Method Optimization for the Measurement of Aerosol Particle Size Characterization from Heated Tobacco Products
CHIH-HSIANG CHIEN, Matt Melvin, Weiling Li, Yezdi Pithawalla, Altria Client Services LLC
Abstract Number: 647
Working Group: Instrumentation and Methods
Abstract
Heated Tobacco Products (HTP) contain a tobacco substrate heated to temperatures below 350°C, resulting in an inhalable nicotine-containing aerosol. Previously a new pressure-feedback loop sampling interface was developed to measure particle size distribution (PSD) of HTP aerosols using a low-flow rate cascade impactor which was presented at AAAR 2023. The objective of this study is to use the interface to systematically investigate the influence of experimental conditions such as the shape of puff profiles, humidity level of the dilution air, and dilution volume on the HTP aerosol particle size distribution.
The results demonstrated no significant difference in the particle size distribution and aerosol mass collected on the impactor between bell-shape and square-shape puffing profiles. The results also showed that using humid air for aerosol dilution can minimize aerosol evaporation compared to dry air and result in more accurate PSD measurements. A minimal dilution ratio with humid air of 1.21: 1 was established for measuring the mass median aerodynamic diameter of HTP aerosols. Additionally, another methodology was developed to measure emission-based PM2.5 of HTP aerosols, which is another aerosol design parameter required for regulatory submissions as per the Premarket Tobacco Product Applications (PMTAs) and Recordkeeping Requirements Final Rule issued by the Food and Drug Administration (FDA) in 2021. Potential transportation loss and sampling artifacts were evaluated to understand the measurement uncertainty associated with PM2.5 measurements. Minimal transportation loss was observed in the interface. As previously mentioned, the humidity of dilution air significantly impacted downstream aerosol mass collection, and using humidified air during sampling can minimize aerosol sampling loss. The measured PM2.5 concentrations across three HTP products were within the same order of magnitude.