Analysis of 2,4,6-trinitrotoluene, pentaerythritol tetranitrate and cyclo-1,3,5-trimethylene-2,4,6-trinitramine using negative corona discharge ion mobility spectrometry T. Khayamian , M. Tabrizchi, M.T. Jafari Department of Chemistry, Isfahan University of Technology, Isfahan 84154, Iran Received 25 March 2002; received in revised form 20 September 2002; accepted 25 September 2002 Abstract In this study, the capability of negative corona discharge ion mobility spectrometry (IMS) for quantitative magnitude of several explosives including 2,4,6-trinitrotoluene (TNT), pentaerythritol tetranitrate (PETN) and cyclo-1,3,5- trimethylene-2,4,6-trinitramine (RDX) has been evaluated for the first time. The total current obtained with the negative corona discharge was about 100 times larger than that of IMS based on 63 Ni, which results in a lower detection limit and a wider linear dynamic range. The detection limits for PETN, TNT and RDX were 8 /10 11 ,7 /10 11 and 3 /10 10 g, respectively. The calibration plots for these explosives showed linear dynamic ranges of about four orders of magnitude. # 2002 Elsevier Science B.V. All rights reserved. Keywords: Negative corona discharge; Explosives; Ion mobility spectrometry 1. Introduction The analysis of explosive compounds at trace levels is a crucial research field for security purposes. Explosives can be analyzed by a variety of methods such as: HPLC-UV [1,2], GC-ECD [3] and ion mobility spectrometry (IMS) [4  /7]. Due to low detection limit, fast response, simplicity, and portability, IMS has been proved to be one of the best methods for the detection of trace levels of explosives [8]. Ionization source is one of the key parts of an IMS instrument. A variety of ionization sources have been used for IMS [8]. Recently, we have investigated the capability of continuous corona discharge as an ionization source for IMS in both positive [9,10] and negative modes [11]. In sum- mary, corona discharge is one of the different varieties of electric discharge. A corona discharge may develop in a strongly non-uniform field that is insufficient for electrical breakdown. This situa- tion arises when the characteristic size of the electrode is much smaller than the interelectrode distance. For example a point-to-plane geometry  Corresponding author. Tel.:  /98-311-3912351; fax:  /98- 311-3912350 E-mail address: taghi@cc.iut.ac.ir (T. Khayamian). Talanta 59 (2003) 327  /333 www.elsevier.com/locate/talanta 0039-9140/02/$ - see front matter # 2002 Elsevier Science B.V. All rights reserved. PII:S0039-9140(02)00521-0