Abstract
PurposeThe hydrodynamics in USP dissolution apparatus 3, at five different dip rates, was characterized by analyzing phase-averaged velocity fields obtained using Particle Image Velocimetry (PIV).MethodsPhase locked 2 Component-PIV (2C–PIV) measurements were recorded on a typical dissolution apparatus 3 configuration with a black painted tablet fixed at the center of the bottom porous screen of the reciprocating cylinder. A trigger mechanism was employed to capture data over 12 phase positions for each reciprocation cycle. Data were captured over a fixed number of cycles, based on dip rate, and the resultant images were post-processed to obtain phase-averaged velocity fields at each phase.ResultsFor all dip rates studied, the sinusoidal nature of the cylinder’s reciprocating motion was evident in the images. The phase positions, in which the cylinder was completely submerged, were characterized by recirculation of liquid through the cylinder, top fitting cap, vessel-cylinder annulus, and bottom fitting cap. The direction of recirculation was opposite for phase positions during the up- and downstrokes. The end positions of the up- and downstrokes were characterized by vortices below and above the cylinder respectively. Increasing dip rates led mainly to increasing velocity magnitudes while all flow characteristics, in general, were retained.ConclusionsThe hydrodynamics in typical USP dissolution apparatus 3 is characterized by cyclic phase-dependent flow fields. Specifically, the velocity field distribution within dissolution apparatus 3 is greatly influenced by the relative position of the top cap to the liquid level in the cylinder.
Highlights
USP dissolution apparatus 3, known as the reciprocating cylinder apparatus, is a compendial dissolution apparatus introduced in the US Pharmacopeia in 1991 for investigating the performance of modified-release solid oral dosage forms [1]
The hydrodynamics in typical USP dissolution apparatus 3 is characterized by cyclic phase-dependent flow fields
The velocity field distribution within dissolution apparatus 3 is greatly influenced by the relative position of the top cap to the liquid level in the cylinder
Summary
USP dissolution apparatus 3, known as the reciprocating cylinder apparatus (referred to as App 3 in this paper), is a compendial dissolution apparatus introduced in the US Pharmacopeia in 1991 for investigating the performance of modified-release solid oral dosage forms [1]. With porous screens attached at the top and bottom by fitting caps, are allowed to reciprocate in and out of their corresponding vessels at a specific dip rate for a specific time. Evaporation caps fitted at the top of the vessels complete the vessel-cylinder assemblies. At the end of the time allocated for the first row, the cylinders are lifted out and, usually following an additional drain time, moved to subsequent rows. The number of reciprocation cycles in a particular row is defined by the dip rate, measured in dips per minute (dpm), and the time allocated for that row. The dimensions of various components of a vessel-cylinder assembly, along with their allowable tolerances, are specified in USP general chapter Dissolution < 711> [2]
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