Adsorption thermodynamics distribution coefficient

Diphenylcarbazide as adsorption indicator, 358 as colorimetric reagent, 687 Diphenylthiocarbazone see Dithizone Direct reading emission spectrometer 775 Dispensers (liquid) 84 Displacement titrations 278 borate ion with a strong acid, 278 carbonate ion with a strong acid, 278 choice of indicators for, 279, 280 Dissociation (ionisation) constant 23, 31 calculations involving, 34 D. of for a complex ion, (v) 602 for an indicator, (s) 718 of polyprotic acids, 33 values for acids and bases in water, (T) 832 true or thermodynamic, 23 Distribution coefficient 162, 195 and per cent extraction, 165 Distribution ratio 162 Dithiol 693, 695, 697 Dithizone 171, 178... 

Both the In k values and the sorption enthalpies, AHm s, may be determined experimentally from the temperature dependence of retention. To calculate the sorption entropy, the phase volume ratio must be known. However, the thermodynamic data may be regarded simply as formal quantities, since the capacity factors correlate directly with AGm >s via the distribution coefficient according to Eq. (38), and since sorption exhibits both distributive and adsorptive character. 

Under these circumstances the distribution coefficient for MiXi is zero, and that for M2X2, infinity. It follows that the Galvani potential difference is not defined for this interface. However, the thermodynamics of the interface can be derived on the basis of the Gibbs adsorption isotherm. 

Alternatively, Jaroniec and Martire have described liquid-solid chromatography in terms of classical thermodynamics (82). They show that a rigorous consideration of solute and solvent competitive adsorption in systems with a nonideal mobile phase and a surface-influenced nonideal stationary phase leads to a general equation for the distribution coefficient of a solute involving concurrent adsorption and partition effects. This equation is phrased in terms of interaction parameters and activity coefficients, which would need to be evaluated or estimated in actual applications. 

In the present work, the concentration effect has been correlated with the preferential solvation phenomenon. Eirst, the observed non-exclusion mechanism has been quantified by means of the distribution coefficient, Kp, representing the concentration ratio of macromolecules inside the pores (i.e., in the quasistationary phase) to those in the mobile phase. Second, the shifts in the elution volume owing to either adsorption or, on the contrary, incompatibility of the solute with the gel packing, have been related to the preferential or selective sorption phenomenon. From a thermodynamic viewpoint, the... 

The subsequent three chapters are devoted to the electric double-layer structure at the interface between immiscible electrolytes examined by the electrocapillary curves method (Prof. Senda and coauthors) and by measurement of the electric double-layer capacity (Dr. Samec and Dr. Mare ek) as well as to the investigation of the Galvani and Volta potentials in the above-mentioned systems (Prof. Koczorowski). These chapters will be of interest to many electrochemists since the results obtained here are comparable with the thoroughly studied metal/electrolyte solution interface. An insignificant potential shift in the compact layer at the interface between immiscible electrolytes in the absence of specific ion adsorption - this is the main conclusion arrived at by the authors of Chaps. 4 and 5. Chapter 6 deals with the scale of potentials in a system of immiscible electrolytes and the thermodynamic relation between the distribution coefficients and the Volta potentials. 

SPME is a multiphase equilibrium technique and, therefore, the analytes are not completely extracted from the matrix. Nevertheless, the method is useful for quantitative work and excellent precision and Unearity have been demonstrated. An extraction is complete when the concentration of analytes has reached distribution equilibrium between the sample and coating. This means that once the equihbrium is achieved, the amount extracted is independent of further increase in extraction time. If extraction is terminated before the equihbrium is reached, good precision and reproducibihty is still obtained if incubation temperature, sample agitation, sample pH and ionic strength, sample and headspace volume, extraction and desorption time are kept constant. The theory of the thermodynamic, kinetic and mass transfer processes underlying direct immersion and HS-SPME has been extensively discussed by Pawhszyn [2]. The sensitivity and time required to reach adsorption equilibriiun depends on the partition coefficients between the fiber and the analytes, and the thickness of the phase. Limits of detection and quantitation are often below 1 ppb. 

The emulsifying effects of a small quantity of a block copolymer, A-B, added to immiscible blend of homopolymers A and B, were examined by Leibler (1988). The theory predicted the reduction of the interfacial tension coefficient, Vi2, caused by equilibrium adsorption of a copolymer at the interface. For well-chosen compositions and molecular weights of the copolymer, low values of Vj2 are to be expected. This suggests a possible existence of thermodynamically controlled stable droplet phase, in which the minor phase homopolymer drops are protected by an interfacial film of the copolymer, interfacing the matrix polymer. The size distribution of the droplets is expected to depend on the rigidity and spontaneous radius of curvature of the interfacial film that can be controlled by molecular structure of the copolymer. 

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