AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Device and Method for Generation of Aerosol Distributions with Tuneable Geometric Mean Diameter down to 5 nm
JAMES FARNSWORTH, Jason Johnson, TSI Incorporated
Abstract Number: 27 Working Group: Instrumentation and Methods
Abstract Polydisperse test aerosols are prepared for a variety of reasons including inhalation research, filter media testing, and instrumentation development. Nebulization is a simple and useful means for generating test aerosols. However, it is difficult to obtain distributions of mean sizes below 25 nm, as droplet diameters produced in nebulization are large and dissolved residue in the diluent interferes with the size distribution of interest. Flame and furnace methods can be used to generate sub-25 nm aerosols, but these techniques have disadvantages related to easy of use, repeatability, and potential health concerns. All generation methods typically struggle with controlling size while maintaining constant output concentration and geometric standard deviation (GSD).
Here we present a device and method for generating a lognormally-distributed aerosol distribution with an adjustable mean diameter, prepared from a single dissolved solution, while maintaining good stability of concentration and GSD. An aqueous solution of 10 percent NaCl was prepared, and the new TSI Model 3485 Nanoparticle Nebulizer was used to generate aerosols over a range of mean diameters using the 1000X dilution capabilities of the instrument. The mean diameter range of the device was further extended by adjusting droplet impaction distance, thus varying droplet diameter. The aerosol size distribution was measured using a TSI 3936 SMPS. The resulting aerosol was lognormally distributed with a mean diameter tuneable over the range 5-30 nm geometric mean number diameter (10-130 nm geometric mean volume diameter). The GSD for these particle distributions was 1.5 ± 0.2 and number concentration ranged from 10^6 to 10^7 #/cc for all generated distributions.
These results demonstrate the use of a nebulizer such as the TSI 3485 for generation of concentration-stable challenge aerosols over a wide size range, and offer a cheaper and safer alternative to furnace or flame nanoparticle generation techniques for obtaining sub 20nm aerosols.