Hadamard Transform Time-of-flight Mass Spectrometry: Implementation and Characteristics PDF Download
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Author: Néstor Rodriguez
Publisher:
ISBN:
Category :
Languages : en
Pages : 260
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Author: Néstor Rodriguez
Publisher:
ISBN:
Category :
Languages : en
Pages : 260
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Author: Griffin Kehrwald Barbula
Publisher:
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Category :
Languages : en
Pages :
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This thesis describes the construction and use of a Hadamard transform time-of-flight mass spectrometer (HTTOFMS). HTTOFMS is a multiplexed TOF technique that employs a modulation/demodulation strategy to decouple both mass range and resolution from duty cycle. By multiplexing, HTTOFMS has a 100% duty cycle allowing it to efficiently couple to continuous ionization sources such as electrospray ionization. The multiplexing is accomplished by spatially modulating a continuous ion beam using a Bradbury-Nielsen Gate. The theory of HTTOFMS and the development and implementation of the HTTOFMS are the subjects of Chapters 2 and 3 respectively with Chapter 1 providing a brief introduction to mass spectrometry. A desorption electrospray ionization (DESI) source with a circular, rotating sample platform was built and interfaced with the HTTOFMS. By chemically patterning a surface and rotating it at programmed rates, the maximum sampling rates of DESI were analyzed to test its viability for high throughput screening. The platform showed DESI is capable of analyzing in excess of 100 samples/s in the absence of MS sensitivity concerns. This experiment is detailed in Chapter 4. The DESI rotating disc platform was also used to couple capillary-based electrokinetic separations to MS. Traditional electrokinetic separation buffers have high salt and for some separation modes detergent concentration. These buffers can cause substantial ion suppression and source contamination in mass spectrometers so they are generally avoided. Because DESI exhibits high salt tolerance, it allowed the bridging of electrokinetic separations and MS without buffer concerns. The coupling occurs by depositing the effluent from a capillary column onto the rotating paper-covered disc. The temporal separation of the eluting analytes (i.e., the electropherogram) is spatially encoded on the surface as the disc rotates. Then, using DESI, surface-bound analytes are preferentially ionized, reducing the effects of ion suppression and inlet contamination. This work is detailed in Chapter 5. Two other experiments are discussed in Chapter 6: a kinetics project studying polypeptide hydrolysis and an attempt to observe spatial stratification of different species in an ion guide quadrupole. The rapid spectral acquisition rates of HTTOFMS make it an ideal mass analyzer for kinetics experiments. To purse these experiments, a stopped-flow (SF) apparatus was also constructed for the HTTOFMS instrument. Using the SF-HTTOFMS, the hydrolysis of polypeptides by trypsin was studied. The SF-HTTOFMS was validated using a standard assay and an optical SF instrument. After validation, the hydrolysis of unlabeled polypeptides with either one and two cut sites was studied and fit with Michaelis-Menten curves. The imaging detector of the HTTOFMS instrument enabled the study of ion guide stratification of different mass-to-charge ratio species, a theoretically suggested phenomenon. Theory suggest that as the charge density inside an ion guide quadrupole increases that lower mass-to-charge ratio species focus more tightly, but it has not been seen experimentally. Data is presented that suggests the observation of this behavior, and future work is suggested. The thesis closes with an appendix of useful MATLAB scripts for processing the data used in various experiments.
Author:
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Category :
Languages : en
Pages : 15
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This program applied the Hadamard transform method to atmospheric pressure ion mobility separation (IMS) for the analysis of trace species. Target applications include chemical and biological agent detection as well as protein sequencing and identification. We demonstrate that the Hadamard transform approach improves sensitivity by increasing sample throughput, yet requires only minimal modification to the existing hardware. In Phase I we programmed commercially available DSP electronics that operated an existing IMS for Hadamard transform modulation and collected ion signal synchronous with yet at higher rates than the Hadamard modulation sequence. This strategy allows for parsing of the analog signal to avoid noise associated with the pulsing of the Bradbury Nielson ion gate and also allowed for easy comparison of various modulation rates and sequence lengths.
Author: Oh Kyu Yoon
Publisher:
ISBN:
Category :
Languages : en
Pages : 320
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Author:
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Category :
Languages : en
Pages : 27
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This report details advances in theory and technology for the precise deflection of high kinetic energy ion beams using Bradbury-Nielsen gates (BNGs) and their application to high duty cycle miniaturized mass spectrometry. We have developed methods to fabricate BNGs using template assisted manual weaving and silicon-on-insulator microfabrication. These devices have been characterized using ion beam imaging techniques, and the results compared to mathematical models of the deflection process developed for this purpose. A new vacuum-compatible electronic system has been constructed to allow the deflection of ions using BNGs following an arbitrary digital sequence that minimizes the impact of impedance mismatching within the circuit and improves the precision of deflection. The aforementioned advances have been integrated to develop a new form of time-of-flight mass spectrometry that allows for 100% duty cycle detection of a continuous ion beam. Experiments detailing 100% duty cycle operation are described. The statistical advantages to this form of detection over other forms of mass spectrometry in a shot noise dominant environment are presented.
Author: Joel Reid Kimmel
Publisher:
ISBN:
Category :
Languages : en
Pages : 178
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Author: E.W. Schlag
Publisher: Newnes
ISBN: 0444596186
Category : Science
Languages : en
Pages : 424
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The resurgence of time-of-flight mass spectrometry (TOF-MS) has had its origin in the simplicity of construction and application of such instruments together with the high transmission and the great increase in resolution that has been achieved. The instrument lends itself naturally to a coupling with pulsed laser sources, though this is not a prerequisite. It also affords a time resolution far beyond that traditionally achieved with mass spectrometric rapid scan techniques - a recent example being the real-time analysis of a multi-component mixture from an automobile exhaust. Furthermore, the mass range appears to be extremely large: mass up to 500 kDa and beyond what is being readily measured in the laboratory today. The present set of contributions attempts to give a survey of current applications from many of the active groups in the field. A variety of new applications are considered which are no doubt just the beginning of large new areas of application. By presenting this work in book form it is hoped that it will be of help to the many groups intending to initiate work in this rapidly expanding new area of mass spectrometry.
Author: Ignacio Zuleta
Publisher:
ISBN:
Category :
Languages : en
Pages : 136
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Author:
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Category : Dissertations, Academic
Languages : en
Pages : 884
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Author:
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ISBN:
Category : Dissertation abstracts
Languages : en
Pages : 848
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