All dissolution apparatuses, or perhaps more accurately dissolution testing in general, have serious problems regarding the lack of appropriate and standardized agitation (stirring and mixing) value. Analysts do not know what should be an appropriate rpm (in the case of Apparatuses 1 and 2), flow rate (in the case of Apparatus 4) and dip-rate (in the case of Apparatus 3). This is a big problem. Every analyst sets this (e.g. rpm) based on his or her preference to achieve some desired dissolution characteristics, thus the test loses its usefulness.
Considering this deficiency, a common agitation speed has been suggested using a new spindle (crescent-shaped). It is to be noted that the crescent-shape spindle was chosen for this purpose because Paddle/Basket would not provide appropriate stirring and mixing. These apparatuses have a design/operation problem, which is very well and extensively documented in the literature. I am of the opinion that if one could make a slight adjustment to the Apparatus 1 and 2 by using crescent-shaped spindle then the current problems in dissolution testing can easily and economically be resolved.
