Partition constant

In order to calculate the effect of several passes an iterative calculation is needed using the initial profile at each pass to represent Cq. Clearly for the second pass, die concentration profile given in the right-hand side of tire above equation must be used. It is clear that tire partition constant of the impurity between the solid and liquid is the most significant parameter in tire success of zone refining. 

The effects of pH on electrokinetic velocities in micellar electrokinetic chromatography was studied by using sodium dodecyl sulfate solutions [179]. Micellar electrokinetic capillary chromatography with a sodium dodecyl sulfate pseudostationary phase has been used to determine the partition constants for nitrophenols, thiazolylazo dyes, and metal chelate compounds [180]. A similar technique was used to separate hydroquinone and some of its ether derivatives. This analysis is suitable for the determination of hydroquinone in skin-toning creams [181]. The ingredients of antipyretic analgesic preparations have also been determined by this technique [182], The addition of sodium dodecyl sulfate improves the peak shapes and resolution in chiral separations by micellar electrokinetic chromatography [183]. 

The homologous series of (/ -methyibenzyl)alkylamines [387] indicates an interesting 8/log P ct plot, shown in Fig. 5.5. The slope factor of the smaller members of the series, —1.02, is larger than that of the phenol series. The value being near 1 indicates that log m is invariant with the octanol partition constant—the... 

Danielsson, L.-G. Zhang, Y.-H., Methods for determining n-octanol-water partition constants, Trends Anal. Chem. 15, 188-196 (1996). 

The proportions of C02 in the space above the liquid and in the liquid are fixed according to an equilibrium constant, which we call the partition constant ... 

This partition constant has a value of 4, which means that four times as much C02 resides in the drink as in the liquid of the space above the drink. Stated another way, four-fifths of the C02 is in the gas phase and one-fifth is in solution (in the drink). 

An alternative way of expressing the partition constant of a sparingly soluble salt is to define its solubility product Rsp (also called the solubility constant Rs). Ks is defined as the product of the ion activities of an ionic solute in its saturated solution, each raised to its stoichiometric number v . Ks is expressed with due reference to the dissociation equilibria involved and the ions present. 

Dithiocarbamates and xanthates form particularly stable, neutral complexes with Cu(II), Cd(II) (and also Ni, Hg, Pb), which are membrane permeable and increase the apparent bioaccumulation of these metals [13]. In the series of sulfoxine, oxine, and chloroxine, the hydrophobicity of the neutral and the charged form, as well as of the Cu complex, increases. While the sulfoxine is not hydrophobic and does not modulate copper toxicity [220], the Cu-oxine complex is hydrophobic with an octanol-water partition constant, log Kok, of 1.7 [221] or 2.6 [222]. Chloroxine can be assumed to be even more hydrophobic, but so far its influence on uptake and toxicity has not been investigated. Uptake of Cu2+ into unilamellar liposomes was increased in the presence of 8-hydroxy-chinoline, and decreased again after adding HA [223],... 

Table II. Partition Constant Ratios for the Reactions of Azide and MeOH with Various Bromonium Ions Formed via Electrophilic Addition of Br2 to Stilbenes in Methanol at 25 °C. 

Partition constant tor the distribution of various aromatic substances (mono-, di-, tri-, and tetramethyl, and chlorobenzenes) between water and an aquifer material (0.15 % organic carbon) as a function of the octanol-water partition coefficient, K<,w. The values of log Kp have been adjusted to be correct for a sorbent of 100 % organic carbon. Kow is defined for the partition of a substance A between octanol water Kow = [A0Ct]/[A(aq)]. 

It is possible to calculate a partition constant (A"d) for a solute in terms of the access gained to the gel matrix ... 

These authors reported a significant correlation between the Koc values obtained from the sorption of organic compounds on three sediments and the partition constants (K0Vf) for the partitioning of the compounds between octanol and water (Eq. 2) ... 

Nicotine aa> values in tobacco smoke particulate matter can be estimated based on nicotine volatility from the smoke particulate matter phase, as controlled by the gas/partitioning constant Kp (Pankow et al. 1997) ... 

Here Cp (ng 4g ) is the total (protonated -I- free - base) nicotine concentration in the particulate matter phase and Cg (ngm ) is the equilibrium concentration of nicotine s free-base form in the gas phase. Only the free-base form has appreciable volatility and would be present in the gas phase, so only the free-base form of nicotine can transfer between the particle and gas phases. The concentration of free-base nicotine is afbCp. An underlying partitioning constant for free-base nicotine is given by (Pankow et al. 1997 Pankow 2001) ... 

There is no internationally recommended symbol for the distribution constant, but the symbol P (for partition constant) is common usage in this context. Coordination (complex) chemists (as in Chapter 3) prefer the symbol K-o (for the German Tonstante for constant ) sometimes other symbols are used. The important point is that the symbol should be properly defined in the text. 

The equilibrium distribution of a solute B between water and an organic solvent is described by the partition constant or by its function, the free... 

In our opinion, the differences in partition constants of neutral complexes of metal ions of the same charge with the same number of the same ligands, extracted to inert organic solvents, are almost entirely due to the differences in hydration of these complexes in the aqueous phase or, more precisely, to... 

However, even this simplified formula does not justify the use of the ratio of stability constants of the extracted complexes as the only measure of selectivity of extractive separations. Such a widely used approach is obviously based on an implicit assumption that the partition constants of neutral complexes ML of similar metal ions are similar, so that their ratio should be close to unity. This is, however, an oversimplification because we have shown that the ifoM values significantly differ even in a series of coordi-natively saturated complexes of similar metals [92,93]. Still stronger differences in the values have been observed in the series of lanthanide acetylacetonates, due to different inner-sphere hydration of the complexes (shown earlier), but in this case, self-adduct formation acts in the opposite direction [100,101] and partly compensates the effect of the differences in. Tdm on S T(see also Fig. 4.15). Such compensation should also be observed in extraction systems containing coordinatively unsaturated complexes and a neutral lipophilic coextractant (synergist). 

One can easily conclude that under certain conditions the differences in partition constants may exert a decisive effect on SF. The effect of differences in the stability constants of the complexes is significantly reduced if the aqueous phase concentration of the uncomplexed metal ions is not much higher than that of the [ML,]" complexes. In the extreme case, when (at a moderate acidity) practically the only form of the metal in the aqueous... 

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