Spatially Resolved Laser and Thermal Desorption/Ionization Coupled with Mass Spectrometry

The work discussed in this dissertation is aimed at creating novel approaches to chemical imaging that ultimately allow for submicron resolution. This goal has been approached from two direction using laser based desorption and coupling it with an AFM using apertureless tip-enhanced laser ablation/ionization. The second direction was through the development a new approach to thermal desorption based mass spectrometry experiments by using a proximal probe to spatially desorb the surface and ionizing the plume of neutrals using a secondary ionization source at atmospheric pressure. The thermal desorption approach allows for the easy scaling of the technique all the way from the millimeter to the nanometer regime. In the nanometer regime an AFM platform with silicon based heating AFM probes is used to locally desorb material from nanometer sized craters. The final work in this thesis focused on trying to improve laser based desorption through a secondary ionization of the neutrals plume by capturing the laser desorption plume into a liquid and then electrospaying the solution into a MS. The added benefit of being able to capture the desorption plume into a liquid is the ability to carry out post sampling processing of the captured analyte via high performance liquid chromatography. The ability to clean up a sample via HPLC also allow for the detection of isobaric compounds as well as trace level materials which otherwise would be obscured by matrix effects in complicated sample matrixes like tissues. This application of laser desorption with a secondary ionization by capture into a liquid could be envisioned to be applied to AFM based laser desorption techniques where boosting the ionization efficiency is crucial for signal detection

Nové metody hmotnostní spektrometrie pro stopovou analýzu látek v lidském dechu.

Tato disertační práce shrnuje výsledky experimentů, na kterých jsem pracovala během svého postgraduálního studia zaměřeného na nové metody hmotnostní spektrometrie pro stopovou analýzu látek v lidském dechu. Disertační práce je rozdělena na teoretickou a experimentální část. Úvodní kapitola shrnuje současný výzkum v oblasti analýzy dechu, přičemž popisuje metabolity běžně obsažené v dechu, benefity a podněty této metody pro terapeutické monitorování, klinickou diagnózu a též současné oblasti aplikace. Další kapitola teoretické části popisuje techniky vhodné pro tuto oblast výzkumu, se zvláštním důrazem na hmotnostně spektrometrické techniky (zejména pak hmotnostní spektrometrii v proudové trubici s vybranými ionty, SIFT-MS, metodu, jež umožňuje přesnou kvantifikaci stopových plynů a par ve vlhkém vzduchu/lidském dechu). Obě kapitoly jsou zpracovány formou rešerše. Navazující kapitoly se pak přímo týkají mého vlastního výzkumu a popisují provedené experimenty i dosažené výsledky. Experimentální část "Výsledky a diskuze" je rozdělena do několika podkapitol, jež jsou koncipovány jako komentáře již publikovaných výsledků v impaktovaných časopisech. První podkapitola se detailně zabývá iontovou chemií (základ metody SIFT-MS), včetně stanovení poměrů větvení a rychlostních konstant reakcí reakčních iontů...This dissertation thesis summarizes results of experiments that have been carried out during my PhD studies related to the new mass spectrometric methods for trace gas analysis of human breath. The thesis is divided into the theoretical and experimental part. The chapter at the beginning of this dissertation summarizes the current research in the area of breath analysis. It is describing the common breath metabolites, benefits and challenges of the method for therapeutic monitoring and clinical diagnosis and current applications. The next chapter of the theoretical introduction describes the techniques suitable for this area of research, with a special emphasis on mass-spectrometric techniques (in particular the selected ion flow tube mass spectrometry, SIFT-MS, method that allows accurate quantification of trace gases and vapours in humid air/human breath). All these parts are elaborated via the scientific literature review. The following chapters are then directly related to my own research and describes the conducted experiment, including the results obtained. This experimental part "Results and Discussion" is divided to the individual subsections, which are conceived as the commentaries to the enclosed research papers published in peer reviewed journals. The first is the detailed step by step...Katedra fyzikální a makromol. chemieDepartment of Physical and Macromolecular ChemistryFaculty of SciencePřírodovědecká fakult

Nové metody hmotnostní spektrometrie pro stopovou analýzu látek v lidském dechu.

Tato disertační práce shrnuje výsledky experimentů, na kterých jsem pracovala během svého postgraduálního studia zaměřeného na nové metody hmotnostní spektrometrie pro stopovou analýzu látek v lidském dechu. Disertační práce je rozdělena na teoretickou a experimentální část. Úvodní kapitola shrnuje současný výzkum v oblasti analýzy dechu, přičemž popisuje metabolity běžně obsažené v dechu, benefity a podněty této metody pro terapeutické monitorování, klinickou diagnózu a též současné oblasti aplikace. Další kapitola teoretické části popisuje techniky vhodné pro tuto oblast výzkumu, se zvláštním důrazem na hmotnostně spektrometrické techniky (zejména pak hmotnostní spektrometrii v proudové trubici s vybranými ionty, SIFT-MS, metodu, jež umožňuje přesnou kvantifikaci stopových plynů a par ve vlhkém vzduchu/lidském dechu). Obě kapitoly jsou zpracovány formou rešerše. Navazující kapitoly se pak přímo týkají mého vlastního výzkumu a popisují provedené experimenty i dosažené výsledky. Experimentální část "Výsledky a diskuze" je rozdělena do několika podkapitol, jež jsou koncipovány jako komentáře již publikovaných výsledků v impaktovaných časopisech. První podkapitola se detailně zabývá iontovou chemií (základ metody SIFT-MS), včetně stanovení poměrů větvení a rychlostních konstant reakcí reakčních iontů...This dissertation thesis summarizes results of experiments that have been carried out during my PhD studies related to the new mass spectrometric methods for trace gas analysis of human breath. The thesis is divided into the theoretical and experimental part. The chapter at the beginning of this dissertation summarizes the current research in the area of breath analysis. It is describing the common breath metabolites, benefits and challenges of the method for therapeutic monitoring and clinical diagnosis and current applications. The next chapter of the theoretical introduction describes the techniques suitable for this area of research, with a special emphasis on mass-spectrometric techniques (in particular the selected ion flow tube mass spectrometry, SIFT-MS, method that allows accurate quantification of trace gases and vapours in humid air/human breath). All these parts are elaborated via the scientific literature review. The following chapters are then directly related to my own research and describes the conducted experiment, including the results obtained. This experimental part "Results and Discussion" is divided to the individual subsections, which are conceived as the commentaries to the enclosed research papers published in peer reviewed journals. The first is the detailed step by step...Katedra fyzikální a makromol. chemieDepartment of Physical and Macromolecular ChemistryPřírodovědecká fakultaFaculty of Scienc

Development of sample preparation and chromatographic mass spectrometric techniques for determination of selected organic pollutants in wastewater

Abstract : In the recent past, there has been a great concern on the ever-increasing emergence of organic contaminants in the various environmental compartments, that pose great health concerns to humans and aquatic life. These organic pollutants have been ubiquitous in the environment for decades, however, they were not identifiable until the emergence of new and advanced analytical technologies. Therefore, the main objective of this study was to develop robust and efficient analytical and modelling techniques, for the extraction and analysis of selected multiclass organic contaminants from wastewater samples. This is because their analytical determination is very challenging due to their occurrence in trace levels (ng L-1 to μg L-1) in the environment. The analytical techniques comprise of optimization of both the sample preparation procedures and instrumental analysis for detection and quantification. Solid phase extraction (SPE), dispersive liquid-liquid microextraction (DLLME) and ultrasonic-assisted magnetic solid phase dispersive extraction (UA-MSPDE) were the selected sample preparation techniques used for the extraction and preconcentration of methylparaben, ethylparaben, propylparaben, ethoprofos, parathion methyl, azinphos methyl and chlorpyrifos in water samples. This was followed by instrumental analysis for their detection and quantification using liquid chromatography tandem mass spectrometry (LC-MS/MS). The developed analytical techniques were applied in real environmental samples obtained from different water treatment stages of a local wastewater treatment plant in Gauteng province, South Africa. Experimental factors that had an influence on the analytical response in terms on highest percentage recoveries were optimized using both univariate (one factor a time) and multivariate approach for all the experiments in this study. Multivariate optimization was accomplished using Statistica and Minitab software. The performance characteristics of the LC-MS/MS facilitated the determination of these organic contaminants at trace levels. Multiple reaction monitoring mode (MRM) was used for specific and sensitive targeted analysis, where the quadrupole analyzers were set at multiple ion frequencies for the specific analytes under investigation together with their product fragment ions. MRM is ideally suitable for trace level analysis of complex mixtures. Oasis HLB cartridges were found to be suitable for extraction of parabens giving satisfactory results. Vortex assisted dispersive liquid-liquid microextraction (VA-DLLME) was used for the extraction and enrichment of organophosphorus pesticides in wastewater samples. Selection of the appropriate organic solvent (extractant and disperser solvents) used for this method was of utmost importance and was performed using univariate optimization. v The results revealed chloroform to be the most suitable extractant solvent while acetone was the optimum disperser solvent. This was followed by the chemometric optimization of the independent variables that significantly affect the outcome of the analytical response. The organophosphorus compounds that were extracted in wastewater samples using this technique with satisfactory results were ethoprofos, parathion methyl and azinphos methyl. Also, a novel method was developed for the extraction and preconcentration of multiclass organic compounds (parabens and organophosphorus pesticides) using synthesized pristine carbon nanodots (CNDs) applied as SPE adsorbent. A comparison between the synthesized CNDs and commercial based SPE sorbent was analyzed. Two-level factorial design and response surface methodology based on central composite design were used for multivariate optimization of the experimental variables. Furthermore, the CNDs were also functionalized with magnetite. The magnetic CNDs were applied for the development of magnetic solid phase dispersive extraction method with ultrasonic dispersion for the simultaneous extraction of chlorpyrifos and triclosan in environmental water samples. This method offered a very rapid and simple extraction and preconcentration of these organic contaminants with satisfactory results.Ph.D. (Chemistry

Space programs summary no. 37-46, volume IV FOR the period June 1 to July 31, 1967. Supporting research and advanced development

Spacecraft guidance and control, propulsion, telecommunications, and systems analysis, and space science researc

NASA Tech Briefs, September 1990

Topics covered include: New Product Ideas; NASA TU Services; Electronic Components and Circuits; Electronic Systems; Physical Sciences; Materials; Computer Programs; Mechanics; Machinery; Fabrication Technology; Mathematics and Information Sciences; Life Sciences

Design and engineering of microreactor and smart-scaled flow processes

This book is a reprint of the special issue that appeared in the online open access journal Processes (ISSN 2227-9717) in 2013 (available at: http://www.mdpi.com/journal/processes/special_issues/smart-scaled_flow_processes)