OPTIONS IN ELECTROLYTE SYSTEMS FOR ONLINE COMBINED CAPILLARY ISOTACHOPHORESIS AND CAPILLARY ZONE ELECTROPHORESIS

A theoretical description of the electrolyte systems that can be used in the on-line combination of isotachophoresis and zone electrophoresi s is given. A classification of these systems is presented, based on t he type of electrolyte used for the zone electrophoretic separation st ep. It is shown that transient sample stacking effects always persist from the isotachophoretic step to the beginning of the zone electropho retic step and that they may negatively influence the zone electrophor etic separation and detection of the sample components. A mathematical description of these effects is given that allows the calculation of their magnitude and consequently the selection of operating conditions such that the stacking is decreased to an acceptable extent. In order to verify the reliability of the theoretical model, a modified PC sim ulation pack was prepared and used for investigating the behaviour of some model systems.