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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.
121

New Gas Sensor for Exhaust Emissions of Internal Combustion Engines / Nouveau capteur de pollution pour les gaz d'échappement dans les moteurs thermiques

Lakkis, Sari 17 December 2014 (has links)
L’analyse des gaz d’échappement des moteurs à combustion interne a été traditionnellement réalisée en laboratoires en utilisant des analyseurs de gaz en vrac avec des équipements coûteux. Afin de créer un système capable de réaliser le travail de ces analyseurs, un capteur pouvant détecter plusieurs gaz simultanément est indispensable pour en mesurer la concentration. En effet, utiliser un capteur pour chaque gaz est couteux et peut amener à des procédures complexes d’analyse en raison des différentes technologies utilisées. De plus, l’utilisation de multiples capteurs donne lieu à une perte de ressources financières et humaines. Pour pallier ce problème, une approche alternative proposée dans cette thèse consiste à utiliser un seul capteur pour l’analyse simultanée des différents gaz. Cette approche contribue à réduire la complexité des analyses, la taille et la collecte de données des mesures de gaz mentionnés précédemment. Elle permet également la baisse du coût de l’ensemble du système des mesures.Cette thèse présente la conception, la méthodologie et le développement d’une nouvelle approche pour la mesure de la concentration de gaz utilisant le traitement d’images numériques à travers la modélisation du mélange des couleurs d’émission de lumière dans le tube de décharge de gaz. L’application du modèle inverse permet d’obtenir le pourcentage de chaque gaz dans un mélange contenant jusqu'à quatre gaz connaissant la couleur d’émission du mélange et la couleur d’émission de chaque gaz. Nous discutons aussi le potentiel de certaines méthodes quant à leurs propriétés de miniaturisation et leurs limites. Une comparaison entre les différents capteurs miniaturisés est réalisée en termes suivant la sensibilité, la sélectivité, le coût et d’autres conditions. Pour atteindre les objectifs de recherche, les problèmes techniques rencontrés tels que la modélisation de mélange des couleurs, l’étalonnage de capteurs pour l’acquisition d’images, et le traitement des erreurs de mesures ont été identifiés et des solutions ont été proposées. / Gases represent one of the most important key measurands in many industrial and domestic activities. The need to detect single gas or a group of gases at the same time varies from one application to another. One of the most important applications of gas sensing is in the concentration measurement of exhaust emissions in internal combustion engines. The variety of gases emitted by these engines and the necessity for a precise measurement of their concentrations are the major incentives for researchers to develop gas sensors that are not only limited to a certain type of gases but to a variety of gases. The most interest gases include CO, NO, NO2, NH4, SO2, CO2, CH4 and other hydrocarbons. These gases can be harmful to human health if present beyond a certain concentration. The analysis of exhaust emissions of internal combustion engines has traditionally been achieved in laboratories using bulk gas analyzers and costly equipments. In order to create a system which can do the work of these analyzers, a sensor that can measure the concentration of multiple gases at the same time is needed. Instead of using a sensor for each gas which is costly and introduce another complexity to the analysis procedure due to the different technologies that are used in the detection of different types of gases. This directly translates into loss of financial and human resources that could otherwise be productively used. In an effort to remedy this situation, this dissertation proposes an alternate approach that uses one sensor to analyze multiple gases simultaneously. This has a significant potential in reducing the aforementioned complexity, size and data collection tasks, and at the same time can lower the cost of the overall system.This dissertation presents the design, methodology, and development of a new method for gas concentration measurement using digital image processing through modeling the color mixing of light emissions in gas discharge tube. The application of the inverse model allows us to get the percentages of each gas in a mixture of up to four gases knowing already the color of emission of the whole mixture and the color of emission of each gas alone. It also discusses the miniaturization potential of some of the methods that are promising in the ability of their miniaturization but suffer from different problems. A comparison is also done among the miniaturized sensors in terms of different parameters like sensitivity, selectivity, cost and other terms. In achieving the research objectives, major technical challenges such as color mixing modeling, imaging sensor calibration, and measurements’ error handling have been successfully identified and addressed.
122

Novel Analytical Methodologies for the Monitoring of Traditional and Non-traditional Pollutants in different Environmental Compartments of South Florida

Ramirez, Cesar E. 04 November 2013 (has links)
Routine monitoring of environmental pollution demands simplicity and speed without sacrificing sensitivity or accuracy. The development and application of sensitive, fast and easy to implement analytical methodologies for detecting emerging and traditional water and airborne contaminants in South Florida is presented. A novel method was developed for quantification of the herbicide glyphosate based on lyophilization followed by derivatization and simultaneous detection by fluorescence and mass spectrometry. Samples were analyzed from water canals that will hydrate estuarine wetlands of Biscayne National Park, detecting inputs of glyphosate from both aquatic usage and agricultural runoff from farms. A second study describes a set of fast, automated LC-MS/MS protocols for the analysis of dioctyl sulfosuccinate (DOSS) and 2-butoxyethanol, two components of Corexit®. Around 1.8 million gallons of those dispersant formulations were used in the response efforts for the Gulf of Mexico oil spill in 2010. The methods presented here allow the trace-level detection of these compounds in seawater, crude oil and commercial dispersants formulations. In addition, two methodologies were developed for the analysis of well-known pollutants, namely Polycyclic Aromatic Hydrocarbons (PAHs) and airborne particulate matter (APM). PAHs are ubiquitous environmental contaminants and some are potent carcinogens. Traditional GC-MS analysis is labor-intensive and consumes large amounts of toxic solvents. My study provides an alternative automated SPE-LC-APPI-MS/MS analysis with minimal sample preparation and a lower solvent consumption. The system can inject, extract, clean, separate and detect 28 PAHs and 15 families of alkylated PAHs in 28 minutes. The methodology was tested with environmental samples from Miami. Airborne Particulate Matter is a mixture of particles of chemical and biological origin. Assessment of its elemental composition is critical for the protection of sensitive ecosystems and public health. The APM collected from Port Everglades between 2005 and 2010 was analyzed by ICP-MS after acid digestion of filters. The most abundant elements were Fe and Al, followed by Cu, V and Zn. Enrichment factors show that hazardous elements (Cd, Pb, As, Co, Ni and Cr) are introduced by anthropogenic activities. Data suggest that the major sources of APM were an electricity plant, road dust, industrial emissions and marine vessels.
123

Spårmängdsanalys av explosivämnen

Loorents, Cheryl January 2020 (has links)
There is an alarming increase of explosions with devastating consequences, the ultimate being loss of life. Furthermore, these kinds of substances have a toxic effect on animals, nature and humans if they are incorrectly disposed. In order to counteract the rising trend and increase the feeling of security within the society, the Swedish Defense Research Agency (FOI) has started a new project which in the future might be used by the police in order to prevent possible terrorist attacks. The aim with this new project is to perform trace analysis of explosives in wastewater in order to receive an indication of where illegal production of explosives takes place. This method has the potential to be used for other matrixes, such as soil instead of wastewater or other water matrixes, thereby exposing possible harmful and contaminated places.   The aim with this thesis was to develop a method for an Ultra-High-Performance Liquid Chromatography (UHPLC) instrument in order to perform trace analysis of explosives in wastewater. Furthermore, the aim was also to develop a method for an automated solid phase extraction (SPE) instrument for sample clean-up. Lastly mass spectrometry was performed with a triple-quadrupole. A performance analysis was made for the developed UHPLC-method which resulted in a good repeatability. Furthermore, several experiments were conducted on the SPE-instrument in order to receive a yield close to 100%. The different experiments included comparison between the most beneficial eluent, volume of eluent and evaporation step. The highest yield was received with 3 ml acetonitrile without any evaporation step. A performance analysis was made of the developed method for the SPE-robot, which resulted in a good accuracy and precision. In hopes of lowering the detection limit, mass spectrometry was conducted by a preciously validated instrument based at FOI. A lower detection limit was received for all substances; R-salt 0,025 µg/ml, TNT 0,094 µg/ml and PETN 0,103 µg/ml.
124

Stanovení reziduí vybraných pesticidních účinných látek ve víně metodou GC/MS / Determination of residues of the selected pesticide effective substances in wine using the GC/MS method

Ehrenbergerová, Martina January 2010 (has links)
The grape is one of the oldest cultivated plants. It can be consumed as a fruit or it can be used as a raw material for making stews, juices or the cultivated drink – wine. Generations of wine-makers have been striving to improve both the cultivating conditions of vineyards and the quality of wine. Many harmful elements, such as herbivorous pests, diseases and storms are important factors that can have a negative impact on crop quality. To regulate the effects of these factors, an integrated protection system is used, incorporating agronomical measures, resistant varieties and a wide spectrum of pesticides. However, increasing the usage of pesticides brings certain dangers to both the production quality and the environment. This necessitates the monitoring of the negative effects, including the content of pesticide residues in the grapes. My thesis studies and experimentally assesses selected pesticide residues in certain wine samples.
125

Extrakce vybraných flavonoidů bezu černého pro potravinářské účely / Extraction of selected elderberry flavonoids for food industry purposes

Grulichová, Hana January 2010 (has links)
Amount of rutin and quercetin in bark and leaves from different type of Sambucus nigra was determined in this diploma thesis. Records of amounts were compared with amounts in significant sources of these flavonoids. Matters from raw matrix were obtained with pressurized solvent extraction (PSE) and pressurized hot water extraction (PHWE). There was use temperature 120°C, pressure 150 bar, three times 5-min cycles for PSE. There were used 80°C, 150 bar, three 5-min cycles for rutin extracted with PHWE and the same condition were used for extraction of quercetin only the temperature was changed to 100 °C. Analysis of rutin and quercetin were carry out high performance liquid chromatography (HPLC) with diode array detection (DAD), where was used SUPELCOSILTM LC 8DB column (5µm; 250 x 4.6 mm). Methanol: water: formic acid (36: 61.5: 2.5, pH 2.17 2.28) was used like a mobile phase. The flow of the mobile phase was set up 0.7 ml/min. Size of sample was 10 µl. The most amount of rutin was determined in the leaves of wild kind of Sambucus nigra with methanol extraction and hot water too. Extraction with PHWE was more effectively. There were determined 5.58 mg of rutin in one gram of sample from wild Sambucus nigra. There were determined the smallest amount of rutin in Sambucus nigra Körsör. There was found only 0.13 mg/g with extraction PHWE. The quercetin wasn’t determined in any Sambucus nigra leaves. There were found both of the flavonoids (rutin and quercetin) in the branch of Sambucus nigra. The rutin was determined in the small amount in wild kind but it was found in the important amount in Sambucus nigra cultivar. Whereas the quercetin was found in higher concentration than rutin when was finding the ideal conditions for extraction of branch. The quercetin was chosen like more important in light of amount. In the end the quercetin wasn’t detected in any Sambucus nigra cultivars. The most amount of quercetin was determined in wild sambucus nigra, 0.24 mg/g. The most amount of rutin was found in Sambucus nigra Albida, 2.33 mg/g.
126

Stanovení palladia metodou ET-AAS po předchozí prekoncentraci na pevných sorbentech / Determination of palladium by ET-AAS after previous preconcentration by solid phase extraction

Hajdová, Jana January 2014 (has links)
The theoretical part of this master’s thesis focuses on the characteristic of Palladium, his uses in the automotive convertors, the occurrence in the environment, bioaccumulation and human health risks. Next there are described the basics of biomonitoring and summarize suitable biomonitoring method for capturing airborne dust. There are also evaluated appropriate methods for preconcentration and determination of Palladium. The aim of experimental part of this thesis is description and evaluation optimalization preconcentration method SPE by using sorbents silicagel C18 and QuadraSil TA. Optimization of method conditions of electrothermal atomic absorption spectrometry (ET – AAS). The determination of Palladium using optimal conditions follows in real samples in the form of exposure lichen (Hypogymnia physodes) by automobile traffic in Brno.
127

Prekoncentrace stopových prvků na modifikovaných sorbentech a jejich stanovení ve vodách / Preconcentration of Trace Analytes on Modified Sorbents and their Determination on Waters

Holubová, Zuzana January 2013 (has links)
The work has been focused on the preconcentration techniques for determination of 9Be, 51V, 59Co, 60Ni, 89Y, 111Cd, 208Pb, 232Th and 238U on the modified sorbents, all measurements were performed on ICP-MS. The instrument setup was optimized. The solution of internal standard (200 µg•l-1) was used during all measurements. The internal standard were chosen as follows: 6Li for 9Be, 45Sc (51V), 72Ge (59Co, 60Ni, 89Y), 103Rh (111Cd), 209Bi (206Pb, 207Pb, 208Pb, 232Th and 238U). Another parameters such as influence of mineral acids (HCl, HNO3), surfactant (Septonex®, Zephyramin, Ajatin, Brij 35 and Sodium dodecyl sulphate) and organic reagents (Ammonium pyrrolidinedithiocarbamate, 8-Hydroxyquinoline-5-sulphonic acid, 1,2-Dihydroxyanthraquinone-3-sulphonic acid and 4-(2-Pyridylazo)resorcinol) and the effect of some matrix components on intensity of instrument signal determination was investigated. For preconcentration polar Silicagel and modified nonpolar Silicagels (Silicagel-C18, C8 nad Phenyl) were used. Another experimantal part was dedicated to preconcentration on nonpolar Amberlite XAD-16 and Strata SDB-L and intermediately polar sorbent Amberlite XAD-7. Recoveries of sorption process were observed in the presence of all testing types of surfactants in certified concentration 5•10-4 mol•l-1. Surfactants were always applied in the conditioning step. The suitable combinations of surfactant and organic reagent were tested for increasing of recoveries of analytes. Testing organic reagents were added in five times mass excess againts concentration of analytes, the concentration of the organic reagents was 900 µg•l-1. The organic reagent was always added to the solution for preconcentration before this solution was led on the sorbent. The composition and a necessary volume of elution mixture for quantitative elution were tested, too. Only one sorbent was chosen from each group of sorbents with similar properties. The chosen sorbent showed the best recoveries in majority of target analytes. The highest recoveries from silica-group was reached for Silicagel-C18, from nonpolar Amberlite was chosen Strata SDB-L and intermediately polar Amberlite XAD-7. The influence of some matrix components (anionts and cations) on recoveries of analytes was investigated for chosen sorbent. The optimized process was applied on real samples of nature water and industry water. In experimental part all analytes are marked as specific izotopes, which were measured by ICP-MS. Of course, all izotopes of analytes undergo preconcentration techniques.
128

Využití moderních separačních a spektrometrických metod k identifikaci lipidomu z biologického vzorku / Modern separation and spectrometric techniques for biological sample lipidom investigation

Havelková, Eva January 2013 (has links)
Modern separation and spectrometric techniques for biological sample lipidom investigation Due recent progress in field of mass spectrometry the lipidomics, part of metabolomics, is increasing its importance for broad fields of biological study. The aim of this study is to test the lipid extraction techniques and to optimize the preseparation and separation of lipids suitable for mass spectrometry detection. The fragmentation patterns of four, the most abundant lipid classes of glycerolipids (PC, PE, TG, DG), were acquired for the proposed system. These patterns were compared with literature. The most appropriate method for extraction was declared technique according Folch based on methanol and chloroform solution. The preseparation due SPE method is very useful tool for lipid determination. The optimized were focused to reach higher recovery especially in polar lipid fraction. Proposed HPLC system is based on methanol with ammonium buffer, water and isopropanol. The testing was done on three columns with different type of sorbents (Gemini, Syncronis and Kinetex). The separation was evaluated according mass spectrometer response, shape and wide of particular analytes peaks. Composition contains 20% of water was determinate as the best and also the best separation was achieved by Kinetex column. The proposed...
129

Development and validation of sample clean-up using solid phase extraction prior oil spill fingerprinting

Loorents, Cheryl January 2022 (has links)
In a forensic investigation involving oil, a comparative analysis named oil spill fingerprinting between a source and an oil spill is normally performed. It is based on detecting a certain selection of biomarkers with gas chromatography (GC) coupled to mass spectrometry (MS) which are later divided into diagnostic ratios (DRs). An international guideline formed by European Committee for Standardization (CEN) denoted CEN/TR 15522-2:2012 describes the process of conducting oil spill fingerprinting. This method is currently being inspected and adjusted for standardization into EN 15522-2:2022. One section of the upcoming standard describes sample clean-up which is important to inhibit possible matrix effect that could either enhance or reduce peak intensity in the chromatogram. There is yet no conclusive SPE (Solid Phase Extraction) protocol in the current draft version of EN 15522-2:2022. The aim with this study was to develop such a protocol. Development included comparative testing of the recommended stationary phases silica and Florisil®. Additionally, the effect of both elution solvent and elution volume were investigated. The protocol must pass validation criteria to be implemented at National Forensic Centre (NFC) and possibly be used in the final version of EN 15522-2:2022. A successful method for Heavy Fuel Oil (HFO), diesel and lubricating oil was achieved with activated Florisil® as stationary phase, eluted with 6 ml dichloromethane (DCM). If the evidence material is suspected to contain FAMEs (Fatty Acid Methyl Esters), then 2 % acetone should be added to the DCM. The final SPE column was packed with 0.5 glass wool, 4 cm Florisil® and 0.5 cm sodium sulfate. Based on successful validation result, the SPE protocol should be considered for the final version of EN 15522-2:2022 as well as for implementation at NFC.
130

Capillary Electrophoresis of Proteins with Selective On-line Affinity Monoliths

Armenta Blanco, Jenny Marcela 14 November 2006 (has links) (PDF)
The analysis of proteins in biological fluids by capillary electrophoresis (CE) is of interest in clinical chemistry. However, due to low analyte concentrations and poor concentration limits of detection (CLOD), protein analysis by this technique is frequently challenging. Coupling preconcentration techniques with CE greatly improves the CLOD. An on-line preconcentration-CE method that can selectively preconcentrate any protein for which an antibody is available would be very useful for the analysis of low abundance proteins and would establish CE as a major tool in biomarker discovery. To accomplish this, an on-line protein G monolithic preconcentrator CE system for enrichment and separation of proteins was developed. This system proved effective for on-line sample extraction, clean-up, preconcentration, and CE of IgG in human serum. IgG from diluted (500 and 65,000 times) human serum samples was successfully analyzed using this system. The approach can be applied to the on-line preconcentration and analysis of any protein for which an antibody is available. The desire to separate all proteins present in human tissues, cells and biological fluids has challenged the separation research community for many years. The difficulty of this task resides in the complexity of the sample. Blood serum, for instance, may express up to 10,000 proteins with an estimated dynamic range of 9 orders of magnitude. Additionally, most of these proteins are present at very low concentrations (ng/mL). Identification and quantification of low abundance proteins is hindered by the presence of high abundance proteins, such as human serum albumin (HSA) and immunoglobulins (IgG). Therefore, in most cases, removal of the high abundance proteins or enrichment of low abundance proteins is necessary prior to the analysis of low abundance proteins. To address this, a coupled affinity-hydropobic monolithic column for the simultaneous removal of IgG, preconcentration of low abundance proteins, and separation by capillary zone electrophoresis was designed. The system proved to be very reproducible. The run-to-run %RSD values for migration time and peak area were less than 5%, which is typical of CE. Finally, a new method was developed to prepare monoliths with anion exchange functionality. Polymer monoliths were prepared by in situ polymerization of methacrylate monomers. The monoliths were coated with a water soluble polymer and used for the analysis of proteins. Using this approach, a model monolith was prepared. Subsequent coating yielded a monolith with quaternary ammonium groups on the surface, which was confirmed by strong anodic electroosmotic flow. Analysis of standard proteins by ion exchange LC and CEC was demonstrated. This simple and rapid method for surface modification opened new avenues for the preparation of monoliths with a broad range of functionalities.

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