Microwave plasma torch desorption ionization mass spectrometry for chemical characterization of aromatic secondary organic aerosol

Benzene and toluene, primarily emitted from vehicle exhaust, are common volatile organic compounds (VOCs). These aromatic compounds in the atmosphere undergo further photooxidation to form secondary organic aerosol (SOA), which are a primary factor in haze weather. Aromatic SOA is more difficult to detect by traditional detection methods. Microwave plasma torch (MPT) is an ambient ionization source based on microwave plasma developed in recent years. Herein, a microwave plasma torch desorption ionization high-resolution mass spectrometry (MPT-HRMS) technique was designed for the direct analysis of aromatic SOA in the environment. For environmental haze samples, no pretreatment is required, and over twenty types of aromatic hydrocarbon derivatives or oxidation products can be detected in situ using MPT-HRMS. The possible mechanisms underlying the formation of aromatic SOA were investigated. MPT-HRMS is a powerful technical tool for rapidly tracking non-targeted aromatic SOA and their transformations in the environment. This contributes to an in-depth understanding of the formation mechanisms of SOA and their impact on air pollution. [Display omitted] •In situ detection: utilizing in situ analysis eliminates the need for a pre-processing extraction step.•On-line mass spectrometry detection: high-resolution analysis at the scale of a few milliseconds.•Chemical characterization of haze: tracking aromatic SOA and their transformations.•Explored the possible mechanisms of aromatic SOA: the formation pathways from toluene to oxidation products.•DFT calculations: the mechanism of the reaction was evaluated by ΔG.