International Journal of Mass Spectrometry 279 (2009) 93–99 Contents lists available at ScienceDirect International Journal of Mass Spectrometry journal homepage: www.elsevier.com/locate/ijms Fast gas chromatography negative chemical ionization tandem mass spectrometry of explosive compounds using dynamic collision-induced dissociation Olivier L. Collin, Carolyn M. Zimmermann, Glen P. Jackson ∗ Center for Intelligent Chemical Instrumentation, Department of Chemistry and Biochemistry, Ohio University, Clippinger Laboratories, Athens, OH 45701, United States article info Article history: Received 13 October 2008 Accepted 14 October 2008 Available online 21 October 2008 Keywords: Tandem mass spectrometry Dynamic collision-induced dissociation (DCID) Gas chromatography Explosive abstract The analysis of nine explosive compounds by gas chromatography tandem mass spectrometry (GC–MS/MS) using negative chemical ionization (NCI) was performed under two different conditions: first, a conventional GC separation coupled with a standard ion dissociation method in a quadrupole ion trap (QIT) was performed in segmented selected reaction monitoring mode; second, a fast GC separation on a microbore capillary column was combined with a faster method of collisional activation in ion traps wherein fragmentation is deliberately accomplished during the mass acquisition scan. The conventional GC–MS/MS method provided separation times in 10 min with detection limits between 0.8 and 280 pg on column. The fast GC method with dynamic collision-induced dissociation (DCID) offered a confirma- tory method for the analysis of high explosives with separation times under 2.5min and detection limits between 0.5 and 5 pg on column, without any hardware modifications to the instrument. The implemen- tation of DCID in combination with three-times-faster mass scanning allows the acquisition of tandem mass spectra to at least 5Hz (while averaging three scans per spectrum). Although detection limits for GC-NCI–MS/MS using conventional CID or DCID are not quite on par with LODs achieved by GC-ECD, the combination of NCI with DCID tandem MS leads to detection limits at least comparable, if not superior, to other mass spectrometric methods. Selected reaction monitoring in the negative ionization mode is antic- ipated to offer the most selective approach to detecting explosives and eliminating potential interferences, which could ultimately lead to the best detection limits for real, contaminated samples. © 2008 Elsevier B.V. All rights reserved. 1. Introduction The analysis of explosives requires highly selective and sensi- tive analytical methods that can detect trace amounts of residues in diverse complex matrices. To eliminate or reduce matrix inter- ference, chromatography is often employed to separate the various components; both gas and liquid chromatographic methods have been developed for this purpose. Mass spectrometry (MS) has long been used to study explosives compounds [1–3] and has always been perceived as the ideal confirmatory detection method for explosive compounds because of its selectivity and confirmatory power. However, the limits of detection (LODs) achievable by MS were not always compatible with the trace analysis requirements of a forensic laboratory on a routine basis. For this reason, screen- ing methods relying on detectors with no confirmatory power are ∗ Corresponding author. Tel.: +1 740 593 0797; fax: +1 740 593 0148. E-mail addresses: olivier.collin@mail.mcgill.ca (O.L. Collin), cz293105@ohio.edu (C.M. Zimmermann), jacksong@ohio.edu (G.P. Jackson). often used prior to confirmation with MS, and concentration pro- cedures are applied to the positive samples in order to bring the explosives into a concentration range that can be detected by the mass spectrometer. Screening methods are also important to pro- vide a double check mechanism and insure that samples are not mishandled. Low detection limits for explosive compounds have made electron capture detectors (ECD) [4–8] and chemilumines- cence detectors (CL) [9–11], the most common types of detectors for gas chromatography screening methods. Modern mass spectrometers now offer improved detection lim- its and have been combined with LC and GC separations for the analysis of explosives at low levels [12,13], reducing the needs for pre-concentration procedures. LC analyses often offer the ability to screen for a larger number of explosives simultaneously because, unlike GC separations, there is no thermal degradation of the explo- sives in an LC separation. GC analysis of explosives is nonetheless favored in many forensic laboratories because of the lower cost and greater availability of instrumentation. Analysis of explosives by GC–MS has previously been performed using electron ionization (EI) and chemical ionization (CI) in both positive and negative mode 1387-3806/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.ijms.2008.10.009