Improved lower particle size limit for aerosol time-of-flight mass spectrometry

The lower detectable particle size limit for a transportable aerosol time-o f-flight mass spectrometer (ATOFMS) has been improved to 0.08 mum. This is lower than previously reported and has been achieved through instrumental m odifications described in this paper. The uncertainty in the size measureme nt of particles with aerodynamic diameters less than 0.18 mum does not allo w for determination of an exact size for unknown particles, but particles w ith aerodynamic diameters as low as 0.08 mum can still be detected and chem ically analyzed. A calibration curve covering the size range 0.18-2.1 mum i s presented. Simultaneously acquired positive and negative ion mass spectra of an individual 0.08 mum polystyrene latex sphere and an ambient particle with an aerodynamic diameter of 0.18 mum or less obtained with a transport able ATOFMS instrument are shown. The ability to precisely size and chemica lly analyze particles from a polydisperse sample down to 0.18 mum makes ATO FMS unique from other single particle mass spectrometry instruments.