Ion partitioning

Ion partition equilibria at ITIES were first studied by Walther Nemst in 1892. Nemst derived the fundamental relationship linking the equilibrium difference of the inner (or Galvani) potentials, to the ratio of ion concentrations in... 

The log D value at a single pH is often influenced by ion partitioning, especially at neutral pH where log D may be used in quantitative structure-permeation relationships. Therefore, the lipophilicity profile may be essential to interpreting PK... 

Scherrer, R. A. The treatment of ionizable compounds in quantitative structure-activity smdies with special consideration to ion partitioning. In Pesticide Synthesis Throi h Rational Approaches (ACS Symp. Ser. 255), Magee, P. S., Kohn, G. K., Menn, J. J. (eds.), American Chemical Society, Washington, DC, 1984, pp. 225-246. 

The investigations of interfacial phenomena of immiscible electrolyte solutions are very important from the theoretical point of view. They provide convenient approaches to the determination of various physciochemical parameters, such as transfer and solvation energy of ions, partition and diffusion coefficients, as well as interfacial potentials [1-7,12-17]. Of course, it should be remembered that at equilibrium, either in the presence or absence of an electrolyte, the solvents forming the discussed system are saturated in each other. Therefore, these two phases, in a sense, constitute two mixed solvents. 

QSARs based on ionic compounds have thus been dramatically restricted due to the neglect of ion partitioning, which consequently meant that no technique was dedicated to such measurements and that modeling never took account of ionic species. To become fully accepted, potentiometry and electrochemistry at the ITIES need now to prove interesting in QSARs. As numerous lipophilicity data of ionizable compounds become available, one can expect that solvatochromic equations for ions will soon be developed in various solvent systems, which would greatly facilitate QSAR studies. 

The only potential that varies significantly is the phase boundary potential at the membrane/sample interface EPB-. This potential arises from an unequal equilibrium distribution of ions between the aqueous sample and organic membrane phases. The phase transfer equilibrium reaction at the interface is very rapid relative to the diffusion of ions across the aqueous sample and organic membrane phases. A separation of charge occurs at the interface where the ions partition between the two phases, which results in a buildup of potential at the sample/mem-brane interface that can be described thermodynamically in terms of the electrochemical potential. At interfacial equilibrium, the electrochemical potentials in the two phases are equal. The phase boundary potential is a result of an equilibrium distribution of ions between phases. The phase boundary potentials can be described by the following equation ... 

Negative decadic logarithm of the relative activity of H3O+ ions Partition coefficient... 

The Treatment of lonizable Compounds in Quantitative Structure-Activity Studies with Special Consideration to Ion Partitioning... 

In developing some of the relationships, it is helpful to use a four-quadrant diagram in which each quadrant represents a species in a lipid or water phase. The diagram below shows a typical distribution of an acid, AH, between two phases where ion partitioning is assumed to be negligible. The partition coefficent, P, is the ratio of the concentration of AH in the octanol to the concentration of AH in the aqueous phase. The distribution coefficient, D, is the ratio of the concentration in the octanol to that of all forms in the water. This is also called the apparent partition coefficient. 

Effect of organic coatings and microbial biofilms on metal oxide surface reactivity - X-ray standing wave studies of metal ion partitioning between coating and surface... 

In the absence of micelles, all neutral molecules reach the detector in time /0. Micelles injected with the sample reach the detector in time rmc, which is longer than t0 because the micelles migrate upstream. If a neutral molecule equilibrates between free solution and the inside of the micelles, its migration time is increased, because it migrates at the slower rate of the micelle part of the time. The neutral molecule reaches the detector at a time between f0 and /nlc. The more time the neutral molecule spends inside the micelle, the longer is its migration time. Migration times of cations and anions also are affected by micelles, because ions partition between the solution and the micelles and interact electrostatically with the micelles. 

Omitted from this elementary theory are effects of plasticizer and ion pairing. Ion pair formation constants in the organic phase increase with decreasing dielectric constants of the plasticizer, in the absence of specific bonding effects. In the more general theory the single ion partition coefficients are replaced by the product of partition coefficient and ion pair formation constant. 

Fundamental Aspects of Metal Ion Partitioning into Ionic Liquids... 

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