Polymer distribution, coefficient

The liquid phase which is absorbed by the synthetic polymer granules (e.g., Sephadex) is mostly available in a wide range as solvent for solute molecules in contact with the gel. It has been observed that the actual distribution of the solute in between the inside and outside of the respective gel granules is nothing but a criterion of the available space. However, the underlying distribution coefficient occurring between the granular and interstitial aqueous phases is found to be independent of three major factors, namely ... 

The fact that X for both salts lies in the range 0.20-0.25 shows that water in the membrane is a less effective solvent for ions than is bulk water i.e. the low-dielectric-constant matrix polymer lies well within the range of the electrostatic fields around the ions. Our value of Xg, the molar distribution coefficient of sodium chloride between polymer and solution, is in good agreement with values obtained by direct measurement (1,5,10, 11,12). This is further evidence in favour of our theories and assumptions. 

In order to account for the well known sorption and swelling properties of polymer ion exchangers, Helfferich s model [427] is frequently used for liquid phase reactions. According to this, the pore liquid of the resin, where the reaction occurs, is treated as a homogeneous system and the reactant is assumed to be distributed according to a distribution coefficient... 

We have calculated the energy 0 in this way for some polymers and separation conditions (Table 2) and, using the lattice-like model and a slit-like pore, we have found the distribution coefficients, K 1, for these macromolecules as a function of N, D, 0 and 0f 65). It turned out that for such a crude model not only the calculated KJj 1 values were close to the experimental ones, but also, which is especially important, that the chemical nature of the macromolecule, the functional groups and the separation conditions (the mobile phase composition) were correctly accounted for. Two examples of such calculations are given in Figs. 8 and 9. 

Blood plasma proteins from patients with malignant breast tumors differ from proteins from healthy people in their solubility in the presence of various polymers. When the polymers dex-tran and poly(ethylene glycol) are dissolved in water, a two-phase mixture is formed. When plasma proteins are added, they distribute themselves differently between the two phases. The distribution coefficient (K) for any substance is defined as K = [concentration of the substance in phase A]/[concentration of the substance in phase B]. Proteins from healthy people have a mean distribution coefficient of 0.75 with a standard deviation of 0.07. For cancer victims the mean is 0.92 with a standard deviation of 0.11. 

Figure for Problem 4-5. Distribution coefficients of plasma proteins from healthy people and from people with malignant breast tumors. [Data from B. V Zaslavsky, Bionalytical Applications of PaitKonlng in Aqueous Polymer Two-Phase Systems," Anal. Chem. 1992, 64, 765AJ... 

First, it is necessary to establish the phase diagram of the aqueous two-phase system formed by water and two water-soluble polymers. Second, a method must be established for calculating the distribution coefficient of a biomolecule that partitions between the two aqueous phases. A simple molecular-thermodynamic description is provided by the osmotic virial... 

The state of equilibrium in the investigated system is proved to be true, thermodynamic by the fact that the phase distributing coefficient of polymers does not depend on the following ... 

Proceeding from said above the coefficient of polymer distribution between the phases of POO-emulsion can be written down in the following way ... 

The template la can be split off by water or methanol to an extent of up to 95% (see Scheme 4.II). The accuracy of the steric arrangement of the binding sites in the resulting imprinted cavity can be tested by the ability of the polymer to resolve the racemate of the template, namely phenyl-a-D,L-mannopyranoside. The polymer was equilibrated in a batch procedure with a solution of the racemate under conditions that allowed a thermodynamically controlled partition of the enantiomers between polymer and solution. The enrichment of the antipodes in the polymer and in solution was determined and the separation factor a, i.e. the ratio of the distribution coefficients of the d- and L-enantiomer between polymer and solution, was calculated. After extensive optimisation of the procedure, a values between 3.5 and 6.0 were obtained [4]. This is an extremely high selectivity for racemic resolution that cannot be reached by most other methods. 

Factors influencing the rate of monomer diffusion are surface tension distribution coefficient of monomers between the two phases rate of monomer transfer from phase to phase solvent power of organic phase for the polymer permeability of polymer film to monomers adsorption of monomers by the polymer film viscosity of the system. 

Vapour-phase calibration (VPC) is based on the principle that the concentration of the volatile analyte in the gas phase can be determined by external-standard calibration. If the total amount present in the vial is known, the concentration in the sample phase at equilibrium is calculated from the difference. This technique, where the distribution of a volatile compound between two phases in a headspace vial is determined by using a pure vapour as reference, was originally implemented by Kolb using automated head-space equipment to determine distribution coefficients in gas-liquid [77] and gas-solid systems [78], and later by Schoene et al. [79] to determine solubility coefficients in vapours of both solid and liquid polymers. Although these investigations focused on... 

The degree of the metal extractions depends on its concentration. Por example, with increasing europium concentration the distribution coefficients in the alkali-DOBTA system decrease, while in the alkali-tartaric acid system a maximum at 7x10 4 M Eu concentration is observed. As we suggested the enhancement in the metal distribution coefficient is evidently due to the metal polymerization in the organic phase, and the decrease is caused by polymerization in the aqueous phase, which eventually results in low extractable polymer form. The latter assumption is supported by the fact that as the alkali concentration increases the maximum on extraction curves undergoes a shift towards lower concentration of the metal. 

Figure 2 shows conclusively that DHDECMP can extract trivalent as well as tetravalent and hexavalent actinides from moderately concentrated nitric acid solutions. The valence (III) actinides, Am, Cm, and Cf, have distribution coefficients greater than one above 1.5M HNO3, while valence (IV) and (VI) actinides have values greater than one above 0.5M HNO3. In addition, DHDECMP shows very favorable back extraction or stripping characteristics below 0.3M HNO3. Pu(IV) polymer formation undoubtedly occurred in low-acid measurements and may account for the low distribution coefficients. 

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