Current Approaches to APSD Measurements of OIPs Based on Inertial Impaction - Good Cascade Impactor Practices, AIM and EDA for Orally Inhaled Products - page 28

Table 2.4 Stage d 50 values for the ACI with standard
configuration for operation at 28.3 L/min compared with
specialized configurations for use at 60 and 90 L/min ( From
[ 27 ] —used with permission )
Stage 28.3 L/min 60 L/min 90 L/min
−2 - - 8.0
−1 - 8.6 6.5
0 a 9.0 6.5 5.2
1 5.8 4.4 3.5
2 4.7 3.2 2.6
3 3.3 1.9 1.7
4 2.1 1.2 1.0
5 1.1 0.55 0.22
6 0.7 0.26 -
7 0.4 - -
a The version of stage 0 used at 60 and 90 L/min has external
modification permitting another stage, rather than the inlet
adapter cone to be fitted above it. Its internal characteristics
and performance are unaltered

Table 2.5 Design characteristics of the current ACI for Q = 28.3, 60, and 90 L/min
Stage - 2 a - 1 a 0 1 2 3 4 5 6 7

W (mm) 5.50 4.50 2.55 1.89 0.914 0.711 0.533 0.343 0.254 0.254

N 95 96 96 96 400 400 400 400 400 201

Re f at 28.3 L/min - - 163 221 110 141 188 292 394 782

Re f at 60 L/min - 194 346 469 233 299 399 619 835 -

Re f at 90 L/min 241 291 518 703 350 448 598 929 - -

S /W b at all Q 0.29 0.36 0.63 0.85 1.75 2.25 3.00 4.66 6.30 6.30

X c at all Q N/A N/A N/A N/A 1.2 0.93 0.69 0.44 0.33 0.16

a Stage

1 data provided by Mike Smurthwaite (Westech Instrument Services, UK), 2011—
other data from Byron et al. [ 27 ] (Used with permission)
b The nominal value of S used in the calculations of S / W is 1.6 mm, but values between 1.5 and
1.7 mm have been observed with individual CIs

- 2 and -

close to the value predicted by extrapolation from the 60 L/min value of 0.55 m.

Indeed the values of d 50 of stage 6 at 60 L/min and stage 5 at 90 L/min recorded in
Table 2.4 are much smaller than the values predicted by extrapolating from the pre-
vious lower flow rate figures. And although the user guides of manufacturers of the
ACI may cite the Vaughan calibration of the ACI at 28.3 L/min [ 19 ] as definitive,
Vaughan actually reported the d 50 for stage 2 to be 5.7

μ

μ m, rather than the generally

accepted value of 4.7 m for this particular stage.

Note also that the value of 4.7

μ

m for stage 2 at 28.3 L/min has recently been
confirmed by Roberts, undertaking a more rigorous calibration with monodisperse
standard particles akin to that used for the archival NGI calibration measurements
[ 32 ]. It should also be noted that the jet-to-plate distance, S , is 1.6 mm, as reported
by Roberts [ 14 ].

μ