Effect on partition coefficient

Kumbar, S.G., Kulkarni, A.R., Dave, A.M., and Aminabhavi, T.M. An assessment of solubility profiles of structurally similar hazardous pesticide in water + methanol mixture and co-solvent effect on partition coefficient, J. Haz. Mater., 89 (2-3) 233-239, 2002. 

Availance, effect on partition coefficient, 192f Avermectin(s)... 

Figure 3 A schematic showing the effects on partition coefficient of the parameters in the Brice Equation (10). The best-fit ion has radius r and a corresponding partition coefficient at the peak of the parabola. Partition coefficients decrease as deviates in either positive or negative direction away from r. The derivative (0D/0r) (or the tightness of the parabola) increases with increasing E, the Young s modulus of the site Dq, and to a much lesser extent E, varies as a function of pressure and temperature, r varies primarily with crystal composition.

Small changes in temperature, such as 5°, have little effect on partition coefficients. 

Hansch C., Anderson, S. (1967) The effect of intramolecular hydrophobic bonding on partition coefficients. J. Org. Chem. 32, 2583-2586. 

In regard to the potential effects of silicone membrane or film thickness (e.g., polydimethylsiloxane [PDMS]) on partition coefficients, Paschke and Popp (2003) have shown that that at equilibrium an SPME fiber with a 7 xm thick film of PDMS had about a 6-fold higher ATpw than a similar fiber with a 100 xm thick film. However, this could be the result of interactions with the silica core. Recent research (Smedes, 2004) has shown that silicone sheeting with PRCs can be employed for water sampling with good results. 

Figure 2. Effect of partition coefficient on concentration within tissue bounded by barriers with different permeability characteristics.

Figure 3. Effect of partition coefficient (P) on availance within a multilaminate septum in which detoxifying reactions occur with rate constants (k) = 1 and (k) = 0.04. Redrawn from Hartley and Graham-Bryce (13).

An understanding of partition coefficient and the effect of pH on partition coefficient is useful in relation to the extraction and chromatography of drugs. The partition coefficient for a compound (P) can be simply defined as follows ... 

Using the expression introduced in Chapter 2 for the effect of pH on partition coefficient of an acid, it is possible to predict approximately the effect of pH on retention time since the effect of pH on partition coefficient will reflect its effects on capacity factor and in theory ... 

Holmes, H.L., Lough, C.E. (1976) Effect of Intramolecular Hydrogen Bonding on Partition Coefficients. Suffield Tech. Note No. DRES-TN-365. Defence Res. Establishment Suffield/Information Canada. U.S. NTIS Report No. AD-A030683. 

Comparing the lipophilicity of the barbiturates in Table 2.2 with their uptake across the GI tract (colon) demonstrates that the membrane permeability of each member of the series is proportional to its partition coefficient. Apparently, there can be some differential effect on partitioning depending upon which organic solvent is used in making the determination. For example, the GI membrane is believed to behave more like an octanol/water pairing, while drug uptake into the brain is more closely mimicked by a heptane/water combination. 

TABLE 8 Effect of Molecular Weight of Dextran on Partition Coefficient of Proteins with Different Molecular Weights0... 

FIGURE 16 Effect of PEG concentration difference in the two phases on partition coefficient K in PEG 6000-dextran 70-water system containing 0.15 mol /kg NaCI in 0.01 mol /kg sodium phosphate buffer at pH 7.4 (I) myoglobin, (2) cytochrome c, (3) human serum albumin. (Reprinted from Zaslavsky8 by courtesy of Marcel Dekker, Inc.)... 

TABLE 3 Effect of Nucleic Acids on Partition Coefficients... 

Oligomers of glycine show little appreciable retention on octyl silica with 20 mM phosphate buffers over the pH range 2.10-7.83 (46), or on octadecyl silica with 100 mM phosphate buffer, pH 2.1 (33), or 5 mM phosphate buffers, pH 2.1, containing hydrophobic alkyl sulfonates (30). It is thus likely that the peptide chain proper makes only a very small contribution to the retention of peptides under these conditions. Based on partition coefficient considerations, oligomers of alanine, and the other nonpolar amino acids, should show a linear dependence of log A on the number of residues. This, in fact, has been observed. For example, the plot of log A versus the number of alanine residues shows (33) a linear dependence with a uniform log A increment due to the methyl group of the aliphatic side chain (Fig. 2), i.e., the effect is additive (45a, 46a). 

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