Enhancer/Immersion Cells

Testing of semi-solid dosage forms such as creams, gels, and ointments has become more common since the introduction of USP chapter <1724>. While use of the Franz Diffusion Cell (also known as the vertical diffusion cell) is most common, it often requires the purchase of new instrumentation for labs that typically rely on dissolution testing. The Immersion Cell offers an alternative means of testing by using existing dissolution testers.

The Immersion Cell is primarily a means of release rate testing for semi-solid products. The user places a membrane into the cell then fills the cavity with the dosage. After the cavity is filled, the user will place the cell into a flat bottomed dissolution vessel where the drug passes through the membrane and is released into receptor media.

The difference between the Model A Enhancer cell (Agilent) and the Model B Immersion cell (Hanson) is the capacity of the donor chamber for the Model A Enhancer cell can be adjusted while the donor chamber for the Model B Immersion cell cannot be adjusted.

The Enhancer cells and Immersion cells have slightly different dimensions on the paddle.  The vessels are also slightly different as the Agilent vessel has a small bump located in the center while the Hanson vessel is flat.  While these are technical differences none would make any kind of difference with the test result.

It should be noted that while a Model A Enhancer cell could be used in a Hanson Vessel;  due to the bump on the bottom of the vessel, the Model B Immersion cell should not be used in an Agilent vessel.