Chemical orthogonality in tandem differential mobility spectrometry at ambient pressure

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With support from the Chemical Measurement and Imaging Program in the Division of Chemistry and the Office of Experimental Program to Stimulate Competitive Research (EPSCoR), Professor Gary Eiceman at New Mexico State University and his group will explore and develop enhanced capabilities in chemical measurements using ion mobility spectrometry (IMS). Increases in specificity of a chemical identification of substances through IMS will be introduced using orthogonality provided by ion transformations in a tandem differential IMS analyzer. Ions which are mobility selected in a first mobility analyzer and passed into a reactive zone, are subsequently reacted or fragmented using molecule selective pathways before entering a second mobility analyzer. Orthogonality can be added through changes in strong electric fields and studies will disclose quantitatively the effect of field strength and ion structure on dissociation or fragmentation reactions. Investigations will focus, for selected pharmaceutical substances and pesticides, on the stability and mobility of clusters formed between sample-derived ions and specific reagent gases. The influence on ion chemistry and chemical orthogonality of temperature, moisture, and vapor concentrations in air at ambient pressure will be explored and assessed for specificity of chemical measurements toward a next generation of IMS instruments. Ion mobility spectrometry is central to military preparedness and commercial aviation security with emerging impact in clinical diagnostics and industrial process control. Impacts of these studies should include the education of a new generation of students in gas phase ion-molecule chemistry at ambient pressure and should provide new capabilities for specific measurement challenges within industry and government.