Plug Flow in CE
In a capillary, the charge from electrode to electrode is conducted by the buffer system (ions in a water solution) or what is better described as the Back Ground Electrolyte (BGE). Ions of the BGE conducts electricity and provide the current needed in CE. This current is evenly distributed over the entire capillary diameter and the phenomenon of EOF occurs (evenly). The water molecules in the BGE also naturally move toward the cathode in a very even manner. The electro osmotic flow that occurs is called a “plug flow” because of its plug like shape. Due to this very even flow and flat front, extremely high Theoretical Plate Counts are observed in CE. The diagram below shows the difference between the Plug Flow of CE and the Parabolic Flow of pressure induced flow as in HPLC.