Measurement of airborne nanoparticle surface area using a filter-based gas adsorption method for inhalation toxicology experiments

Abstract

Measurement of the surface area of airborne nanoparticles as administered to an experimental subject is critical for characterizing exposures during inhalation experiments. A filter-based surface area measurement methodology is described herein that allows for such determinations. Krypton gas adsorption was used to determine total particle surface area. Track-etched polycarbonate 0.4 μm pore filters were chosen as the collection substrate for metal oxide particles due to their highly reproducible surface areas and low background weights. The subject nanomaterials included two different batches of ultrafine TiO₂, TiO₂ nanorods, and SiO₂. The instrument detection limit for surface area was 200 cm² (0.02 m²). Ninety percent confidence interval estimates of method accuracy were 17.7–23.5% with a point estimate of 20.8%. The filter-based surface area measurement strategy is demonstrated to be a viable sampling and analysis methodology that provides much needed physical characterization information of particles as administered in an animal inhalation chamber.

Keywords::

• Nanoparticles
• surface area
• ultrafine titanium dioxide
• sampling methodology

Acknowledgments

The authors would like to thank Emanuele Cauda and Arthur L. Miller for their thorough review of this manuscript and Jared Cumpston and Eleanor Wade for assistance with sampling of the nanomaterials, as well as Matthew G. Duling for assistance with measurements. Financial support of this project was provided by the US Government.

Declaration of interest: The authors report no conflict of interest. The authors alone are responsible for the content and writing of the paper.