOFMS) detection for the analysis of three families of biological compounds that act as mediators and/or indicators of disease, namely, catecholamines (dopamine, epinephrine, norepinephrine) and their O-methoxylated metabolites (3-methoxytyramine, norepinephrine, and normetanephrine), indolamines (serotonin, tryptophan, and 5-hydroxytryptophan), and angiotensin peptides. While electrophoretic separation techniques provided high separation efficiency, mass spectrometric detection afforded specificity unsurpassed by other types of detectors. Both catecholamines and indolamines are present in body fluids at concentrations that make it possible for them to be determined by capillary zone electrophoresis coupled to TOFMS without employing any preconcentration scheme beyond sample work up by solid phase extraction (SPE). Using this hyphenated approach, submicromolar levels of catecholamines and metanephrines in normal human urine and indolamines in human plasma were detected after the removal of the analytes from their biological matrices and after preconcentration by SPE on mixed mode cation-exchange sorbents. The CE-TOFMS and SPE methods were individualized for each group of compounds. While catecholamines and metanephrines in urine samples were quantitated using 3,4-dihydroxybenzylamine as an internal standard, deuterated isotopes, considered ideal internal standards, were used for the quantitation of indolamines. Because the angiotensin peptides are present in biological fluids at much lower concentrations than the previous two families of analytes, their analysis required the application of additional preconcentration techniques. In this work, the coupling of either of two types of electrophoretic preconcentration methods - field amplified injection (FAI) and isotachophoresis (ITP) - to capillary zone electrophoresis with both UV and MS detection was evaluated. Using FAI-CE-UV, angiotensins were detected at ~1 nM concentrations. Using similar conditions but TOFMS detection, the detection limits were below 10 nM. ITP was evaluated in both single-column and two-column comprehensive arrangements. The detection limits achieved for the ITP-based techniques were approximately one order of magnitude higher than for the FAI-based preconcentration. While the potential usefulness of these techniques was demonstrated using angiotensins standards, substantial additional research would be required to allow these approaches to be applied to plasma as part of clinical assays. capillary electrophoresis field amplified injection isotachophoresis time-of-flight mass spectrometry electrospray ionization catecholamines dopamine epinephrine norepinephrine metanephrine normetanephrine indolamines serotonin tryptophan 5-hydroxytryptophan angiotensins plasma urine solid phase extraction Biochemistry Chemistry
175	Chirální rozeznávání pomocí hmotnostní spektrometrie / Chiral recognition by mass spectrometry Kosíková, Lenka January 2012 (has links) Title: Chiral recognition by mass spectrometry Author: Bc. Lenka Kosíková Department: Department of Organic Chemistry Supervisor: doc. Mgr. Jana Roithová, Ph.D. This work is focused on the use of mass spectrometry as the analytical method for chiral recognition in the gas phase. We have examined formation of complexes (S and R) isomers [dimethyl-2,2'-dihydroxy-1,1'binaphthalene-3,3'-dicarboxylate] with sodium. Chiral effect for the fomation of sodium dimers is 1,34±0,06 and that for formation of trimers 2,38±0,22 in favor of the formation of homochiral complexes. Part of the work is devoted to the preparation of isotopically labeled ester [(R)-(−)- di(D3-methyl)-2,2'-dihydroxy-1,1'binaphthalene-3,3'-dicarboxylate]. Mixing of equimolar amounts of D3-(R) and unlabeled (S) isomers leads to the artificial racemate, while we can still distinguish the enantiomers using mass spectrometry. Another part represents the study of the complex formation between (S and R) isomers of [dimethyl-2,2'-dihydroxy-1,1'binaphthalene-3,3'-dicarboxylate] with the metal complex [(S,S)-1,5-diaza-cis-decalin]Cu(OH)I depending on the molar ratios in the solution. I have showed that the molar concetration of the catalyst in the solution plays an important role in the complex formation and that the ESI source spectra of...
176	AMBIENT IONIZATION MASS SPECTROMETRY FOR HIGH THROUGHPUT BIOANALYSIS Nicolas Mauricio Morato Gutierrez (16635960) 25 July 2023 (has links) <p>The rapid analysis of complex samples using mass spectrometry (MS) provides valuable information in both point-of-care (e.g. drug testing) and laboratory-based applications, including the generation of spectral libraries for classification of biosamples, the identification of biomarkers through large-scale studies, as well as the synthesis and bioactivity assessments of large compound sets necessary for drug discovery. In all these cases, the inherent speed of MS is attractive, but rarely fully utilized due to the widespread use of sample purification techniques prior to analysis. Ambient ionization methodologies can help circumvent this drawback by facilitating high-throughput qualitative and quantitative analysis directly from the complex samples without any need for work-up. For instance, the use of swabs or paper substrates allows for rapid identification, quantification, and confirmation, of drugs of abuse from biofluids or surfaces of forensic interest in a matter of minutes, as described in the first two chapters of this dissertation. Faster analysis can be achieved using an automated desorption electrospray ionization (DESI) platform which allows for the rapid and direct screening of complex-sample microarrays with throughputs better than 1 sample per second, giving access to rich spectral information from tens of thousands of samples per day. The development of the bioanalytical capabilities of this platform, particularly within the context of drug discovery (e.g. bioactivity assays, biosample analysis), is described across most other chapters of this dissertation. The use of DESI, a contactless ambient ionization method developed in our laboratory and whose 20 years of history are overviewed in the introduction of this document, provides an additional advantage as the secondary microdroplets generated through the DESI process act as reaction vessels that can accelerate organic reactions by up to six orders of magnitude, facilitating on-the-fly synthesis of new compounds from arrays of starting materials. Unique implications of this microdroplet chemistry in the prebiotic synthesis of peptides and spontaneous redox chemistry at air-solution interfaces, together with its practical applications to the synthesis of new drug molecules, are also overviewed. The success obtained with the first automated DESI-MS system, developed within the DARPA Make It program, led to increased interest in a new-generation platform which was designed over the past year, as overviewed in the last section of this dissertation, and which is currently being installed for validation prior to the transfer of the technology to NCATS, where we anticipate it will make a significant impact through the consolidation and acceleration of the early drug discovery workflow.</p> Analytical biochemistry Enzymes Analytical spectrometry Bioassays Biologically active molecules Forensic chemistry Mass spectrometry High-throughput screening Ambient ionization Desorption electrospray ionization Drug discovery Biological assays Forensic analysis Microdroplet chemistry High-throughput analysis
177	DEVELOPMENTS AND APPLICATIONS IN AMBIENT MASS SPECTROMETRY IMAGING FOR INCREASED SENSITIVITY AND SPECIFICITY Daniela Mesa Sanchez (14216684) 06 December 2022 (has links) <p> Mass spectrometry imaging (MSI) is an advanced analytical technique that renders spatially defined images of complex label-free samples. Nanospray desorption electrospray ionization (nano-DESI) MSI is an ambient ionization direct liquid extraction technique in which analytes are extracted by means of a continuous liquid flow between two fused-silica capillaries. The droplet generated between the two capillaries is controlled by a delicate balance of solvent flow, solvent aspiration, capillary angles, and distance from the surface. This technique produces reproducible ion images with up to 10 µm resolution and can be used to identify and quantify multiple analytes on a given surface. This thesis discusses some of the applications of this technique to biological systems, as well as the work done to develop methodology to further improve this technique’s specificity and sensitivity. Herein, applications that push the limits of the current capabilities of nano-DESI are presented, such as the high-resolution imaging of lipid species in skeletal muscle at the single-fiber level, and the quantification of low-abundance drug metabolites. The second theme of this thesis, developing new capabilities, introduces ion mobility mass spectrometry imaging. This integrated technique increases the selectivity previously possible with MSI. To support these efforts, the work in this thesis has generated data analysis workflows that not only make these experiments possible but also further endeavor to increase sensitivity and combat instrument limitations on mobility resolution. Finally, this thesis present streamlined workflows for tandem MS experiments and modifications to a recently introduced microfluidic variant of the nano-DESI technique. In all, this thesis showcases the current capabilities of the nano-DESI technique and lays the groundwork for future improvements and capabilities. </p> Analytical biochemistry Analytical spectrometry mass spectrometry mass spectrometry imaging ion mobility ion mobility mass spectrometry imaging drug distribution ratios drug imaging Data Analysis Workflow Microfluidic Probe Integrated Device bioanalytical applications
178	Forensic Applications of Gas Chromatography/Mass Spectrometry, High Performance Liquid Chromatography--Mass Spectrometry and Desorption Electrospray Ionization Mass Spectrometry with Chemometric Analysis Sun, Xiaobo 18 April 2012 (has links) No description available. Analytical Chemistry Chemistry Food Science fast gas chromatography high performance liquid chromatography desorption electrospray ionization mass spectrometry FuRES chemometrics classification single droplet micro-extraction jet fuel Panax quinquefolius L ionic liquid methamphetamine
179	Analysis of Glycerophospholipids and Sphingolipids in Murine Brain Using Liquid Chromatography – Electrospray Ionization - Tandem Mass Spectrometry and Matrix-Assisted Laser Desorption Ionization – Imaging Mass Spectrometry Nguyen, Thao January 2017 (has links) Mass spectrometry is an indispensable tool in lipidomics research. Current advances and progress in the technology of mass spectrometry have allowed for the identification, quantification and characterization of lipid molecular species to further our understanding of their biological roles. In this thesis, I assessed the influence post-mortem times have on quantitative lipidomics. Using liquid chromatography - electrospray ionization tandem mass spectrometry (LC-ESIMS/MS) on a triple-quadrupole mass spectrometer and multiple-reaction-monitoring (MRM) mode, the glycerophosphocholine (GPC) metabolites and second messengers in the hippocampus of N3 & N4 C57BL/6 x 129/SV were profiled at various post-mortem interval (PMI). I found that disruption to the GPC metabolite and second messengers lipidome occured as early as 1 hour postmortem and fluctuate up till at least 12 hours post-mortem. Therefore, PMI is a variable in lipidomic studies that must be controlled for, and brain samples which are collected with PMI variations must be matched to avoid misinterpretation. Subsequently, I developed a working protocol to visualize the location and distribution of different classes of glycerophospholipids, ceramides, and sphingomyelin in whole mouse brain sections. This visualization technique is novel because it does not require tissue staining or immunohistochemistry; instead, it was performed using an atmospheric-pressure matrix-assisted laser desorption/ionization (AP-MALDI) source coupled to an orbitrap mass spectrometer. As part of this lipid visualization technique, I also developed a protocol for sublimation as a simple, effective and reproducible matrix application method for brain tissue. The lipid-compatible matrix, 2,5-dihydroxybenzoic acid (DHB), was assessed and optimized for imaging lipid targets. The high mass-resolution and accuracy characteristics of the orbitrap mass spectrometer and its capability to perform tandem mass spectrometry via high-collision dissociation allowed for the identification of approximately 200 different lipid species directly from brain tissue using the visualization technique I developed. Altogether, the work in this thesis has showed that post-mortem changes in the lipidome are quantifiable and has provided a novel avenue to further assess these changes by means of imaging mass spectrometry. Mass Spectrometry Imaging Mass spectrometry Lipidomics Lipids High-Performance Liquid Chromatography HPLC Electrospray Ionization ESI MALDI Tandem Triple Quadrupole Orbitrap Glycerophospholipids Sphingolipids Post-mortem Brain
180	Aspects of Porous Graphitic Carbon as Packing Material in Capillary Liquid Chromatography Törnkvist, Anna January 2003 (has links) <p>In this thesis, porous graphitic carbon (PGC) has been used as packing material in packed capillary liquid chromatography. The unique chromatographic properties of PGC has been studied in some detail and applied to different analytical challenges using both electrospray ionization-mass spectrometry (ESI-MS) and ultra violet (UV) absorbance detection. </p><p>The crucial importance of disengaging the conductive PGC chromatographic separation media from the high voltage mass spectrometric interface has been shown. In the absence of a grounded point between the column and ESI emitter, a current through the column was present, and changed retention behaviors for 3-O-methyl-DOPA and tyrosine were observed. An alteration of the chromatographic properties was also seen when PGC was chemically oxidized with permanganate, possibly due to an oxidation of the few surface groups present on the PGC material. </p><p>The dynamic adsorption of the chiral selector lasalocid onto the PGC support resulted in a useful and stable chiral stationary phase. Extraordinary enantioselectivity was observed for 1-(1-naphthyl)ethylamine, and enantioseparation was also achieved for other amines, amino acids, acids and alcohols. </p><p>Finally, a new strategy for separation of small biologically active compounds in plasma and brain tissue has been developed. With PGC as stationary phase it was possible to utilize a mobile phase of high content of organic modifier, without the addition of ion-pairing agents, and still selectively separate the analytes. </p> Analytical chemistry PGC porous graphitic carbon stationary phase packing material LC liquid chromatography miniaturized chiral enantiomer ESI electrospray ionization mass spectrometry polar compounds L-DOPA dopamine biological samples biological matrix Analytisk kemi PGC poröst grafitiserat kol stationärfas packningsmaterial LC vätskekromatografi miniatyriserade system kiral enantiomer ESI electrospray jonisation mass spektrometri polära föreningar L-DOPA dopmamine biologiska prover biologisk matris Analytical chemistry Analytisk kemi

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