Abstract. The mass resolution of laser desorption ionization (LDI) single-particle
aerosol mass spectrometry (SPAMS) is usually low (∼500),
which has been greatly improved by the recent development of the delayed ion
extraction technique. However, due to large fluctuations among LDI processes
during each laser shot, accurate calibration of the mass-to-charge ratio for
high-resolution SPAMS (HR-SPAMS) spectra is challenging. Here we developed an automatic
linear calibration method to improve the accuracy of mass-to-charge (m∕z)
measurement for single atmospheric aerosol particles. Laboratory-generated
sea spray aerosol and atmospheric ambient aerosol were tested. After the
calibration, the fluctuation ranges of the reference ions' (e.g., Pb+ and SO4+) m∕z reaches ±0.018 for sea spray aerosol and ±0.024 for ambient aerosol in average mass spectra. With such m∕z accuracy, the HR-SPAMS spectra of sea spray aerosol can easily identify elemental compositions of organic peaks, such as Cx, CxHy and CxHyOz. While the chemical compositions of ambient aerosols are more complicated, CxHy, CxHyOz and CNO peaks can also be identified based on their accurate mass. With the improved resolution, the time series of peaks with small m∕z differences can be separated and measured. In addition, it is also found that applying high-resolution data with enhanced mass calibration can significantly affect particle classification (identification) using the ART-2a algorithm, which classify particles based on similarities among single-particle mass spectra.
Supplementary material to "Development of an Automatic Linear Calibration Method for High Resolution Single Particle Mass Spectrometry: Improved Chemical Species Identification for Atmospheric Aerosols"
