Electrophoretic mobility measurement procedure

A short description of the copolymerization procedure is as follows Prior to the copolymerization, the relevant acrylate monomer was mixed with styrene, and the initiator was dissolved in this mixture which was then added to PS latex diluted with water. This medium was stirred at room temperature for 24 h to allow the adsorption of monomers on the PS particles. The adsorbed monomer layer at the outer shelf of the particles were then polymerized for 24 h at 85°C with a stirring speed of 200 rpm. Note that the coating procedure did not change the size and monodispersity of the original PS particles. The existance of the functional groups on the PS particle surfaces were confirmed by ESCA, FTIR and electrophoretic mobility measurements (55). 

In close vicinity to the salting out phase transition, the effective charge density was determined by conductivity measurements in combination with the known and estimated electrophoretic mobilities of the counterions and the polyions, respectively. The procedure is based on the fact that, shortly before the precipitation of the polyion, the conductivity comprises contributions of polyions, free counterions and added salt. After precipitation of the polyion by reducing the temperature the conductivity is given solely by the supernatant aqueous salt solution, thus the difference Act is due to polyions and free counterions... 

The results of measurements by the microscopic method show that the electrophoretic mobility of the particles varies with the distance from the wall of the cell particles close to the wall move in a direction opposite to that in which those in the center migrate. In any event, the results show an increase in velocity from the walls to the center of the cell. The explanation of this fact lies in the electro-osmotic movement of the liquid a double layer is set up between the liquid and the walls of the cell and under the influence of the applied field the former exhibits electro-osmotic flow. For the purpose of obtaining the true electrophoretic velocity of the suspended particles it is neceasary to observe particles at about one-fifth the distance from one wall to the other. A more accurate procedure is to make a series of measurements at different distances from the side of the cell and to apply a correction for the electro-osmotic flow. The algebraic difference of the corrected electrophoretic velocity and the speed of the particles near the walls gives the electro-osmotic mobility of the liquid in the particular cell. If the solution contains a protein which is adsorbed on the surface of the walls of the vessel and on the particles, it is possible to compare the electrophoretic and electro-osmotic mobilities in one experiment reference to the significance of such a comparison was made on page 532. 

Measurements were carried out using three methods (a) A Zeta meter (Zeta Meter, Inc., New York) was used for determining electrophoretic mobilities. The gelatin was first coated on glass beads or AgBr grains, and the mobility of these particles was measured as a function of pH according to established procedures (6). 

The experimental procedure used for the measurement of interfacial tension and the electrophoretic mobility to determine the... 

Some types of electrophoretic cells are stationary layer problem free , but in the other cells the electroosmotic flow can lead to erroneous results. The observed velocity of particles is a sum of the electroosmotic flow of the fluid and the velocity of particles with respect to the fluid. The latter is a function of the potential of the particles and the former is a function of the position in the cell cross section. Hydrodynamic calculations make it possible to find the stationary levels, i.e. the positions in the cell cross section where the electroosmotic flow equals zero. Certainly the position of stationary levels in commercial electrophoretic cells can be found in the user s manual, and there is no need to perform any calculations. The fastest method to determine the electrophoretic mobility is from the velocity at one stationary level, but such a procedure can lead to substantial errors. For example, when the cell position is adjusted at room temperature and then measurements taken... 

Experimental. Samples for electrophoretic mobility (EM) measurements were prepared as previously described for the titration experiments except that violent mixing with destruction of carbon agglomerates was desirable here and was promoted with a 5-10 minute treatment of the capped serum bottles in an ultrasonic bath. The indicator was, of course, deleted in the EM sample preparation procedure. Following mixing, a few drops of the mixture was transferred to a 25 ml flask of benzene and given another ultrasonic treatment. This procedure produced a fairly stable colloid suspension of the carbon black which was used to fill the glass-Teflon commercially available EM cell manufactured by Zeta-Meter, Inc. 

Even without molecular sieving or charge retardation associated with the support, observed electromigration velocities will generally be affected by electroosmotic flow and by capillary flow through the porous medium. These flow effects make the process unsuitable for mobility measurements. However, by somewhat empirical means, it is today the principal analytical procedure used for protein and amino acid analysis because it is simple, cheap, enables complete separation of all electrophoretically different components, and because small samples can be studied, which is often important for biochemical analyses. 

Multi-variable or cold-ethanol precipitation techniques yielded plasma protein fractions rich in lipoprotein (Oncley et al. 1949). These isolation procedures were extremely important. They demonstrated that physical properties such as solubility could be studied with lipoproteins as well as other proteins. Electrophoretic mobilities and specific refractive increments of lipoproteins were shown to be measurable properties (Armstrong et al. 1947 a and 1947 b). A detailed analysis of lipoprotein composition was undertaken (Oncley et al. 1950). 

Heat Mn(N03)2 with Cr(N03)3 or NH4VO3 such that the atom percent of dopant is around 0.1. Follow the same procedure as above for the preparation of pMn02. Use a fine fraction of the doped samples to measure the electrophoretic mobility at different... 

Table I lists nonhormonal plasma sialoglycoproteins, and when known, their molecular weight, number of sialic acid residues per mole, and carbohydrate content. Sialic acid content was estimated by either the Warren procedure (1959) or by treatment with microbial sialidase and measurement of sialic acid release and concomitant change in electrophoretic mobility or isoelectric point. Some of the physical and biological changes observed in the plasma sialoglycoproteins after removal of sialic acid residues are described below.

Adsorption isotherms are habitually obtained using the solution depletion method, which consists of comparing the solute concentrations before and after the attainment of adsorption equilibrium. Electrokinetic or zeta potentials are determined by two techniques microelectrophoresis [12,14,17] and streaming potential [13,58,59]. The former is employed to measure the mobility of small particles of chemically pure adsorbents, whereas the latter is adopted to investigate the electrophoretic behaviour of less pure coarser mineral particles. A correlation between the adsorption and electrophoretic results is usually examined with the aim of sheding light on the mechanism by means of which the surfactants are adsorbed at the solution-solid interface. This implies the necessity of maintaining the same experimental conditions in both experiments. For this purpose, the same initial operational procedure is applied. 

Chemical separations are achieved using chromatographic and, to a much lesser extent, electrophoretic methods. In chromatographic methods, separation is based on variation in the distribution of different compounds between two dissimilar phases—a stationary phase and a mobile phase. Further differentiation can be made between chromatographic procedures in which the individual components elute from the stationary phase and are monitored on line (column chromatography) and procedures in which the components are measured in situ on the chromatographic stationary phase [e.g., thin-layer... 

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