Electrical migration method

Electrical migration method. An interesting electrical migration method for rapid separation of carrier-free radioisotopes has been reported (9 ) The apparatus consists of a stack of filter papers (30 filter papers were used) moistened with electrolyte and placed between two platinum electrodes. ... 

Sample introduction To introduce the sample, the left end of the capillary is dipped into a sample vial with several centimeters hydrostatic pressure for a fixed number of seconds. This will force a small volume of liquid sample into the end of the capillary. Another method of sample introduction is to dip the end of the capillary into the sample vial and turn on the power for a few seconds. Sample ions thus flow into the system by electrical migration. 

When the governing model is given by the convection-diffusion equation (no electrical migration effects are considered), well-established numerical methods can be used directly in electrochemical cell design. When using commercial software, it should be remembered that the code has probably been benchmarked for applications different from those found in metallization, where spatial distributions of flux at high Schmidt numbers may be of more interest than the spatial average flux. Freitas has recently provided a comparison of several commercial CFD codes. Many of these codes are based on a finite-volume method (FVM) or a finite-element method. West jj yg discussed the application of... 

In both methods of the apparent diffusion coefficient measurements the acceleration of diffusion process in an electric field is frequently applied. Sometimes this method is called as the studies of migration . The interpretation of measurement results is based on the assumption that the migration mechanism in cement paste is analogous to the diffusion. However, there are seldom experimental works comparing the resirlts obtained with these two methods. Tang and Nilsson [200] found a good correlation between the resirlts of measrrrements in variable conditions and by migration method the latter one in variable conditions too. Contradictory data... 

Another method of sample introduction is to dip the end of the capillary into the sample vial and turn on the power for a few seconds. Sample ions thus flow into the system by electrical migration. 

Moya AA, Hayas A, Homo J (1995) Study of electrical migration in electrochemical cells by the network method. Ber Bunsenges Phys Chem 99 1037-1042... 

Theorell s (1934) electrophoresis apparatus, shown in Fig. 22, although built for analytical purposes to study the electrical migration of biologically active substances by the transference method, may well be mentioned as a micro preparative instrument also. The U-tube of this... 

Electroosmosis is a serious complication in this method. The shifting of the bands due to this effect is often greater than that due to electric migration. Adsorption of the substances undergoing separation on the gel material is a further complicating factor. 

The second method of exploitation occurs when the electric field is of a polarity such that the charged-particle migration occurs away from the filter medium. The contribution to the net-particle velocity of the elec trqphoreticaUy induced flow away from the filter medium is generally orders of magnitude less than the contribution to the net-... 

Transport numbers are intended to measure the fraction of the total ionic current carried by an ion in an electrolyte as it migrates under the influence of an applied electric field. In essence, transport numbers are an indication of the relative ability of an ion to carry charge. The classical way to measure transport numbers is to pass a current between two electrodes contained in separate compartments of a two-compartment cell These two compartments are separated by a barrier that only allows the passage of ions. After a known amount of charge has passed, the composition and/or mass of the electrolytes in the two compartments are analyzed. Erom these data the fraction of the charge transported by the cation and the anion can be calculated. Transport numbers obtained by this method are measured with respect to an external reference point (i.e., the separator), and, therefore, are often referred to as external transport numbers. Two variations of the above method, the Moving Boundary method [66] and the Eiittorff method [66-69], have been used to measure cation (tR+) and anion (tx ) transport numbers in ionic liquids, and these data are listed in Table 3.6-7. 

The amorphous orientation is considered a very important parameter of the microstructure of the fiber. It has a quantitative and qualitative effect on the fiber de-formability when mechanical forces are involved. It significantly influences the fatigue strength and sorptive properties (water, dyes), as well as transport phenomena inside the fiber (migration of electric charge carriers, diffusion of liquid). The importance of the amorphous phase makes its quantification essential. Indirect and direct methods currently are used for the quantitative assessment of the amorphous phase. 

Log k appears to correlate with log P for standards between log P —0.5 to 5.0. One limitation of this method is that solutes must be electrically neutral at the pH of the buffer solution because electrophoretic mobility of the charged solute leads to migration times outside the range of Tm and TEof- Basic samples are therefore run at pH 10, and acidic samples at pH 3, thus ensuring that most weak acids and bases will be in their neutral form. This method has been used in a preclinical discovery environment with a throughput of 100 samples per week [24]. 

An important pre-concentration method is the sample-stacking procedure [68,69]. When the sample is dissolved in a solvent with an electrical conductivity lower than that of the buffer electrolyte, sample stacking occurs because of the difference in electric field strength in the sample and the electrolyte medium. As the field strength in the sample zone is higher, the migration velocity in the sample zone is also higher. At the interface of the sample and the buffer electrolyte zone... 

A particle with a net charge moves under the influence of an electric held toward an oppositely charged electrode. This phenomenon, defined as electrophoresis, is the basis for various electrophoretic methods in biochemistry research. Separation of particles via electrophoresis is achieved through the difference in their migration distances, which is dependent upon their electrophoretic mobility. 

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