What is cascade impaction?

Cascade impaction is a commonly used method in pharmaceutical and aerosol research for characterizing the aerodynamic particle size distribution (APSD) of aerosols and dry powder inhalers (DPIs). In a cascade impactor, the aerosol is passed through a series of stages with progressively smaller orifices (0.2-10 microns) that capture and collect the particles on a substrate.

Each stage of the impactor measures the particle aerodynamic diameter range that is captured, and the total mass of the particles is often determined by weighing the substrates before and after the sampling. The resulting APSD provides information about the size range of particles that can be inhaled and deposited in different regions of the respiratory system, and its measurement is critical for evaluating inhalation drug delivery efficacy and safety.

Cascade impactors are also used to evaluate the performance of air filters and to assess the characteristics of particulate matter in air pollution studies.