Published Online: 1 July 2002
Page Count: 21
de Vos, B-J
Forensic chemist and analytical scientist, CSIR Bio/Chemtek, PROBE, Modderfontein, SA
Organics manager and director of research, Activation Laboratories Ltd, Ancaster, Ontario
Professor in mass spectrometry and chromatography, University of Pretoria, Pretoria, SA
Fire investigation specialist, Advanced Forensic Services, Pretoria, SA
(Received 30 January 2002; accepted 26 January 2002)
Gas chromatography/mass spectrometry (GC/MS) is a well-known instrumental technique used for the analysis of fire debris for accelerant detection. However, matrix problems, such as pyrolysis product interference, are still encountered. These interferences often lead to inconclusive interpretation of the chromatographic results obtained.
This paper describes a method of analyzing arson accelerants using gas chromatography coupled with ion trap mass spectrometry/mass spectrometry (GC/MS/MS). Petrol was investigated as an accelerant. Analysis incorporated an ion preparation method (IPM) that manipulates the ion population in the ion trap following ionization but prior to ion analysis. Parent ions of selected mass-to-charge (m/z) values, characteristic for petrol, are stored within the ion trap. All other unwanted ions are physically removed from the trap by sophisticated electrostatic waveforms. The parent ions fill the trap and are then fragmented by means of collision-induced dissociation (CID). The resultant daughter ion spectra are obtained, which can be used for identification purposes. In this manner, ions of pyrolysis origin are removed.
Paper ID: JFS15446J