Multiplicity -partition coefficient

Of course, the shape of the lipophilicity profiles becomes much more complicated for molecules with multiple ionized forms. Nevertheless, the partition coefficients may be calculated from the distribution coefficient using the general equation [113] ... 

Measurements of gas chromatographic retention time are often used as a fast and easy method of estimating vapor pressure. These estimated pressures are related to the gas/substrate partition coefficient, which can be regarded as a ratio of solubility of the substance in the gas to that in the substrate, both solubilities being of the substance in the liquid state. As a result the estimated vapor pressures are of the liquid state. To obtain the solid vapor pressure requires multiplication by the fugacity ratio. It is important to establish if the estimated and reported property is of the vapor or liquid. 

Kaiser, K.L.E. (1983) A non-linear function for the calculation of partition coefficients of aromatic compounds with multiple chlorine substitution. Chemosphere 12, 1159-1165. 

The matrix on the right-hand side is singular (its determinant is clearly zero), so that the partition coefficients cannot be independently determined. However, the allotments x of Nd between the two reservoirs can be retrieved by adding the two lines of equation (7.4.7) after multiplication of the first row by xmNd and of the second row by xcNd. The terms involving the partition coefficients cancel out and we get... 

The observation that the macroscopic proton coefficient is a function of adsorption density and pH has several implications for macroscopic modeling of cation and anion adsorption. The dependency of x on pH and T affects 1) the relationship of the macroscopic partitioning coefficient to pH and adsorption density, 2) the notion of metal ion preferences for a particular surface in systems with multiple solid phases, 3) the accuracy of predictive models when used over a range of adsorption density and pH values, and 4) conclusions about site heterogeneity based upon partitioning expressions which use constant proton coefficients. 

For some compounds in the Wilschut database more than one permeability coefficient was gathered from literature. In some cases, the differences in kp were greater than one log unit underlining the interlaboratory variations of such measurements. For the development of a new QSPR model one may now either choose one representative data point for each molecule or combine the multiple data points in a reasonable way. In some cases authors even employed all the available data for a single compound. Apart from the permeability data, the data on the partition coefficient and even on the molecular weight may vary from one report to another. Differences in the partition coefficient are easily explained Some collections list experimentally determined values which depend on the experimental procedure employed... 

Brachet, A. and Chaintreau, A. Determination of air-to-water partition coefficients using automated multiple headspace extractions. Anal Chem., 77(10) 3045-3052, 2005. 

The procedure described above is simple to model in a computer programme and has a number of significant advantages (1) The Scheil equation is only applicable to binary alloys and is not easily derived with multiple k values, which would be necessary for a multi-component alloy. A calculation as described above can be applied to an alloy with any number of elements. (2) The partition coefficients need not be constant, which is a prerequisite of the Scheil equation . (3) The Scheil equation carmot take into account other phases which may form during such a solidification process. This is handled straightforwardly by the above calculation route. 

Modular design. Synthetic molecules were constructed of multiple, closely related nonsymmetric repeat units that can be covalently attached from either end. This approach allows rational design of various congeners, controlling their physical properties, such as iron-binding capacities and partition coefficients (lipophilic/hydrophilic... 

It is expected that the hydrophilic groups would make the compound less oleophilic, and thus decrease the octanol-water partition coefficient, or log P, which is also demonstrated in figure 6.4. When multiple functional groups are added, there are often interactions among them, so that the results are not simply additive. Figure 6.5 shows that each addition of chlorine to benzene from one to three would depress the water solubility of these benzene derivatives by a factor of six to eight, but the totally chlorinated hexachlorobenzene has a water solubility that is six orders of magnitude smaller than benzene. The partition coefficients show a very consistent pattern in parallel with... 

Partition coefficients (at 37°C) are from multiple literature sources. 

Liquid-liquid extractions, although valuable in sample preparation procedures, are often time-consuming, laborious, and costly, necessitating multiple partitioning in order to achieve adequate isolation of the analytes. Thus, whenever distribution problems exist or the partition coefficients of the analytes do not favor their... 

The usefulness of the LSER approach hinges on the similarity of the partitioning coefficients obtained from the sensing experiments (Ks) and the gas chromatographic experiments (Kqc)- In other words, it is assumed that the relationship Ks Kgc holds. This is how LSER is used for evaluation of a new sensing material. First, the coefficient Kqc is obtained from the tabulated database or experimentally. Second, the multiple linear regression technique (see Chapter 10) is used to obtain the best fit for the sensor test data, and the individual coefficients in (2.3) are evaluated. This approach has been used successfully in evaluation of multiple materials for gas sensors (Abraham et al., 1995 Grate et al., 1996). 

Other fatty acids as absorption enhancers have been reported. Ogiso et al. [112] demonstrated that lauric acid (C12) produced the largest increase in permeation rate, penetration coefficient, and partition coefficient of propranolol. Onuki et al. [113] reported that docosa-hexaenoic acid (DHA) has a strong insulin permeability enhancement effect and little toxicity, compared to oleic acid and eicosapentaenoic acid (EPA) using a water-in-oil-in-water (W/O/W) multiple emulsion with no or little mucosal damage. 

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