Particle analysis by mass spectrometry

Abstract

Mass spectra have been measured for single aerosol particles in the micron size range on a continuous, real-time basis. Particle beams of dioctyl phthalate, glutaric acid, adipic acid, ammonium sulfate, and some of the amino acids were generated by expansion of these aerosols through a capillary nozzle (throat diameter = 0.1 mm and length = 5 mm) and a skimmer (diameter = 0.331 mm). The transmission efficiency of the beam generator has been measured for different particle sizes. Individual particles were volatilized by impaction on a hot rhenium V-type filament (300 to 1400°C) and the resulting vapor plume ionized by electron bombardment in the ionizer of a quadrupole mass spectrometer. Ion currents for different masses from individual particles have been measured. The intensity of the characteristic mass peaks of different size aerosol particles increased linearly with their volume. Ammonium sulfate aerosols produce signals at SO +, SO 2 +, SO 3 + mass fragments whereas no SO 3 + mass peak could be detected from sodium sulfite particles. The absence of SO 3 + from sulfite can be used to differentiate between the sulfate/sulfite contents of aerosol particles.