EMERSION PEAKS IN CAPILLARY ELECTROPHORESIS

An anomalous phenomenon in capillary electrophoresis (CE), referred to as the 'emersion peak,' has been observed. The emersion peak is gener ated at the inlet end of the capillary whenever this end is temporaril y removed from the solution prior to application of the electrophoreti c field. This phenomenon, which is believed to have physical origins a t the capillary inlet, is transported along the capillary at the rate of electroosmotic flow and is detected by on-column UV absorbance. Eme rsion peaks have been observed in a CE system with a uniform sodium be nzoate electrolyte without sample injection or deliberately-formed con centration boundaries, and are attributed to the adsorption of benzoat e at the air-solution interface formed upon emersion of the capillary inlet. Emersion peak size has been found to depend on the number of em ersions, the duration of each emersion, the height to which the inlet is raised above the supply electrolyte reservoir during an emersion, t he delay between completion of the emersion and application of the ele ctric field, and the cut of the capillary forming the inlet end.