ISOTACHOPHORESIS AT PH EXTREMES - THEORY AND EXPERIMENTAL VALIDATION

The evolution of an isotachophoresis (ITP) system in acidic or basic p H ranges can be quite different from that predicted by the existing th eory. It was found theoretically and proved experimentally that the co ntribution of hydrogen or hydroxyl ion to conductivity of solution and /or its net charge changes the behavior of the ITP system, creating in the terminating electrolyte an additional zone close to the initial i nterfaces between electrolytes (leader and terminator). One boundary o f the zone, being either sharp or dispersed, moves toward the leader; the other is always sharp and stationary and coincides with initial el ectrolytes' discontinuity. The latter can be registered in the presenc e of electroosmotic flow which delivers it to the detection point. In order to describe the dynamics of the ITP system at pH extremes an alg orithm of analytical solution was developed, based on the revised Kohl rausch theory. Its predictions coincide well with computer simulations and experimental data. The results presented can help in a correct an alysis of ITP data and explain some confusing phenomena which were con sidered to be artifacts.