A new approach to determine the specific surface area of collected nanoparticles by Kr gas adsorption and application of the BET method

Engineered nanomaterials in powder form were increasingly used in industry for these last twenty years, leading to legitimate concerns about their impact on workers health. Several studies have shown evidence that the surface area is a relevant criterion to estimate potential toxicological effects of nanoparticles. Measuring the surface area of airborne nanoparticles is therefore crucial for estimating potential biological effects on workers. To that end, a method based on aerosol particles collection followed by gas adsorption analysis is proposed.
Polycarbonate 0.4 m pore size filters were chosen to collect particles as they present all the required physical properties. The contribution of the blank filter was removed to access the specific surface area of the collected particles only. Krypton gas was used as it is more suitable for low surface area measurements. In this configuration, the limit of quantification for BET-surface area measurement was established at 0.05 m and the associated uncertainty at 15%. The proposed method has been validated in the laboratory on powders of different chemical compositions and particles sizes. It could thereafter serve as the basis for a standardization project as it is the only method to date that provides a relatively fast and reliable result to determinate the specific surface area of a small amount of nanomaterial collected from air sampling.