(206b) Pharmaceutical Powder Characterization By Droplet Penetration Technique

Determination of the contact angle between a liquid and a pharmaceutical granular material is crucial for many reasons. On the one hand, wettability of pharmaceutical powders has critical effect on pharmaceutical processes like wet granulation, and product quality attributes like dissolution. On the other hand, it allows determining the surface energy of pharmaceutical ingredients by measuring the contact angle between the powder and different liquids. Surface energy is an important particle attribute as it correlates to electrostatic charging, particle cohesion, agglomeration and wall adhesion to name some important properties that determines powder behavior in many pharmaceutical processes.

Determination of the contact angle between a liquid and a granular material is not trivial. In this work, we use the droplet penetration technique which has the advantages over the more traditional â??Washburnâ? column technique in that the amount of material necessary to perform the experiment and the time it takes are orders of magnitude smaller.

The droplet penetration technique we use to characterize the contact angle of pharmaceutical powders with a liquid is based on a new development that is described in a different presentation. In essence, it is the comparison between the non-dimensional volume of liquid penetrated at the same non-dimensional times when using two different liquids: the test liquid (water or Diiodomethane) and a reference liquid (PDMS), which completely wets the granular material. This approach is useful when a large part of the penetration process occurs at constant contact area between the external droplet and the powder bed, condition that is amply confirmed for our systems.

Two case-studies are considered: the first one in which the blends have the same formulation and they only differ in the processing and though in the lubrication level, displaying different wettability shown in our results. A second case study, where different active ingredients: Caffeine and Acetaminophen of different particle sizes are measured with respect to a polar and non-polar liquid respectively. In both cases PDMS is used as a wetting reference.