Investigating\nthe Kinetics of Heterogeneous Lipid\nOzonolysis by an Online Photoionization High-Resolution Mass Spectrometry\nTechnique

Lipid oxidation-induced imbalance in the redox system\nis one of\nthe key causative factors leading to accelerated aging in living organisms\nand related diseases. Online sampling and analysis of the heterogeneous\nozonolysis kinetics of lipid aerosols are highly important in revealing\nthe oxidation-driven aging process of lipids. In this paper, an online\ndetection method based on atmospheric pressure photoionization combined\nwith ultrahigh resolution mass spectrometry (APPI-HRMS) is developed\nfor real-time analysis of the heterogeneous reactions between lipid\nparticles (oleic acid and squalene) and ozone. The online APPI-HRMS\ntechnique serves as an ideal platform for analyzing the heterogeneous\noxidation of particles, exhibiting remarkable stability, sensitivity,\nand responsiveness across a wide range of particle concentrations.\nOwing to the distinctive characteristics of soft ionization, the heterogeneous\neffective oxidation rate of lipid aerosols was quantitatively measured.\nThis has facilitated the detection of a series of fingerprint particle-phase\nproducts, including aldehydes, secondary ozonides, and hydroperoxides.\nAdditionally, the kinetics evolution of these products with the ozone\nconcentration was captured. Consequently, the ability of this online\nAPPI-HRMS technique in assessing the multiphase oxidation of organic\nparticles has been demonstrated, positioning it as a promising and\nfeasible tool for revealing the heterogeneous reactions of particles.