Characterization of organic aerosol in Beijing by laser desorption ionization coupled with Fourier Transform Ion Cyclotron Resonance Mass spectrometry

Abstract

In order to resolve the organic compositions in the atmospheric aerosol which is significant for understanding the formation mechanism of particulate matter and their harm for human health, a direct laser desorption ionization (LDI) coupled with Fourier Transform Resonance Mass (FT-ICR MS) was utilized for characterizing the aerosol particles collected in Beijing during winter. A lot of organic compounds can be detected by direct laser desorption ionization of the aerosol particular with different size collected on aluminum foil without complicated sample pretreatment process. In addition, semi quantification of the organic compounds can be achieved with solvent extraction procedure. It was found that the ubiquitous polycyclic aromatic hydrocarbons (PAHs) contaminants in the aerosol could serve as matrix, which helps the detection of many kinds of compounds including highly saturated amphiphilic long alkyl chain compounds (carbon number>16), like aliphatic amines in positive ion mode and organosulfates in negative ion mode. Based on the accurate mass measurement results, elemental compositions of over 1500 peaks in the mass spectrum were derived, and we categorized them into five groups according to their elemental compositions in order to provide helpful information for tracing the pollution source. It is demonstrated that abundant information about the organic components in the atmospheric aerosol can be provided by direct LDI FT-ICR MS method, and these information will largely facilitate further studies on origin and formation process of the aerosol.