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Research

The ultimate goal of analytical chemistry is to provide what G.E.F. Lundell described as, "the chemical analysis of things as they are."  In other words, the ideal analytical method would be one that quickly (i.e. in real-time) provides a comprehensive assessment of sample constituents in such a way that is non- or minimally destructive, while the sample is interrogated in its native environment (i.e. in situ).  By combining specially designed ionization sources with the sensitivity and selectivity of mass spectrometry, samples can be analyzed in the open atmosphere and without the need for any sample preparation or pretreatment; these types of analyses have led to a field that has been called ambient desorption/ionization mass spectrometry (ADI-MS).

In general, our group is interested in the developing, characterizing and improving plasma-based sources for ADI-MS analyses.  Specifically, we aim to create a research program in analytical chemistry based around the development and fundamental characterization of instrumentation that provides rapid and in-depth information of samples in situ.  Our group is initially focusing on expanding the capabilities of ambient mass spectrometry through added dimensionality of analysis without compromising the speed of the analysis.  The goal is to develop an ionization source, which operates at atmospheric pressure that can provide molecular, structural, and atomic information of species present on a sample surface.

While the basis of the research is focused around novel tools for mass spectrometry, we also use and develop other analytical methods, including optical spectroscopy, electrochemistry, and electron paramagnetic resonance, for the characterization of plasma sources.  The ultimate goal is to devise analytical systems that enable fast and selective quantitative analyses of samples from their native environments.

Overall, this research addresses a major focus of modern analytical chemistry - rapid, in situ detection of relevant compounds without the need for sample modification or a priori information of sample constituents.  Such methods of analysis are needed in a wide range of areas including homeland security, drug development and production, chemical synthesis, and environmental analyses.

Scholarly, Creative & Professional Activities

1. Venter, A. R.; Douglass, K. A.; Shelley, J. T.; Hasman, G.; Honarvar, E., "Mechanisms of Real-Time, Proximal Sample Processing During Ambient Ionization Mass Spectrometry." Anal. Chem., 2014, 86 (1), 233-249.
2. Shelley, J. T.; Stindt, A.; Riedel, J.; Engelhard, C., "Time-Resolved Mass-Spectral Characterization of Ion Formation from a Low-Frequency, Low-Temperature Plasma Probe Ambient Ionization Source." J. Anal. At. Spectrom., 2014, 29 (2), 359-366.
3. Hendricks, P. I.; Dalgleish, J. K.; Shelley, J. T.; Kirleis, M. A.; McNicholas, M. T.; Li, L.; Chen, T.-C.; Chen, C.-H.; Duncan, J. S.; Boudreau, F.; Noll, R. J.; Denton, J. P.; Roach, T. A.; Ouyang, Z.; Cooks, R. G., "Autonomous in Situ Analysis and Real-Time Chemical Detection Using a Backpack Miniature Mass Spectrometer: Concept, Instrumentation Development, and Performance." Anal. Chem., 2014.
4. Dalgleish, J. K.; Wleklinski, M.; Shelley, J. T.; Mulligan, C. C.; Ouyang, Z.; Graham Cooks, R., "Arrays of Low-Temperature Plasma Probes for Ambient Ionization Mass Spectrometry." Rapid Commun. Mass Spectrom., 2013, 27 (1), 135-142.
5. Pfeuffer, K. P.; Schaper, J. N.; Shelley, J. T.; Ray, S. J.; Chan, G. C. Y.; Bings, N. H.; Hieftje, G. M., "Halo-Shaped Flowing Atmospheric Pressure Afterglow: A Heavenly Design for Simplified Sample Introduction and Improved Ionization in Ambient Mass Spectrometry." Anal. Chem., 2013, 85 (15), 7512-7518.
6. Wiley, J. S.; Shelley, J. T.; Cooks, R. G., "Handheld Low-Temperature Plasma Probe for Portable "Point-and-Shoot" Ambient Ionization Mass Spectrometry." Anal. Chem., 2013, 85 (14), 6545-6552.
7. Pfeuffer, K. P.; Shelley, J. T.; Ray, S. J.; Hieftje, G. M., "Visualization of Mass Transport and Heat Transfer in the Fapa Ambient Ionization Source." J. Anal. At. Spectrom., 2013, 28 (3), 379-387.
8. Shelley, J.; Chan, G.; Hieftje, G., "Understanding the Flowing Atmospheric-Pressure Afterglow (Fapa) Ambient Ionization Source through Optical Means." J. Am. Soc. Mass. Spectrom., 2012, 23 (2), 407-417.
9. Schaper, J. N.; Pfeuffer, K. P.; Shelley, J. T.; Bings, N. H.; Hieftje, G. M., "Drop-on-Demand Sample Introduction System Coupled with the Flowing Atmospheric-Pressure Afterglow for Direct Molecular Analysis of Complex Liquid Microvolume Samples." Anal. Chem., 2012, 84 (21), 9246-9252.
10. Shelley, J. T.; Wiley, J. S.; Hieftje, G. M., "Ultrasensitive Ambient Mass Spectrometric Analysis with a Pin-to-Capillary Flowing Atmospheric-Pressure Afterglow Source." Anal. Chem., 2011, 83 (14), 5741-5748.
11. Chan, G. C. Y.; Shelley, J. T.; Wiley, J. S.; Engelhard, C.; Jackson, A. U.; Cooks, R. G.; Hieftje, G. M., "Elucidation of Reaction Mechanisms Responsible for Afterglow and Reagent-Ion Formation in the Low-Temperature Plasma Probe Ambient Ionization Source." Anal. Chem., 2011, 83 (10), 3675-3686.
12. Shelley, J. T.; Hieftje, G. M., "Ambient Mass Spectrometry: Approaching the Chemical Analysis of Things as They Are." J. Anal. At. Spectrom., 2011, 26 (11), 2153-2159.
13. Chan, G. C. Y.; Shelley, J. T.; Jackson, A. U.; Wiley, J. S.; Engelhard, C.; Cooks, R. G.; Hieftje, G. M., "Spectroscopic Plasma Diagnostics on a Low-Temperature Plasma Probe for Ambient Mass Spectrometry." J. Anal. At. Spectrom., 2011, 26 (7), 1434-1444.
14. Shelley, J. T.; Hieftje, G. M., "Ionization Matrix Effects in Plasma-Based Ambient Mass Spectrometry Sources." J. Anal. At. Spectrom., 2010, 25 (3), 345-350.
15. Schilling, G. D.; Shelley, J. T.; Barnes Iv, J. H.; Sperline, R. P.; Denton, M. B.; Barinaga, C. J.; Koppenaal, D. W.; Hieftje, G. M., "Detection of Positive and Negative Ions from a Flowing Atmospheric Pressure Afterglow Using a Mattauch-Herzog Mass Spectrograph Equipped with a Faraday-Strip Array Detector." J. Am. Soc. Mass. Spectrom., 2010, 21 (1), 97-103.
16. Shelley, J. T.; Hieftje, G. M., "Fast Transient Analysis and First-Stage Collision-Induced Dissociation with the Flowing Atmospheric-Pressure Afterglow Ionization Source to Improve Analyte Detection and Identification." Analyst, 2010, 135 (4), 682-687.
17. Schilling, G. D.; Shelley, J. T.; Broekaert, J. A. C.; Sperline, R. P.; Denton, M. B.; Barinaga, C. J.; Koppenaal, D. W.; Hieftje, G. M., "Use of an Ambient Ionization Flowing Atmospheric-Pressure Afterglow Source for Elemental Analysis through Hydride Generation." J. Anal. At. Spectrom., 2009, 24 (1), 34-40.
18. Shelley, J. T.; Wiley, J. S.; Chan, G. C. Y.; Schilling, G. D.; Ray, S. J.; Hieftje, G. M., "Characterization of Direct-Current Atmospheric-Pressure Discharges Useful for Ambient Desorption/Ionization Mass Spectrometry." J. Am. Soc. Mass. Spectrom., 2009, 20 (5), 837-844.
19. Andrade, F. J.; Shelley, J. T.; Wetzel, W. C.; Webb, M. R.; Gamez, G.; Ray, S. J.; Hieftje, G. M., "Atmospheric Pressure Chemical Ionization Source. 2. Desorption-Ionization for the Direct Analysis of Solid Compounds." Anal. Chem., 2008, 80 (8), 2654-2663.
20. Andrade, F. J.; Shelley, J. T.; Wetzel, W. C.; Webb, M. R.; Gamez, G.; Ray, S. J.; Hieftje, G. M., "Atmospheric Pressure Chemical Ionization Source. 1. Ionization of Compounds in the Gas Phase." Anal. Chem., 2008, 80 (8), 2646-2653.
21. Shelley, J. T.; Ray, S. J.; Hieftje, G. M., "Laser Ablation Coupled to a Flowing Atmospheric Pressure Afterglow for Ambient Mass Spectral Imaging." Anal. Chem., 2008, 80 (21), 8308-8313.
22. Dattelbaum, A. M.; Hicks, R. K.; Shelley, J.; Koppisch, A. T.; Iyer, S., "Surface Assisted Laser Desorption-Ionization Mass Spectrometry on Patterned Nanoporous Silica Thin Films." Microporous Mesoporous Mater., 2008, 114 (1-3), 193-200.