In a homogeneous buffer system, the identity and concentration of buffer components are the same in the gel and the tanks. Most forms of DNA and RNA electrophoresis generally use homogeneous buffer systems. Electrophoresis of proteins is most often performed under multiphasic conditions, where tank and gel buffers differ.
In a homogeneous system the buffer performs the functions of protecting the samples and carrying the current. Problems most often arise with homogeneous systems if the ionic strength is for some reason different in the gel versus either of the tanks. Most often this occurs due to the inadvertent omission of a component, a mistake in stoichiometric calculations, or precipitation in a stock solution (
10X TBE is especially prone to this problem). One consequence of a concentration gradient between the tank and the gel, is a "salt wave" which migrates through the gel during electrophoresis. Accompanying this concentration gradient will be changes in the electrical parameters leading to localized distortions in the band pattern.
