Distribution coefficients definition

Salt Effects. The definition of a capacity factor k in hydrophobic interaction chromatography is analogous to the distribution coefficient, in gel permeation chromatography ... 

A general definition of log P and log D, in its simplest form, can be given as the logarithm of the ratio (P or D) of the concentration of species of interest (the drug in a pharmaceutical context) in each phase, assuming the phases are immiscible and well separated prior to analysis. P is defined as the partition coefficient, whereas D is the distribution coefficient. However, the simplest form does not reveal some of the intricacies of the determination and use of these parameters, and further explanation is necessary. 

From the above dependence, and from the definition of the limiting or activity distribution coefficient of electrolyte, i.e., from the equation ... 

Suppose your audience consisted of chemists only. The concept of a distribution coefficient is a topic that should definitely be discussed but is often not. If you have chemists and engineers, you cannot ignore heat engines even for chemists alone discussions of heat engines could be omitted. Entropy can... 

With the definition of the thermodynamic distribution coefficient, Equation (10.252) can be written as... 

We can describe the retention behaviour in GSC in similar terms as we did for GLC in the previous section. However, we have to reconsider our definitions of the concentration in the stationary phase and of the distribution coefficient. It is common practice to express the concentration of the solute adsorbed onto the stationary phase in terms of moles per gram of adsorbent, i.e. 

For the calcite decomposition reaction, the equilibrium constant. Kg, has the same definition as the distribution coefficient, K, given in equation (5.7) giving the equilibrium partial pressure of CO2. The dependence of the equilibrium constant on temperature is given by the Clausius—Claperon equation [2] ... 

There are several technical details in a rigorous definition of the autocorrelation function for velocity. First, one has to remember the vectorial character of velocity, because clearly the direction in which the particle is knocked is important to its subsequent dynamic history. Then, according to the way it is defined, one has to take the product of the velocity at f = 0, Vg, and that at the later chosen time, v,. However, it is not as simple as just multiplying together the two veetors, Vg and v,. One has to allow for the distribution of positions and momenta of the particle in the system at the beginning, that is, at i = 0. To allow for this, one can introduce symbolically a probability distribution coefficient, g. Therefore, the expression for the autocorrelation function will involve the product gVgV,. 

As follows from the definition, the distribution coefficient is dependent on the pH. It is usually assumed that in the oil-phase drug molecule could exist in only nonionic form thus the distribution coefficient,, for basic drug B could be written as... 

The partition coefScient is defined as the ratio of the concentration of a solute in the organic phase to its concentration in the water phase. This definition applies to the same neutral microspecies. However, many small molecules of pharmaceutical, agricultural and environmental interest may assume different protomeric and tautomeric forms, which increases the complexity of the above (simple) definition. Indeed, many small molecules contain moieties that ionize in water, thus contributing to a decrease in lipophilicity. The distribution coefficient, log D y, measures the pH-dependent distribution of drug in octa-nol-water phases at pH xy. 

With obvious modifications, Equation 12.1 is valid also for MMLLE. The definition of the relevant distribution coefficient is different. For MMLLE it is... 

Note that the recovery column is still a liquid/liquid extractor however, the toluene s role is now the raffinate and the caustic water is the solvent. In addition, the distribution coefficient needs to be defined as or the inverse of the definition for the... 

The partition coefficient refers to the intrinsic lipophilicity of the drug, in the context of the equilibrium of unionized drug between the aqueous and organic phases. If the drug has more than one ionization center, the distribution of species present will depend on the pH. The concentration of the ionized drug in the aqueous phase will therefore have an effect on the overall observed partition coefficient. This leads to the definition of the distribution coefficient (log D) of a compound, which takes into account the dissociation of weak acids and bases. 

And, from the definition of the vapor-liquid distribution coefficient (Chapter 1),... 

In modem chromatography it is more convenient to use the capacity factor (k or k ) instead of the distribution coefficient. The name retention factor has been suggested to replace the name capacity factor. The definition for capacity factor or retention factor is the same ... 

This equilibrium or partitioning of a solute between micelles and the aqueous surroundings has not been uniformly described in the literature. We speak of distribution coefficient or constant, partition coefficient or constant, or equilibrium constant to describe equilibria that are the same qualitiatively speaking. However, the definition of the above-mentioned coefficients or constants varies. In this chapter we refer to the process as a partitioning of a molecule between micelles and the aqueous surroundings, and we term it the partition coefficient regardless of the concentration units used to define it. 

In accordance with the soil properties considered in the case of Pu02 migration a bulk density p = 1.59 g/cm and a porosity p = 0.40 can be assumed. Some difficulty arises when choosing a value for the distribution coefficient Kplutonium exchange going on in soil/water system, the definition of Kh doesn t suit the description of plutonium distribution between soil and water. Assuming, however, that plutonium is tetravalent a distribution coefficient of Kd = 5 103 seems to be a reasonable one (5). Such conditions involve a relative migration velocity of r = 8.4 10 S... 

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