Nontargeted screening of air samples using TD-GC-HRMS to identify volatile compounds as markers of an industrial plant fire in Rouen, France

An accidental industrial fire happened in Rouen (France) in september 2019 from a plant specialized in the production of mineral oils and engine additives. A few days after, passive sampling of the air was performed on thermodesorption tubes, from 09/30/2019 to 10/07/2019 using Tenax® TA and Carbopack B&X sorbents. Two identical samplings were carried out 18 (2021) and 26 months (2022) after the fire in the same place to evaluate the urban and in-house background noises. Analyses were performed using a thermodesorption gas chromatograph coupled to a hybrid quadrupole Orbitrap mass spectrometer (TD-GC-Q-Orbitrap) in full scan mode. A non-targeted screening allowed to detect thousands of molecules (about 8,000 on Tenax® TA and 3,000 on Carbopack B&X sorbents) including a large number of hydrocarbons, alkylbenzenes and polycyclic aromatic hydrocarbons in the tubes collected in 2019. But such hydrocarbons were not specific of the fire and then were not identified as industrial fire markers, as their presence were detected in the samples collected in 2021 and/or 2022. However, 22 sulfur-containing compounds were considered as potential markers because they were only detected in the samples collected in 2019 or at significantly higher level than in 2021 and/or 2022 and were detected in samples collected during Laboratory fire of engine oils. Moreover, these compounds were annotated with good confidence level. Among them, the identification of 6 sulfur-containing compounds, 2-acetylthiophene, 2-propionylthiophene, 2,2’-bithiophene, 3,3’-bithiophene, thieno[3,2-b]thiophene and di-tert-butyl-disulfide, and one oxygen-containing compound, 1,3,5-trioxane, was confirmed by injection of corresponding standards. Highlights : • The study explored passive sampling for pollutant collected after an industrial fire • Nontargeted analyses were performed using TD-GC-Q-Orbitrap in full scan mode • 5,000 compounds were tentatively identified mostly hydrocarbons and alkylbenzenes • ►21 sulfur compounds and one oxygenated compound were proposed as markers • thiophene derivatives and di-tert-butyl-disulfide were unambiguously identified