Validating AIM-Based Instrumentation and Associated Measurement Techniques - Good Cascade Impactor Practices, AIM and EDA for Orally Inhaled Products - page 302

Fig. 10.23 FPM <4.7μm as percentage of TEM (mass/actuation) ex-MDI for the various systems
evaluated by Chambers et al . ( From [ 32 ]— used with permission )
IM, determined by the FPD-AVCI, was greater than with the control ACI by +3.4%
for the surfactant (Brij)-coated FPD-AVCI, and +6.5% for the same CI when Brij-
coated filters were used. Importantly, the addition of Brij-coated filters to the sACI
resulted in a similar increase in IM relative to the ACI, in this instance being +6.7%.
These data are suggestive of decreased internal losses when the Brij-soaked fil-
ters were used to mitigate particle bounce further than could be achieved by simply
coating the collection plates with the same surfactant. The measure of agreement
between sACI with coated plates and the ACI control is probably to be expected,
given the similarity in internal geometry and dead space.
All abbreviated systems were closely correlated to the 6-stage ACI in terms of
either CPM >4.7μm or FPM <4.7μm (Fig. 10.23 ). The sACI slightly underestimated
CPM >4.7μm relative to that measured with the reference ACI, but that introduction of
the Brij-coated filter papers on the sACI stages resulted in an increase in CPM >4.70μm ,
providing additional support for an argument that bounce and re-entrainment were
not entirely eliminated when the plates were coated with surfactant, without the
means to stabilize the coating when flow passed through these CIs.
FPM <4.7μm determined by the Brij-coated sACI and the FPD data both agreed
closely with the same measure obtained using the reference ACI. The addition of
Brij-coated filters increased FPM <4.7μm in line with similar effects associated with
both CPM >4.7μm and IM .
When both FPM <4.7μm and CPM >4.7μm were calculated as a percentage of IM
(Fig. 10.24 ), this form of data presentation highlighted more clearly that both
abbreviated CIs correlated well with the ACI; although, CPM >4.7μm was slightly
underestimated by the sACI. The increase in upper stage deposition with this formu-
lation was confirmed by the addition of Brij-coated filters paper to the sACI.
However, these observed differences are slight and comparable with true variability
associated with the product itself.