Elemental Composition of Nanoparticles with the Nano Aerosol Mass Spectrometer

摘要

The nano aerosol mass spectrometer (NAMS) irradiatesnindividual, size selected nanoparticles with a high energynlaser pulse to generate a mass spectrum consisting ofnmultiply charged atomic ions. The elemental compositionnof the particle is determined from the ion signal intensitiesnof each element, which requires deconvoluting isobaricnion signals at 4 m/z (O4+ and C3+) and at 8 m/z (O2+nand S4+). A method to deconvolute these ion signalsnusing sucrose and ammonium sulfate as calibrants isnpresented. The approach is based on the assumptionnthat the charge state distribution of a given element isnindependent of the chemical form of that element innthe particle. Relative to previously reported methodology,nthe new approach permits accurate and precisendetermination of sulfur, which is crucial for interpretationnof ambient nanoparticle data sets. With thisnapproach, the differences between expected and measurednelemental ratios of C, O, N, and S for a varietynof test particles were generally much less than 10%,nalthough a difference as high as 16% was observed.