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, small volume USP 2 dissolution apparatus has gained a great deal of attention, especially for cases where small amount of drug product is available for testing in research and design step or evaluations are to be made on a tablet containing trace amounts of the active pharmaceutical ingredient. In this work, firstly, small volume USP 2 apparatus was designed and manufactured using downscaling rules and considering standard USP 2 as a reference. Then, 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 agitation speed of 50 and 100 rpm, respectively, in the standard USP 2. Comparison between experimental and computational results showed acceptable adaptation. Instantaneous velocity data showed eddies and secondary flows in different zones of the vessel, which is desirable for micro-mixing but undesirable in terms of system consistency and reproducibility, as sampling from these zones are known to lead to inconsistent data. Furthermore, 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 of paddle stirring from 66 to 133 rpm.