Borate complexes mobilities

Indirect conductimetry with a mobile phase containing polyol-borate complexes allows a detection limit of 10-5 mol of carbohydrate (53). A lower sensitivity is reached with the moving-... 

The neutral polysaccharides have little electrophoretic mobility, but, in borate buffers, separations can be obtained, and this method should be more widely used. With smaller amounts of material, separations can be made on glass-fiber paper, where borate complexes of polysaccharide and cellulose are avoided and methods of detection are simpler. ... 

Modify mobility Borate Complex with carbohydrates, diols... 

A.) these react more strongly with borate ions than do their trans isomers (0-0, 3.40 A.). In the planar, zigzag conformation of acyclic cis- and irans-l, 2-diols, the oxygen atoms are separated by a distance of 3.65 and 2.82 A., respectively, but can, in an eclipsed conformation, approach each other to a distance of 2.49 A. The greater electrophoretic mobility of the acyclic interaction energy of the nonbonded atoms in the essentially planar diol-borate complex. ... 

Arsenious acid, As(OH)s, behaves as a weak acid with a dissociation constant of about 8X10 at 25°. As is the case with boric acid, the addition of n-mannitol to aqueous solutions of arsenious acid increases the acidity of the solution. The formation constants for complexes between polyhydroxy compounds and the arsenite ion have been found to be considerably smaller than those for the corresponding borate complexes. This is also reflected in the absolute mobilities of such compounds during electrophoresis in arsenite solution. 

Fig. 4.6. Anion-exchange chromatography of carbohydrates as their borate complexes. Chromatographic conditions column, Aminex A-28 10 /im (50x0.3 cm I.D.) mobile phase, gradient of 40 ml of 0.124 M borate, pH 7.0 to 40 ml of 0.58 M borate, pH 10.0 flow rate, 10 ml/h temperature, 55°C detection, orcinol reagent reacted at 100°C for 20 min and measured by UV at 420 nm. Reproduced from Morrison et al. (1976), with...

The movement of an electrically charged particle of mass m and charge Q under the influence of a uniform electric field of strength E is called electrophoresis. These particles may be biological cells, colloids, macromolecules, or low-molar-mass substances. Even electrically neutral particles can be made electrophoretically mobile through formation of suitable complexes. An example is the formation of borate complexes by polysaccharides ... 

If substances which influence the mobilities in a specific way, for example by the formation of complexes, are added to the solutions to be studied, interesting new possibilities may turn up. Thus a recent development of zone electrophoresis that has rapidly gained importance is the electrophoresis of carbohydrates or other substances (see above) which possess hydroxyl groups in cis position, as borate complexes. In this... 

CZE-ELD, with a An microelectrode at —0.6 V vs. SCSE and a Pt wire as auxiliary electrode, using sodium borate buffer and dodecyltrimethylammonium bromide for dynamic coating of the capillary internal surface, can be applied for separation and determination of hydroperoxides in ultra-trace amounts. Thus, various hydroperoxides derived from linoleic acid undergo total dissociation to carboxylates in borate buffer however, due to their similar molecular masses, in order to resolve the ELD signals, it is necessary to add /3 -cyclodextrin (83) to form complexes with the analytes and reduce their mobility, in accordance with the value of the complexation equilibrium constants . 

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