Comparison of the Particle Size Distribution and Vapor Phase of Electronic Nicotine Delivery Systems Using Two Impactors

Electronic Nicotine Delivery Systems (ENDS) contain numerous volatile aerosol constituents (e.g., nicotine, propylene glycol, flavors, etc.). Past work clearly indicates the temporal and chemical dynamics of ENDS aerosol requires consideration of these volatile constituents when measuring the particle size distribution. An MSP-135-8 Mini MOUDI™ and Electrical Low Pressure Impactor (ELPI^®+) were used to measure the particle size distribution of two JUUL ENDS products. Volatile chemicals were measured from each cascade impactor's exhaust airflow to assess their effect on collection efficiency. Similar mass median aerodynamic diameters were obtained for both ENDS products by both cascade impactors, however the geometric standard deviation from the ELPI^®+ measurements were larger for both products than measurements using the Mini MOUDI™ impactor. Although the measured mass of volatile chemicals was greater in the exhaust from the Mini MOUDI™ impactor, a greater variety of volatile chemicals were found within the exhaust of the ELPI^®+. The greater variety of volatile chemicals correlated with more room air sampling by the ELPI^®+. The reduced amount of volatile chemicals measured in the exhaust of the ELPI^®+ may be due to their collection by the vacuum oil used in the sintered collection plates of the ELPI^®+. Accounting for the measured volatile chemicals improved the recovery efficiency of the Mini MOUDI™ impactor by 2.9–7.5% with the average recovery efficiency exceeding 82% for the two JUUL ENDS Products. In comparison, accounting for the measured volatile constituents increased the recovery efficiency of the ELPI^®+ impactor by 0.4% or less, which did not narrow the recovery efficiency range, that based upon the estimated dilution, consistently exceeded the measured mass loss from both JUUL ENDS products.