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Showing 1 to 5 of 5 (0.167 seconds)Spelling suggestions: "subject:"time5of5flight mass spectrometer"" "subject:"timelight mass spectrometer""
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Implementation of an In-line Surface-induced Dissociation Device in a Quadrupole Time-of-flight Instrument and Its PerformanceGalhena, Asiri S. January 2008 (has links)
The focus of this dissertation is the introduction of surface-induced dissociation (SID) into a commercially available quadrupole time-of-flight mass spectrometer as an alternative ion fragmentation method. The performance of the SID device was characterized and its applications were demonstrated by dissociating peptides, proteins, inorganic salt clusters and non-covalent protein complexes. The SID setup allowed direct comparison of SID with conventional collision-induced dissociation (CID) on the same instrument, taking advantage of the characteristics of Q-TOF instrumentation, including extended mass range, high sensitivity and resolution. With the SID setup installed, no significant reduction of the ion transmission was evident. SID fragmentation patterns of peptides are, in general, similar to CID, with slight differences in the relative intensities of immonium ions, backbone cleavage b- versus y- type ions, and y- versus y-NH3 ions. This suggests enhanced accessibility to high energy/secondary fragmentation channels with SID. SID studies on cesium iodide clusters (CsI) also revealed that SID deposits more internal energy.The utility of mass spectrometric methods to probe the gas phase cyclization process was studied with [D-Ala2]-Leucine Enkephalin amide. This peptide showed prominent formation of the [M-NH3]+ ion which is believed to be the linear b5 ion with a C-terminal oxazolone structure. Other fragments in the spectra indicate that the linear b5 ion undergoes cyclization, subsequent ring opening and further dissociation to rearranged fragments that cannot be explained by the initial sequence. The similarities between the cyclic and b5-ion from the linear peptide indicated the formation of a heterogeneous ion population and this is further supported by gas-phase H/D exchange experiments. An ion funnel interface to improve ion transmission at high pressures was tested in a custom built quadrupole-surface-quadrupole instrument. The ion transmission efficiency for selected bio-molecules such as YGGFLR, insulin chain-B, ubiquitin and cytochrome c showed to approach almost 90%, with the funnel interface installed. The ion transmission efficiency was effected by several factors including: the size of the analyte, the DC gradient, the RF frequency, and the RF amplitude. The higher fragmentation efficiencies for SID in the presence of the funnel interface indicated higher internal energy deposition for the funnel interface.
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Molecular cluster cations of carbon monoxide and carbon dioxideBulat, Muhammer 27 December 2010 (has links)
Diese Dissertation handelt vom metastabilen Zerfall und von der Oberflächenwechselwirkung im hyperthermalen Energiebereich relativ schwach gebundener molekularer Kohlenmonoxid und Kohlendioxid Clusterkationen mit einer Edelstahloberfläche und einer Siliziumoberfläche. Im Rahmen dieser Arbeit wurde ein hierfür geeignetes spezielles Flugzeitmassenspektrometer entwickelt und aufgebaut. Entwurf, numerische Optimierung der Auflösung, ionenoptische Simulationen und Aufbau der jeweiligen Komponenten wie Elektronenquellen, Beschleuniger, Ablenkplatten, Massenfilter und Reflektron werden detailliert beschrieben. Das entwickelte Flugzeitmassenspektrometer besitzt mit einer kompakten Gesamtfluglänge von ~1.5m eine hohe Massenauflösung von m/Delta m = 3000. Es bietet die Möglichkeit, eine Massentrennung von Clusterionen mit einer Größe von bis zu n = 190 vorzunehmen. Diese massenselektierten Clusterionen können daraufhin auf metastabilen Zerfall und auf ihre Wechselwirkung mit einer Oberfläche untersucht werden. Dazu wurden Kohlendioxid-Clusterionen mit n / This thesis deals with the metastable decay and the surface scattering in the hyperthermal energy range of relatively weakly bound molecular cluster cations. With carbon monoxide and carbon dioxide two related model systems were chosen for a systematic size dependent study. Surface impact experiments were carried out with stainless steel and silicon surfaces. Results were obtained by a new, reflectron time-of-flight mass spectrometer (Re-TOFMS). Additional to the experimental data we present in this work a detailed description of the instrumental design considerations, numerical optimization, ion optical simulations. Hence each ion optical component like electron guns, accelerator, deflector, mass gate and reflectron are described. Despite the compact dimensions with a total flight length of ~1.5m the developed instrument possesses a high mass resolution above m/Delta m = 3000. Additionally it offers the possibility to perform mass separation of big cluster ions with sizes n
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The Characterization of Fine Particulate Matter in Toronto Using Single Particle Mass SpectrometryRehbein, Peter J. G. 13 January 2011 (has links)
An Aerosol Time-of-Flight Mass Spectrometer (ATOFMS) was used to obtain mass spectra of individual aerosol particles in the 0.5 – 2 µm size range in downtown Toronto, Canada for one to two month periods during each season of 2007. A modified version of the Adaptive Resonance Theory (ART-2a) clustering algorithm, which clusters particles based on the similarity of their mass spectra, was shown to be more accurate than the existing algorithm and was used to cluster the ambient data. A total of 21 unique particle types were identified and were characterized based on their chemical composition, their size, and their temporal trends and seasonal variations. Potential sources are also discussed.
Particles containing trimethylamine (TMA) were also observed and a more detailed investigation of ambient trends in conjunction with a laboratory experiment was performed in order to elucidate conditions for which TMA will be observed in the particle phase in Southern Ontario.
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The Characterization of Fine Particulate Matter in Toronto Using Single Particle Mass SpectrometryRehbein, Peter J. G. 13 January 2011 (has links)
An Aerosol Time-of-Flight Mass Spectrometer (ATOFMS) was used to obtain mass spectra of individual aerosol particles in the 0.5 – 2 µm size range in downtown Toronto, Canada for one to two month periods during each season of 2007. A modified version of the Adaptive Resonance Theory (ART-2a) clustering algorithm, which clusters particles based on the similarity of their mass spectra, was shown to be more accurate than the existing algorithm and was used to cluster the ambient data. A total of 21 unique particle types were identified and were characterized based on their chemical composition, their size, and their temporal trends and seasonal variations. Potential sources are also discussed.
Particles containing trimethylamine (TMA) were also observed and a more detailed investigation of ambient trends in conjunction with a laboratory experiment was performed in order to elucidate conditions for which TMA will be observed in the particle phase in Southern Ontario.
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Photodissoziation von Halogenwasserstoff- und orientierten Wasserstoff-Edelgas-Halogen-Molekülen in Clusterumgebungen / Photodissociation of hydrogen halide and oriented hydrogen-rare gas-halogen molecules in cluster environmentsNahler, Nils Hendrik 28 October 2002 (has links)
No description available.
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