Complex ation constant

A theoretical study to compare the methods of gas-liquid chromatography and spectrometry in the measurement of weak complex-ation constants is given by Eon and Guiochon (11). They show that both chromatography and spectrometry should lead to the same results when necessary corrections are made and the solvent is properly chosen. Discrepancy in the data from comparison of these methods usually can be attributed to misinterpretation of the chromatographic measurements. 

Tables of this sort are extremely useful, because they feature much chemical and electrical information condensed into quite a small space. A few electrode potentials can characterize quite a number of cells and reactions. Since the potentials are really indices of free energies, they are also ready means for evaluating equilibrium constants, complex-ation constants, and solubility products. Also, they can be taken in linear combinations to supply electrochemical information about additional half-reactions. One can tell from a glance at an ordered list of potentials whether or not a given redox process will proceed spontaneously.

Here, electrophoresis often employs principles used in chromatography - interaction of the separands with another phase, which is called the pseudo-stationary phase. The pseudostationary phase is a substance that is added to the separation system in the column, and can interact with the species to be separated. The substance can be neutral, then it does not have its own electrophoretic movement or it can be charged, then it can move in the column with certain mobility. In both cases, the analytes with their own electrophoretic movements encounter on their way the molecules of the pseudostationary phase and interact with them by forming a temporary complex or by association. During the time when the separands are bound to the pseudostationary phase its mobility is different however, when it is free it moves with its own mobility. As the rate constants of the interaction are mostly very high, in analogy with weak electrolytes, the analyte then moves with a certain mean mobility that lies somewhere between the bound and free mobilities. The mean mobility is in this way dependent on the interaction (complex-ation) constant. Many substances can used for this purpose, such as 2-hydroxyisobutyric acid, which forms complexes with many ions, especially with lanthanides, and enables their electrophoretic separation when added to the separation systems. 

For chelator agents, we will use the complex-ation constant. 

Martire and co-workers (31,32) developed a method of determining complex-ation constants that is much less time-consuming than the Cadogan-Pumell method (33) but makes additional assumptions. They have demonstrated that the specific retention volume of A is related to the complex formation constant ... 

LIQUID-PHASE BEHAVIOR. The liquid phase contains dissolved substances and contacts the solid phase. For our purposes, the liquid phase is used synonymously with aqueous phase , and all processes discussed in this section take place in aqueous solutions. The dissolved monomers of the solid phase are formed in equilibrium with their uncomplexed components. Such components may be uncomplexed ions (which are charged atoms or molecules) free in solution or ionic complexes in equilibrium with dissociated ions. Concentrations of the uncomplexed ions, therefore, depend upon the concentrations of all chemical substances competing for binding interactions with them. Each complex-ation reaction is defined by either a solution equilibrium constant ... 

A calcium ion indicator dye (based on the structure of the chelator EGTA) that exhibits a strong fluorescence at 385 nm and can be used to measure changes in intracellular Ca concentration. The approximate dissociation constant for the Ca -Fura-2 complex is 0.1 juM, depending on cellular ion composition and pH. An esteri-fied derivative of Fura-2 readily crosses the peripheral membrane of many cells and, after hydrolysis, the release of Fura-2 permits calcium ion measurements within cells. See Calcium Ion Indicator Dyes Metal Ion Complex-ation... 

The ( >p pjj values needed for the computation of the Vp/Op values associated with the linear polyion, DxS, were obtained by interpolation of the ( )p versus a/b plots accessible for ionic polysaccharides (Fig. 12) where the b values were calculated with Eq. (16). Tlie log Kc and the log K, values determined for the commercially available DxS sample (Pharmacia), with a DS value of ca. 2, were also used at under various NaCl concentration levels. The Kf- values were determined in complex-ation studies facilitated by potentiometric measurements, whereas the Kj values due to Mattai and Kwak [46], were obtained by a dye method. In spite of the difference in valence of the counterions and the binding constants, the Vp/np values resolved for both systems are consistent with... 

Bresnahan, W. T., Grant, C. L., and Weber, J. H. (1978). Stability constants for the complex-ation of copper(II) ions with water and soil fulvic acids measured by an ion selective electrode. Anal. Chem. 50, 1675-1679. 

As detailed above, the adsorption behavior of most actinides varies widely with solution pH, Eh, complexation, competitive adsorption and ionic strength, and the surface properties of sorbent phases. For this reason, many researchers have modeled actinide adsorption using surface complex-ation (SC) models that can quantitatively account for such variables. These models include the constant capacitance (CC), diffuse-layer (DL), and triple-layer (TL) models (Chap. 10). Much of the ra-... 

Ka, Kd and Kim being constants for association, dissociation and ionomolecular complex-ation respectively. 

The WP6 can bind strongly with organic pyridinium salt Gl (Scheme 10.9) in water through hydrophobic and electrostatic interactions. The complex-ation of GlcWPS vras investigated using WP6 and a model compound of Gl, i.e., 1-octylpyridinium bromide (OPB), and the association constant (/fa) in water was determined to be (3.26 0.28) x 10 by fluorescence titra-... 

Barriers to rotation around the Cca —N bonds have been determined experimentally for diaminocarbenes (3) and (4) and their protonated and lithiated counterparts the possible involvement of lithium or a proton in the dimerization of these acyclic diaminocarbenes was also reported. A computational study of the dimerization of diaminocarbenes has been performed via rate constant calculations using general transition-state theory calculations. Such a dimerization has been shown to be a rapid equilibrium between the carbenes and the tetra-A-alkyl-substituted enetetramines (5), by characterization of metathesis products when two different tetramines were mixed. The thermodynamic parameters of this Wanzlick equilibrium have been determined for the A-ethyl-substituted compound the enthalpy of dissociation has been evaluated at 13.7kcalmol and the entropy at 30.4calmor K . Complex-ation of diaminocarbenes by alkali metals has been clearly established by a shift of the C NMR signal from the carbene carbon of more than 5 ppm. ... 

Because Y is the fraction of occupied binding sites on the host, Equation (15.87) corresponds to Equation (15.58) in the Hill equations with n = 1 (one-step complex-ation) and (= L ). Apparently binding constant is the same as L, from Equation (15.85), (n = 1, i = 1). 

The charge defined by Equation 1.97 cannot be read directly as the slope of the electrocapillary curve, especially when the monolayer desorbs upon complex-ation. Indeed, due to the charge-transfer reaction taking place during the desorption of the complex, it is impossible to vary the potential E while keeping constant the chemical potential of the phospholipid L . Hence, the differentiation of the interfacial tension with respect to the potential does not give the surface charge... 

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