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1. A comparative study of aromatic content in pyrolysis oils from waste plastics and tires: Assessing common refinery methods

   https://doi.org/10.1016/j.fuel.2024.131714  

   Auersvald, Miloš; Šiman, Michal; Lyko_Vachková, Eliška; Kroufek, Jiří; Straka, Petr; Barzallo, Genesis; Vozka, Petr (August 2024, Fuel)

   The conversion of waste plastics and tires via pyrolysis to pyrolysis oil represents one of the most promising ways of chemical recycling. Determining aromatics in pyrolysis oils from these feedstocks is crucial for their utilization as both petrochemicals and fuels. In this study, we compared three standard methods commonly available in refinery laboratories (ASTM D1319 − FIA, EN12916 − HPLC-RI, ASTM D8396 − GC × GC-FID) for analyzing aromatic content across a wide range of waste plastic pyrolysis oils, their middle distillate fractions, and hydrotreated products. Using model compounds, we explained most of the observed differences in aromatic content determined by these methods. HPLC-RI and FIA resulted in significant errors. For instance, the FIA reports some dienes and heterocompounds as aromatics. The results from HPLC-RI showed that monoaromatics are overestimated, while polyaromatics are underestimated. Among the tested methods, GC × GC-FID provided the most reliable results. 

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2. Analysis of oil-based ignitable liquid residues by GC–MS and DART–MS

   https://doi.org/10.1016/j.forc.2025.100701  

   Dong, Wen; Chong, Ngee Sing; Thanni, Qudus Ayodeji; de_Boves_Harrington, Peter; Zhang, Mengliang (September 2025, Forensic Chemistry)

   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. 

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3. Differentiation and identification of fentanyl analogues using GC-IRD

   https://doi.org/doi.org/10.1016/j.forc.2020.100255  

   Winokur, Agnes; Kaufman, Lindsay; Almirall, Jose (June 2020, Forensic chemistry)

   Fentanyl analogues and their positional isomers have similar chemical structural configurations making them difficult to identify and differentiate. Gas chromatography coupled to a gas-phase infrared detector (GC-IRD) is a useful and powerful tool for the unambiguous identification of fentanyl compounds where traditional analytical techniques such as gas chromatography–mass spectrometry (GC–MS) offer limited information for this class of compounds. In this study, we demonstrate the utility of GC-IRD and show how this complementary information enables the identification of fentanyl analogues (2- and 3- furanylfentanyl, 2-furanylbenzylfentanyl, croto- nylfentanyl, cyclopropylfentanyl, methoxyacetylfentanyl, carfentanil, meta-fluoroisobutyryl fentanyl, para- fluoroisobutyryl fentanyl and ortho-fluoroisobutyryl fentanyl) when combined with GC–MS data. A description of the operating conditions including how the optimization of GC-IRD parameters can enhance the spectral resolution and unambiguous identification of these fentanyl analogues is presented, for the first time. In par- ticular, the effects of light pipe temperatures, acquisition resolution, the use of a programmed temperature vaporizing (PTV) inlet, and the analytical concentration of the sample were evaluated. A real-world case ex- ncountered in casework and how the implementation of GC- of these challenges in fentanyl differentiation and identification. 

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4. Molten Plastic Induced Noncovalent Interactions for Tunable Cellulose Fast Pyrolysis

   https://doi.org/10.1039/D3GC01312J  

   Sakirler, Fuat; Tekbas, M Doga; Wong, Hsi-Wu (November 2023, Green Chemistry)

   Fast pyrolysis of lignocellulosic biomass is a promising approach for producing biofuels and renewable chemicals, but the resultant bio-oil quality and diverse product distributions limit its widespread adaptation. Concurrently, the accumulation of waste plastics in the environment, particularly polyolefin thermoplastics, is becoming a growing threat. Co-pyrolysis of biomass with hydrogen-rich thermoplastics has shown promise for producing high-quality bio-oils, presenting an attractive solution to waste management. However, a molecular-level understanding of the synergy of the two components in the molten phase during co-pyrolysis is still lacking. In this work, we report the discovery of catalytic and inhibitory effects on cellulose fast pyrolysis caused by noncovalent interactions (NCIs) induced by molten plastics. Our microreactor experiments demonstrated that selectivity toward cellulose-derived anhydrosugars, small oxygenates, or furans increased due to the presence of polyketone, polyethylene glycol, or polystyrene, respectively, which are three thermoplastics with distinct functional groups. Density functional theory calculations reveal that key cellulose pyrolysis pathways leading to major products are catalyzed or inhibited due to perturbations of transition state geometries and partial charges caused by the NCIs induced by plastic functional groups. This discovery offers insights and opportunities for tuning cellulose fast pyrolysis via NCIs using a new family of unconventional molten plastic catalysts or inhibitors 

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5. Comparison of portable and benchtop GC–MS coupled to capillary microextraction of volatiles (CMV) for the extraction and analysis of ignitable liquid residues

   https://doi.org/10.1016/j.forc.2020.100240  

   Torres, Michelle; Valdes, Nicole; Almirall, Jose (April 2020, Forensic chemistry)

   A novel extraction device, capillary microextraction of volatiles (CMV) was coupled to a TRIDION-9 GC–MS with a needle trap (NTD) and evaluated for the analysis of ignitable liquids fire debris. The performance of the TRIDION-9 was compared to a benchtop GC–MS using CMV. A system detection limit of ~10 ng for each of 20 key ignitable liquid residue (ILR) compounds was determined for the T9 GC–MS. Dynamic headspace sampling of simulated ILRs was performed in closed and open-air systems. Closed system evaluations the CMV/NTD technique resulted in extraction performance similar to the CMV alone; however, ILR analysis on the T9 was impacted by limited chromatographic resolution. Compound identification was possible for 14 out of the 20 selected compounds on the T9 when 1 μL of a 1% standard accelerant mixture (SAM) was sampled, compared to 17 compounds on the benchtop GC–MS for the same mass loading. Open-air sampling with a modified vapor source resulted in the retention of most compounds with as low as 5 min. sampling, and equilibrium concentrations were reached after 10 min. No significant differences were observed between CMV and CMV/NTD sampling suggesting that the combined technique does not suffer from affinity bias. While the potential of the CMV/NTD extraction coupled to a T9 GC–MS for fire debris analysis was limited by the chromatographic resolution of the instrument, this study serves as proof of concept for the CMV’s potential for the extraction of ILRs in combination with portable GC–MS systems. 

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