Isotopic exchange method

Darensbourg and coworkers—isotopic exchange method and energetics considerations in assessing potential intermediates (e.g., formate, carboxylic acid). 

Results are similar for films deposited on YSZ however, there appears to be a difference between films deposited on ceria vs YSZ in terms of interfacial electrochemical resistance. As shown previously in Figure 6c, LSC films on YSZ often exhibit a second high-frequency impedance associated with oxygen-ion exchange across the electrode/electrolyte interface.That this difference is associated with the solid—solid interface has been confirmed by Mims and co-workers using isotope-exchange methods. As discussed in greater detail in sections 6.1—6.3, this interfacial resistance appears to result from a reaction between the electrode and electrolyte, sometimes detected as a secondary phase at the interface. 

Fig. 1.7 Schematic representation of the three-isotope exchange method. Natural samples plotted on the primary mass fractionation hne (PF). Initial isotopic composition are mineral (Mo) and water (Wo) which is well removed from equilibrium with Mq in 8 0, but very close to equUibrium with Mo in 5 0. Complete isotopic equihbrium is defined by a secondary mass fractionation hne (SF) parallel to PF and passing through the bulk isotopic composition of the mineral plus water system. Isotopic compositions of partially equilibrated samples are Mf and Wf and completely equilibrated samples are Mg and Wg. Values for Me and W. can be determined by extrapolation from the measured values of M , Mf, Wo, and Wf (after Matthews et al. 1983a...

The oxygen atoms in the silicalite framework can be classified into approximately three kinds by the isotope exchange method proposed by Endoh et al. [12]. On the exchange reaction of in the zeolite framework with C 02 in the gas phase at 773 K, the most reactive oxygen atoms were in the terminal SiOH... 

We synthesized nine silicalites which had different concentrations of defect sites in the zeolite framework determined by isotope exchange method. These silicalites were treated with aluminium trichloride vapor under the same reaction conditions 923 K temperature, 1 h time, 11 kPa aluminium trichloride vapor pressure. Figure 1 shows the plots of the amount of aluminium atoms introduced into the framework against the amount of oxygen atoms on the defect sites. A... 

Kolar, Z.I., Verburg, T.G., and van Dijk, H.J.M. (2002). Three kinetically different inorganic phosphate entities in bovine casein micelles revealed by isotopic exchange method. J. Inorg. Biochem. 90, 61-66. 

The isotope exchange method is based on the exchange between two different forms or compounds of the element M to be determined ... 

An advantage of isotope exchange methods is that in special cases individual chemical forms (species) can be determined with high sensitivity. The systems applied have to be selected by the following criteria knowledge of the species between which exchange occurs, relatively rapid attaimnent of the exchange equilibrium, and exclusion of side reactions. 

Most of the classical physicochemical methods for the study of hydration of ions fail to distinguish between water in the first coordination sphere and water more remote from the central ion which also comes under the influence of its charge. Some of the methods more recently applied have provided a clearer picture. The oxygen isotope exchange method, where applicable, not only can define the composition of the first coordination sphere but also can be used to measure the lability of the aquo ion. Thus it has served to establisli Cr(0H2)e (64) (NHs)6Co (0H2)+++ H4) > and (NHs)4Co(OH2)2 " + (.105) as well-defined species in solution and also to fix the half-time for exchange of... 

Celis, R. and W.C. Koskinen. 1999. An isotope exchange method for the characterization of the irreversibility of pesticide sorption-desorption in soil. J. Agric. Food Chem. 47 782-790. 

Investigation of Oxygen Mobility in Synthetic Zeolites by Isotopic Exchange Method... 

He, Z.L., Yuan, K.N., Zhu, X.Z. and Zhang, Q.Z. (1991) Assessing the fixation and availability of sorbed phosphate in soil using an isotopic exchange method. Journal of Soil Science 42, 651-669. 

An analytical method based on isotopic exdiange was introduced in the 1950s. A few papers on the isotopic exchange method include the exchange system between metal and metal species, for example silver and solid silver chloride and silver and silver dithizonate in a liquid-liquid extraction system In a direct isotopic exchange,... 

The diffusion of oxygen in PUO2 has quite recently been measured by Deaton and Wiedenheft (313) using the 0 isotope exchange method in the temperature range 700 1100°C, resulting in a diffusion coefficient of D = 1.19 X 10 exp( - 42,200/RT). 

Product inhibition in the Bi Uni system. In the reverse direction, P + Q -> A, and in the presence of A, the writing of the velocity equation is complicated by the reaction in the A -> P + Q direction. However, if one apphes the isotope exchange method, the reaction A — P -f Q can be made negligible. If A inhibits while one is stiU far from equilibrium, the reverse reaction is unimportant and one can measure product inhibition by A. It helps to keep either P or Q saturating to stay far from equilibrium. In this case, in the P -H Q - A direction, the initial velocity equation is obtained by replacing PaAeq/Pi from the Haldanes ... 

Isotopes Exchanger, method, conditions 1Cfe Remarks Author (year)... 

Isotope-exchange method based on the exchange of isotopes between two different compounds of one element, with a radioactive isotope in one of the compounds and a nonradioactive isotope in the other, usually the analyte. 

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