BIDIRECTIONAL ISOTACHOPHORESIS .1. VERIFICATION OF BIDIRECTIONAL ISOTACHOPHORESIS AND SIMULTANEOUS DETERMINATION OF ANIONIC AND CATIONIC COMPONENTS

Bidirectional isotachophoretic migration was confirmed by the direct measurement of the pH profiles and the boundary velocities of the separated zones. The anolyte used was 10 mM HCl-beta-alanine (pH 3.6) and the catholyte was 10 mM KOH-acetic acid (pH 4.8). It was shown that bidirectional isotachophoresis could be achieved with an electrolyte system consisting of a leading electrolyte for an anionic analysis and one for a cationic analysis. The combination was not arbitrary but the pH difference between the anolyte and the catholyte was restricted to keep the effective mobility of the terminating ion not too small. The simultaneous separation and determination of anions and cations in a test mixture were demonstrated on the basis of the time-based zone length measured by the use of a dual detection system.