ORIGINAL PAPER Identification of volatile chemical signatures from plastic explosives by SPME-GC/MS and detection by ion mobility spectrometry Hanh Lai & Alfred Leung & Matthew Magee & José R. Almirall Received: 26 November 2009 / Revised: 19 January 2010 / Accepted: 20 January 2010 / Published online: 13 March 2010 # Springer-Verlag 2010 Abstract This study demonstrates the use of solid-phase microextraction (SPME) to extract and pre-concentrate volatile signatures from static air above plastic explosive samples followed by detection using ion mobility spectrom- etry (IMS) optimized to detect the volatile, non-energetic components rather than the energetic materials. Currently, sample collection for detection by commercial IMS analyzers is conducted through swiping of suspected surfaces for explosive particles and vapor sampling. The first method is not suitable for sampling inside large volume areas, and the latter method is not effective because the low vapor pressure of some explosives such as RDX and PETN make them not readily available in the air for headspace sampling under ambient conditions. For the first time, headspace sampling and detection of Detasheet, Semtex H, and C-4 is reported using SPME-IMS operating under one universal setting with limits of detection ranging from 1.5 to 2.5 ng for the target volatile signatures. The target signature compounds n-butyl acetate and the taggant DMNB are associated with untagged and tagged Detasheet explosives, respectively. Cyclohexa- none and DMNB are associated with tagged C-4 explosives. DMNB is associated with tagged Semtex H explosives. Within 10 to 60 s of sampling, the headspace inside a glass vial containing 1 g of explosive, more than 20 ng of the target signatures can be extracted by the SPME fiber followed by IMS detection. Keywords Plastic explosives . C-4 . Detasheet . Semtex . Solid-phase microextraction . Ion mobility spectrometry Introduction Of the common explosives used in terrorist bombings, plastic explosives have been frequently used because they can be easily molded for concealment [1]. Researchers and manufacturers are encouraged to develop and commercialize systems that can detect plastic explosives at security check- points. Recently, RedXDefense commercialized a portable plastic explosive detection kit, which is a luminescent polymer spray and UV light for visualization [2, 3]. A vapor detector based on monolayer-coated microcantilevers was developed with the aim to also detect plastic explosives [4]. Other vapor-detection technologies include: single- compound detectors such as mass spectrometers [5, 6], ion mobility spectrometers [7, 8], biological detectors such as canines and chemical-based sensors such as metal oxide (MOX) [9], surface acoustic wave (SAW) [10, 11], conduct- ing and conjugated polymer sensors [12, 13]. At present, canines and ion mobility spectrometry are still the most commonly used trace explosive detection systems employed at security checkpoints [14–16]. The one feature that the above explosives vapor-detection technologies (excluding canine detectors) have in common is that their detection H. Lai : J. R. Almirall Florida International University, 11200 SW 8th St. OE 116A, Miami, FL 33199, USA A. Leung : M. Magee Transportation Security Laboratory, Science and Technology Directorate, U.S. Department of Homeland Security, William J. Hughes Technical Center, Building 315, Atlantic City International Airport, Atlantic City, NJ 08405, USA J. R. Almirall (*) Department of Chemistry and Biochemistry, International Forensic Research Institute, Florida International University, 11200 SW 8th St. OE 116A, Miami, FL 33199, USA e-mail: almirall@fiu.edu Anal Bioanal Chem (2010) 396:2997–3007 DOI 10.1007/s00216-010-3501-6