Effect of electroosmosis on detection in isotachophoresis

The effect of electroosmosis on the relative sharpness of the zone boundaries and hence the detection limit in isotachophoresis is discussed. A high concentration and a low pH of the leading electrolyte were found to be favourable. The magnitude and sign of the ¿-potential of the capillary wall was measured by streaming potential determinations as a function of concentration, pH and additives. Poly(vinyl alcohol), hydroxyethylcellulose and hydroxypropylmethylcellulose decrease the ¿-potential sufficiently, whereas cationic detergents reverse its sign and thus the direction of the electroosmotic flow. Both were found to be favourable in anionic separation. Fused-silica capillaries and the effect of methanol were also investigated