The Franz Diffusion Cell is a simple, reproducible test for measuring the in vitro drug release from creams, ointments and gels. 
The Franz Cell consists of two primary chambers separated by a membrane. The test product is applied to the membrane via the top chamber- donor compartment. The bottom chamber- receptor compartment contains fluid from which samples are taken at regular intervals for analysis. This testing determines the amount of active that has permeated the membrane at each time point.