Boundary (Tiselius) electrophoresis

One of the earliest forms of electrophoresis  was the  so-called moving boundary method,  in which a protein  mixture  was introduced  into  a U-tube and subjected to an electric field (Fig. 1).

In this  method,  the  proteins  are  not  completely  separated,  but, theoretically, the  number of proteins  in a mixture can be determined by analysis of the  number of boundaries formed  after  a period of electrophoresis. The boundaries can be detected by schlieren optics, which detects changes in refractive index.

Figure 1.  Moving boundary (Tiselius) electrophoresis.

In practice, the sensitivity of moving boundary electrophoresis is very low and so it is not much used today  for protein  analysis.  However, it is an interesting  example of free  electrophoresis,  i.e.  where there  is no supporting medium, and it is conceptually different from all modern forms of electrophoresis  which are all so-called zone  electrophoresis methods, in which zones of different proteins can become completely separated from one another.

References 

Dennison, C. (2002). A guide to protein isolation . School of Molecular mid Cellular Biosciences, University of Natal . Kluwer Academic Publishers new york, Boston, Dordrecht, London, Moscow .