A new cascade impactor design having low interstage losses is described. A novel feature is the use of external stage collection cups, to simplify applications requiring chemical determination of the mass collected on each stage. The design has been executed in versions to operate at two flow rates: 30 and 60 L/min. Calibration data are presented for these flow rates, and, in addition, for the latter version at 90 L/min. Size results using the new impactor on a typical pharmaceutical inhalation product are shown to be equivalent to those obtained using a current cascade impactor. An example is presented to indicate the utility of gathering size data at more than one flow rate.
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