The Development of Electrostatic Precipitation-Electrospray Ionization Mass Spectrometry (EP-ESI-MS) for Atmospheric Aerosol Analysis

Abstract:

Chemical composition analysis of atmospheric aerosols is of considerable interest and has been facilitated by mass spectrometry. Electrospray ionization (ESI) is a suitable mode of ion generation of many organic species comprising aerosol particles, as it leads to minimal analyte fragmentation. However, particles exist in the atmosphere at mass concentrations of the order 10 µg/m³ or less in many environments and are highly heterogeneous; low concentrations and chemical complexity have limited ESI application in aerosol analysis. In this presentation, the development of an approach to apply ESI to molecules within submicrometer and nanometer scale aerosol particles is discussed. The technique, which we term electrostatic precipitation-ESI-MS (EP-ESI-MS), utilizes unipolar ionization to charge particles, electrostatic precipitation to collect particles on the tip of a tungsten rod, and subsequently, by flowing liquid over the rod, ESI and mass analysis of dissolved species originating from the collected particles. EP-ESI-MS is shown to enable analysis of nanogram quantities of collected inorganic and organic components. Furthermore, it is coupled with a tandem mass spectrometry and challenged with oxidation products of α-pinene to investigate its capability of enabling structure analysis of complex organic compounds in aerosol particles. With EP-ESI-MS, the identification of chemical components in aerosol particles is realized and the integrated mass spectrometric signals are found to be a monotonic function of the analyte mass concentration in the aerosol phase. Additionally, it is shown to have a dynamic range of 5 orders of magnitude in mass, making it suitable for molecular analysis of aerosol particles in laboratory settings, as well as analysis of atmospheric aerosols in ambient air.