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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.
171

Stanovení léčiv v pitných vodách metodou HPLC / Determination of pharmaceuticals in drinking waters using HPLC

Králová, Radka January 2015 (has links)
The aim of the diploma thesis is the determination of macrolide antibiotics in drinking water by using of high performance liquid chromatography. Erythromycin and clarithromycin were selected such as representative macrolides due to frequently prescribed pharmaceuticals in this time. Solid phase extraction (SPE) by using of Oasis HLB cartridges was applied for pre concentration and purification of chosen analytes in real samples of drinking water. Optimalization of method and analysis were performed by using of high performance liquid chromatography with mass spectrometry detection (HPLC-MS). The suitable method was selected for determination of macrolides in real samples taken from two sources of drinking water, the interception of water in Litovel and Černovír Olomouc.
172

Biodegradace polychlorovaných bifenylů pomocí ligninolytických hub a jejich enzymů / Biodegradation of polychlorinated biphenyls by white - rot fungi and their enzymes

Linhartová, Lucie January 2010 (has links)
Polychlorinated biphenyls (PCB) represent relevant persistent organopollutants of the environment and the estimated amount of PCB released into the environment is 750000 metric tons. White-rot fungi have been studied for long time due to their degradative potential toward various aromatic pollutants and it is known that these fungi are able to decompose PCB in vivo. Biodegradation of PCB by the fungus Pleurotus ostreatus was studied in the frame of this work. A high degradative efficiency of P. ostreatus was observed in the first set of experiments, even in the presence of relative high amount of added PCB. Fungus was able to transform 780±50 µg out of the intial amount 1000 µg in 20 ml of a cultivation media within 42 days. A decrease in toxicity was recorded during the degradation that suggests the suitability of this organism for a practical use in decontamination. In vitro experiments with purified laccase induced with Cu2+ from this fungus did not prove any participation of the enzyme in the first step of PCB transformation. The enzyme did not show an ability to degrade PCB even after purification from cultivation media containing PCB. It was found that the first step of PCB transformation can be performed by an intracellular process with microsomal fraction. A degradation of 44-67% was observed for...
173

Stanovení proteinogenních aminokyselin vysokoúčinnými separačními technikami / Determination of proteinogenic amino acids by high-performance separation techniques

Hodek, Ondřej January 2019 (has links)
(EN) Proteinogenic amino acids are key components of living organisms. Thus, the latest metabolomics research has focused on developing fast and sensitive methods for the determination of amino acids. In this context, this thesis contains two studies describing development of high-performance separation techniques for the quantification of amino acids. In the first study, a capillary electrophoresis method was developed for the determination of free amino acids in tobacco plants, particularly focusing on optimizing the extraction of amino acids from solid plant materials. The extraction procedure was optimized using design of experiments (DoE) to obtain the highest possible extraction yield of amino acids. Factors such as volume and concentration of the extraction solvent (hydrochloric acid) were assessed as the most significant. Subsequently, the optimal values of these factors were determined using response surface methodology (RSM). Lastly, proteinogenic amino acids were quantified using capillary electrophoresis with contactless conductivity detection and calibration with internal standard, which improved the precision of the method. The second study aimed at developing a supercritical fluid chromatography method for the determination of free proteinogenic amino acids in human plasma. The most...
174

Etude en atmosphère simulée de la formation d'Aérosol Organique Secondaire issue de la photooxydation du n-dodécane : impact des paramètres environnementaux / Study under simulated condition of the secondary organic aerosol from the photooxydation of n-dodecane : Impact of the physical-chemical processes

Lamkaddam, Houssni 24 March 2017 (has links)
L’aérosol organique secondaire (AOS), fraction majoritaire de l’aérosol submicronique, joue un rôle important sur la santé, l’environnement et le climat. L’évaluation de son impact constitue un véritable enjeu pour la communauté scientifique. Toutefois, nos connaissances actuelles sur les processus de formation d’AOS et sa composition chimique sont encore très lacunaires, et en l’occurrence, limitent le développement des modèles atmosphériques permettant de quantifier les impacts des AOS sur la qualité de l’air et le système climatique. Ainsi, l’objectif de ce travail est de produire un ensemble de données expérimentales fournissant des points de contrainte afin d’évaluer et d’améliorer les modèles. Pour ce faire, la formation d’AOS a été étudiée à partir de la photooxydation d’un précurseur modèle, le n-dodécane, dans la chambre de simulation atmosphérique CESAM. La composition chimique a été élucidée par des techniques spectrométriques et chromatographiques permettant d’identifier les différentes espèces constituant la phase gazeuse et particulaire. En particulier, de nouveaux mécanismes en phase condensée ont été proposés afin d’expliquer la formation des acides carboxyliques et des lactones, identifiés pour la première fois dans l’AOS d’un alcane. Ces derniers pourront être implémentés dans les modèles. Une grande diversité de conditions environnementales, telles que la température, l’humidité relative et la présence/absence de particules préexistantes, a été prise en compte dans ces travaux. Notamment, l’étude de l’influence de la température a mis en évidence une faible sensibilité de ce paramètre sur les rendements de production d’AOS. Tandis que l’étude sur l’effet de l’humidité relative, elle, a montré que l’ajout d’eau dans le système réactionnel au-delà de 5% abaisse les rendements d’AOS de près d’un facteur 2 en comparaison à des conditions sèches. Ainsi, la formation potentielle d’AOS sous ces différentes conditions a permis d’aboutir à des paramétrisations directement utilisables par les modélisateurs. Une caractérisation des effets de paroi dans CESAM, i.e. les pertes en phase gazeuse et particulaire, a également été menée / Secondary Organic Aerosol (SOA), the major fraction of the submicron aerosol, plays a key role on health, environment and climate. The evaluation of its impacts is a real challenge for the scientific community. Our current knowledge of SOA formation processes and chemical composition is still very deficient and limit the development of atmospheric models to quantify the impacts of SOA on air quality and climate system. Therefore, the aim of this work is to produce a set of experimental data to use to constrain and improve the models. To do that, the SOA formation has been studied from the photooxidation of a model precursor, n-dodecane, in the CESAM environmental chamber. The chemical composition has been investigated by spectrometric and chromatographic techniques which allowed us to identify the reaction products constituting the gaseous and particulate phases. In particular, new condensed phase mechanisms have been proposed to explain the formation of carboxylic acids and lactones, identified for the first time. These could be implemented in the models. A wide variety of environmental conditions, such as temperature, relative humidity and the presence/absence of preexisting particles, have been taken into account in this work. The study of the temperature influence has shown a low sensitivity of this parameter on the SOA production. While the study relative humidity effect has shown that adding water to the reaction system beyond 5% lowers SOA yields by almost a factor of 2 in comparison to dry conditions. The SOA formation potential, under these conditions, has been evaluated, and resulted in parameterizations which could be useful for modelers. Furthermore, a characterization of the wall effects in CESAM, i.e. gas and particulate phase wall losses, has been carried out
175

Nové metody používané při zjišťování příčin vzniku požárů / Newe methods used for the finding of fire causes

Přichystal, Lukáš January 2011 (has links)
Master’s thesis deals with a determination problem of ignitable liquids from fire debris. The aim of this work is to introduce the properties of used fire accelerants and to give an overview and evaluation of the various techniques which can be conducive to the fire investigator. Determination of fire accelerants from fire debris was made by the technique of solid phase microextraction (SPME) with subsequent chemical analysis by GC/MS. Based on the chromatographic results were established the target compounds and reconstructed ion chromatograms which are typical for some kinds of flammable liquids. There were used gasoline, diesel, kerosene and technical gasoline (white spirit) as the fire accelerants. This work also deals with the influence of interfering products in fire debris analysis, including their identification and characterization. Different kinds of substrates were burned, extracted and analyzed in order to identify all the interfering products that they may release.
176

Indoor Air Monitoring of Ethanol and Benzene in a Pilot Winery Using Active Sampling

Kaneda, Andrew I 01 March 2019 (has links) (PDF)
Acute indoor concentrations of benzene and ethanol were evaluated in the California Polytechnic State University San Luis Obispo’s pilot winery workroom. Air samples were collected during four different wine-making activities: fermentation, fermentation with Brix content testing, post-alcoholic fermentation pressing, and storage/finishing. Average workroom benzene concentrations ranged from 0.05 to 0.12 mg/m3. Ethanol concentrations in the winery workroom varied with the activity, ranging from 0.9 to 12 mg/m3. Pressing and fermentation with Brix content testing both led to higher indoor ethanol concentrations than fermentation without Brix content testing and storage/finishing. Tracer gas decay air exchange tests were conducted to determine the air exchange rate of the winery workroom. A single-space mass-balance model was used to estimate the air exchange rate for the entire workroom. The calculated air exchange rates were correlated with wind speeds and wind direction to create a linear model estimating air exchange rates based on wind speed. These air exchange rates and the indoor concentrations of ethanol were used with the single-space mass-balance model to calculate an ethanol emission rate for each activity. Total estimated ethanol emissions for the four activities were 3.1 lbs. ethanol per 1000 gallons of wine produced.
177

Gas Chromatography: Mass Spectrometry of Chemical Agents and Related Interferents

Zhai, Lailiang 26 March 2006 (has links) (PDF)
One of the main problems encountered in chemical analysis operations in the field is collecting sufficient sample from the source and transferring that sample to the measurement instrument for fast separation and identification. I have been involved in developing a field-portable gas chromatography-mass spectrometry (GC-MS) system with solid phase microextraction (SPME) sampling for point detection of chemical agents. The objective is to minimize the analysis time between sampling and detection of a potential chemical threat. SPME offers a convenient means for sampling gaseous and liquid samples, concentrating the analytes, and transferring the analytes to the injection port of a GC system for separation and identification. GC-MS has advantages of high efficiency, speed, and applicability for field analysis. Work was done to optimize the SPME fiber coating, capillary column dimensions, and GC operating conditions to provide complete analysis within 3 minutes. Since isothermal operation of the GC was a prior requirement, many components in the chromatograms were unresolved. Therefore, a peak de-convolution algorithm was applied to allow for identification and quantitation of poorly resolved and often completely obscured trace components. Details of the instrumentation and optimization of operating conditions are described in this thesis.
178

High Flow Air Sampling for Field Detection Using Gas Chromatography-Mass Spectrometry

Murray, Jacolin Ann 01 December 2010 (has links) (PDF)
The ability to rapidly detect and identify hazardous analytes in the field has become increasingly important. One of the most important analytical detection methods in the field is gas chromatography-mass spectrometry (GC-MS). In this work, a hand-portable GC-MS system is described that contains a miniature toroidal ion trap mass analyzer and a low thermal mass GC. The system is self-contained within the dimensions of 47 x 36 x 18 cm and weighs less than 13 kg. Because the instrument has a small footprint, it was used as the detector for an automated near-real-time permeation testing system. In permeation testing, materials that are used to make individual protective equipment such as gloves, masks, boots, and suits are exposed to hazardous analytes to determine how long the equipment can be worn safely. The system described herein could test five samples simultaneously. A multi-position valve rotated among the various sample streams and delivered time aliquots into the MS for quantitation. Current field air sampling techniques suffer from long desorption times, high pressure drops, artifact formation and water retention. These disadvantages can be avoided by concentrating the analytes in short open tubular traps containing thick films. There are several advantages to using polymer coated capillaries as traps, including fast desorption, inertness and low flow restriction. An air sampling trap was constructed utilizing open tubular traps for the concentration of semi-volatile organic compounds. The system consisted of multiple capillary traps bundled together, providing high sample flow rates. The analytes were desorbed from the multi-capillary bundle and refocused in a secondary trap. The simultaneous focusing and separation effect of a trap subjected to a negative temperature gradient was also explored. In this configuration, analytes were focused because the front of the peak was at a lower temperature than the rear of the peak and, hence, moved slower. In addition to the focusing effect, analytes with different volatilities focused at different temperatures within the gradient, allowing for separation.
179

Differentiation of <em>Bacillus</em> Endospores from Gas Chromatography-Mass Spectrometry of Biomarkers Produced by Thermochemolysis Methylation

Truong, Tai Van 20 April 2011 (has links) (PDF)
Methods for fast, simple detection of biomarkers to detect and differentiate closely related Bacillus endospores including Bacillus anthracis (BA), Bacillus thuringiensis (BT), Bacillus atrophaeus (BG), and Bacillus cereus (BC) using thermochemolysis and methylation (TCM), coiled wire filament (CWF), solid phase micro extraction (SPME) and gas chromatography-mass spectrometry (GC-MS) were developed. The main biomarkers detected and used for differentiation include dipicolinic acid methyl ester (DPAME), fatty acid methyl esters (FAMEs), 3-methyl-2-butenoic acid methyl ester (3M2BAME), 2-butenoic acid methyl ester (2BAME), and several methylated sugars. TCM of endospores was performed based on hydrolysis and methylation at elevated temperature after the endospores were mixed with sulfuric acid (H2SO4) with or without addition of tetramethylammonium hydroxide (TMAH) in methanol (MeOH). TCM products were then introduced into a heated GC injector port using a coiled wire filament (CWF) or solid phase microextraction (SPME) for detection and differentiation of the endospores by GC-MS.The CWF, which consisted of a tiny platinum helical wire coil attached to a retractable plunger that moved the coil in and out of a syringe needle housing, allowed for sampling to be accomplished by dipping the CWF in an endospore sample suspension, evaporating the suspension liquid, and then introducing the CWF into the injection port to enable on-line TCM. New SPME techniques, including half-half extraction, coated-needle extraction (CNE), and a new home-made polymer coated needle were used to speed up solid phase micro extraction of biomarkers produced from TCM. These simplified the detection of anthrose and other biomarkers. TCM with a CWF and TCM with SPME produced high intensity profiles of DPAME, FAMEs, 2BAME, 3M2BAME and methylated sugars. While the presence of DPAME can be used for the general detection of endospores (Bacillus and Clostridium) and the presence of 3M2BAME for the detection of BA, specific saturated and unsaturated C15, C16, and C17 fatty acid methyl esters and methylated sugars provide additional information for differentiating various Bacillus species grown at different temperatures and in different media. DPAME was detected in samples containing as few as 2,500 and 6,000 endospores using TCM-CWF with and without a concentration step, respectively. GC-MS peak area percent reproducibility for FAMEs using TCM and CWF varied from 3 to 13% (RSD). Better than 97% correct predictability of Bacillus species identity was obtained from a blind experiment consisting of 145 samples using DPAME and specific FAMEs. Conventional SPME and a modified form of "in-needle" extraction allow for detection of the biomarkers in less than 35 min. The detection limits with SPME sample introduction injection were approximately 5 x 103 endospores.Using these approaches, differentiation of Bacillus endospores and other biological agents grown under different conditions were based on the following characteristics: (1) presence of DPAME and specific FAMEs (iso or anteiso C15:0 and iso or anteiso C17:0) in Bacillus endospores, (2) unique presence of 3M2BAME (anthrose by-product) in BA, (3) absence of 2-butenoic acid methyl ester in BG, and (4) presence and absence of specific methylated monosaccharides in various Bacillus species. Clostridium endospores and non-sporulating bacteria, such as Yersinia pestis (YP) and Francisella tularensis (FT) could also be easily distinguished from Bacillus endospores based on the presence and absence of several specific sugar derivatives and fatty acid methyl esters (FAMEs), such as iso or anteiso C15:0 and iso or anteiso C17:0, and > C18 FAMEs which were simultaneously produced during TCM.
180

Novel Developments on the Extraction and Analysis of Polycyclic Aromatic Hydrocarbons in Environmental Samples

Wilson, Walter 01 January 2014 (has links)
This dissertation focuses on the development of analytical methodology for the analysis of polycyclic aromatic hydrocarbons (PAHs) in water samples. Chemical analysis of PAHs is of great environmental and toxicological importance. Many of them are highly suspect as etiological agents in human cancer. Among the hundreds of PAHs present in the environment, the U.S. Environmental Protection Agency (EPA) lists sixteen as "Consent Decree" priority pollutants. Their routine monitoring in environmental samples is recommended to prevent human contamination risks. A primary route of human exposure to PAHs is the ingestion of contaminated water. The rather low PAH concentrations in water samples make the analysis of the sixteen priority pollutants particularly challenging. Current EPA methodology follows the classical pattern of sample extraction and chromatographic analysis. The method of choice for PAHs extraction and pre-concentration is solid-phase extraction (SPE). PAHs determination is carried out via high-performance liquid chromatography (HPLC) or gas chromatography/mass spectrometry (GC/MS). When HPLC is applied to highly complex samples, EPA recommends the use of GC/MS to verify compound identification and to check peak-purity of HPLC fractions. Although EPA methodology provides reliable data, the routine monitoring of numerous samples via fast, cost effective and environmentally friendly methods remains an analytical challenge. Typically, 1 L of water is processed through the SPE device in approximately 1 h. The rather large water volume and long sample processing time are recommended to reach detectable concentrations and quantitative removal of PAHs from water samples. Chromatographic elution times of 30 - 60 min are typical and standards must be run periodically to verify retention times. If concentrations of targeted PAHs are found to lie outside the detector's response range, the sample must be diluted (or concentrated), and the process repeated. In order to prevent environmental risks and human contamination, the routine monitoring of the sixteen EPA-PAHs is not sufficient anymore. Recent toxicological studies attribute a significant portion of the biological activity of PAH contaminated samples to the presence of high molecular weight (HMW) PAHs, i.e. PAHs with MW ≥ 300. Because the carcinogenic properties of HMW-PAHs differ significantly from isomer to isomer, it is of paramount importance to determine the most toxic isomers even if they are present at much lower concentrations than their less toxic isomers. Unfortunately, established methodology cannot always meet the challenge of specifically analyzing HMW-PAHs at the low concentration levels of environmental samples. The main problems that confront classic methodology arise from the relatively low concentration levels and the large number of structural isomers with very similar elution times and similar, possibly even virtually identical, fragmentation patterns. This dissertation summarizes significant improvements on various fronts. Its first original component deals with the unambiguous determination of four HMW-PAHs via laser-excited time-resolved Shpol'skii spectroscopy (LETRSS) without previous chromatographic separation. The second original component is the improvement of a relatively new PAH extraction method - solid-phase nanoextraction (SPNE) - which uses gold nanoparticles as extracting material for PAHs. The advantages of the improved SPNE procedure are demonstrated for the analysis of EPA-PAHs and HMW-PAHs in water samples via GC/MS and LETRSS, respectively.

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