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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. 

Cardiac performance is tightly regulated at the cardiomyocyte level by sarcomere length, such that increases in sarcomere length lead to sharply enhanced force generation at the same Ca 2+ concentration. Length-dependent activation of myofilaments involves dynamic and complex interactions between a multitude of thick- and thin-filament components. Among these components, troponin, myosin, and the giant protein titin are likely to be key players, but the mechanism by which these proteins are functionally linked has been elusive. Here, we investigate this link in the mouse myocardium using in situ FRET techniques. Our objective was to monitor how length-dependent Ca 2+ -induced conformational changes in the N domain of cardiac troponin C (cTnC) are modulated by myosin–actin cross-bridge (XB) interactions and increased titin compliance. We reconstitute FRET donor- and acceptor-modified cTnC(13C/51C)AEDANS-DDPM into chemically skinned myocardial fibers from wild-type and RBM20-deletion mice. The Ca 2+ -induced conformational changes in cTnC are quantified and characterized using time-resolved FRET measurements as XB state and sarcomere length are varied. The RBM20-deficient mouse expresses a more compliant N2BA titin isoform, leading to reduced passive tension in the myocardium. This provides a molecular tool to investigate how altered titin-based passive tension affects Ca 2+ -troponin regulation in response to mechanical stretch. In wild-type myocardium, we observe a direct association of sarcomere length–dependent enhancement of troponin regulation with both Ca 2+ activation and strongly bound XB states. In comparison, measurements from titin RBM20-deficient animals show blunted sarcomere length–dependent effects. These results suggest that titin-based passive tension contributes to sarcomere length–dependent Ca 2+ -troponin regulation. We also conclude that strong XB binding plays an important role in linking the modulatory effect of titin compliance to Ca 2+ -troponin regulation of the myocardium.