Development of a robust procedure for assessing powder flow using a commercial avalanche testing instrument

The objectives of this work were to develop a robust procedure for assessing powder flow using a commercial avalanche testing instrument and to define the limits of its performance. To achieve this a series of powdered pharmaceutical excipients with a wide range of flow properties was characterized using such an instrument (Aeroflow, TSI Inc., St. Paul, MN, USA). The experimental conditions (e.g., sample size, rotation speed) were rationally selected and systematically evaluated so that an optimal standard-operating-procedure could be identified. To evaluate the inherent variability of the proposed methodology samples were tested at multiple sites, using different instruments and operators. The ranking of the flow properties of the powders obtained was also compared with that obtained using a conventional shear-cell test. As a result of these experiments a quick, simple, and rugged procedure for determining the flow properties of pharmaceutical powders in their dilated state was developed. This procedure gave comparable results when performed at four different testing sites and was able to reproducibly rank the flow properties of a series of common pharmaceutical excipient powders. The limits of the test method to discriminate between different powder samples were determined, and a positive correlation with the results of a benchmark method (the simplified shear cell) was obtained.