Bo Olsson

Next Generation Pharmaceutical Impactor (A New Impactor for Pharmaceutical Inhaler Testing). Part I: Design

A new cascade impactor has been designed specifically for pharmaceutical inhaler testing. This impactor, called the Next Generation Pharmaceutical Impactor (NGI), has seven stages and is intended to operate at any inlet flow rate between 30 and 100 L/min. It spans a cut size (D50) range from 0.54-microm to 11.7-microm aerodynamic diameter at 30 L/min and 0.24 microm to 6.12 microm at 100 L/min. The aerodynamics of the impactor follow established scientific principles, giving confident particle size fractionation behavior over the design flow range. The NGI has several features to enhance its utility for inhaler testing. One such feature is that particles are deposited on collection cups that are held in a tray. This tray is removed from the impactor as a single unit, facilitating quick sample turn-around times if multiple trays are used. For accomplishing drug recovery, the user can add up to approximately 40 mL of an appropriate solvent directly to the cups. Another unique feature is a micro-orifice collector (MOC) that captures in a collection cup extremely small particles normally collected on the final filter in other impactors. The particles captured in the MOC cup can be analyzed in the same manner as the particles collected in the other impactor stage cups. The user-friendly features and the aerodynamic design principles together provide an impactor well suited to the needs of the inhaler testing community.

Calibration at Different Flow Rates of a Multistage Liquid Impinger

ABSTRACT The multistage liquid impinger (MLI) is an impactor suitable for size-selective characterization and testing of pharmaceutical inhalation products, especially dry powder inhalers (DPIs). The four-stage version of the MLI, which was adopted by the European Pharmacopoeia for testing at 60 L/min, has been calibrated by two different laboratories (Astra Draco AB, Sweden, and AEA Technology, UK), reaching consistent results. The MLI has been extended with an additional impaction stage and all impaction stages have been calibrated at flow rates of 30, 40, 50, 60, 80, and 100 L/min. It is shown that in this flow range, the cutoff diameter depends on the flow rate according to a simplified impaction equation, i.e., the cutoff diameter is proportional to the inverse of the square root of the flow rate. Based on the calibration data and the simplified equation, a cutoff value for any flow rate in the range 30–100 L/min can be assigned. This is an important possibility as a DPI should be tested at a flow ra...