Experimental and Computational Study on Hydrodynamic of a Downscaled Mini Vessel USP Dissolution Test Apparatus II

Although not listed on the United States Pharmacopeia (USP), like standard USP 2, the small-volume USP 2 dissolution apparatus has gained a great deal of attention, especially for cases where a small number of drug products are available for testing in the research and design step or evaluations are to be conducted on a tablet containing trace amounts of active pharmaceutical ingredients. In this study, firstly, a small-volume USP 2 apparatus was designed and manufactured using downscaling rules with the standard USP 2 as a reference. Then, the velocity profile, flow patterns, and shear rate were obtained by PIV and COMSOL simulation software at paddle speeds of 66 and 133 rpm, corresponding to the agitation speeds of 50 and 100 rpm, respectively, in the standard USP 2. The comparison of the experimental and computational results showed acceptable agreement between the two. The instantaneous velocity data showed eddies and secondary flows in different zones of the vessel that are desirable for micro-mixing and, yet, undesirable in terms of system consistency and reproducibility, because samplings from these zones are known to generate inconsistent data. Furthermore, the increased agitation rate led to the disappearance of rotational zones around the paddle. The magnitude of velocity and shear rate increased by 35 % with an increment in paddle stirring from 66 to 133 rpm.