Partition coefficient ratio

Q.26.14 (a) Define partition coefficient ratio, theoretical plate, and retention time, b) Choose a protein property (size, or charge, etc.) and describe the liquid-solid chromatographic technique you would use to separate it. Draw the device, labeling the essential parts needed for separation. 

A.26.14 (a) The partition coefficient ratio is the ratio of die time the analyte spends in the mobile phase compared stationary phase. Tlreoretical plates refers to the number of times an analyte partitions between the phases. Retention time is the time required for die analyte to travel past the stationary phase, (b) Answers will vary. 

General feed concentration 0.03 to 95% w/w for minerals, typically 0.01 to 2% w/w separation factor a = partition coefficient ratio with values 2 to 500 and should be >5. 

This argument was explored by Reynard et al. (1999), using values of E and Vg obtained from the experimental partitioning data of Fujimaki (1986). Reynard et al. (1999) used Equation (1) to predict equilibrium REE-apatite partition coefficients at surface temperature and pressure, assuming that the crystal chemistry of bone apatite is broadly similar to that of HAP, and that crystal-melt partition coefficients can be used to estimate crystal-water partitioning. Reynard et al. (1999) then compared the predicted partition coefficients with measured adsorption coefficients for the REE between seawater and HAP derived by Koeppenkastrop and DeCarlo (1992), and concluded that incorporation of REE into bone via a substitution mechanism produces bell shaped REE patterns with relatively little fractionation between La and Lu. Incorporation of REE into bone via an adsorption mechanism, on the other hand, produces significant fractionation between La and Lu (La/Lu = 5). Based on REE patterns found in fossil fish teeth, they concluded that REE uptake in fossil bone was dominated by adsorption mechanisms, but that subsequent recrystallization may superimpose a degree of substitution-related fractionation over the initial, adsorption related REE pattern. It is important to note, however, that these predictions are based on crystal chemistry of hydroxyapatite and fluorapatite, and not dahllite and francolite. Variations in E and Vo will affect relative adsorption and/or partition coefficients, and may alter the predicted partition coefficient ratios (e.g., La/Lu and La/Sm). 

The concentration of Trolox in the water phase was lower in mixtures of linoleic acid and water and of methyl linoleate and water than in the mixture of com oil triglycerides and water (Figure 10.12). The partition coefficient (ratio of concentrations between different phases) of Trolox between linoleic acid or methyl linoleate and water is twice as high (6.4) as between com oil and water (3.8). Trolox has, therefore, a much lower affinity toward the triglyceride than toward either linoleic acid or methyl linoleate. In the corresponding oil-in-... 

The additive concentrations at both sides of the interface between the polymer and the solvent are equal, according to a partition coefficient (ratio of additive concentrations in polymer and solvent) of 1. This is justified as the solubility of Irganox 1076 in ethanol is good. In practice, as the solvent volume is large with respect to the polymer volume, the solvent concentration will always be almost equal to zero. Mathematically, the concentration in the polymer at the interface is assumed to be equal to the concentration in the solvent at one time-step earlier. This assumption is justified as long as the step size in time is very small. The concentration in the solvent was calculated using the mass balance (Equation 14.39). 

Solubilizate (mmol/kg) Partitioning coefficient (ratio of mole fractions) ... 

There are many other applications. They include detemiination of the ratios of the partition coefficients P IPq) of solutes B and C in two different solvents by using the themiodynamic cycle ... 

The constant K is termed the distribution or partition coefficient. As a very rough approximation the distribution coefficient may be assumed equal to the ratio of the solubilities in the two solvents. Organic compounds are usually relatively more soluble in organic solvents than in water, hence they may be extracted from aqueous solutions. If electrolytes, e.g., sodium chloride, are added to the aqueous solution, the solubility of the organic substance is lowered, i.e., it will be salted out this will assist the extraction of the organic compound. 

Herein Pa and Pb are the micelle - water partition coefficients of A and B, respectively, defined as ratios of the concentrations in the micellar and aqueous phase [S] is the concentration of surfactant V. ai,s is fhe molar volume of the micellised surfactant and k and k , are the second-order rate constants for the reaction in the micellar pseudophase and in the aqueous phase, respectively. The appearance of the molar volume of the surfactant in this equation is somewhat alarming. It is difficult to identify the volume of the micellar pseudophase that can be regarded as the potential reaction volume. Moreover, the reactants are often not homogeneously distributed throughout the micelle and... 

Herein [5.2]i is the total number of moles of 5.2 present in the reaction mixture, divided by the total reaction volume V is the observed pseudo-first-order rate constant Vmrji,s is an estimate of the molar volume of micellised surfactant S 1 and k , are the second-order rate constants in the aqueous phase and in the micellar pseudophase, respectively (see Figure 5.2) V is the volume of the aqueous phase and Psj is the partition coefficient of 5.2 over the micellar pseudophase and water, expressed as a ratio of concentrations. From the dependence of [5.2]j/lq,fe on the concentration of surfactant, Pj... 

Elution volume, exclusion chromatography Flow rate, column Gas/liquid volume ratio Inner column volume Interstitial (outer) volume Kovats retention indices Matrix volume Net retention volume Obstruction factor Packing uniformity factor Particle diameter Partition coefficient Partition ratio Peak asymmetry factor Peak resolution Plate height Plate number Porosity, column Pressure, column inlet Presure, column outlet Pressure drop... 

When the solute exists in only one form in each phase, then the partition coefficient and the distribution ratio are identical. If, however, the solute exists in more than one form in either phase, then Kd and D usually have different values. For example, if the solute exists in two forms in the aqueous phase, A and B, only one of which, A, partitions itself between the two phases, then... 

This distinction between Kd and D is important. The partition coefficient is an equilibrium constant and has a fixed value for the solute s partitioning between the two phases. The value of the distribution ratio, however, changes with solution conditions if the relative amounts of forms A and B change. If we know the equilibrium reactions taking place within each phase and between the phases, we can derive an algebraic relationship between Kd and D. 

In the simplest form of liquid-liquid extraction, the only reaction affecting extraction efficiency, is the partitioning of the solute between the two phases (Figure 7.20). In this case the distribution ratio and the partition coefficient are equal. 

For a simple liquid-liquid extraction, the distribution ratio, D, and the partition coefficient, Kd, are identical. 

A sample contains a weak acid analyte, HA, and a weak acid interferent, HB. The acid dissociation constants and partition coefficients for the weak acids are as follows Ra.HA = 1.0 X 10 Ra HB = 1.0 X f0 , RpjHA D,HB 500. (a) Calculate the extraction efficiency for HA and HB when 50.0 mF of sampk buffered to a pH of 7.0, is extracted with 50.0 mF of the organic solvent, (b) Which phase is enriched in the analyte (c) What are the recoveries for the analyte and interferent in this phase (d) What is the separation factor (e) A quantitative analysis is conducted on the contents of the phase enriched in analyte. What is the expected relative erroi if the selectivity coefficient, Rha.hb> is 0.500 and the initial ratio ofHB/HA was lO.O ... 

Partition coefficients Partition ratio Parts Parure... 

The constant is not a tme partition coefficient because of difference, — V, includes the soflds and the fluid associated with the gel or stationary phase. By definition, IV represents only the fluid inside the stationary-phase particles and does not include the volume occupied by the soflds which make up the gel. Thus is a property of the gel, and like it defines solute behavior independently of the bed dimensions. The ratio of to should be a constant for a given gel packed in a specific column (34). 

Once the composition of each equiHbrium phase is known, infinite dilution activity coefficients for a third component ia each phase can then be calculated. The octanol—water partition coefficient is directly proportional to the ratio of the infinite dilution activity coefficients for a third component distributed between the water-rich and octanol-rich phases (5,24). The primary drawback to the activity coefficient approach to estimation is the difficulty of the calculations involved, particularly when the activity coefficient model is complex. 

When a dilute solution of a polymer (c << c ) is equilibrated with a porous medium, some polymer chains are partitioned to the pore channels. The partition coefficient K, defined as the ratio of the polymer concentration in the pore to the one in the exterior solution, decreases with increasing MW of the polymer (7). This size exclusion principle has been used successfully in SEC to characterize the MW distribution of polymer samples (8). 

This experiment requires that the solvents 0 and S be immiscible then the ratio cs/co is the partition coefficient. The experiment should be carried out at sufficiently low concentrations that solute-solute interactions are negligible in both solvents. 

It was experimentally established by Berthelot and Jungfleisch (1872), that a body brought in contact with two liquids, in each of which it is soluble, always divides itself between them in a simple ratio, how ever great may be its solubility in one of them, and the excess of the volume of this same solvent. The quantities dissolved simultaneously by the two liquids stand to one another in a constant ratio which is independent of the relative volumes of the two liquids. This ratio is called the coefficient of distribution, or the partition coefficient, k. 

If the substance shared between two solvents can exist in different molecular states in them, the simple distribution law is no longer valid. The experiments of Berthelot and Jungfleiscli, and the thermodynamic deduction show, however, that the distribution law holds for each molecular state separately. Thus, if benzoic acid is shared between water and benzene, the partition coefficient is not constant for all concentrations, but diminishes with increasing concentration in the aqueous layer. This is a consequence of the existence of the acid in benzene chiefly as double molecules (C6H5COOH)2, and if the amount of unpolymerised acid is calculated by the law of mass action (see Chapter XIII.) it is found to be in a constant ratio to that in the aqueous layer, independently of the concentration (cf. Nernst, Theoretical Chemistry, 2nd Eng. trans., 486 Die Verteilnngssatz, W. Hertz, Ahrens h annulling, Stuttgart, 1909). 

Volatility, Relative Volatility, and Distribution Ratio (DR) or Partition Coefficient... 

Barrett and Thomas (10)proposed that these effects of differential monomer adsorption could be modeled by correcting homogeneous solution copolymerization reactivity ratios with the monomer s partition coefficient between the particles and the diluent. The partition coefficient is measured by static equilibrium experiments. Barrett s suggested equations are ... 

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