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 im- proved 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 parti- cles with aerodynamic diameters less than 0.18 ¹mdoes not allow for determination of an exact size for unknown particles, but par- ticles 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 aerody- namic 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.