title: Analysis of nitrogen-based explosives with desorption atmospheric pressure photoionization mass spectrometry.
abstract: BACKGROUND
  Fast methods that allow the in situ analysis of explosives from a variety of surfaces are needed in crime scene investigations and home-land security. Here, the feasibility of the ambient mass spectrometry technique desorption atmospheric pressure photoionization (DAPPI) in the analysis of the most common nitrogen-based explosives is studied.
  
  
  METHODS
  DAPPI and desorption electrospray ionization (DESI) were compared in the direct analysis of trinitrotoluene (TNT), trinitrophenol (picric acid), octogen (HMX), cyclonite (RDX), pentaerythritol tetranitrate (PETN), and nitroglycerin (NG). The effect of different additives in DAPPI dopant and in DESI spray solvent on the ionization efficiency was tested, as well as the suitability of DAPPI to detect explosives from a variety of surfaces.
  
  
  RESULTS
  The analytes showed ions only in negative ion mode. With negative DAPPI, TNT and picric acid formed deprotonated molecules with all dopant systems, while RDX, HMX, PETN and NG were ionized by adduct formation. The formation of adducts was enhanced by addition of chloroform, formic acid, acetic acid or nitric acid to the DAPPI dopant. DAPPI was more sensitive than DESI for TNT, while DESI was more sensitive for HMX and picric acid.
  
  
  CONCLUSIONS
  DAPPI could become an important method for the direct analysis of nitroaromatics from a variety of surfaces. For compounds that are thermally labile, or that have very low vapor pressure, however, DESI is better suited.
authors.affiliation: Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, Finland.
authors.forename: T J
authors.initials: TJ
authors.lastname: Kauppila
authors.affiliation: Division of Pharmaceutical Chemistry and Technology, Faculty of Pharmacy, University of Helsinki, Finland.
authors.forename: A
authors.initials: A
authors.lastname: Flink
authors.affiliation: Crime Laboratory, National Bureau of Investigation, Vantaa, Finland.
authors.forename: J
authors.initials: J
authors.lastname: Pukkila
authors.affiliation: Department of Forensic Medicine, Faculty of Medicine, University of Helsinki, Finland.
authors.forename: R A
authors.initials: RA
authors.lastname: Ketola
mesh_terms: D053834:Explosive Agents / Q000737:chemistry*; D013058:Mass Spectrometry / Q000295:instrumentation / Q000379:methods*; D010417:Pentaerythritol Tetranitrate / Q000032:analysis; D014227:Triazines / Q000032:analysis; D014303:Trinitrotoluene / Q000032:analysis
chemical_list: D053834:Explosive Agents; D014227:Triazines; D010417:Pentaerythritol Tetranitrate; D014303:Trinitrotoluene; C009160:cyclonite