Electrokinetics mechanisms

It used to be thought that cations simply precipitated polyanions, but it was recognized later that electrolytes had special valence and solvent-mediated effects on a hydrosol other than neutralization of opposite charges (Holmes, 1922). It is now firmly established that ionization of the carboxyl and sulfuric acid groups in ionic polysaccharides, or adsorption of ions on neutral macromolecules, is an initial step in electrokinetic mechanisms of stabilization and destabilization. 

As we mentioned above, the electrokinetic mechanisms, which includes electrophoresis, DEP, ACEO, electrothermal effect, and electro-orientation, are main driving force for particle manipulation using an optoelectrofluidic device. In addition, we could also observe the electrostatic interactions due to the polarization of dielectric particles like cells. 

Electrokinetics is currently the preferred method for moving and transporting fluids in microchannels due to the ease of electrode fabrication and since electrokinetic mechanisms involve no moving mechanical parts which are... 

We consider that this model satisfactorily illustrates the total characteristics of the contraction phenomenon and demonstrates that the contraction of a gel in an electric field occurs through an electrokinetic mechanism. 

The following example is a versatile electrokinetic mechanism that can be applied to a variety of electron transfer reactions. The micellar systems is composed of anionic micelles incorporating MPTH, in which the counterion Cu is replaced by Eu. If Eu is the only counterion, the Krafft temperature range (or MTR) of the surfactant is too high to use, so micelles with mixed Eu " and Na" counterions are used instead. The electron transfer... 

Injecting the Sample The mechanism by which samples are introduced in capillary electrophoresis is quite different from that used in GC or HPLC. Two types of injection are commonly used hydrodynamic injection and electrokinetic injection. In both cases the capillary tube is filled with buffer solution. One end of the capillary tube is placed in the destination reservoir, and the other is placed in the sample vial. 

Electroosmotic flow (EOE) is thus the mechanism by which liquids are moved from one end of the sepai ation capillai y to the other, obviating the need for mechanical pumps and valves. This makes this technique very amenable to miniaturization, as it is fai simpler to make an electrical contact to a chip via a wire immersed in a reservoir than to make a robust connection to a pump. More important, however, is that all the basic fluidic manipulations that a chemist requires for microchip electrophoresis, or any other liquid handling for that matter, have been adapted to electrokinetic microfluidic chips. 

Leger C, Elliott SJ, Hoke KR, Jeuken LJC, Jones AK, Armstrong FA. 2003. Enzyme electrokinetics Using protein film voltammetry to investigate redox enzymes and their mechanisms. Biochemistry 42 8653-8662. 

Different separation mechanisms, which determine selectivity, can be exploited in HPCE by appropriate choice of operating conditions. There are four principal modes of operation (Table 4.22) and it should be noted that in only one, micellar electrokinetic capillary chromatography (MEKC), is it possible to separate neutral species from one another. 

Several modes of capillary electrophoretic separation are available ordinary CE, capillary zone electrophoresis, capillary electrokinetic chromatography, capillary gel electrophoresis, capillary electrochromatography, capillary isota-chophoresis, and capillary isoelectric focusing. The different separation mechanisms make it possible to separate a wide variety of substances depending on their mass, charge, and chemical nature.53... 

The mechanism of interaction of amino acids at solid/ aqueous solution interfaces has been investigated through adsorption and electrokinetic measurements. Isotherms for the adsorption of glutamic acid, proline and lysine from aqueous solutions at the surface of rutile are quite different from those on hydroxyapatite. To delineate the role of the electrical double layer in adsorption behavior, electrophoretic mobilities were measured as a function of pH and amino acid concentrations. Mechanisms for interaction of these surfactants with rutile and hydroxyapatite are proposed, taking into consideration the structure of the amino acid ions, solution chemistry and the electrical aspects of adsorption. 

Electrokinetic soil treatment is a commercially available in situ technology for the removal of metals and organic compounds. The application of direct current (DC) in a porous medium leads to two transport mechanisms electromigration and electro-osmosis. The combination of these two transport phenomena results in the movement of contaminant ions toward either the cathode or anode. Nonionic contaminants are transported by electro-osmosis alone. 

Electrokinetics has been used to mobilize metals and dissolved contaminants to in situ treatment or recovery zones. Electrokinetic transport uses these mechanisms to move bacteria through the subsurface to the contaminated media. The technology can be used to treat organic contaminants that adsorb to aquifer soils including halogenated hydrocarbons and non-aqueous-phase liquids (NAPLs). 

In on effort to establish the mechanism of coal flotation and thus establish the basis for an anthracite lithotype separation, some physical and chemical parameters for anthracite lithotype differentiation were determined. The electrokinetic properties were determined by streaming potential methods. Results indicated a difference in the characteristics of the lithotypes. Other physical and chemical analyses of the lithotypes were mode to establish parameters for further differentiation. Electron-microprobe x-ray, x-ray diffraction, x-ray fluorescent, infrared, and density analyses were made. Chemical analyses included proximate, ultimate, and sulfur measurements. The classification system used was a modification of the Stopes system for classifying lithotypes for humic coals. 

---