Simultaneous pH and ionic strength effects and buffer selection in capillary electrophoretic techniques

Parameters controlling the elution window and retention factors in micellar electrokinetic capillary chromatography

“…Applying the same instrumentation as in capillary zone electrophoresis, in MECC uncharged compounds can be separated based on differences in their partitioning between two phases, just as in chromatographic techniques. Since the introduction of MECC by Terabe et al [1,2], several authors have paid attention to the fundamental characteristics of this separation method [3,4] and to the effect of different separation parameters on the migration behavior [5][6][7][8][9][10][11]. Also the theoret-the solute in the micellar and the aqueous phase, and ts, tEO F and tMC are the migration times of the solute, the electroosmotic flow (EOF) and the micelles, respectively.…”

Theoretical and nomenclatural considerations of capillary electrochromatography with monolithic stationary phases

“…However, these variables are influenced by other factors such as surface (charge density), electrolyte characteristics (concentration, ionic strength, and pH), temperature, cosolvents, or other additives. Electroosmotic (and electrophoretic) mobilities depend on buffer concentration [84][85][86][87][88] and ionic strength [22,[86][87][88]. The studies confirm that, at fixed pH, the electroosmotic mobility decreases with increasing ionic strength (ionic strength is being a more meaningful quantity than electrolyte concentration) [88].…”

“…The pH dependence of u eo in bare fused capillaries has been determined [89][90][91][92] and it has been observed that u eo is very low in strongly acidic buffers, start rising above pH 3, and increasing strongly between pH values of 7 and 8. At higher pH values the mobility still increases, but quite modestly [22]. Please note that these values are variable, influenced by the buffer system used and also the capillary quality [93].…”

“…In free zone electrophoresis mode, the separation process occurs in the absence of such anticonvective media as a gel. In this case the axial diffusion is the main zone broadening source not just only in theory [5,22] but also in practice, assuming that adsorption of the analyte to the capillary wall is negligible. On the other hand, in EC, the basis of separation originates from the partitioning of the analyte molecules between the mobile and stationary phases [22].…”

“…In this case the axial diffusion is the main zone broadening source not just only in theory [5,22] but also in practice, assuming that adsorption of the analyte to the capillary wall is negligible. On the other hand, in EC, the basis of separation originates from the partitioning of the analyte molecules between the mobile and stationary phases [22]. Earlier suggestion that the term EC should only be used for conventional stationary phases in conjunction with electroosmosis should be revised by the appearance of monolithic columns (originally called continuous beds [23]) primarily designed for electrochromatographic separations in capillary and microchip formats.…”