It is a process by which a solid oral pharmaceutical form (tablet, capsule, etc.) dissolves in a certain solvent or quantity of a solid substance which reaches the solution in a unit of time. Dissolution testing is done using an instrument called a dissolution tester, which is available in different types such as basket type and paddle type (USP, BP, and IP). It consists of bath, containers, rotary motor, temperature controller, etc.
Diffusion
It is a process of mass transit of molecules, which are produced by random molecular motion associated with a driving force such as concentration gradients. Diffusion tests are used to measure the rate of release of an API or sample in semi-solid form as it seeps out of solution through the skin membrane. The study of diffusion is carried out in the device called diffusion cell. This device has a cell, a membrane, and a water-jacketed receptor support chamber to withdraw drug sample and can be analyzed.