Detection of Trace Levels of Gasoline in Arson Cases by Gas Chromatography-Mass Spectrometry with an Automatic On-Line Thermal Desorber

A method for the analysis of trace levels of gasoline in arson debris using an automatic thermal desorber (TD) and commercial Tenax adsorbent tubes is described. First, a static headspace screening test is performed by gas chromatography using a flame ionization detector (GC-FID). Suspected gasoline is reanalyzed by gas chromatography-mass spectrometry (GC-MS). Gasoline traces smaller than 10 μL in a 1 liter volume are analyzed by a dynamic heated headspace procedure with thermal desorption and GC-MS after adsorption on 45 mg Tenax tubes. The desorption of adsorbed vapors is carried out by heating the tubes; the analytes are focused in cryogenic units cooled with liquid nitrogen. The cryofocused vapor sample is flash-heated for injection into the capillary column of the GC. The dynamic heated headspace technique (TD-GC-MS) is suitable for analyses of trace amounts of gasoline (0.1–10 µL in 1 liter volume).