Experimental determination of the velocity distribution in USP Apparatus 1 (basket apparatus) using Particle Image Velocimetry (PIV)

The USP Apparatus 1 (basket apparatus) is commonly used to evaluate the dissolution performance of oral solid dosage forms. The hydrodynamics generated by the basket contributes, in general, to the dissolution rate and hence the dissolution results. Here, the hydrodynamics of Apparatus 1 was quantified in a vessel filled with 900-mL de-ionized water at room temperature by determining, via Particle Image Velocimetry (PIV), the velocity profiles on a vertical central plane and on 11 horizontal planes at different elevations at three different basket agitation speeds. The flow field was dominated by the tangential velocity component and was approximately symmetrical in all cases. Despite all precautions taken, small flow asymmetries were observed in the axial and radial directions. This appears to be an unavoidable characteristic of the flow in Apparatus 1. The magnitudes of the axial and radial velocity components varied with location but were always low. A small jet was seen emanating radially near the top edge of the basket. Velocities typically scaled well with increasing agitation speed in most regions of the vessel except for a region directly below the basket. The results of this work provide a major insight into the flow field inside the USP Apparatus 1.