Abstract
The aim of this work was to find a relationship between electroosmotic flow (EOF) velocity of the mobile phase in pressurized planar electrochromatography (PPEC) and physicochemical properties like zeta potential, dielectric constant, and viscosity of the mobile phase as well as its composition. The study included different types of organic modifiers (acetonitrile, methanol, ethanol, acetone, formamide, N-methylformamide and N,N-dimethylformamide) in the full concentration range. In all experiments, chromatographic glass plates HPTLC RP-18 W from Merck (Darmstadt) were used as a stationary phase. During the study we found that there is no linear correlation between EOF velocity of the mobile phase and single variables such as zeta potential or dielectric constant or viscosity. However, there is quite strong linear correlation between EOF velocity of the mobile phase and variable obtained by multiplying zeta potential of the stationary phase–mobile phase interface, by dielectric constant of the mobile phase solution and dividing by viscosity of the mobile phase. Therefore, it could be concluded that the PPEC system fulfilled the Helmholtz–Smoluchowski equation.
Highlights
Capillary Electromigration TechniquesOver the last decades growing interest of researchers in electromigration techniques can be seen
The linear velocity of the mobile phase flow is described by the following equation (Helmholtz–Smoluchowski equation): uEOF = ε0εrζ E/η where ε0 is the electrical permittivity of vacuum, εr the dielectric constant of a liquid mobile phase, ζ the electrokinetic potential, E the electric field strength and η the mobile phase viscosity
The largest scatters of the data were obtained for methanol and formamide (RSD over 8 % for three concentrations)
Summary
Capillary Electromigration TechniquesOver the last decades growing interest of researchers in electromigration techniques can be seen. There are increasing examples of their applications [especially capillary electrochromatography (CEC) and capillary electrophoresis (CE)] for efficient separation of the different components. In those techniques the mobile phase/ buffer solution is driven into movement by the electric field. Many works have been published on electroosmotic flow (EOF) of the mobile phase in abovementioned techniques [1,2,3,4,5]. Much attention is devoted to the explanation of the mechanisms of the electroosmosis [5,6,7,8].
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