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Fatty acid-based ignitable liquids (ILs), such as biodiesels and bio-based lighter fluids, represent a growing class of accelerants with limited forensic characterization. In this study, we applied gas chromatography–mass spectrometry (GC–MS) and direct analysis in real time mass spectrometry (DART–MS) to analyze plant oil-derived IL residues on wood and fabric substrates. ILs were prepared from ten different plant oils, subjected to burning, and extracted from fire debris using the ASTM E1412 activated charcoal method. GC–MS analysis resolved characteristic fatty acid methyl esters (FAMEs) and identified diagnostic fragment ions (m/z 55, 67, 74, 79). The fragmentation patterns of unsaturated and saturated FAMEs were systematically examined and compared against experimental data and reference spectra from online databases, demonstrating strong agreement and validating the reliability of these ion ratios as qualitative indicators of FAME saturation. DART–MS enabled rapid confirmation of major unsaturated FAMEs through the detection of protonated molecular ions, offering complementary identification without chromatographic separation. Chemometric analysis using principal component analysis (PCA) and analysis of variance-PCA revealed that FAME profiles were strongly dependent on the IL sources and remained reliable across replicate preparations and synthesis conditions, while substrate and combustion effects were mitigated using targeted ion extraction. These findings demonstrate the practical casework relevance of combining GC–MS and DART–MS for the detection and classification of fatty acid–based ILs in fire debris, providing robust chemical evidence to support arson investigations and to guide the inclusion of these emerging accelerants in forensic ignitable-liquid classification schemes. 

Accurate quantitation of cannabinoids, particularly Δ9-tetrahydrocannabinol (THC) and cannabidiol (CBD), is essential for regulatory compliance, forensic investigations, and cannabis product development. Traditional methods, such as liquid chromatography (LC) and gas chromatography (GC) coupled with mass spectrometry, provide reliable results but are time-consuming and resource-intensive. This study introduces a rapid and high-throughput analytical method using zone heat-assisted direct analysis in real time mass spectrometry (DART-MS) combined with in-situ flash derivatization. The method employs trimethylphenylammonium hydroxide (TMPAH) for efficient derivatization, allowing for the differentiation of THC, CBD, and their acidic precursors, Δ9-tetrahydrocannabinolic acid (THCA) and cannabidiolic acid (CBDA). A custom heated transfer zone was implemented to enhance derivatization efficiency and reduce carryover effects. The method was optimized for reagent concentration and gas stream temperature, achieving high specificity by minimizing interference from isomeric cannabinoids. Validation studies demonstrate good accuracy (relative error within ±15.9 %) and precision (relative standard deviation ≤15 %), with limits of quantitation of 7.5 µg/mL for THC/CBD and 0.5 µg/mL for THCA/CBDA. Comparative analysis of cannabis samples showed a strong correlation with reference LC/MS results, highlighting the reliability of the proposed method. DART-MS offers a significant time advantage, requiring only 10 s per analysis, making it a promising tool for high-throughput screening of cannabis samples in forensic laboratories. 

In this study, direct analysis in real time mass spectrometry (DART-MS) was coupled to the solid phase microextraction (SPME) to extract and analyze the ignitable liquid residues (ILR) present in the sample matrices. The SPME extraction parameters, such as extraction temperature and extraction time, were optimized using a two factor central composite design. The SPME-DART-MS setup was utilized to analyze the substrates and fire debris matrices spiked with gasoline. The results indicate that the less volatile marker compounds from gasoline were recovered from the substrates and fire debris, and their profiles matched well with the gasoline liquid samples analyzed directly by DART-MS. As expected, the effective extraction of marker compounds in gasoline required a relatively high temperature, i.e., 150 ℃. In the presence of a matrix, a higher extraction temperature and longer extraction time could benefit the extraction efficiency. The desorption of ILR on SPME fiber was performed by inserting the fiber into the DART-MS helium gas stream at 300 ℃ for 1 min with no carry-over residues being observed between successive samples. The chemical information attained with this method is typically not observed in the current GC/MS-based practice. The SPME-DART-MS was also extended to reanalyze less volatile components of ILR on substrates after the ASTM E1412 activated charcoal method, which indicates its possible application subsequent to the traditional GC/MS ILR analysis. The SPME-DART-MS has shown promise in ILR detection as an important complementary tool.