Radioisotope tracer methods

Jackson (Jl), 1955 Flow of films of ethyl acetate, methanol, water, water + surfactant, 2-propanol, glycerol solutions (with and without surfactant), inside tube of 3.6 cm. diameter. Film thicknesses by radioisotope tracer method heights of waves measured. Surface tension had little effect. 

D2. Deacon, A. L., Hulme, P., Hesp, R., Green, J. R., Teller, M., and Reeve, J., Estimation of whole body bone resorption rate A comparison of urinary total hydroxyproline excretion with two radioisotopic tracer methods in osteoporosis. Clin. Chim. Acta 166, 297-306... 

Cation exchange can be conveniently studied by radioisotopic tracer methods because of the fairly broad concentration range that can be used, from tracer (carrier-free isotopes) to high (applying an inactive carrier) concentrations. 

The basic information in the study of sorption processes is the quantity of substances on the interfaces. In order to measure the sorbed quantity accurately, very sensitive analytical methods have to be applied because the typical amount of particles (atoms, ions, and molecules) on the interfaces is about I0-5 mol/m2. In the case of monolayer sorption, the sorbed quantity is within this range. As the sorbed quantity is defined as the difference between quantities of a given substance in the solution and/or in the solid before and after sorption processes (surface excess concentration, Chapter 1, Section 1.3.1), all methods suitable for the analysis of solid and liquid phases can be applied here, too. These methods have been discussed in Sections 4.1 and 4.2. In addition, radioisotopic tracer method can also be applied for the accurate measurement of the sorbed quantities. On the basis of the radiation properties of the available isotopes, gamma and beta spectroscopy can be used as an analytical method. Alpha spectroscopy may also be used, if needed however, it necessitates more complicated techniques and sample preparation due to the significant absorption of alpha radiation. The sensitivity of radioisotopic labeling depends on the half-life of the isotopes. With isotopes having medium half-time (days-years), 10 14-10-10 mol can be measured easily. 

The analytical procedures presented in this study are relatively simple and sample through-put through the mass spectrometer is reasonable (15 min per replicate). The results indicate that the method has promise as an alternative to radioisotope tracer methods. Long-term studies and studies with infants, children, and women are feasible without hazards to the subjects. 

The direct radioisotope tracer method, in which the accumulation of radiolabeled product from added radiolabeled substrate over time yields a rate estimate, is not very practical for measuring rates of nitrification in the environment. Capone et al. (1990) were able to quantify nitrification rates using but the isotope is so shortlived (10 min half-life) that its use is usually impractical. 

Nuclear radiation absorption methods have many technical applications. These methods are not to be confused with radioisotope tracer methods, although radioisotopes may be used as radiation sources. In the tracer method the chemical properties of the radionuclide are important while in the applications discussed in this section only the type and energy of radiation emitted are irqx>rtant. 

The excess surface concentration F, can be determined from the linear portion of the surface tension-log surfactant concentration curve. Although direct determination of r is experimentally more difficult, several satisfactoiy methods have been developed [12-30]. McBain and co-workers [13,14] analyzed a slice of the surface removed with a microtome. Radioisotope tracer methods [15-21] are simpler and the agreement with calculated values has been satisfactory. Recently, the structure and composition of the adsorbed surface layer has been determined by neutron reflection [22-30]. 

Jl. Jackson, T. M., and Ekins, R. R, Theoretical limitations on immunoassay sensitivity. Current practice and potential advantages of fluorescent Eu + chelates as non-radioisotopic tracers. J. Immunol Methods 87, 13-20 (1986). 

There are a number of tracers that have been used to help understand chemical reactions and interactions. Historically, development of modem tracer methods began with the pioneering work of the Hungarian physical chemist, George Charles de Hevesy, in the early 1900s. De Hevesy s work focused on the use of radioactive tracers to study chemical processes, for which he was awarded the Nobel Prize in Chemistry in 1943. Radioactive tracers, also known as radioactive labels, are based on the use of a given radioisotope. However, it is important to note that there are also isotopic tracers (or isotopic labels). Isotopes are forms of a chemical element with different atomic mass, which have nuclei with the same atomic number (i.e. number of protons) but different numbers of neutrons. Examples include H, " C, and which are radioactive forms of stable elements... 

This method is commonly used with radioisotope tracers that undergo radioactive decay. The tracer concentration will decrease over time following an exponential decay law ... 

Radiochemical tracers or radiotracers are compounds labeled with radioisotopes. For tracer methods, the compound to be measured or a suitable reagent is radiolabeled. A measurement of the redistribution of tracer within such a sample-reagent reaction system provides the required quantitative analytical information. Major advantages of tracer methods are high sensitivity, simplicity, and speed. Radiotracers are more commonly used for following mechanisms of biological and/or chemical processes or if there is need to eliminate complicated separation procedures, especially in biological processes. 

For the case of radioisotope tracer experiments, nonintrusive methods are used to get the outlet concentration of tracer by utilizing collimated scintillation detectors. Radioisotope tracers have many advantages such as on-line detection, high detection sensibility, and availability in different compatible forms over conventional tracers.This method can also help in troubleshooting and checking the performance of industrial TBR under operational conditions. 

ILM Gas Flux Measurement. Several methods have been used to measure fluxes through ILMs a transient pressure measurement (24), a radioisotope tracer technique ( ), and a flow cell techniqueTsO, 34). 

The radiochemical methods of analysis to be discussed in this chapter will be divided into two groups for convenience tracer methods will be defined as those methods where the radioisotope is introduced into the analytical technique independently of the sample, and activation methods those where the radioisotope is incorporated into the sample by nuclear reaction. The different types of method may each have advantages in a particular situation, depending upon the availability of particular isotopes, the concentration at which the method is to be applied, and the instrumental facilities available to the individual analyst. 

The most widely used experimental method for determining surface excess quantities at the liquid-vapor interface makes use of radioactive tracers. The solute to be studied is labeled with a radioisotope that emits weak beta radiation, such as H, C, or One places a detector close to the surface of the solution and measures the intensity of beta radiation. Since the penetration range of such beta emitters is small (a ut 30 mg/cm for C, with most of the adsorption occurring in the first two-tenths of the range), the measured radioactivity corresponds to the surface region plus only a thin layer of solution (about 0.06 mm for C and even less for H). 

The abundance of a trace element is often too small to be accurately quantihed using conventional analytical methods such as ion chromatography or mass spectrometry. It is possible, however, to precisely determine very low concentrations of a constituent by measuring its radioactive decay properties. In order to understand how U-Th series radionuclides can provide such low-level tracer information, a brief review of the basic principles of radioactive decay and the application of these radionuclides as geochronological tools is useful. " The U-Th decay series together consist of 36 radionuclides that are isotopes (same atomic number, Z, different atomic mass, M) of 10 distinct elements (Figure 1). Some of these are very short-lived (tj j 1 -nd are thus not directly useful as marine tracers. It is the other radioisotopes with half-lives greater than 1 day that are most useful and are the focus of this chapter. 

Wolfe, R.R. 1984 Tracers in Metabolic Research Radioisotope and Stable Isotope/Mass Spectrometry Methods. A.R. Liss, NY. 

Gordon and Wahl have used the radioisotope "°Ag as a tracer for a study of the exchange of silver between Ag(II) and Ag(I) in acidic media. The precipitation of Ag(phen)2(C104)2, brought about by the addition of o-phenanthroline, formed the basis of the separation method. The experimental data were obtained using a... 

Section II will summarize experimental work designed to determine the extent and manner of benzene chemisorption by the use of physical methods and the radioisotope carbon-14. In Section III, evidence obtained by use of deuterium as a tracer is examined. The relatively small amount of information concerning the mode of benzene chemisorption that is afforded by studies of its hydrogenation is presented in Section IV. 

A radioisotope can be used as a tracer instead of the enzyme used in immunochemical tests. This method, introduced in 1960 for the measurement of insulin in serum, is called radio-immunology. It is the transposition in immuno-chemistry of the same principle as that used to determine the sulphate ion (cf. 17.5). Radioimmunoassays are similar to ELISA assays in the way in which the analysis is... 

Measurement of the serum concentrations of administered antibodies is a general tool to evaluate their persistence in circulation. This is usually performed by introducing a sufficient amount of the test antibody either by the intravenous or by the intraperi-toneal routes (see Note 3), in a quantity that can be easily detected and quantified in serum samples, even after a two log reduction in concentration. The antibody tracer can be labeled with radioisotope which permits direct quantification in serum samples. To minimize radioactive isotope use, we use an antibody tracer that is unmodified or labeled with biotin or other derivation chemistries, and then determine its serum concentrations by ELISA techniques. We commonly inject 100 xg of the test antibody in a 200 xl volume of phosphate-buffered saline into each mouse intraperitoneally (i.p.) (see Note 4). This amount can vary depending on the goals of the experiment and the sensitivity of the detection method. A minimum of five inbred mice, sex-matched and age-matched, at 8-16 weeks of age are recommended for each antibody to be tested. 

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