Bubble electrophoresis

Good descriptions of practical experimental techniques in conventional electrophoresis can be found in Refs. [81,253,259]. For the most part, these techniques are applied to suspensions and emulsions, rather than foams. Even for foams, an indirect way to obtain information about the potential at foam lamella interfaces is by bubble electrophoresis. In bubble microelectrophoresis the dispersed bubbles are viewed under a microscope and their electrophoretic velocity is measured taking the horizontal component of motion, since bubbles rapidly float upwards in the electrophoresis cells [260,261]. A variation on this technique is the spinning cylinder method, in which a bubble is held in a cylindrical cell that is spinning about its long axis (see [262] and p.163 in Ref. [44]). Other electrokinetic techniques, such as the measurement of sedimentation potential [263] have also been used. 

An indirect way to obtain information about the potential at foam lamella interfaces is by bubble electrophoresis, in which an electric field is applied to a sample causing charged bubbles to move toward an oppositely charged electrode. The electrophoretic mobility is the measured electrophoretic velocity divided by the electric field gradient at the location where the velocity was measured. These results can be interpreted in terms of the electric potential at the plane of shear, also known as the zeta potential, using well-known equations available in the literature (29—31). Because the exact location of the shear plane is generally not known, the zeta potential is usually taken to be approximately equal to the potential at the Stem plane (Figure 11) ... 

Electrophoresis can be observed in solutions containing suspended matter (solid parhcles, liquid drops, gas bubbles) in a highly disperse state (Fig. 31.2a). Under the influence of an electric held, these particles start to be displaced in the direchon of one of the electrodes. Often, this movement is toward the negative electrode or cathode hence, electrophoresis has occasionally been called cataphoresis. 

The Hb solutions generally used are obtained by simple osmotic hemolysis of normal red cells followed by elimination of the ghosts. The molecular heterogeneity of such solutions of adult Hb is revealed by the starch-gel electrophoresis. The Hb line is therefore not quite distinct, which is a minor drawback when the solutions are used for Hp typing. To stabilize the Hb solutions, it is advisable to bubble CO through them before they are ampouled and stored in the frozen state. 

The gel cassette is mounted into the electrophoresis apparatus and electrophoresis tanks are filled with electrode buffer (Soln. H). Remove air bubbles at the interfaces between electrode buffer and... 

Important Remove the comb after filling the electrophoresis chambers with electrode buffer and remove air bubbles within the slots. ... 

Put the plate on the cooling plate of a horizontal electrophoresis apparatus. Fill the buffer chambers with 1 1 diluted Soln. B (= electrode buffer) and connect the electrode buffer to the gel by filter paper bridges, wetted with electrode buffer. The filter paper covers the gel for about 5 mm. Remove carefully air bubbles between papers and gel. 

Several different analytical and ultra-micropreparative CEC approaches have been described for such peptide separations. For example, open tubular (OT-CEC) methods have been used 290-294 with etched fused silicas to increase the surface area with diols or octadecyl chains then bonded to the surface.1 With such OT-CEC systems, the peptide-ligand interactions of, for example, angiotensin I-III increased with increasing hydrophobicity of the bonded phase on the capillary wall. Porous layer open tubular (PLOT) capillaries coated with anionic polymers 295 or poly(aspartic acid) 296 have also been employed 297 to separate basic peptides on the inner wall of fused silica capillaries of 20 pm i.d. When the same eluent conditions were employed, superior performance was observed for these PLOT capillaries compared to the corresponding capillary zone electrophoresis (HP-CZE) separation. Peptide mixtures can be analyzed 298-300 with OT-CEC systems based on octyl-bonded fused silica capillaries that have been coated with (3-aminopropyl)trimethoxysilane (APS), as well as with pressurized CEC (pCEC) packed with particles of similar surface chemistry, to decrease the electrostatic interactions between the solute and the surface, coupled to a mass spectrometer (MS). In the pressurized flow version of electrochromatography, a pLC pump is also employed (Figure 26) to facilitate liquid flow, reduce bubble formation, and to fine-tune the selectivity of the separation of the peptide mixture. 

Remove gel sandwich from casting stand and install it in the electrophoresis apparatus according to manufacturer s instructions. Make sure bottom of gel cassette is free of bubbles. 

In electrophoresis an electric field is applied to a sample causing charged dispersed droplets, bubbles, or particles, and any attached material or liquid to move towards the oppositely charged electrode. Their electrophoretic velocity is measured at a location in the sample cell where the electric field gradient is known. This has to be done at carefully selected planes within the cell because the cell walls become charged as well, causing electro-osmotic flow of the bulk liquid inside the cell. From hydrodynamics it is found that there are planes in the cell where the net flow of bulk liquid is zero, the stationary levels, at which the true electrophoretic velocity of the particles can be measured. 

Figure 4.11 Illustration ofan electrophoresis system forthe study of bubbles, which are generated by the electrolysis of water.

The pressurization of the flow system is carried out on both the inlet and the outlet side of the buffer reservoir with the same pressure as was first suggested by Knox and Grant [8], Thus the analysis takes place at a higher pressure than the normal pressure. This reduces the risk of bubble formation in both the packed part and the unpacked part (where the detection window is situated) of the capillary. In this variant of pressurization, the mobile phase is only electro-driven. The advantage of this method is the high efficiency of the capillary electrophoresis caused by the flat flow profile. The majority of CEC separations that have been published were performed by this method. Commercially available instruments allow the pressurization of both ends of capillaries up to about 12 bar. 

From the area of thermal process engineering, the mass and heat transfer in stirred vessels and in bubble columns is treated. In the case of mass transfer in the gas/liquid system, coalescence phenomena are also dealt with in detail. The problem of simultaneous mass and heat transfer is discussed in association with film drying and in continuous electrophoresis. 

Make the acrylamide/urea solution up to 99 ml with H20, add 0.8 ml 10% ammonium persulphate and 50 p TEMED (NNN N -Tetramethylethylene-diamine). Mix briefly by swirling and pour into the electrophoresis cell (Section 3.1.2.) making sure that no bubbles are trapped in the gel mixture. Insert the slot former (12—20 slots) made from a piece of Plasticard (Fig. 3.3.), place the gel raised slightly from the horizontal and put a weight over the top of the gel to ensure a tight fit of the slot former. 

There are several practical applications involving interactions between starch and saccharides. For example, starch-derived sugars are used as plasticizers for starch.956 Thus, the addition of potato starch to sugar syrup increases the solution viscosity to a level where it retains gas bubbles and is suitable for producing froths.957 Agaran, starch, and swollen Sephadex G-200 form a mixed support for zone electrophoresis.958 A plywood of improved strength resulted from the blending of an aqueous solution of... 

Electrophoresis of bubbles and drops is a story on its own. As long ago as 1861 Quincke ) observed the electrophoresis of small air bubbles in water. Such a motion is possible only when there is a double layer at the Interface, containing free ions. It is extremely difficult to keep oil-water or air-water Interfaces rigorously free from adsorbed ionic species. When these are present, especially for surfactants, Marangoni effects make the surface virtually inexten-slble then the drops or bubbles behave as solid spheres. Electrophoretic studies... 

Place the gel holder in one of the dishes. Put a wetted Scotch-Brite pad on one side of the holder and then three sheets of Whatman paper saturated with transfer buffer on the pad. Place the gel on the paper direcdy after taking it out from the electrophoresis apparatus. The upper stacking gel should be carefully removed because it sticks to nitrocellulose. Pour a few milliliters of transfer buffer on top of the gel and carefully place on it a sheet of prewetted nitrocellulose. Roll over the nitrocellulose with a glass rod to remove any air bubbles between the gel and the membrane. Next, place three Whatman 3MM sheets prewetted with transfer buffer on top of the nitrocellulose, and finally another wet Scotch-Brite pad. 

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