Paddle Shafts | Dissolution

Paddles should comply with the specifications listed in USP <711> for wobble, verticality, and physical dimensions. In addition, paddles should be in good condition. If the finish on stainless steel paddles appears fl at and gray, there is corrosion on the paddle and it could result in a greater chance of adsorption of drug. If a PTFE-coated paddle is used, it needs to be free to scratches, fine protrusions of PTFE, etc. These are additional sources of surface area and result in greater and more variable hydrodynamics in the dissolution vessel, causing higher means and %CV. Degradation of the PTFE paddles can be areas for air bubble attachment, as well as other issues

http://www.usp.org/sites/default/files/usp_pdf/EN/USPNF/2011-02-25711DISSOLUTION.pdf