Electroosmotic flow, effect electrophoresis

V. P. Andreev and E. E. Lisin, Investigation of the electroosmotic flow effect on the efficiency of capillary electrophoresis, Electrophoresis 13 832 (1992). 

Effects of buffer composition on electroosmotic flow in capillary electrophoresis. /. Microcol. Sep. 2, 176-180. 

The key operational parameter in free-solution capillary electrophoresis is the pH of the running buffer, as the electroosmotic flow and ionization of the analyte can be regulated by this variable. The role of buffers in capillary electrophoresis has been discussed in detail, with emphasis on buffer concentration, buffer type, and pH effects [10]. The effect of organic solvents on separation and migration behavior has been studied for dipeptides [11] and somatostatin analog peptides [12]. The order of migration as well as the selectivity may be manipulated by organic modifiers in... 

Chankvetadze et al. have demonstrated the potential of flow-counterbalanced capillary electrophoresis (FCCE) in chiral and achiral micropreparative separations [27], Unlimited increase of separation selectivity can be achieved for binary mixtures, such as (+ )-chlorpheniramine with carboxymethyl-(3-cyclodextrin chiral selector, or a- and (3-isomers of a asparatame dipeptide. The carrier of the chiral selector or pseudo-stationary phase, electroosmotic flow (EOF), pressure-driven flow, or hydrodynamic flow can be used as a counterbalancing flow to the electrophoretic mobility of the analyte or vice versa, resulting in dramatic changes of the effective mobilities of the sample mixture components [28], This approach can be used for micropreparative CE, stepwise separations, and fraction collection of multicomponent mixtures [27],... 

Besides electrophoretic migration, analytes in CE move by a process called electroosmosis (or electroendoosmosis). This phenomenon, occurring also in slab gel electrophoresis, produces electroosmotic flow, the electrically driven flow of the liquid within the capillary. However, while in slab gel electrophoresis the gel matrix reduces EOF to an annoyance, in CE this liquid flow can have a significant effect on the separation process. 

Figure 13. Basic electrokinetic effects. (According to Atkins et al. [242].) (a) Electroosmotic flow (EOF), (b) electrophoresis (EP), (c) dielectrophoresis (DEP).

Figure 8.1. Influence of buffer pH on the effective electrophoretic mobility of a monovalent weak acid in capillary electrophoresis. The separations show the relative position of the anion (A) and a neutral compound (M), used as an electroosmotic flow marker.

In capillary electrophoresis, what is the effect on the electroosmotic flow of ... 

Narasimhan and Sri Ranjan (2000) made simplifying assumptions to model the electrokinetic flow phenomena. The structure of the soil was assumed to be uniform with the net electroosmotic flow taking place toward the cathode. The applied voltage was assumed to be useful in transporting the water and ions. The flux due to hydraulic, electrical, and chemical gradients were superimposed linearly while neglecting the effect of electrophoresis in the fine-grained media. The hydraulic conductivity and porosity were assumed to be constant in time. 

Tang, G.Y., et al., Modeling of electroosmotic flow and capillary electrophoresis with the joule heating effect The Nernst-Planck equation versus the Boltzmann distribution. Langmuir, 2003, 19 10975-10984. 

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