126 - 



concentration, the mixture forms a zone that migrates slowly with a 

 faster-migrating, diffuse leading regiono At low concentration of the 

 mixture, the ions yield uniform zones, and the rate of migration is 



independent of concentration down to the smallest quantities that can 



12 

 be detected by the most sensitive tracer methods o 



Ions that are sorbed by the stabilizing medium migrate slower 

 than if there were no sorption^5„ Under these conditions, the zones 

 remain well-defined at the leading boundary but become diffuse at the 

 trailing boundary like the zones in a chromatographic columno This 

 sorption provides a resistive force that is often sxifficiently selec- 

 tive to determine the separability of mixtures and the sequence of the 

 separated componentso (See Figure V,5o) 



Ions that are not sorbed by the stabilizing medium migrate 

 slower in the stabilized solution than they do in the backgroimd solu- 

 tion alone o This retardation may be attributed to the fact that the 

 ions follow a more circuitous path in the stabilized solution than in 

 the nonstabilized solution-^'o 



Mth many stabilized media, the electrical potential produces 

 elect roosmotic flow of the background solution through the stabilizing 

 agent. This flow of the solution and the corresponding transport of 

 the zones of the migrating ions is usually much smaller than the elec- 

 trical migration of the ionso It may be determined by adding a zone 

 of a nonionized, easily detectable substance such as hydrogen peroxide 

 to the medium before the migrationo Dependent upon the stabilizing 



agent and the nature and pH of the background electrolytic solution, 



1 R 

 the electroosmotic flow may be toward the anode or toward the cathode o 



