A sampler designed for nanoparticles and respirable particles with direct analysis feature

Abstract

A sampler has been designed to collect particles in the nanometer and respirable sizes directly onto a membrane filter and transmission electron microscopy (TEM) grid. The novel design aspects of this sampler include the selection of the diameter of the inlet probe, geometry of the sampler, and the resulting air flow to the sampler. Together, they control the cutoff diameter, which was determined experimentally to be a mass median aerodynamic diameter (MMAD) of 3.8 μm. The maximum aerodynamic diameter entering the sampler is designed to be approximately 8 μm. Nanometer-sized particles are collected on both the filter and grid through diffusion, as confirmed by testing with aluminum oxide engineered nanoparticles collected on the filter which measured a count median diameter (CMD) of 500 nm and a geometric standard deviation (GSD) of 1.97. The primary particles and small agglomerates collected on the grid have a CMD of 100 nm and GSD of 2.3. This diffusion sampler collected close to, if not 100%, of the particles entering the sampler. The sampler is easily wearable for personal exposure and environmental sampling, operates at 0.3 L/min, and can collect particles in various settings at indoor and outdoor environments. Particles are analyzed directly by transmission electron microscope on the grid and by scanning electron microscope on the filter to assess the exposure through particle counts and elemental composition analysis.