Principle of Isotachophoresis

Isotachophoresis means migration with the same speed. Many "non physisists" complain, that they do not understand isotachophoresis as easily as other biophysical methods. The reason: several things occur simultaneously. To understand the effects and the features of the technique, one should imagine the four facts of isotachophoresis, which are equally important and which happen at the same time:

• Migration of all ions with the same speed
• Separation of components as an "Ion train"
• Zone sharpening effect
• Concentration regulating effect

In isotachophoresis (ITP), the separation is carried out in a discontinuous buffer system. The ionized sample migrates between a leading electrolyte with a high mobility and a terminating - sometimes called trailing - ion with a low mobility, all of them migrating with the same speed. The different components are separated according to their electrophoretic mobilities and form stacks: the substance with the highest mobility directly follows the leading ion, the one with the lowest mobility migrates directly in front of the terminating electrolyte. In ITP there is a concentration regulating effect which works against diffusion.

In an anionic separation, the leading electrolyte will be at the anodal, and the terminating electrolyte at the cathodal side. The sample is applied between the two. The system also contains a common cationic counter-ion.

A practical example: Chloride is the leading ion, Glycine is the terminating ion, Tris is the counter ion.

ITP is mostly applied for stacking of the samples during the first phase of disc electrophoresis.