2026-04-302026-04-302025AGUIAR, Deborah Victoria Alves de et al. Unlocking PAH Ionization in negative-mode ESI Orbitrap MS using tetramethylammonium hydroxide: a petroleomic strategy. Journal of The American Society for Mass Spectrometry, Washington, D.C., v. 36, n. 10, p. 2142-2150, 2025. DOI: 10.1021/jasms.5c00170. Disponível em: https://pubs.acs.org/doi/10.1021/jasms.5c00170. Acesso em: 14 abr. 2026.e- 1879-11231044-0305https://repositorio.bc.ufg.br//handle/ri/30258The selective ionization of cyclopentadiene-derived polycyclic aromatic hydrocarbons (PAHs) in complex matrices remains a persistent challenge in direct ionization mass spectrometry, particularly under atmospheric pressure ionization (API) conditions. In this study, tetramethylammonium hydroxide (TMAH) was evaluated as a solvent modifier to enhance the ionization efficiency of PAHs in negative-ion mode using high-resolution Orbitrap MS. A systematic assessment with equimolar mixtures of neutral and acidic model compounds was performed to elucidate the fundamental effects of TMAH on ion suppression, deprotonation mechanisms, and gas-phase ion chemistry. The incorporation of TMAH significantly improved the detection of weakly acidic and neutral PAHs by promoting efficient gas-phase deprotonation, thus overcoming conventional ESI limitations. To demonstrate the method’s analytical robustness, TMAH-assisted ESI was subsequently applied to crude oil samples, enabling the detection of hydrocarbon species otherwise inaccessible under standard conditions, with a particular focus on low-alkylated fluorene derivatives. These results establish a simple and effective strategy for expanding the analytical scope of ESI-MS toward nonpolar and weakly acidic hydrocarbons, offering a valuable tool for the advanced molecular characterization of complex organic mixtures.engAcesso Abertohttp://creativecommons.org/licenses/by-nc-nd/4.0/Tetramethylammonium hydroxidePetroleum-derived samplesPolycyclic aromatic hydrocarbonsElectrospray ionizationOrbitrap MSPetroleomicsArtigo10.1021/jasms.5c00170