DEVELOPMENT AND APPLICATIONS OF PROTON TRANSFER REACTION-MASS SPECTROMETRY FOR HOMELAND SECURITY: TRACE DETECTION OF EXPLOSIVES by Ramón González-Méndez, MSc A thesis submitted to the University of Birmingham for the degree of DOCTOR OF PHILOSOPHY School of Physics and Astronomy The University of Birmingham, UK February 2017 University of Birmingham Research Archive e-theses repository This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder. Abstract This thesis investigates the challenging task of sensitive and selective trace detection of explosive compounds by means of proton transfer reaction mass spectrometry (PTR-MS). In order to address this, new analytical strategies and hardware improvements, leading to new methodologies and analytical tools, have been developed and tested. These are, in order of the Chapters presented in this thesis, the switching of reagent ions, the implementation of a novel thermal desorption unit, and the use of an ion funnel drift tube or fast reduced electric field switching to modify the ion chemistry. In addition to these, a more fundamental study has been undertaken to investigate the reactions of picric acid (PiA) with a number of different reagent ions. The novel approaches described in this thesis have improved the PTR-MS technique by making it more versatile in terms of its analytical performance, namely providing assignment of chemical compounds with high confidence. These techniques are going to be employed in the new generation of PTR-MS instruments being developed by KORE Technology Ltd. Although demonstrated for Homeland Security in this thesis, the developments made can be utilised for improved selectivity in areas such as atmospheric chemistry, and in the environmental, food and health sciences. These techniques have resulted in a more multidimensional and versatile instrument, providing a step change in the analytical applications of PTR-MS for either commercial or research exploitation. -i- Quiero dedicar esta tesis doctoral a mis padres, José Ramón y Marisol, a quienes les debo todo. No hay palabras suficientes para expresarles mi agradecimiento por su bondad y afecto incondicional mostrado a lo largo de todos estos largos años. Sin ellos nada hubiese sido posible. De todo corazón, ¡os quiero! -ii- “That which does not destroy us makes us stronger” Friedrich Nietzsche 1844-1900 “Life can only be understood backwards; but it must be lived forwards.” Søren Kierkegaard 1813-1855 “Confía en el tiempo, que suele dar dulces salidas a muchas amargas dificultades” Miguel de Cervantes Saavedra 1547-1616 -iii- Acknowledgements It is my pleasure to thank here those individuals without whom this thesis would, undoubtedly, not be possible. I would firstly like to thank my supervisor, Dr. Chris. A. Mayhew, for giving me the opportunity to work within his research group. I thank you for all your support, trust and the opportunities for being attracted to the scientific world and, in a broader context, to a new life abroad from my home town. An immense cheers for all that. I would also like to thank Dr. Peter Watts, particularly for his vast knowledge of chemistry and his scientific experience. His contributions and enthusiasm were instrumental in enhancing the quality of the science. Thank you also to Kore Technology Ltd. and particularly to Dr. Fraser Reich for all his support, commitment and time put into the scientific collaboration and beyond. His insight and guidance greatly improved the quality of the research presented in this thesis. Besides that, I really appreciate Fraser very much for opening his home to me. I do not have words to express my gratitude. I would like to thank all the work colleagues of the Molecular Physics Group: Raquel, Danny, Prema, Dave Howse, John Thompson and Kathleen Hynes, for all the laughs (and discussions) and anecdotes for the future. I would also like to acknowledge financial support from the European Union (Proton Ionisation Molecular Mass Spectrometry-ITN Project) under FP7 Marie Skłodowska-Curie Actions (Grant Agreement Number 287382), the Innovative Research Call in Explosives and Weapons Detection 2010 (a Cross-Government programme sponsored by a number of Departments and Agencies under the UK Government’s CONTEST strategy in partnership with the US Department of Homeland Security) and the Defence Science and Technology Laboratory. -iv- List of publications During the course of my postgraduate study within the School of Physics and Astronomy at the University of Birmingham, the following articles, conference abstracts and talks were accepted for publication and/or presentation at conferences. Academic Journal papers Published (in order of publication date) 1. P. Sulzer, B. Agarwal, S. Jürschik, M. Lanza, A. Jordan, E. Hartungen, G. Hanel, L.Märk, T. D. Märk, R. González-Méndez, P. Watts, C. A. Mayhew. Applications of switching reagent ions in proton transfer reaction mass spectrometric instruments for the improved selectivity of explosive compounds. International Journal of Mass Spectrometry 354–355 (2013), 123–128. http://dx.doi.org/10.1016/j.ijms.2013.05.004 2. Bishu Agarwal, Ramón González-Méndez, Matteo Lanza, Philipp Sulzer, Tilmann D. Mark, Neil Thomas and Chris A. Mayhew. Sensitivity and Selectivity of Switchable Reagent-Ion Soft Chemical Ionisation Mass Spectrometry for the Detection of Picric Acid. The Journal of Physical Chemistry Part A, 2014, 118 (37), pp 8229–8236. http://dx.doi.org/10.1021/jp5010192 3. Carolina Matias, Andreas Mauracher, Stefan E Huber, Stephan Denifl, Paulo Limão- Vieira, Paul Scheier, Tilmann D Märk, Ramón González-Méndez, and Chris Mayhew. Dissociative electron attachment to the volatile anaesthetics enflurane and isoflurane and the chlorinated ethanes pentachloroethane and hexachloroethane. International Journal of Mass Spectrometry 379 (2015) 179–186. http://dx.doi.org/10.1016/j.ijms.2015.01.009 4. Ramón González-Méndez, D. Fraser Reich, Stephen J. Mullock, Clive A. Corlett, Peter Watts and Chris A. Mayhew. Development and use of a thermal desorption unit and proton transfer reaction mass spectrometry for trace explosive detection: determination of the limits of detection and an investigation of memory effects. International Journal of Mass Spectrometry 385 (2015) 13-18. http://dx.doi.org/10.1016/j.ijms.2015.05.003 -v- 5. Ramón González-Méndez, Peter. Watts, David Olivenza-León, D. Fraser Reich, Stephen J. Mullock, Clive A. Corlett, Stuart Cairns, Peter Hickey, Matthew Brooks, and Chris A. Mayhew. Enhancement of compound selectivity using a radio frequency ion-funnel proton transfer reaction mass spectrometer: improved specificity for explosive compounds. Analytical Chemistry, 2016, 88 (21), 10624- 10630. http://dx.doi.org/10.1021/acs.analchem.6b02982 6. Materić, D., Blenkhorn, D., González-Méndez, R., Bruhn, D., Turner, C., Mason, N., Morgan, G., and Gauci, V. Monoterpene emission from young scots pine may be influenced by nutrient availability. Applied Ecology and Environmental Research. 2016, 14 (4), 667- 681. http://dx.doi.org/10.15666/aeer/1404_667681 7. Ramón González-Méndez, Peter Watts, David C. Howse, Immacolata Procino, Henry McIntyre and Chris A. Mayhew. Ion mobility studies on the negative ion- molecule chemistry of isoflurane and enflurane. Journal of The American Society for Mass Spectrometry, 2017, 28 (5), 939-946. http://dx.doi.org/10.1007/s13361-017- 1616-0 8. Ramón González-Méndez, Peter Watts, David C. Howse, Immacolata Procino, Steven Taylor, Henry McIntyre and Chris A. Mayhew. Ion mobility studies on the negative ion-molecule chemistry of pentachloroethane. International Journal of Mass Spectrometry (2017) In press. Submitted 1. Célia Lourenço, Ramón González-Méndez, Fraser Reich, Nigel Mason and Claire Turner. A potential method for comparing instrumental analysis of breath gas volatile organic compounds using standards calibrated for the gas phase. Submitted to International Journal of Mass Spectrometry. In preparation 1. Ramón González-Méndez, Peter. Watts, D. Fraser Reich, Stephen J. Mullock, Stuart Cairns, Peter Hickey, Matthew Brooks, and Chris A. Mayhew. Enhancing proton transfer reaction-mass spectrometry selectivity using rapid reduced electric field switching. -vi- 2. Ramón González-Méndez, Peter Watts and Chris A. Mayhew. Proton transfer reaction mass spectrometry and the detection of explosive taggants. A study of reactivity in the gas phase. 3. Ramón González-Méndez, Peter Watts and Chris A. Mayhew. Proton transfer reaction mass spectrometry and nitroanilines. Abstracts 1. Ramón González-Méndez, Bishu Agarwal, Matteo Lanza, Philipp Sulzer, Tilmann D. Mark, Neil Thomas and Chris A. Mayhew. Sensitivity and selectivity of switchable reagent-ion soft chemical ionisation for the detection of picric acid. Accepted for poster presentation at XIXth International Symposium on Atomic, Cluster and Surface Physics, 2014. Universitätszentrum Obergurgl, Austria 2. Ramón González-Méndez, Fraser Reich, Steve Mullock, Clive Corlett, Peter Watts and Chris A. Mayhew. The application of a recently developed thermal desorption