DISCONTINUITIES OF PH AT ZONE BOUNDARIES IN ISOTACHOPHORETIC SYSTEMS WITH POORLY BUFFERING LEADING ELECTROLYTES

Discontinuities of pH at zone boundaries of strong ion sample zones in isotachophoretic systems with poorly buffering leading electrolytes h ave been discovered by dynamic computer simulations of isotachophoreti c separations with uncommon electrolyte systems. When using a salt sol ution containing a strong cation (anion) as leading ion and a weak ani on (cation) as counterion for the isotachophoretic separation of stron g cations (anions), severe pH discontinuities are present at zone boun daries of these cations (anions). The magnitude of these pH discontinu ities has been investigated as a function of several parameters, namel y counter ion/leading ion concentration ratio of the leading electroly te, pK values, and mobilities of sample ions and counterion.