Ion retention by immobilized pH matrices

The effect of the interaction between polyacrylamide matrices containing covalently bound acidic and basic residues and free ions was indirectly evaluated from the width of the residual salt fronts after electrophoresis under standard conditions. Around neutrality the front width is larger than at alkaline, and much larger than at acidic pH, and in all instances much higher for anions than for cations. The width decreases faster with the buffering power of the matrix than with its ionic strength. After about 5000 V x h, the migration of the salt front is very slow, and becomes negligible when diffusion is prevented. When inadequately buffered by the matrix, H+ and OH(-)--comigrating with anions and cations--increase the conductivity within the salt front and drastically lower the electrical field strength.