Dynamic control for ultra-fast separations of organic acids in capillary zone electrophoresis

Dynamic control and pH changes in the system have been utilized for the separation of twelve organic acids in less than 3 min using capillary electrophoresis (CE). High-speed separations of organic acids under weak acidic conditions indicate the existence of high electroosmotic flow (EOF) caused by treatment of the capillaries with 0.1 M NaOH before each separation. However, strong polyprotic acids can only be detected at higher applied voltages with shorter capillaries, since local EOF decreases significantly when migration time increases. In terms of resolution and speed, the optimal voltage is around 20 kV in 22.5-cm capillaries. The effects of the electric field strength and capillary length on the resolution of organic acids have been investigated to show the existence of dynamic flow. For both methods, dynamic flow is of great importance for the enhancement of resolution for stronger acids. On comparing all of the results, the change in voltage is more efficient for improving the separation resolution in this study. More importantly, this new method can be used in any commercial CE instrument because of its features of high resolution, high speed and simplicity.