Influence of transference number on migration and deformation of concentration boundaries in capillary zone electrophoresis.

The change of the position and shape of a concentration boundary existing in the background electrolyte in capillary zone electrophoresis is treated theoretically. Such boundaries may occur when the ionic concentration, c, of the sample differs from that of the background electrolyte. Both mathematical treatment and numerical simulation lead to the result that when an (initially symmetrical) concentration boundary migrates in the capillary it becomes nonsymmetrical. The reason for this is the nonsymmetry of the function, which is obtained as the difference of the transference number (which is a function depending on c) and its linear approximation at the average value of the concentration. Numerical simulations for capillary zone electrophoresis with LiI or potassium benzorate as a hypothetical background electrolyte show the formation of asymmetrical plugs for samples of more diluted electrolyte solutions.