Improved Lower Particle Size Limit for Aerosol Time-of-Flight Mass Spectrometry

Abstract

The lower detectable particle size limit for a transportable aerosol time-of-ight mass spectrometer (ATOFMS) has been improved to 0.08 ¹m. This is lower than previously reported and has been achieved through instrumental modi cations described in this paper. The uncertainty in the size measurement of particles with aerodynamic diameters less than 0.18 ¹m does not allow for determination of an exact size for unknown particles, but particles with aerodynamic diameters as low as 0.08 ¹m can still be detected and chemically analyzed. A calibration curve covering the size range 0.18 -2.1 ¹m is presented. Simultaneously acquired positive and negative ion mass spectra of an individual 0.08 ¹m polystyrene latex sphere and an ambient particle with an aerodynamic diameter of 0.18 ¹m or less obtained with a transportable ATOFMS instrument are shown. The ability to precisely size and chemically analyze particles from a polydisperse sample down to 0.18 ¹m makes ATOFMS unique from other single particle mass spectrometry instruments.