Radiotracer method

A development project has been initiated with the aim of providing a radiotracer method that ultimately can be implemented as a routine calibration method for permanently installed multiphase flowmeters. The project is supported by a research grant from the Danish Ministry of Energy. 

Interdiffusion of bilayered thin films also can be measured with XRD. The diffraction pattern initially consists of two peaks from the pure layers and after annealing, the diffracted intensity between these peaks grows because of interdiffusion of the layers. An analysis of this intensity yields the concentration profile, which enables a calculation of diffusion coefficients, and diffusion coefficients cm /s are readily measured. With the use of multilayered specimens, extremely small diffusion coefficients (-10 cm /s) can be measured with XRD. Alternative methods of measuring concentration profiles and diffusion coefficients include depth profiling (which suffers from artifacts), RBS (which can not resolve adjacent elements in the periodic table), and radiotracer methods (which are difficult). For XRD (except for multilayered specimens), there must be a unique relationship between composition and the d-spacings in the initial films and any solid solutions or compounds that form this permits calculation of the compo-... 

Met. = Method. C = chronocoulometry, CC = corrosion current method, EC = Electrocapillary method, EL = Ellipsometric method, IR = Infrared spectroscopic method, CV = cychc voltammetry, RT = Radiotracer method, T = Tensammetry, TF = Thin film resistance, WL = weight loss method. When a combination of methods was used aU methods are listed separated by slashes. See also list of symbols. 

The plot of the various reactants is most revealing. It is compared in Figure 6 with the radiotracer and potentiodynamic methods. It will be seen that there is a rough kind of agreement between the data here obtained and the radiotracer method data, though the potentiodynamic method is evidently less sensitive. On the other hand, the FTIR data distinguishes between the two, CO in the triple bond form and CO in the double bond form. 

The concentration dependence and non-linearity observed in do/pH curves indirectly show that it is not legitimate to ignore complexation. Direct experimental evidence, obtained with radiotracer methods (21,30,31), confirms the importance of complexation in the generation of surface charge do. Thus, we need to add the following equations to Equations 2 and 3, assuming for simplicity that the electrolyte is NaCl ... 

Most earlier papers dealt with the mercury electrode because of its unique and convenient features, such as surface cleanness, smoothness, isotropic surface properties, and wide range of ideal polarizability. These properties are gener y uncharacteristic of solid metal electrodes, so the results of the sohd met electrolyte interface studies are not as explicit as they are for mercury and are often more controversial. This has been shown by Bockris and Jeng, who studied adsorption of 19 different organic compounds on polycrystaUine platinum electrodes in 0.0 IM HCl solution using a radiotracer method, eUipsometry, and Fourier Transform Infrared Spectroscopy. The authors have determined and discussed adsorption isotherms and the kinetics of adsorption of the studied compounds. Their results were later critically reviewed by Wieckowski. ... 

An Improved Radiotracer Method for Studying Formation and Structure of Lignin... 

Finally, it should be noted that the structure of the DHP varies greatly depending on the polymerization conditions employed. Additionally, the yield and chemical and physical properties of these DHP preparations differ substantially from protolignin. Further improvements in simulation of the lignification process are therefore needed, and the radiotracer method can be employed as one approach to solve such problems. 

This improved radiotracer method can be employed as a non-degrada-tive method for examining the distribution, structure and reactions of lignin within the cell wall. 

In the last few decades, the study of adsorption phenomena at nickel electrodes by a radiotracer method has been the subject of several studies (see [34-40] and literature cited therein). M ost of these studies were carried out at smooth electrodes however, in some cases, nickel powder and Raney-nickel catalysts were used. 

A radiotracer method was elaborated for the study of the adsorption phenomena on nickel electrodes formed by electrodeposition of nickel ( nicke-lized nickel electrode). Adsorption studies were carried out with labeled HCl, Fi2S04, H3PO4, thiourea, phenylacetic, and acetic acids in 0.1 mol dm HCIO4 supporting electrolyte. The potential dependence of the adsorption of these species was determined in the potential range —200 to +200 mV vs. relative hydrogen electrode (RHE). It was found... 

It was demonstrated that the radiotracer method, using labeled anions, is an adequate tool to follow anion adsorption in the course of voltammetric measurements and to gain simultaneous information on hydrogen and anion adsorption [163]. Coupling voltammetric and radiometric measurements in the study of platinized platinum electrodes gave insight in the anion-hydrogen atom coadsorption process. 

The specific adsorption of H2P04 ions that accompany the UPD of Zn + ions on Pt (platinized electrodes obtained by Pt electrodeposition on the gold-plated plastic foil) electrodes was studied by using a radiotracer method with P phosphate species in the presence of a great excess of C104 ions [196]. It was found that the specific adsorption of species induced... 

Several features of this experiment (5 — 7) as a radiotracer method are as follows (1) since the relative adsorbability has been determined from the ratio of radiocounts of dried samples, it is not affected by errors in the absolute values for radioactivity and (2) specific activity, which has to be large usually for the study of surface phenomena, may be very small and yet the radioactive measurements yield accurate results. The concentrations of solutions examined were all close to but less than the c.m.c. values of respective surfactant solutions. The foams were stable enough to carry the experiment in this concentration range and the mole ratio of counterions in the bulk was equal to the stoichiometric mole ratio —i.e., there was no shift in mole ratio of dispersed counterions owing to the micelle formation at the present study. 

Wang, C. H., D. L. Willis, and W. D. Loveland. Radiotracer Methodology in the Biological, Environmental and Physical Sciences, Prentice-Hall, Englewood Cliffs, NJ, 1975. A somewhat out-of-date survey of radiotracer methods that includes an introduction to nuclear science for life scientists. 

Perhaps the most outstanding advantage of the use of radioisotopes is the opportunity offered to trace dynamic mechanisms. Such biological phenomena as ion transport across cell membranes, turnover, intermediary metabolism, or translocation in plants could, before the advent of radiotracer methods, be approached only indirectly. 

The radiotracer method for estimating efficiency of initiation was applied by Bevington and Eaves (32) to polymerization in benzene and in carbon tetrachloride. Whereas they had calculated that about 47% of the radicals from AIBN initiate polymer chains in DMF solvent, efficiency in benzene was about 50% and in carbon tetrachloride about 30%. This low efficiency in carbon tetrachloride is attributed to attack of radicals from AIBN on the carbon tetrachloride solvent, especially at high concentrations of solvent. Chains initiated by secondary radicals derived in this way from the solvent would not be detected by the tracer method. 

Radiotracer methods where the probe degradation occurs through a label-specific pathway are not suitable (33). 

The adsorption of Cd(II) and oxalate or citrate ions was calculated from an uptake of their concentration from solution. The ion concentration in solution was determined by the radiotracer method. For labelling the solution, 14C or 115Cd isotopes were used. Radioactivity of the solutions before and after adsorption was measured using a liquid scintillation counter (LS5000 TD Beckmann). Co-adsoprtion of Cd(II) and carboxylate ions was determined simultaneously. The adsorption of measured ions was conducted in a pH range from 3.0 to 10.0. 

Deposits which start as liquids may crystallize after exposure, and their evaporation rate will fall. Supercooling is more likely to occur and lead to this complication when the deposit density is extremely low, as often happens with radiotracer methods. 

EQCM can be combined with other techniques, e.g., with -> probe beam deflection (PBD) [viii], radiotracer methods (- tracer methods) [ix], and - scanning electrochemical microscopy [x]. 

Refs. [i] Horanyi G (1999) Radiotracer studies of adsorption/sorption phenomena at electrode surfaces. In Wieckowski A(ed) Interfacial electrochemistry, theory, experiment, and applications. Marcel Dekker, New York, pp 477-491 [ii] Kalman E, Lakatos M, Karman FH, Nagy F, Klenc-sar Z, Virtes A (2005) Mossbauer spectroscopy for characterization of corrosion products and electrochemically formed layers. In Freund HE, Zewi I (eds) Corrosion reviews. Freund Publishing House, Tel Aviv, pp 1-106 [iii] Horanyi G, Kalman E (2005) Recent developments in the application of radiotracer methods in corrosion studies. In Marcus PH, Mansfeld F (eds) Analytical methods in corrosion science and engineering, CRC Press, Boca Raton, pp 283-333 [iv] Stivegh K, Horanyi TS, Vdrtes A (1988) Electrochim Acta 33 1061... 

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