The use of short columns, higher carrier gas velocity and fast temperature programs in Comprehensive Two-Dimensional Gas Chromatography coupled to Time-of- Flight Mass Spectrometry (GC x GC/TOFMS) technique is expected to increase the speed of analysis up to several orders of magnitude when compared to conventional gas chromatography (GC) or gas chromatography/mass spectrometry (GC/MS). A systematic evaluation of the GC x GC/TOFMS configuration for high-speed applications has received little attention in the literature. The feasibility of High Speed Comprehensive Two-Dimensional Gas Chromatography coupled to Mass Spectrometry (High speed GC x GC/MS) for complex mixtures has been investigated in this thesis. A particular focus was placed on comparing conventional scanning quadrupole mass spectrometry (qMS) with a newly available non-scanning time-of-flight instruments (TOFMS). Experiments were carried out using GC/qMS, GC x GC/qMS, GC/TOFMS and GC x GC/TOFMS both in normal (slow) and fast temperature rates coupled with high frequency modulation in GC x GC. Initially a complex mixture consists of 24 semivolatile compounds was used as the analyte for the above purpose. In the initial experiments parameters like acquisition rate and duty cycle for qMS were determined to evaluate the effectiveness of the instrument for fast analysis. The practical duty cycle value obtained for the qMS was only about 18 % for single ion and one compound at a dwell time of 10 ms in SIM mode. In both high-speed GC/qMS and high-speed GC x GC/qMS techniques only about 40 % of the components in the complex mixture were found to be well separated. The acquisition rate of scanning instruments like qMS is incompatible for fast eluting peaks in high speed GC. TOFMS that has an acquisition rate of several hundred spectra per second offer the potential to define the fast GC peaks accurately. The high quality spectra from TOFMS also enable deconvolution of coeluting peaks in the complex mixtures. The advantage of the automated spectral deconvolution is demonstrated for the identification of the coeluting peaks in the complex mixtures. Coelution of peaks is also observed with highspeed GC/TOFMS technique. The high-speed GC x GC/TOFMS was also tested with two different analyte system ??? A pesticide mixture and platformate (an aromatic mixture) to evaluate the suitability for high-speed analysis of complex mixtures. A poor resolution was observed for the pesticide mixture in the two-dimensional plane and it appeared, as there was nearly no orthogonal separation in the second dimension. The platformate mixture displayed a better two-dimensional separation. Chromatographic peak resolution is not really a primary requirement for locating and identifying the coeluting compounds in high-speed GC x GC/TOFMS technique. However, it was observed that the high-speed GC x GC/TOFMS too faced problem to unscramble the mass spectra of those compounds with similar structure and sharing the same unique masses.

<p>Today there are no fully general analytical techniques available for detection and confirmation of known and unknown substances in toxicological screening, further tools are therefore needed. The development of mass spectrometry with time-of-flight (TOF) detection is promising but there are still areas to be further developed and evaluated, both instrumentation and applications.</p><p>During 2009 The National Board of Forensic Medicine-Department of Forensic Genetics and Forensic Toxicology, (RMV) started cooperation with the instrumentation company Waters (Manchester, UK) and the Department of Clinical Pharmacology (KI, Solna) evaluating a new TOF-instrument for toxicological screening. My assignment as a part of this project has been to create a limited and relevant database of drugs and toxics in Excel, including monoisotopic mass, used when screening for pharmaceutical substances and their metabolites most probable to be found in Swedish autopsy material.</p><p>A limited database has been developed based on information from several sources, it ended up in 875 analytes and metabolites. A limited but complete database is more reliable in practise than a big database, by means of a lower frequency of isobars and more information included (e.g. retention time from liquid chromatography) making analysis faster. Commercial databases are generally theoretical, lacking information about for example retention time that often is an important criterion for identification.</p>

Identification of fungi is based on macroscopic observations of morphology and microscopic characteristics. These conventional methods are time-consuming and requires expert knowledge. For the past years Matrix-assisted laser desorption ionization-time of flight mass spectrometry has been used for routine bacterial identification in clinical laboratories but not yet in the same extension for fungi. In this study three preanalytic preparation methods for fungi were evaluated in order to shorten the processing time in routine laboratory performance. Clinically relevant strains (n=18) of molds and dermatophytes were cultivated on agar plates and prepared according to the different preparation methods for protein extraction. Each strain was analyzed in quadruplicate by the MALDI Biotyper and the database Filamentous Fungi Library 1.0. The results showed that the genus and species identification rates of the least time-consuming direct extraction method were 33% and 11% respectively. Using the formic acid extraction method, the genus and species identification rates were 83% and 44%, respectively. For the longest sample preparation method, liquid media culturing before formic acid extraction, successfully identified all strains except one, which resulted in an identification rate of 94% and 78% respectively. This study shows that preparing samples in cultured liquid media MADLI-TOF MS effectively identified fungal strains to both genus- and species-level. This method was however too time-consuming and cumbersome to be recommended as a replacement to the conventional method. Future studies should be aimed at expanding the reference library and making the direct extraction method more reproducible in terms of obtaining more reliable identification rates.

The use of short columns, higher carrier gas velocity and fast temperature programs in Comprehensive Two-Dimensional Gas Chromatography coupled to Time-of- Flight Mass Spectrometry (GC x GC/TOFMS) technique is expected to increase the speed of analysis up to several orders of magnitude when compared to conventional gas chromatography (GC) or gas chromatography/mass spectrometry (GC/MS). A systematic evaluation of the GC x GC/TOFMS configuration for high-speed applications has received little attention in the literature. The feasibility of High Speed Comprehensive Two-Dimensional Gas Chromatography coupled to Mass Spectrometry (High speed GC x GC/MS) for complex mixtures has been investigated in this thesis. A particular focus was placed on comparing conventional scanning quadrupole mass spectrometry (qMS) with a newly available non-scanning time-of-flight instruments (TOFMS). Experiments were carried out using GC/qMS, GC x GC/qMS, GC/TOFMS and GC x GC/TOFMS both in normal (slow) and fast temperature rates coupled with high frequency modulation in GC x GC. Initially a complex mixture consists of 24 semivolatile compounds was used as the analyte for the above purpose. In the initial experiments parameters like acquisition rate and duty cycle for qMS were determined to evaluate the effectiveness of the instrument for fast analysis. The practical duty cycle value obtained for the qMS was only about 18 % for single ion and one compound at a dwell time of 10 ms in SIM mode. In both high-speed GC/qMS and high-speed GC x GC/qMS techniques only about 40 % of the components in the complex mixture were found to be well separated. The acquisition rate of scanning instruments like qMS is incompatible for fast eluting peaks in high speed GC. TOFMS that has an acquisition rate of several hundred spectra per second offer the potential to define the fast GC peaks accurately. The high quality spectra from TOFMS also enable deconvolution of coeluting peaks in the complex mixtures. The advantage of the automated spectral deconvolution is demonstrated for the identification of the coeluting peaks in the complex mixtures. Coelution of peaks is also observed with highspeed GC/TOFMS technique. The high-speed GC x GC/TOFMS was also tested with two different analyte system ??? A pesticide mixture and platformate (an aromatic mixture) to evaluate the suitability for high-speed analysis of complex mixtures. A poor resolution was observed for the pesticide mixture in the two-dimensional plane and it appeared, as there was nearly no orthogonal separation in the second dimension. The platformate mixture displayed a better two-dimensional separation. Chromatographic peak resolution is not really a primary requirement for locating and identifying the coeluting compounds in high-speed GC x GC/TOFMS technique. However, it was observed that the high-speed GC x GC/TOFMS too faced problem to unscramble the mass spectra of those compounds with similar structure and sharing the same unique masses.

Thesis (Ph.D.)--Ohio University, March, 2005. / Includes bibliographical references (p. 163-176)

Thesis (Ph.D.)--Ohio University, March, 2005. / Title from PDF t.p. Includes bibliographical references (p. 163-176)

No description available.

Lanthanum-mediated bond activation reactions of small hydrocarbon molecules, including alkenes, alkynes, and alkadienes, were carried out in a laser vaporization metal cluster beam source. Time-of-flight mass spectrometry and mass-analyzed threshold ionization (MATI) spectroscopy, in combination with quantum chemical and multi-dimensional Franck-Condon factor calculations, were utilized to identify the reaction products and investigate their geometries, electronic structures, and formation mechanisms. La-hydrocarbon association was only observed in the reaction of La with isoprene. C-H bond activation was observed in all reactions, hydrogen elimination was observed as the prominent reaction for the alkenes (2-butene, isobutene, 1-pentene, and 2-pentene), alkynes (1-butyne, 2-butyne, and 1-pentyne), and 1,4-pentadiene, and C-C bond activation was observed for the five-membered hydrocarbons (1-pentene, 2-pentene, 1-pentyne, isoprene, and 1,4-pentadiene). The La-hydrocarbon radicals formed in these reactions had lanthanacyclic structures in various sizes, and each of the La-hydrocarbon complexes had a doublet ground state with a 6s1 La-based electron configuration. Ionization removed the 6s electron, and the resultant ion was in a singlet state. Formations of dehydrogenated products were either through a concerted hydrogen elimination process or the dehydrogenation after ligand isomerization. The C-C bond activation proceeded through La-assisted hydrogen migration, followed by C-C bond cleavage, or vice versa.

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 132-140).

Today there are no fully general analytical techniques available for detection and confirmation of known and unknown substances in toxicological screening, further tools are therefore needed. The development of mass spectrometry with time-of-flight (TOF) detection is promising but there are still areas to be further developed and evaluated, both instrumentation and applications. During 2009 The National Board of Forensic Medicine-Department of Forensic Genetics and Forensic Toxicology, (RMV) started cooperation with the instrumentation company Waters (Manchester, UK) and the Department of Clinical Pharmacology (KI, Solna) evaluating a new TOF-instrument for toxicological screening. My assignment as a part of this project has been to create a limited and relevant database of drugs and toxics in Excel, including monoisotopic mass, used when screening for pharmaceutical substances and their metabolites most probable to be found in Swedish autopsy material. A limited database has been developed based on information from several sources, it ended up in 875 analytes and metabolites. A limited but complete database is more reliable in practise than a big database, by means of a lower frequency of isobars and more information included (e.g. retention time from liquid chromatography) making analysis faster. Commercial databases are generally theoretical, lacking information about for example retention time that often is an important criterion for identification.