Electrostatic process

Ion-exchange chromatography involves an electrostatic process which depends on the relative affinities of various types of ions for an immobilised assembly of ions of opposite charge. The stationary phase is an aqueous buffer with a fixed pH or an aqueous mixture of buffers in which the pH is continuously increased or decreased as the separation may require. This form of liquid chromatography can also be performed at high inlet pressures of liquid with increased column performances. 

Electrostatic spraying PVC can be applied by the electrostatic process to continuous galvanised wire mesh. 

Single-step perturbation methods have also been applied to electrostatic processes. One study probed the dielectric properties of several proteins at a microscopic level [41,42], Test charges were inserted at many different positions within or around each protein, and a dielectric relaxation free energy was computed, which is related to a microscopic dielectric susceptibility (see Sect. 12.3). 

Other electrostatic processes studied include proton binding [43] and changing the molecular charge distribution [44], The free energy expansion formula (12.5) was used, including terms up to second order... 

Electrical Conductivity. Changes in the electrical conductivity within or on the surface of a photopolymer film can be used to visualize the results of a photochemical reaction. A limited number of electrophotographic/electrostatic processes have been developed employing this readout method (22). 

It is certain that organic photoconductors will be used on an industrial scale in the near future in methods of reproduction based on photoelectric and electrostatic processes (reviews are given in 10>166)). 

Clearly, proteins can adhere to surfaces by electrostatic mechanisms, particularly at low ionic strength where the electrostatic field of the surface and the protein is much more extended. Indeed, this is the basis of ion exchange chromatography, so widely used for the separation, purification, and characterization of proteins. However, by the time one reaches the 0.15 M salt concentration of the physiologic environment, general electrostatic processes are no longer dominant. 

Figure 5.29 Schematic diagram of new multiduplication processes based on polysilanes (A) an electrophotographic process (B), an electrostatic process. Reprinted with permission from reference 146. Copyright 2000 Kluwer Academic Pulishers.

Boland ED et al (2001) Tailoring tissue engineering scaffolds using electrostatic processing techniques a study of poly(glycolic acid) electrospinning. J Macromol Sci, Pure Appl Chem 38(12) 1231-1243... 

It should be emphasized that this description of solvation as a purely electrostatic process is greatly over-simplified. Short-range interactions exist as well, and the physical exclusion of the solvent from the space occupied by the solute must have its own dynamics. Still, for solvation of ions and dipolar molecules in polar solvents electrostatic solvent-solute and solvent-solvent interactions dominate, and disregarding short-range effects turns out to be a reasonable approximation. Of main concern should be the use of continuum electrostatics to describe a local molecular process and the fact that the tool chosen is a linear response theory. We will come to these points later. 

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