Virgil A. Marple

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A cascade impactor has been developed that is suitable for personal sampling. The impactor can be used with four, six, or eight stages with cut points ranging from 0.5 micron to 21 micron aerodynamic diameter. Although the impactor can be operated over a fairly wide flow rate range, it is designed specifically to be operated at 2 L/min so that a personal(More)
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(More)
A new seven-stage cascade impactor, the Next Generation Pharmaceutical Impactor (NGI), has been developed for the pharmaceutical industry. A calibration following "good laboratory practice (GLP)" procedures has been performed on a specific archival NGI, deemed to be representative of all NGIs. Thus, this impactor had nozzle dimensions for each stage(More)
The characteristics of virtual impactors have been determined by the numerical solution of the Navier-Stokes equations and of the equations of motion of the particles. The effect of the nozzle Reynolds number, the fraction of flow passing through the collection probe, collection probe diameter, nozzle throat length, nozzle-to-collection probe distance, and(More)
The calibration of the first stage of the twin-stage impinger, an instrument proposed for use in measuring the spray size from metered-dose inhalers, was performed with monodisperse aerosols by a standard technique for cascade impactors. The mean cut point was found to be not particularly sensitive to operating variables which may be expected to occur in(More)
An extension of the archival calibration of the recently developed 30-100-L/min seven-stage impactor, the Next Generation Pharmaceutical Impactor (NGI), has been undertaken at 15 L/min. The NGI stage cut sizes are 0.98-14.1 microm aerodynamic diameter at this flow rate. This 15-L/min calibration was motivated by the desire to sample the entire aerosol(More)
Design theory for cascade impactors is well developed, and design principles can be summarized quite succinctly. The key geometric parameters of three commonly used impactors have been compared to design guidelines. Calibration theory and practice have undergone improvement in recent years. Published results show distinctly different characteristics for(More)
A dust generator has been developed to produce dry dust from powderous materials for instrument calibration and laboratory studies. The powder is fed at a constant rate via a chain conveyor into a fluidized bed where the particles are deagglomerated and aerosolized. The powder feed rate is raviable from 1.2 to 36 mm3/min and the air flow rate from 9 to 30(More)