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Truth in Sizing – Electrostatic Effects and Cascade Impactors

Mohan M, Vinchurkar SC, Longest P, Byron PR, Peart J.

RDD Europe 2011. Volume 1, 2011: 67-78.

Abstract:

While the device and formulation are recognized to influence the electrostatic properties of pharmaceutical aerosols, the influence of this electrostatic charge on the deposition of particles within cascade impactors is not clearly understood. In this paper, an existing computational fluid dynamics (CFD) model has been extended to predict the influence of electrostatic charge on particle deposition within the Andersen Cascade Impactor (ACI). Validation of the CFD model was attempted with an in vitro study of the deposition of charge neutralized, inherently charged and artificially charged fluorescein disodium powder aerosols within a physical ACI. The CFD model of the ACI predicted that a saturation charge level, considered to be representative of that thought to exist on particles emitted from dry powder inhalers (DPIs), increases the deposition of aerosol particles passing through any stage compared to neutral aerosol particles. However, in the physical ACI, the deposition of highly charged fluorescein particles did not influence the apparent particle size distribution compared to neutral fluorescein particles. Until the CFD analysis is refined, it remains prudent to couple mathematical predictions with experimental results when attempting to gain insight into the role of charge on the deposition of pharmaceutical aerosols.