Mass spectrometers are analytical instruments that convert neutral atoms and molecules into gaseous ions and separate those ions according to the ratio of their mass to charge, m/z. The measurement is reported as a mass spectrum: a plot of relative intensity vs. m/z that can be used to deduce the chemical structure and composition of materials and compounds. Initially, the use of mass spectrometers was restricted to the analysis of volatile compounds. Recent advances in the development of ionisation techniques to produce intact molecules directly from samples in the liquid or solid phase, has extended the powerful use of mass spectrometry to compounds of increasingly higher molecular mass. The aim of this study was twofold: develop diagnostic techniques for the in-situ measurement of isotope ratios in laser isotope separation experiments; and to correlate it with the measured isotope ratios on the collected product. The outcome is a thesis that can be divided into two distinct fields of application: Firstly; the Atomic Vapour Laser Isotope Separation (AVLIS) of lithium, and secondly the Molecular Laser Isotope Separation (MLIS) of uranium, In both AVLIS and MLIS pulsed laser systems were used to ionise and/or dissociate atomic or molecular beams. The pulsed nature of the lasers is ideally suited to in-situ time-of-flight detection of the produced ions. Different types of inter-changeable ion sources are common to the same TOF mass spectrometer. Each of these sources is selected according to its application. For instance, applications vary from photo- and multiphoton ionisation (laser ionisation) to surface analysis (laser desorption or particle bombardment) to chromatography (electron impact ionisation). Four different source configurations were considered in this study: (i) Atomic Laser Isotope Separation (AVLIS) of lithium; (ii) Multiphoton Ionisation (MPl) of UF6 gas; (iii) Non-resonant ionisation during Laser Desorption (LDI) of solids; and (iv) Matrix-Assisted Laser Desorption (MALD) of biopolymers. The design of each of these sources will be discussed in detail in chapters to follow. Bulk analysis of harvested laser-produced products needs to be in correlation with in-situ analysis. Three different characterisation methods were used in this study: (i) Laser Desorption Time-of-Flight Mass Spectrometry (LD-TOF-MS) (ii) Quadrupole-based Secondary Ion Mass Spectrometry (SIMS); and (iii) TOF-MS-based Secondary Ion Mass Spectrometry (TOF-SIMS). Chapter I describes the principles of time-of-flight mass spectrometry, design parameters, as well as the instrumentation that were designed and constructed for the purposes of this study. Chapter II describes the principles of Secondary Ion Mass Spectrometry (SIMS). In particular, research done on the establishment of tools to the non-expert user of SIMS to select analyses conditions, is described. Chapter III reports on the application of TOF-MS and SIMS during the AVLIS of lithium. Chapter IV reports on the application of the different combinations of TOF-MS, LD-TOF-MS, SIMS, and TOF-SIMS during the MLIS of uranium. / Thesis (Ph.D.)-University of Natal, Durban, 1999.

Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (p. 161-186).

Thesis (M. S.)--Chemistry and Biochemistry, Georgia Institute of Technology, 2006. / Fernandez, Facundo, Committee Chair ; Janata, Jiri, Committee Member ; Mizaikoff, Boris, Committee Member.

Includes bibliographical references (p. 162-177).

Thesis (Ph. D.)--University of Texas at Austin, 2008. / Vita. Includes bibliographical references.

In the present work, the abnormal glow discharge at atmospheric pressure was generated in the nitrogen-methane (1 to 5 %) gaseous mixtures related to the atmosphere of Titan. The discharge itself was monitored by optical emission spectrometry that confirmed presence of active nitrogen species and various radicals formed from methane. Besides them, the CN spectral bands were observed. Intensities of all light emitting species were studied in the dependence on applied power and composition of nitrogen-methane mixture. The rotational temperature of about 2000 K was calculated from the second positive nitrogen system. The vibrational temperature also obtained from neutral nitrogen molecule increased nearly directly with methane from 3000 K (1 % CH4) to 3600 K (5 % CH4). In the contrary, vibrational temperature obtained from nitrogen molecular ion decreased with methane in the gaseous mixture and increased with applied discharge power from 3700 K to 4200 K. The same trend showed the vibrational temperature calculated from violet system of CN with value from 4600 K to 5800 K. The stable discharge products were analysed by proton transfer time of flight mass spectrometry of the exhausting gas. Presence of many aliphatic and some aromatic hydrocarbons was confirmed as well as quite a lot of amino and cyano compounds. Increasing concentrations of methane have produced more substances with higher molecular weight and less simple substances that were likely to be consumed on more complex substances. Their relative intensities were determined under the same conditions as optical emission spectra were collected.

The ability to identify and confirm a compound using mass spectrometry usually involves time consuming sample preparation and method development. The open-air ion source DART (Direct Analysis in Real Time) can ionize compounds in the gas, solid, or liquid phase without chromatography or sample preparation due to the interactions of helium metastable atoms with gas molecules commonly found in air. The coupling of the DART to a time-of-flight (TOF) mass spectrometer allows the rapid determination of an analyte's elemental composition based on accurate mass measurement and isotope peak intensities. Mass spectrometric fragmentation data can aid in the structural identification of an analyte as compounds produce characteristic fragment-ions based on their structure. The TOP's ability to produce fragmentation spectra was compared to the more traditional tandem mass spectral method (MS/MS) considering the TOF lacks the ability to select pre-cursor ions. The TOF produced in-source CAD (collisionally activated dissociation) spectra comparable to MS/MS spectra for three well known pharmaceuticals acetaminophen, phenylbutazone and clenbuterol. Further structural confirmation was explored through a determination of the number of active hydrogen atoms in an analyte molecule achieved by hydrogen/deuterium (H/D) exchange by treatment with deuterium oxide (D20) in the DART sample gap. Mass spectra acquired in the presence of D20 of analytes containing active hydrogen atoms associated with hydroxyl, amino and carboxylic acid groups showed that H/D exchange was predictable and reproducible. Using accurate mass measurement and isotope peak intensities, the elemental composition of an unknown captured on filter paper was identified as dipropylene glycol (DPG) analyzed directly from the surface of the filter paper. Data from in-source CAD and H/D exchange of both the unknown and authentic standards confirmed that the unknown was DPG. The cross-correlation of accurate mass measurement and isotope peak intensities, in-source CAD and HID exchange data provided an unambiguous identification of the contaminant melamine in dog food without the need for any sample preparation. Once analytes are identified and confirmed, quantitation of the analyte is desirable. The calibration curves here are constructed using the net extracted ion-current associated with the analyte relative to the internal standard. In cough syrup, a complicated matrix, the linearity, R2, is shown to be 0.992.

No description available.

Objectives: Fusobacteria are prominent participants in the maturation of subgingival dental plaque biofilms in humans. A number of various species belonging to the Fusobacterium genus have been recovered from the subgingival microbiota of chronic periodontitis patients. However, conventional Fusobacterium species identification is labor-intensive, time-consuming, and complicated by shortcomings in phenotypic-based classification schemes, where many fusobacteria display overlapping and non-distinguishing morphologic features and biochemical properties. In addition, molecular identification of fusobacteria is plagued with difficulties of validating the specificity of nucleic acid probes and primers to various Fusobacterium species that have closely-related interspecies genetic profiles. Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry, and its associated analytic software, was recently approved for clinical microbiology diagnostic use by the United States Food and Drug Administration. MALDI-TOF mass spectrometry has the potential to rapidly identify cultivable clinical isolates to a species level for 4,613 different bacterial species based on mass spectra of their bacterial protein profiles, including many Fusobacterium species. The purpose of this study was to use MALDI-TOF mass spectrometry to rapidly identify the patient distribution of fusobacteria isolated from the subgingival microbiota of chronic periodontitis patients. Methods: A total of 34 chronic periodontitis patients provided 96 fresh subgingival cultivable fusobacteria isolates (one to seven isolates per patient), which were presumptively identified by their chartreuse-positive colony autofluorescence under long-wave ultraviolet light on anaerobically-incubated, non-selective, enriched Brucella blood agar primary isolation plates. Each of the presumptive fusobacteria clinical isolates were subjected to MALDI-TOF mass spectrometry analysis using a bench top mass spectrometer, Bruker FlexControl 3.0 software, and MALDI Biotyper 3.1 software (Bruker Daltonics, Billerica, MA, USA), which contains mass spectra for a variety of fusobacteria in its reference library of bacterial protein profiles. Each clinical isolate underwent on-target plate formic acid protein extraction, and was taxonomically classified with MALDI-TOF mass spectrometry within an approximately 30-45 minute time period from the point of colony harvesting from primary isolation culture plates. A MALDI Biotyper log score of equal to or larger than 1.7 was required for reliable taxonomic classification of the clinical fusobacteria isolates. Results: A majority (58.8%) of the chronic periodontitis patients yielded two or three different species of subgingival Fusobacterium on non-selective enriched Brucella blood agar primary isolation plates. Fusobacterium naviforme was identified by MALDI-TOF mass spectrometry analysis in 14 (41.2%) chronic periodontitis study patients, Fusobacterium nucleatum subspecies vincentii in 13 (38.2%) patients, Fusobacterium nucleatum subspecies polymorphum in 9 (26.5%) patients, Fusobacterium nucleatum and Fusobacterium species each in 6 (17.6%) patients, Fusobacterium nucleatum subspecies nucleatum in 4 (11.8%) patients, and Fusobacterium nucleatum subspecies animalis in 3 (8.8%) patients. Three patients additionally yielded subgingival isolates of Fusobacterium canifelinum, normally an inhabitant of the oral cavity of dogs and cats. 52 (54.2%) of the fusobacteria clinical isolates revealed MALDI Biotyper log scores of equal to or larger than 1.7, the threshold for reliable taxonomic classification, while in comparison, 44 (45.8%) had log scores less than 1.7, indicating a less reliable species identification. No other microbial species, other than one of the Fusobacterium species, was listed by the MALDI-TOF mass spectrometry analytic software as the most likely organism for the tested clinical isolates. Conclusions: These findings indicate that a variety of Fusobacterium species may be identified with MALDI-TOF mass spectrometry in the subgingival microbiota of chronic periodontitis patients. F. naviforme and F. nucleatum subspecies vincentii were the most frequently isolated subgingival fusobacteria species in the evaluated study patients. Three chronic periodontitis patients also unexpectedly revealed subgingival isolates of the animal species F. canifelinum, which is normally in the oral cavity of dogs and cats. MALDI-TOF mass spectrometry may facilitate rapid identification of cultivable fusobacteria in human subgingival dental plaque biofilms, and enhance understanding of bacterial community structure in periodontal pockets. / Oral Biology

Chan Pui Kwan. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2001. / Includes bibliographical references (leaves 98-104). / Abstracts in English and Chinese. / TABLE OF CONTENTS --- p.i / LIST OF FIGURES --- p.iv / LIST OF TABLES --- p.vii / ABBREVIATIONS --- p.viii / Chapter Chapter one --- Research Background / Chapter 1.1 --- Carbohydrates --- p.2 / Chapter 1.2 --- Impact of molecular weight of polysaccharides --- p.5 / Chapter 1.3 --- Molecular Weight Determination of polysaccharides --- p.6 / Chapter 1.3.1 --- Laser Scattering --- p.6 / Chapter 1.3.2 --- Gel Permeation Chromatography --- p.7 / Chapter 1.3.3 --- Mass spectrometry --- p.9 / Chapter 1.4 --- Matrix assisted laser desorption/ ionization (MALDI) --- p.10 / Chapter 1.4.1 --- Laser desorption --- p.10 / Chapter 1.4.2 --- Matrix-assisted laser desorption / ionization (MALDI) --- p.11 / Chapter 1.5 --- MALDI-TOFMS analysis of polymers --- p.14 / Chapter 1.6 --- Outline of the present work --- p.16 / Chapter Chapter two --- Experimental and Instrumentation / Chapter 2.1 --- Matrix-assisted laser desorption/ ionization Time of flight Mass Spectrometry (MALDI-TOFMS) --- p.18 / Chapter 2.2 --- Delayed extraction --- p.20 / Chapter 2.3 --- Time of flight mass spectrometry (TOFMS) --- p.20 / Chapter 2.3.1 --- Linear time-of-flight mass spectrometry --- p.20 / Chapter 2.3.2 --- Reflectron --- p.21 / Chapter 2.4 --- Instrumentation --- p.23 / Chapter 2.4.1 --- Laser system --- p.24 / Chapter 2.4.2 --- Ion source --- p.26 / Chapter 2.4.3 --- Ion deflection --- p.26 / Chapter 2.4.4 --- Detection --- p.27 / Chapter 2.4.5 --- Reflector --- p.27 / Chapter 2.4.6 --- Data acquisition --- p.29 / Chapter 2.5 --- Experimental --- p.29 / Chapter 2.5.1 --- Sample preparation --- p.29 / Chapter 2.5.2 --- Calibration --- p.33 / Chapter 2.6 --- Data analysis --- p.33 / Chapter Chapter three --- Use of ammonium fluoride as co-matrix / Chapter 3.1 --- Introduction --- p.35 / Chapter 3.2 --- Results and discussion --- p.37 / Chapter 3.2.1 --- Effect of co-matrix --- p.45 / Chapter 3.2.2 --- Effect of sample preparation --- p.49 / Chapter 3.2.3 --- Analysis of dispersed dextran --- p.52 / Chapter 3.3 --- Conclusion --- p.55 / Chapter Chapter four --- Effect of sample preparation / Chapter 4.1 --- Introduction --- p.57 / Chapter 4.2 --- Experimental --- p.57 / Chapter 4.2.1 --- Sample preparation --- p.57 / Chapter 4.3 --- Results and discussion --- p.59 / Chapter 4.4 --- Conclusion --- p.71 / Chapter Chapter five --- Development of liquid matrix systems / Chapter 5.1 --- Introduction --- p.73 / Chapter 5.2 --- Experimental --- p.75 / Chapter 5.2.1 --- Sample preparation --- p.75 / Chapter 5.3 --- Results and discussion --- p.76 / Chapter 5.3.1 --- Formulation of matrix solutions --- p.76 / Chapter 5.3.2 --- Use of liquid matrix system --- p.87 / Chapter 5.3.3 --- Analysis of dispersed dextran --- p.90 / Chapter 5.4 --- Conclusion --- p.93 / Chapter Chapter six --- Conclusion / Chapter 6.1 --- Conclusion --- p.95 / References --- p.98 / Appendix / Appendix 1 Chemical structure of matrices / Appendix 2 Chemical structure of solubilizing agents / Appendix 3 Chemical structure of liquid supports / Appendix 4 Chemical structure of additives