Soot Particle Agglomeration Inlet (SPAI) for Enabling Online Chemical Composition Measurement of Nanoparticles with the Aerosol Mass Spectrometer

ABSTRACT Nanoparticles are a subject of interest because of the effects they have on human health and climate. Chemical composition is one of the key properties that govern the mechanisms of these effects. However, current options for its measurement are very limited and they often require long collection times. The Soot Particle Aerosol Mass Spectrometer (SP-AMS) is an instrument designed for measuring the chemical composition of particles online. Due to losses in the sampling section of the instrument it has a lower particle size limit of 50 nm, preventing the analysis of nanoparticles. In this paper we present a measurement concept and a prototype system enabling the measurement of chemical composition of nanoparticles online. The studied nanoparticles are attached on the surfaces of artificially generated soot particles. We call this soot particle generation and agglomeration process Soot Particle Agglomeration Inlet (SPAI), which is designed as an inlet to the SP-AMS. We applied the prototype in laboratory tests, where the soot particle generation and the agglomeration section were characterized and optimized, and the performance of the SPAI was evaluated with silver nanoparticles as test aerosol. Applying the SPAI resulted in a 35-fold enhancement in the silver nanoparticle detection, compared to the measurement without it. The results indicate that the SPAI is a potential tool in resolving problems related to chemical composition measurement of nanoparticles, either as a standalone addition to the SP-AMS or combined with other sample pretreatment systems.