A Semi‐Continuous Versatile Aerosol Concentration Enrichment System Coupled to Online Extraction and Lc–Ms for Molecular‐Level Analysis of Atmospheric Aerosol Organic Matter

Abstract Organic matter (OM) constitutes a major fraction of atmospheric aerosols. However, achieving molecular‐level and high‐temporal‐resolution analysis of OM remains a significant analytical challenge. Here, an observation system, is developed the versatile aerosol concentration enrichment system coupled to online extraction and liquid chromatography–mass spectrometry (VACE–OE–LC–MS), for online observation of OM in PM _2.5 . This system enables molecular‐level detection and quantification of particle‐bound organic compounds, with chromatographic separation allowing the identification of structural isomers. It integrates a modified VACE module for particle enrichment, an OE module for collecting particles, extracting analytes, and concentrating the extracts, and an LC–MS module for compound analysis. The VACE module delivers a ≈10‐fold enrichment of particle concentration. The OE module innovatively employs N,N ‐dimethylacetamide (DMA) with a swirling aerosol collector, achieving collection efficiencies of 64.0–99.1% and maintaining stable operation for at least 8 h. In field observations, the system successfully quantifies 11 nitroaromatic compounds (NACs) at a 3‐h resolution, revealing diurnal concentration patterns that conventional 12–24‐h sampling cannot capture. Overall, this system offers enhanced temporal resolution while maintaining molecular specificity relative to traditional offline methods, providing a powerful analytical tool for investigating the formation, evolution, and transformation of OM in atmospheric aerosols.