Minimum rotation speed to prevent coning phenomena in compendium paddle dissolution apparatus

The purpose of the present study was to investigate the applicability of the Zwietering equation to coning phenomena which often occur during dissolution testing. The minimum rotation speed at which coning phenomena disappeared (no coning rpm, NCrpm) was experimentally determined for various particle and fluid properties in a compendium paddle apparatus with a round-bottom unbaffled vessel. The particle size, relative density and kinematic viscosity exponents in the Zwietering equation were optimized for NCrpm. The particle size and relative density exponents were found to be similar with those for the general tank configurations of cylindrical flat-bottom baffled vessels. However, the kinematic viscosity exponent was significantly different. The equation obtained in this study showed sufficient accuracy (r2 = 0.98, average error = 12 rpm) to estimate the occurrence of coning. The Zwietering equation was found to be applicable to the coning phenomena in the compendium paddle apparatus.

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