Electrophoresis countercurrent

Countercurrent electrophoresis can be nsed to split a mixtnre of mobile species into two fractions by the electrical analog of elntria-tion. In such countercurrent electrophoresis, sometimes termed an ion still, a flow of the suspending flnid is maintained parallel to the direction of the voltage gradient. Species which do not migrate fast enough in the applied electric field will be physically swept out of the apparatus. An apparatus based mainly on this principle bnt nsing also natural convection currents has been developed (Bier, Electrophoresis, vol. II, Academic, New York, 1967). 

F(=) Elutriation Countercurrent electrophoresis Filtration Ultrafiltration Reverse osmosis Pressure dialysis Zone melting Electrofiltration... 

The relative mass difference of isotopes in ionic liquids is higher than in aqueous solution. This is because solvation of ions by water tends to diminish mass differences. Consequently, greater differences in electrophoretic mobility are possible in ionic liquids. Countercurrent electrophoresis in columns allowed isolation of highly enriched isotope mixtures without great difficulty. Some examples of the mass difference effect are summarized in Table 1. These results depend on the temperature as well as the composition of the ionic liquid. 

Figure 6.3.4. Construction of an electrolyte separation plant for tile self-stabilizing CCEP process (schematic). Explanations are given in the text. Prom Figure 2, p. 487 of Countercurrent Electrophoresis," K. Wagoner, H.D. Freyer, B.A. Billal, Separ. Sci., 6(4), 483 (1971) reprinted by permission of the publisher, Taylor Brands Group.

Countercurrent flow capillary electrophoresis, 4 635 Countercurrent packed tower, 25 810, 811 Countercurrent shaft kilns, 15 47-48 Counterdiffusion, 1 41-42 equimolar, 1 39-40 Counterflow heat exchangers... 

After reviewing the properties and structure of ionic liquids, leading specialists explore the role of these materials in optical, electrochemical, and biochemical sensor technology. The book then examines ionic liquids in gas, liquid, and countercurrent chromatography, along with their use as electrolyte additives in capillary electrophoresis. It also discusses gas solubilities and measurement techniques, liquid-liquid extraction, and the separation of metal ions. The final chapters cover molecular, Raman, nuclear magnetic resonance, and mass spectroscopies. 

Natural convection generally has a negative effect on separation its countercurrent motion leads to the disruption and smearing of component zones. Electrophoresis is particularly subject to such convective flow because the passage of electrical current generates heat that in turn sets up temperature gradients in the electrophoretic medium. 

Examination of the groupings of Table 7.2 verifies most of the more or less traditional associations between separation methods chromatography with countercurrent distribution and distillation, electrophoresis with rate-zonal sedimentation, isoelectric focusing with isopycnic sedimentation, re-... 

Although partition chromatography is established as the most powerful single method for separating these alkaloids, it can often be used to advantage in combination with other methods. Countercurrent distribution (20, 21) and electrophoresis (7, 20, 22) have both been used in this... 

Little work has been published concerning the isolation of oligosaccharides following graded, acidic hydrolysis of heparin. Wolfrom and co-workers have studied the partial, acid hydrolysis of a carefully purified heparin. (Purification was effected through the benzidine salt and the neutral barium salt was fractionally precipitated from water. The less-soluble fraction, after conversion to the barium acid salt, had a N S ratio of 2 5 and 5 sulfate groups per tetrasaccharide period, consumed 1 mole of periodate per tetrasaccharide period, and was shown to be homogeneous by electrophoresis and by countercurrent distribution. The molecular... 

TLC has also been used for the separation of diastereomeric derivatives of enantiomers, but this form of chromatography has not attained widespread use in indirect resolutions. Other chromatographic techniques, for example, supercritical fluid chromatography, capillary electrophoresis, countercurrent chromatography, etc., have not received much attention in indirect enantioseparation. 

Other methods have also been successfully employed in the isolation procedure of stilbenoids, including MPLC [209,299,326], preparative TLC [208,277,299], centrifugal partition chromatography (CPC) [359,360] and the support-free technique of multilayer coil countercurrent chromatography (MLCCC) [32]. A method based on capillary electrophoresis with electrochemical detection (CE-ED) was employed for the determination of oligomeric stilbenes found in the roots of Caragana species [361]. 

The introduction of any new analytical technique seems to inspire its indiscriminate application, without use of proper precautions, to a variety of problems, many of which could be solved more quickly by other methods. It should be emphasized that gas-liquid chromatography is not a panacea for all problems in the analysis of carbohydrate derivatives. Fast, efficient resolution of any given mixture of derivatives requires judicious selection from among the methods of countercurrent partition, liquid-liquid chromatography on columns or paper, adsorption chromatography on columns or thin layers, electrophoresis, and gas-liquid chromatography. The last method is, under the appropriate conditions, a powerful addition to the list because of its high efficiency and rapid operation, and the reliability of both the qualitative and the quantitative results. 

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