Multi-ion pairs

Mozumder and Magee, 1967), the success of the geminate pair model in kinetics (Warman et al., 1969 Rzad et al, 1970) and in free-ion yield determination (Hummel and Allen, 1966 Freeman, 1963a, b) has been rationalized on the basis that in multi-ion pair spurs all but the final e-ion pair would quickly neutralize due to intense internal coulombic interaction. Therefore, emphasis is laid in this section on the geminate pair with two caveats ... 

The non-homogeneous kinetics of single pairs of oppositely charged ions in each other s field can be treated exactly by solving the differential equation that describes the motion of one ion with respect to the other, due to diffusion and drift in the Coulomb field. Also, the scavenging probability can be calculated . For multi-ion-pair groups... 

The multi-ion pair theories discussed in this section suffer from several deficiencies or simplifications. First of all, the electrons are considered to be classical species, and the quantum mechanical nature of all interaction processes is not considered. Even so, the variation of the transport properties with electric field strength (see Section 3.1) and the dependence of electron/ion recombination on the electron mobilities (see Section 3.5) is not taken into account. Bipolar diffusion should be considered in the dense plasma column around the track of an a-particle (Loeb, 1955). 

Bacelon et al.43a have confirmed via far-IR studies that R4N halides exist in CC14 in large aggregates, which are dissociated, however, by phenol into ion pairs hydrogen bonded to phenol and multi-solvated anions. 

Moreover, as schematically shown in Fig. 2.15, three different types of ion-pairs, i.e. solvent-separated (A+SSB-), solvent-shared (A+SB-) and contact (A+B-) types, may be formed depending on the strength of ion-solvent interactions, complicating the treatment of ion association. If we consider the following multi-step equilibrium, the total ion-association constant (KA) is expressed by Eq. (2.21) ... 

Since equilibrium constants are defined by ion activities, which are defined by their concentrations and coefficients (see equation 4.15), they do not include ion pairing or complexation effects. In a multi-ion and multiligand solution, where ion pairing is common, it is necessary to use thermodynamic equilibrium constants to convert the ion-pair concentrations to concentrations of free ions. This equilibrium constant (Kc) is defined by concentrations, making it useful to compute ion speciation. The thermodynamic equilibrium constant (K q) used in calculating Kc is based on the following conditions I = 0 m, 25°C and 1 atm. Thus, Kc is defined by the following equation ... 

These strategies capitalize on the perturbation of an equilibrium system and the measure of the return of the system to equilibrium they are valuable because they apply almost universally to solutions and can shed light on the multi-step association process. Unfortunately they are technologically demanding and expensive even when commercially available. Additionally, only very experienced and capable practitioners can exploit the potential of these strategies since ion-pairing is detected by the observation and appraisal of new features in spectra. 

Narkiewicz-Michalek, J. Electrostatic theory of ion-pair chromatography multi-site occupancy model for modifier and solute adsorption. Chmmatographia 1993, 35, 527-538. 

Usually bi- or multi-dimension separations must be run individually since they utilize different physico-chemical separation principles and differ greatly in selectivity. Ion-pairing and electrophoretic mobility provide two compatible separation models that may be run simultaneously in the same single separation device to achieve a bi-dimensional technique. Since they are respectively based on the complex hydrophobicity and on the analyte change, experiments demonstrated that ion-pairing... 

For the analysis of spectinomycin in milk [56], acid protein precipitation and analyte extraction was combined with SPE, ion-pair LC with HFBA as ion-pair agent, and multi-stage ESI-MS-MS on an ion-trap instalment. [M+H+HjO] at m/z 351 was fragmented to yield [M+H] at m/z 333 in the first stage of MS-MS and further fragmentation of [M+H] in a second stage of MS-MS. The estimated confirmation limit for spectinomycin was 100 pg/kg milk. Further improvement of this method, especially with respect to variability of the ion-trap performance, is required to meet regulatoiy demands. 

MartoreU et al. separated a series of twenty-two 6-fluoroquinolones by ion pair RP-HPLC. The multi-... 

That concept had led to the synthesis of so-called "halato-telechelic polymers" (which means a "salt" or "neutralized" telechelic polymer, acidic or basic). Although that is a very general denomination covering all the chains formed by any type of ion-pair coupling in any way, a particularly handy and representative class of such structures can be obtained from the complete neutralization of a,o)-dicarboxylato-polymers (PX), by a di (or multi-) valent metal derivative, (19), according to the general equation ... 

Sb(V) Anti-leishmaniotic drugs Toluene UV-Vis 7.0 x 10 5—7.2 x 10 1 mol L 1 Multi-commuted flow system ion pair formation between hexachloroantimoniate anion and rhodamine B gravity for phase separation [481]... 

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