Deposition Pattern of Polydisperse Dry Powders in Andersen Cascade Impactor – Aerodynamic Assessment for Inhalation Experimentally and in Silico

INTRODUCTION: An impactor is a standard instrument that applied for particle deposition assessment in the pharmaceutical aerosols. It provides data comparison between inhaler formulations. However, the deposition pattern in the impactor is not clearly understood. In practice monodisperse aerosols were employed to calibrate the impactor.
METHODS: This study used polydisperse aerosols together with the computer simulation to track the particles in the impactor to understand the deposition pattern. Particles deposited on each stage of the Andersen cascade impactor (ACI) were compared with its stage cut-off diameter using polydisperse aerosols by three particle sizing techniques. The relationship of cut-off diameter with particle size distribution (PSD) was established for each stage. Also, the computational verification was used to complement the real experiments.
RESULTS: Projected diameters from microscope images showed that the size of particles varied on the stage’s collection plate, and the median size of each stage decreased along the lower stages from 8.53 to 0.92 μm. The median sizes measured by laser diffraction were close to the impactor’s cut-off diameters. In silico data showed that the outlet mass fractions gradually changed in size towards the lower stages.
DISCUSSION AND CONCLUSION: Polydisperse aerosols and in silico computer fluid dynamics may compliment to standard calibration method.