Reducing bounce effects in the Andersen cascade impactor

Foster®: A High-Efficiency Combination Metered Dose Inhaler with Consistent Particle Size Distribution at Alternative Flow Rates

“…Furthermore, it is known that a combination of low dose number and uncoated impactor plates results in the underestimation of particle size information [2,3,6,7]. In addition, figure two of the Johal et al [5] paper utilizes identical impactor stage cut-off diameters for the Andersen Cascade Impactor (ACI), at both 28.3 and 60 L/min sampling flow rates, rather than calculating precise stage cut-off diameters and appropriately representing the data [8,9].…”

Quantification of Low Pressure Impactor Wall Deposits during Zinc Nanoparticle Sampling

“…Cheng and Yeh (1979) concluded that particle rebound reduced collection efficiency which increased wall losses and shifted aerosol distribution in the Sierra radial slit jet impactor. Dunbar et al (2005) observed statistically significant (P < 0.05) differences in mass median aerodynamic diameter between uncoated and coated impaction plates; they also minimized bounce effects with the use of saturated glass fiber filters. However, they considered interstage losses to be intrinsic to the impactor despite the link between rebound and loss.…”

“…Nevertheless, Marple et al (1991) used silicone on substrates and found up to 35% loss for liquid particles ranging from 0.03 to 20 µm, and up to 20% loss for solid particles ranging from 7 to 20 µm. Dunbar et al (2005) concluded that substrate greasing reduces but does not minimize bounce effects and thus related particle loss. Therefore it seems difficult to avoid particle loss even under the best condition of use.…”

“…For example, liquid particles are more subject to losses than solid particles (Marple et al, 1991). Other parameters such as collection substrate (Fujitani et al, 2006), relative humidity (Yamamoto et al, 2002), and substrate greasing (Yamamoto et al, 2002;Dunbar et al, 2005) also affect wall losses by modifying stage collection efficiencies. Thus wall deposits must be characterized and quantified correctly to avoid the underestimation of particle mass concentration and mass size distribution.…”

Good Cascade Impactor Practice (GCIP) and Considerations for “In-Use” Specifications

“…Furthermore, the behavior of low-density, highly porous particles in IPs during aerodynamic particle size analysis by CI is not well understood. However, Dunbar et al have commented that such particles, having low envelope densities and reduced area in contact with the walls of the CI apparatus, appear to be more susceptible to bounce and re-entrainment compared with non-porous particles or liquid droplets of equivalent aerodynamic diameter (23). Although Dunbar et al focused on quantifying and mitigating particle bounce on the collection surfaces used with one particular CI (Andersen eight-stage non-viable impactor operated at 60 L/min), it is likely that a similar behavior would occur in the IP, given that larger-sized incoming particles are more likely to impact on interior surfaces during passage of the aerosol through the inlet.…”