Mengliang Zhang*, Shruthi Perna, Briza Marie Reyes Dedicatoria, and Ngee Sing Chong | Middle Tennessee State University Abstract: The current protocols (e.g., ASTM E1618) for ignitable liquid (IL) residue detection target the volatile compounds more effectively as the gas chromatography–mass spectrometry (GC/MS) instrument is sensitive to these compounds. The less volatile compounds are more likely to be retained in burned or arson debris, yet they have not received as much attention in forensic investigation. For example, glycol ethers with relatively low vapor pressures are commonly mixed with other volatile organic solvents in paint thinner products. In gasoline and diesel fuels, detergents such as polyisobutylene succinimides and polyether amines are commonly added to control the deposits. These chemicals could be important markers for gasoline and diesel fuels. Nevertheless, these detergents cannot be readily analyzed by traditional GC/MS methods because of their high boiling points (>250°C), high molecular weights, and complex polymeric structures. The less volatile fractions of ILs have relatively less variable chemical profiles and therefore could be more desirable for yielding reliable evidence in arson investigation. In the present study, direct analysis in real time mass spectrometry (DART-MS) was applied to analyze various IL samples, including gasoline, paint thinner, lighter fluid, diesel, and kerosene, and various less volatile compounds were identified in the IL. The similarity and difference of the DART-MS spectra from these IL were compared by chemometric methods. In addition, a sorbent tube–based sampling device and sample introduction strategy for DART-MS were developed to enhance the applicability and data quality for forensic chemical analysis from complex matrices. The rationale for the design of this sampling method is based on the ASTM E1413-13 standard for the separation and concentration of IL residues from fire debris samples by dynamic headspace concentration. This method is designed to prepare extracts from fire debris in both positive and negative pressure systems. A positive system employs an inert gas, such as nitrogen, to purge the headspace vapors through an adsorbent tube, whereas a negative system uses a vacuum to evacuate the headspace vapors out of the container. The samples (i.e., substrates with IL residues) were placed in a one-quart paint can and sealed with a modified lid. The paint can was then placed into the heating mantle, which was heated to the desired temperature, forcing the volatile and less volatile compounds to vaporize into the headspace. For the positive system, the N2 gas from the N2 generator was connected to the copper tube on the lid of the paint can to force the headspace vapors through the sorbent tube attached to the lid. The negative system employed a portable air sampling pump connected to the sorbent tube using a Tygon® or polytetrafluoroethylene (PTFE) tube, which provides a negative pressure to evacuate the headspace vapors from the paint can into the sorbent tube. The effectiveness of the sampling strategy and DART-MS analysis for less volatile compounds in the IL will be discussed in this presentation.