Capillary two- or multi-dimensional electrophoresis in a single capillary

Process for separating the constituents of a mixture M by capillary electrophoresis in a single capillary, the process comprising the steps in which:

• (A) the compounds of the mixture M are introduced into the capillary and caused to migrate therein in accordance with the capillary electrophoresis technique, under the effect of a difference in potential applied between the inlet and the outlet of the capillary, using a first separating medium SM1, in order to produce a separation of the compounds of the mixture M in the capillary in accordance with their migration rate under the conditions of step (A);
• (B) a fraction F of the compounds separated in step (A) is isolated in the capillary, and the isolated fraction F is caused to migrate to the vicinity of one of the ends of the capillary, while keeping this fraction F inside the capillary by implementing one and/or the other of the following steps:
• (B.1) a portion of the compounds having the highest migration rates under the electrophoresis conditions of step (A) is evacuated from the capillary, by allowing those compounds to migrate to the outlet of the capillary, and/or;
• (B.2) a portion of the compounds having the lowest migration rates under the electrophoresis conditions of step (A) is evacuated from the capillary by causing those compounds to migrate towards the inlet of the capillary,
• it being understood that, in the context of step (B), the “inlet” of the capillary means the end of the capillary where the injection is carried out, the “outlet” being the other end;
• (C) while applying a difference in pressure between the ends of the capillary, a second separating medium SM2, different from the separating medium SM1 used in step (A), is introduced into the capillary via the end of the capillary close to which the fraction F is located, as a result of which the fraction F is caused to migrate towards the other end of the capillary, while at the same time the capillary is filled with the separating medium SM2;
• and
• (D) capillary electrophoresis is carried out in the capillary thus filled with the separating medium SM2 by causing the compounds of fraction F to migrate under the effect of a difference in potential applied between the inlet and the outlet of the capillary, using the medium SM2 as the separating medium.