Conventional vs. Monolithic IMS

IMS Schematic

IMS Cross-section

IMS

IMS Timing Sequence

Sequence Types

Experimental Setup

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Conventional vs. Monolithic IMS

Mark Kwasnik                                                                                              

Office:  ES&T L2-108

Office Phone:  404-385-4427

E-mail: gtg904u@mail.gatech.edu

Education

2004 - Present   Georgia Institute of Technology, Ph.D. Student, Analytical Chemistry

2003                 University of Central Florida, B.S. Chemistry, B.S. Forensic Science

Honors and Awards

2005 GAANN Fellowship, Georgia Institute of Technology

2004 Cherry Emerson Fellowship, Georgia Institute of Technology

Research Interests

Atmospheric Pressure Ion Mobility Spectrometry

Ion Mobility Spectrometry (IMS) is a rapid gas phase electrophoretic technique that separates compounds based on their molecular cross-section and mass-to-charge ratio. It has proven to be a valuable structural tool for determining gas-phase ion conformation, and for distinguishing among isomeric species. From the analytical point of view, it has been used in combination with liquid chromatography (LC), with the aim of increasing overall peak capacity, and in standalone mode, for the examination of simple mixtures or model systems. IMS is used in applications such as the detection of chemical warfare agents, identification of pharmaceuticals, proteomics, and air purity monitoring.

Conventional ion mobility spectrometers utilize a drift region built with a stack of ring electrodes. This is known to produce radial variation in the electric field, leading to a decline in resolving power. We have constructed a new high-resolution monolithic nano-electrospray ion mobility spectrometer which attempts to minimize such variations. This instrument uses resistive glass desolvation and drift regions, and Faraday cup detection. The triggering, gating, data acquisition and processing is controlled via LabView 7.0 user-coded software.

A second drawback of conventional ion mobility spectrometers is that they typically have a very low duty cycle ~0.05-0.40%, which is caused by the rapid opening and closing of the ion gate followed by a long drift time. To overcome this problem we are investigating the application of both arbitrary and Hadamard multiplexing. In this approach, a pseudorandom sequence is used to modulate the ion beam, thus increasing the duty cycle from 0.15% up to a maximum of 50%, thus allowing for the analysis of less concentrated samples.

Publications

1. "Multiplexed Ion Mobility Spectrometry and Ion Molbility-Mass Spectrometry", in Ion Mobility Spectroscopy - Mass Spectrometry: Theory and Applications. G. A. Harris*, Mark Kwasnik*, F. M. Fernandez, 2009, Submitted. *Authors contributed equally to this work.

2. "Desorption Electrospray Ionization Mass Spectrometry Reveals Surface-mediated Antifungal Chemical Defense of a Tropical Seaweed", A. Lane, L. Nyadong, A. Galhena, E. Stout, R. Parry, Mark Kwasnik, M. Wang, M. Hay, F.M. Fernandez, J. Kubanek, PNAS, 2009, 106, 7314-7319.

3. "Digitally-Multiplexed Nanoelectrospray Ionization Atmospheric Pressure Drift Tube Ion Mobility Spectrometry", Mark Kwasnik, J. Caramore, F. M. Fernandez, Anal. Chem., 2009, 81, 1587-1594.

4. "Liquid Chromatography and Ambient Ionization Time-of-flight Mass Spectrometry for the Analysis of Genuine and Counterfeit Pharmaceuticals", Facundo M. Fernández, Christina Y. Hampton, Leonard Nyadong, Arti Navare, Mark Kwasnik in LC/TOF-MS for Accurate Mass Analysis: Principles and Applications, ed. by I. Ferrer and E.M. Thurman, Wiley: 2009.

5. "Performance, Resolving Power and Radial Ion Distributions of a Prototype Nanoelectrospray Ionization Resistive Glass Atmospheric Pressure Ion Mobility Spectrometer", Mark Kwasnik, M. Gonin, K. Fuhrer, K. Barbeau, F. M. Fernández, Anal. Chem., 2007, 79, 7782-7791.