Gas chromatography coupled with ion trap mass spectrometry (GC-MS and GC-MS-MS) - for arson debris analysis

Abstract

Gas chromatography - mass spectrometry (GC-MS) is an established 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. This study describes methods for analysing arson accelerants using gas chromatography coupled with ion trap mass spectrometry. The latter technique lends itself to both conventional (GC-MS) as well as tandem mass spectrometry (GC-MS-MS). Since petrol (gasoline) is one of the more common distillate blends used by arsonists, especially in South Africa, the identification of petrol in fire debris samples was investigated. In order to overcome pyrolysis product interference and improve detection selectivity of the aromatic hydrocarbons in petrol residues, tandem mass spectrometry was used in combination with capillary gas chromatography. The added parameter of the third dimension of selectivity proved to be superior to conventional GC-MS in obtaining characteristic aromatic hydrocarbon profiles for petrol without interference from pyrolysis artefacts.