Dissertation
Novel Instrumental Approaches to Ion Mobility Spectrometry: Voltage-Sweep, High-Pressure, and Radiative-Ion-Ion-Recombination
Doctor of Philosophy (PhD), Washington State University
01/2012
Handle:
https://hdl.handle.net/2376/4066
Abstract
Ion Mobility Spectrometry (IMS) provides reliable and fast detection in a multitude of worldwide environments. Many IMS systems are used in security applications where IMS's ability to rapidly detect explosives and narcotics provides an invaluable tool. However, these applications often report a high rate of false positive responses. The work described herein demonstrates the methodical modification of the IMS instrument, leading to novel methods for the operation of ion mobility spectrometry that should lead to reduced false-positive responses.
A comprehensive, open-source software suite has been developed for IMS instruments. This software allows a user control over the timing signals, voltages, signal acquisition and signal processing as required for IMS operation in traditional or novel methods. These methods include both voltage-sweep IMS (VSIMS), and high-pressure IMS (HPIMS). In VSIMS, spectra were acquired under successively higher voltages and compiled into a VSIMS two-dimensional spectrum. The analysis of this data provided improved resolving power, resolution, and peak capacity over traditional drift-time IMS, and solved the general elution problem of IMS by allowing the instrument to simultaneously separate both fast and slow drifting ions.
HPIMS provided a method for applying super-ambient pressures to an IMS experiment through the use of an external pressure chamber. The increased number density of the drift gas increased the number of collisions an ion experienced in the IMS cell, thus improving both resolution and resolving power. Using HPIMS, a resolving power greater than 100 was demonstrated for the first time in stand-alone IMS. In addition, a novel method for the calculation of collision cross section values from HPIMS data was developed and demonstrated.
In order to improve the limit of detection for atmospheric pressure ion detectors, radiative-ion-ion-recombination (RIIR) was utilized to produce a photon from a pair of ions recombining. These photons were detected using a photomultiplier tube (PMT). Negative mode RIIR-IMS was demonstrated using RIIR with a PMT providing the output signal, and was used to detect an IMS separation of nitroglycerin. Positive mode IMS-RIIR provided a negative, quenching peak that was mobility dependant. Fully developed, this work has the potential to allow single-ion counting at atmospheric pressure.
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Details
- Title
- Novel Instrumental Approaches to Ion Mobility Spectrometry
- Creators
- Eric James Davis
- Contributors
- Herbert H. Hill (Advisor)James A Brozik (Committee Member)Jeanne L. McHale (Committee Member)William F. Siems (Committee Member)Cornelius F. Ivory (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- Chemistry, Department of
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Number of pages
- 188
- Identifiers
- 99900581657201842
- Language
- English
- Resource Type
- Dissertation