Aerosol time-of-fl ight mass spectrometer for measuring ultrafi ne aerosol particles

Totti Laitinen, Kari Hartonen, Markku Kulmala, Marja-Liisa Riekkola
2009 unpublished
Laitinen, T., Hartonen, K., Kulmala, M. & Riekkola, M.-L. 2009: Aerosol time-of-fl ight mass spectrometer for measuring ultrafi ne aerosol particles. Boreal Env. Res. 14: 539-549. An aerosol mass spectrometer for ultrafi ne aerosol particles was constructed. The operation of the apparatus is based on the aerosol particle collection onto a metal surface over a short period. The near real-time aerosol particle collection makes possible an analysis of the particle phase compounds with short
more » ... s with short lifetimes. The collected aerosol particles are charged with a bipolar charger, size-separated by a differential mobility analyzer according to their electrical mobility and collected via electrostatic deposition on the electrically charged metal surface of a sampling valve. The collected particles are subjected to a two-step laser desorp-tion ionization before the mass spectrometric analysis. The ionized molecules are analyzed according to their m/z ratios and detected with a micro-channel plate detector. The aerosol mass spectrometer was calibrated with different chemical compounds, and its applicability for the determination of selected organic compounds was studied. The calibration of the mass axis showed a good correlation (R 2 = 0.9996). Mass spectral data for ultrafi ne ambient aerosol particles was obtained at sub-picogram concentrations.