Electroosmotic flow through packed columns

Electrochromatography is a hybrid of HPLC and CE that offers some of the best features of the two methods. Like HPLC and MEKC, it is applicable to the separation of neutral species or charged species. Electrochromatography with packed columns is, however, the least mature of the various electroseparation techniques. In this method, a polar solvent is usually driven by electroosmotic flow through a capillary packed with... 

Capillary electrochromatography (CEC) is a high-efficiency microseparation technique in which mobile-phase transport through a capillary (usually 50- to lOO-pm I.D., packed with stationary-phase particles) is achieved by electroos-motic flow instead of a pressure gradient as in HPLC (342-349). The absence of backpressure in electroosmotic flow allows the use of smaller particles and longer columns than in HPLC. In the reversed-phase mode, CEC has the potential to yield efficiencies 5 to 10 times greater than reversed-phase HPLC. 

Nowadays, porous monoliths have found an extensive use in CEC of organic compounds, which represents a powerful separation tool, complementary to HPLC. CEC is a hybrid method in which the separation is performed through the phase distribution mechanisms of traditional HPLC (reversed-phase, ion exchange, etc.), while the flow of the mobile phase through column packing is affected by electroosmotic forces, as in electrophoresis. The coexistence of a stationary phase and an electric field permits separation not only of ions but also of neutral compounds, due to their different electrophoretic mobhity and different distribution between the mobile and the stationary phases. 

---