Charge distribution basis partitioning

The basis for the separation is that when two polymers, or a polymer and certain salts, are mixed together in water, they are incompatible, leading to the formation of two immiscible but predominantly aqueous phases, each rich in only one of the two components [Albertsson, op. cit. Kula, in Cooney and Humphrey (eds.), op. cit., pp. 451 71]. A phase diagram for a polyethylene glycol (PEG)-Dextran, two-phase system is shown in Fig. 22-85. Proteins are known to distribute unevenly between these phases. This uneven distribution can be used for the selective concentration and partial purification of the products. Partitioning between the two phases is controlled by the polymer molecular weight and concentration, protein net charge and... 

The first and most often encountered separation mechanism in CE is based on mobility differences of the analytes in an electric field these differences are dependent on the size and charge-to-mass ratio of the analyte ion. Analyte ions are separated into distinct zones when the mobility of one analyte differs sufficiently from the mobility of the next. This mechanism is exemplified by capillary zone electrophoresis (CZE) which is the simplest CE mode. A number of other recognized CE modes are variations of CZE. These are micellar electrokinetic capillary chromatography (MECC), capillary gel electrophoresis (CGE), capillary electrochromatography (CEC), and chiral CE. In MECC the separation is similar to CZE, but an additional mechanism is in effect that is based on differences in the partition coefficients of the solutes between the buffer and micelles present in the buffer. In CGE the additional mechanism is based on solute size, as the capillary is filled with a gel or a polymer network that inhibits the passage of larger molecules. In chiral CE the additional separation mechanism is based on chiral selectivity. Finally, in CEC the capillary is packed with a stationary phase that can retain solutes on basis of the same distribution equilibria found in chromatography. 

Recognition of the mechanisms by which trace elements are partitioned into minerals suggests the importance of looking at the relative distributions of groups of elements that have similar chemical behavior. The rare earth elements (REE), or lanthanides, have been particularly useful because they usually occur as trivalent cations that differ from each other only in ionic size. Each mineral, as it is formed, partitions the REE and other trace elements into its crystal lattice on the basis of ionic size and charge. The REE are distributed in minerals on the basis of size, and the total concentration in a rock depends upon the minerals that are present. In some cases, there is an anomaly in the behavior of Eu, which can be separated from the others when it is reduced partially to the 2 + oxidation state. 

The distributed multipole analysis (DMA) embodies a wavefimction partitioning method pioneered by Stone and coworkers [31, 108, 109], similar to a number of procedures developed by others [35, 101, 110]. DMA relies on the expansion of the charge density as a function of a product of basis wavefunctions... 

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