In the arson investigation, the identification of ignitable liquids (IL) and their residues (ILR) found at the crime scene plays a key role in identifying the cause and origin of the fire. In fire debris analysis, Gas chromatography-mass spectrometry (GC/MS) is the most commonly used analytical tool however it can analyze only the volatile chemical components. The non-volatile or less volatile components are likely to be contained in the fire debris and analyzing them could provide corroborating evidence on the use of specific IL to cause the arson fire. Direct analysis in real-time mass spectrometry (DART-MS) is a powerful tool with excellent analytical sensitivity to analyze non-volatile chemical components in IL. In this study the chemical profiles of various IL were studied using DART-MS and GC/MS methods. At arson sites, often the IL are exposed to air for longer periods and their chemistry alters due to the evaporation of volatile chemical components from the IL. One aspect of this study explored the effects of weathering on the chemical profiles of gasoline and paint thinner samples. The weathered samples were prepared at different weathering temperatures and extent, and their chemical profiles were obtained by DART-MS and GC/MS analysis. Analysis of variance-principal component analysis (ANOVA-PCA) was used to evaluate the impact of experimental factors such as weathering temperatures, and weathering degree. The results indicated the weathering percentage is the major factor for causing the variance in the GC/MS Total Ion Chromatogram (TIC) data. For the ILR extraction from the fire debris and substrates, a solid phase microextraction (SPME) coupled to DART-MS technique was developed. The SPME extraction conditions were optimized to achieve the extraction efficiency and the matrix interferences were evaluated. By applying this technique, different substrates such as wood, paper, fabric, sand and their corresponding residues were studied. The data suggested that this setup is valuable in recovering and identifying the volatile and nonvolatile chemical components. Alongside, the chemical profiles of different gasoline brands such as BP, Shell, Speedway and Exxon were studied using a DART-Quadrupole Time-of-flight mass spectrometer to better understand the similarities and differences in the marker compounds present in them. Additionally, the effect of burn area in the identification of IL was studied by using paper as a substrate.
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