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.

Comparison of field portable measurements of ultrafine TiO2: X-ray fluorescence, laser-induced breakdown spectroscopy, and Fourier-transform infrared spectroscopy

“…It has been shown to produce more repeatable analyses than LIBS under similar conditions, 27 and since sample integrity is maintained, it allows for further analyses of samples (e.g. surface area, 10 particle morphology, and confirmation of mass loadings). In addition, more timely exposure characterization is produced by XRF in comparison to traditional shipment to a laboratory and analysis by ICP-AES.…”

“…9 Particle samples were collected on 37 mm polycarbonate track etched (PCTE) filters having 0.4 µm pore size (Sterlitech Corporation, Kent, WA), as previously used in a surface area study of TiO 2 , using two-piece, closed-face cassettes attached to GilAir-5 air sampling pumps (Sensidyne, Clearwater, FL) operated at 3 LPM. 10 Closed-face cassettes produce a non-uniform deposition pattern with heavier loadings on the filter below the inlet orifice, 11 especially when sampling at this relatively high flow rate. This heterogeneous deposition pattern must be considered when analyzing the filter mass loadings using techniques that only interrogate a portion of the filter.…”

Towards a surface metric to measure the dustiness of nanomaterial powders

“…Devices based on diffusion charging give access to the geometric, active or lung-deposited surface area, 47,48 but their performance has not been studied for airborne particles emitted by powders and they are limited to a particle size range of 10 nm to a few mm, which is not sufficient to measure the range of sizes expected for a powderbased aerosol (between 10 nm and over 10 mm). Lebouf et al 49 proposed a methodology to determine the A Ex of particles collected on lters for different aerosols of nano TiO 2 , between 55 and 160 m 2 g −1 , and nano SiO 2 (57 m 2 g −1 ) generated in an inhalation chamber for toxicology experiments. The authors proposed an approach based on the difference in surface area measurement between a sampled and blank collecting support.…”