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

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.