News — Dissolution Paddles

Polytetrafluoroethylene (PTFE) coatings are frequently used on Dissolution bath accessories. Many individual monographs specify this coating on Sinkers, Baskets, Paddles and Vessel interiors. The coating on the accessories can, over time, develop chips or scratches that can expose the substrate to corrosion and affect the results of the test. Technicians handling these coated parts should be familiar with the following guidelines to help extend their service life. Parts with corrosion should be removed from service.  Handling The PTFE coatings are applied at the factory in order to maximize adhesion and durability. The coating, however, is susceptible to chipping and scratching...

The following article has been authored by John Heaney.  Coning of disintegrating dosage forms is fairly common when using Apparatus 2 (Paddles) to perform dissolution testing.  The reason for this is the spinning of the paddle causes a cone shaped zone to form directly beneath it where there is low hydrodynamic activity.  In other words, it’s a bit of a dead zone where the stirring has little effect, and the particles are allowed to settle. Depending on the formulation this coning can be problematic.  It can prevent drug from dissolving in the media due to a reduction in the effective...

The following article has been authored by John Heaney. While determining if a sinker is needed is easy; determining what type of sinker needed may be less obvious.  USP <711> does allow for sinkers made from twists of inert wire.  This can be especially handy for R&D where the method is being developed and an experiment is being run to see if the sinkers provide more consistency to the results.  For use in other environments, such as QC, it would require the users to be trained on the correct length of inert wire to cut, as well as the spacing...

The following article has been authored by John Heaney. Dissolution components are often made of 316 Stainless Steel (316 SS) or equivalent as it is a material specified in USP <711> for the construction of both Apparatus 1 (Baskets) and Apparatus 2 (Paddles).  316 SS has a reputation for being impervious to corrosion but that is not the case as it is merely resistant to corrosion.  It requires care and maintenance just like any other item in the lab. 316 SS’s corrosion resistance is due to the inclusion of additional Molybdenum to the mixture for the steel.  This means compared...