Analytical aspects of carrier ampholyte-free isoelectric focusing.

The applicability of carrier ampholyte-free isoelectric focusing (CAF-IEF) for analyses of ampholytes is demonstrated. The suggested method is based on the principle of both side regulated ionic matrix in CAF-IEF. A sharp step of pH is created in the column filled with a sample dissolved in a background electrolyte by influence of current and solvolytic fluxes. Here, ampholytes are focused upon. The magnitude of the step, its velocity and direction of its movement can be regulated electrically. In this manner, favorable separation properties of the system can be set up, even during the run. This brings several advantages over conventional methods. The principles of the separation can be easily changed, permitting selective pre-concentration (trapping) of minor components by processing large amounts of a sample to be preformed, effective isotachophoresis or IEF pre-separation and final electrophoretic analysis in one run. Advantages of these combinations are discussed together with the right choice of the working electrolyte. A 1000-fold increase in amount of substance in a column can be achieved for both isotachophoresis and capillary zone electrophoresis combined with CAF-IEF pre-concentration at reasonable working conditions. It enables a limit of detection at the nmol/l level with a concentration factor of about 10(7) to be reached.