PERCI Aerosol Mass Spectrometry

The PERCI Aerosol Mass Spectrometer (AMS) consists of 4 main components: 1) Particle inlet; 2.) Particle Vaporization source; 3) PERCI source; and, 4) Time-of-Flight MS. The particle inlet is used to concentrate aerosol particles (in the air sample) with respect to the gas phase while decreasing the sample pressure from atmospheric pressure to about 10-6 mbar. Under given operating conditions, the particle inlet may also be used to deliver only particles of one given diameter to the analytical zone of the instrument. After the particles are focused, they enter the vaporization and ionization region. The particles are thermally vaporized and the molecular components ionized for mass analysis by the reflectron time-of-flight mass spectrometer. The minimal molecular fragmentation caused during ionization allows for easy identification of the components of even the most complex organic particles. The adaptation of PERCI to AMS has been applied to the heterogeneous reaction of gas phase ozone with oleic acid particles and has provided new insights into this well-studied model system.

                          

 
 

 

Particle Inlet

 

 

The particle inlet has been designed to introduce a monodisperse ultrafine aerosol beam into the ionization region of the time-of-flight mass spectrometer (TOF-MS).  The inlet consists of three differentially pumped regions with a series of aerodynamic lenses in the first region (Stage 1).  The aerodynamic lenses serve to focus particles of a given diameter along the central axis of the inlet.  Theoretical studies on this type of system predict that by varying the pressures in stages 1 and 2, the aerodynamic diameter of the focused particles can be varied in a controlled manner.

References

  •  Petrucci, G.; Farnsworth, P.; Cavalli, P.; Omenetto, N., A differentially pumped particle inlet for sampling of atmospheric aerosols into a time-of-flight mass spectrometer: Optical characterization of the particle beam. Aerosol Science and Technology 2000, 33, (1-2), 105-121, doi: 10.1080/027868200410877.