Partition value

Table S.6 Partitioned values of the solubility parameter (after Hansen )...

In laboratory work the following closely related, but not identical, relationship is used to determine the partition value between phases ... 

Johnson and Swindell [77] developed a method for evaluating the complete particle distribution and its effect on dissolution. This method divided the distribution into discrete, noncontinuous partitions, from which Johnson and Swindell determined the dissolution of each partition under sink conditions. The dissolution results from each partition value were then summed to give the total dissolution. Oh et al. [82] and Crison and Amidon [83] performed similar calculations using an expression for non-sink conditions based on a macroscopic mass balance model for predicting oral absorption. The dissolution results from this approach could then be tied to the mass balance of the solution phase to predict oral absorption. 

PCA R ual and Distance from Boundary Table (Model and Sample Di-dgnostk) lhe partitioned values are shown for the class C validation samples with in Table 4.21. 

Jaglan, P.S., Gunther, F.A. (1970) Determination of partitioning values of parathion-methyl and related compounds. Analyst 95, 763-765. 

Tab. 6.5 Atomic fragment values and hydrogen bond donor and acceptor values used in the simulation of drug-octanol and drug-membrane partitioning. Values are taken from ref. 45...

These possible steric effects have been evaluated by an approach involving partition coefficients. In this way, an estimate of comparative lipophilicity can be made since this property is felt to influence the ease of membrane transport and thus eventual availability to the site of action. A number of psychotomimetic phenylisopropylamines have been studied in an octanol-water partition system, and the correlation of the resulting values, with central activity has provided a relationship that suggests an optimum lipophilicity for maximum biological activity (Barfknecht et al. 1975). These partition values have been correlated to serotonin receptor stimulation capability (Nichols and Dyer 1977) and have recently been extended to a number of phenethylamine compounds (Nichols et al. 1977). 

In our opinion, a single set of this laboratory s partition values on serum is not diagnostic in itself of the relative degree of liver and bone involvement. Additional parameters need to be evaluated such as starch gel, neuraminidase treatment, clinical status (Yi), etc. 

Serine and cysteine peptidases are not perfect acyltransferases. Therefore, it is useful to have a method for the prediction of the outcome of the kinetically controlled peptide synthesis. In order to get a simple efficiency parameter we decided to introduce the partition value p11061 analogous with the definition of the Michaelis constant according to Eq. (3), where P2 = Ac-OH, P3 = Ac-N, and N = HN. 

It follows from Eq. (6) that a linear correlation between the partition value p and the nucleophile concentration is obtained. The quotient ks/fe4 corresponds to the ratio of hydrolysis and aminolysis of the EAN complex whereas the term kNk3/k4 is a measure of the nucleophile efficiency. 

The partition value p can be determined by differnt methods l107 109l. In the presence of a large excess of nucleophile ([N] [A]0) the decrease in the nucleophile concentration during the reaction course can be ignored. Under these conditions vh/ vA = [fy/Iffi]- The determination of p can be established out from the product ratio obtained by HPLC analysis according to Eq. (7). 

Let us imagine a system in which A partitions and permeates rapidly, so that its concentration everywhere in the film is the partitioned value in equilibrium with the concentration in solution just outside the film. Suppose also that electrons diffuse rapidly through the structure, so that their concentration is uniform. Finally, suppose that A does not react at the electrode surface. In this situation, depicted in Figure 14.4.5, A is converted to B uniformly in the film, because there is a uniform availability of electrons, reaction sites, and primary reactant. 

Since the partition value of a chemical depends on its relative solubilities (activity coefficients) in the two phases, the solution pH may be expected to have a strong effect on the partition coefficients of organic acids and bases. At high pH, the dissociated anion of an organic acid should be poorly distributed in soil... 

The partitioning of acrylonitrile between particles and the aqueous phase of polybutadiene latex was measured by Raman spectroscopy using rubber latex as substrate. Raman line intensities yielded the partition values in the two phases (295). 

The lEUBK predictive model was used extensively in these non-Box Basin studies. As for the Box evaluations, the biokinetic modeling was necessary for evaluating responses of PbB simulations to environmentally variable media Pb inputs and calibrations for intake—uptake parameters and for determining risk levels linked to various Pb input scenarios. Table 23.9 indicates the concordance between measured and predicted PbB levels for the non-Box subjects and environmental data sets using either default or indicated bioavailability and dust/soil ratios. The site-specific partitioning values... 

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