Development and applications of proton transfer reaction-mass spectrometry for homeland security: trace detection of explosives

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 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