Radiotracer techniques

AH components of the reaction mixture, whatever their source, are subject to the same kind of radical attacks as the starting substrate(s). Any free-radical oxidation is inevitably a cooxidation of substrate(s) and products. The yields of final products are deterrnined by two factors (/) how much is produced in the reaction sequence, and (2) how much product survives the reaction environment. By kinetic correlations and radiotracer techniques, it is... 

A correlation between the amount of adsorbed ions and the electrode potential, in particular E. , has been identified apparently for the first time by Frumkin and Obrutschewa [26Fru]. A minimum of ionic adsorption was found at E, this is equivalent to the absence of specific adsorption at Ep c- The measurement of the amount of adsorbed ions was performed by measuring the ionic concentration in the solution as a function of the electrode potential or by measuring the surface concentration of adsorbed ions by e.g. radiotracer techniques (see also 4.2). (Data obtained with this method are labelled lA). 

Kumar S, Mehta D, Singh S, et al. 1988. Biokinetics of lead in various mouse organs tissues using radiotracer technique. Ind J Exp Biol. 26 860-865. 

Radiotracer techniques involving lsO in the anodization process are used with subsequent neutron activation analysis84 or SIMS.85 Another method involves implantation of inert ion markers into the surface layer of the sample prior to anodization and examination of the position of the markers after the oxide film has grown to a certain thickness.86 Assuming immobility of the inert species, the ratio of the cation to the anion transport number, t+/, should be equal to the ratio of the outer to the inner layer thickness. Numerous experimental determinations72,87 suggest t+ and f to be 0.4 and 0.6, respectively. 

The adsorption of sulfate was confirmed by radiotracer technique as shown in Fig. 14, which clearly shows that the sulfate adsorption feature depends on crystal faces, as reviewed in Ref. 17. 

The pulsed field gradient nuclear magnetic resonance (PFG NMR) technique is experimentally distinct from the radiotracer technique but the principle is very similar. A fraction of the nuclei of each constituent is labelled by flipping their spins and monitoring the diffusion of these species. Both techniques are influenced by the presence of neutral associates unlike the Hittorf/Tubandt method. 

Newman, S.P., Clark, A.R., Talaee, N., and Clarke, S.W., Pressurized aerosol deposition in the human lung with and without an open spacer device. Thorax, 44 706-710 (1989). Newman, S.P., Clark, A.R., Talaee, N., and Clarke, S.W., Lung deposition of 5 mg Intal from a pressurized metered dose inhaler assessed by radiotracer technique, Int. J. Pharm., 74 203-208 (1991). 

Yeager and Steck derived diffusion coefficients for water in totally hydrated Nafion 120 membranes that were exchanged with alkali metal cations, using a radiotracer technique. At 25 °C, 77for the Na+ form was 2.65 X 10 cm /s and the values for the K+ and Cs+ forms were somewhat smaller, which would seem to reflect the lower maximal degree of hydration of these forms. 

Incorporation of Carbon from Coumarin in Deposits. Incorporation of carbon from coumarin was studied by Rogers and Taylor (36) and Edwards and LeWett (34) using a radiotracer technique with C-labeled coumarin. They found that the consumption of coumarin by incorporation into nickel deposits is small compared with consumption by reduction reaction, by a factor of about 10. 

The absorption (following administration by oral, intramuscular and intravenous routes), distribution and elimination of the drug has been studied by radiotracer techniques in rats and rabbits [283, 284]. The substituted benzoic acid was labelled with and the alkanolamine remnant with Almost all radioactivity was recovered from the urine even after oral administration. 

A recent paper by Lairdinvestigated the efficacy of HPAM flocculation of kaolinite, illite and quartz by carrying out visible absorption experiments. He concluded that HPAM more effectively flocculates kaolinite than quartz or illite. This was also the conclusion of previous work by Allen et al. who studied the adsorption of HPAM onto kaolinite, quartz and feldspar at various HPAM concentrations and solution pH by X-ray photoelectron spectroscopy (XPS). Much of the previous work on polyacrylamide adsorption onto aluminosilicates monitored the adsorbed amount by viscometry, carbon analysis and radiotracer techniques. These methods rely on following adsorption by subtraction from that detected in solution. 

The same authors [197] have studied the specific adsorption of other anions, which accompany the Zn UPD on Pt electrodes. Again, radiotracer technique with S-labeled sulfate and Cl-labeled chloride ions has been used. It was found that sulfate ions adsorb on the top of Zn adatoms, and the adsorption strength of Cl ions on the Zn adlayer is significantly lower than that of HS04 (S04 ) ions. 

Zelenay etal. have applied CV and radiotracer technique to study adsorption of benzoic acid from 0.1 M HCIO4 solution on a pc-Au electrode prepared by electroplating [286]. Chemisorption occurred within the entire potential range... 

Adsorption of chlorobenzene on pc-Au electrode has been studied by Czerwinsld and Sobkowski [316] as early as in 1980, using a radiotracer technique. The rate-determining step of this adsorption was diffusion of the reactant. Chlorobenzene was adsorbed in multilayers at sufficiently high bulk concentration. The adsorbed molecules were probably oriented vertically with respect to the Au surface and bounded to it via a Cl atom. 

Fig. 6.21. FTIR spectra of R(111) in 0.1 M HCI04+1 mMTI+ in (a) the absence and (b) in the presence of 1 mM H2S04. (c) Dependence of integrated area on electrode potential for the bands shown in (a) and (b). (O) perchlorate bands, and ( ) bisulfate bands. (Reprinted with permission from N. S. Marinkovit, W. R. Fawcett, J. X. Wang, and R. R. Adzid, J. Phys. Chem. 99 17490, Figs. 3 and 4, copyright 1995, American Chemical Society.) (II) Bisulfate coverages in 0.1 M HCI04 supporting electrolyte, as measured by a radiotracer technique on Pt(111), cH2S04 = 1 mA Pt(100), =...

Fig. 6.94. Comparison of adsorption properties of different electrode surfaces. Bisulfate adsorption as a function of electrode potential on different platinum planes (110), (111), (100) and on polycrystalline platinum. Data obtained by the radiotracer technique. (Re-printed from Y.-E. Sung, A. Thomas, M. Gamboa-Aldeco, K. Franaszczuk and A. Wieckowski, J. Electroanal. Chem. 378 131, copyright 1994, Figs. 14 and 15, with permission from Elsevier Science.)...

Fig. 6.117. Adsorption isotherms for various organic species on platinum in 0.01 N HCI solution, obtained with the radiotracer technique valeric acid (a), butanol ( ), benzoic acid (a), naphtoic acid ( ), naphtol (O). All the data are taken at the maximum adsorption potential. (Reprinted from J. Jeng, dissertation, Texas A M University, 1991.)...

Experimental parameters were obtained from the adsorbance of bisulfate ions on polyciystalline electrodes using a radiotracer technique slightly different from that described in the text, where the working electrode is placed on top of the scintillator. These values are listed in Table P.l. 

Eniistiin and Turkevichf prepared SrS04 (p = 3.96 g cm-3) precipitates under conditions that resulted in different particle sizes. Particle sizes were characterized by electron microscopy, and solubilities were determined at 25°C by a radiotracer technique. In the following data the supersaturation ratios are presented for different preparations, each of which is characterized by an average particle width and a minimum particle width ... 

The distribution of counterions at the charged surface and in the bulk solution was studied combining the radiotracer technique with foam fractionation technique. The relative adsorbability of counterions was determined from the ratio of mole ratios in an adsorbed and in the solution phases. The relative adsorbability was CT CH3COO Br ClOf NOs = 1 0.7 1.5 3.0 4.1 in solution of dodecylammo-nium(0.011 mole/liter), Cl Br ClOf NOf SO/2 = 1 1.2 2.8 1.6 2.3 in solution of dodecyltrimethylammo-nium(0.015 mole/liter), and Na+ Ca2+ = 1 210 in solution of sodium dodecylsulfate(0.006 mole/liter). 

This section deals with spectroscopic methods that depend on nuclear events. Radiotracer techniques that are very valuable in studying the mechanisms of catalytic reactions have been omitted. 

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