Screening of organic nitrate explosives: selective ion/molecule reactions for the diagnostic ion NO2+

✍ Scribed by Liliane Girotto Cabrini; Regina Sparrapan; Maria Anita Mendes; Luis Alberto Beraldo Moraes; Marcos N. Eberlin

• Publisher: John Wiley and Sons
• Year: 2005
• Tongue: English
• Weight: 92 KB
• Volume: 40
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/jms.930

✦ Synopsis

Highly efficient explosive screening has become a major analytical challenge and, owing to its outstanding speed, selectivity and sensitivity, mass spectrometry (MS) is placed at the center of attention in this field. 1 An efficient explosive detection system should be able to discriminate simultaneously a broad range of explosives at trace levels in mixtures with many background compounds normally present at much higher concentrations. The analytical technique employed must therefore provide diagnostic molecular signatures for each explosive to enable detection that is immune to false positives. MS efforts have been concentrated, therefore, on finding the most appropriate ionization technique or selective derivatization method for each single explosive, often using ion/molecule reactions. 2 -5 Because the great majority of explosive screenings are expected (and actually found) to be negative, an explosive-by-explosive multivariate screening approach should greatly benefit from preliminary broad-range screening with much enhanced high-throughput capabilities. When using MS first an 'in/out' screening could be performed for a set of diagnostic ions of each major class of explosives. Fortunately, major explosives belong to just a few classes; actually, the majority of them are organic nitrates such as TNT (trinitrotoluene), DNT (dinitrotoluene), TNB (trinitrobenzene), DNB (dinitrobenzene), NG (nitroglycerine), EGDN (ethyleneglycol dinitrate), PETN (pentaerythritol tetranitrate), RDX (hexahydro-1,3,5-trinitro-1,3,5 triazine), HMX (octahydro-1,3,5,7tetranitro-1,3,5,7 tetrazocine), nitroguanidine and tetryl. It is most interesting that in MS explosive detection most organic nitrates dissociate extensively upon electron ionization (EI), forming the nitronium ion NO 2 C of m/z 46 either at high or at sufficiently high abundances, as Fig. 1 illustrates for RDX.

NO 2 C could serve, therefore, as a selective diagnostic ion for the MS screening of organic nitrates. This ion is also attractive since other isobaric ions of m/z 46 are rare, which should therefore minimize interferences. For broad-range screenings, false positives should, however, be reduced to a nearly null level, so NO 2 C detection based