Radioisotopes in analysis

The use of radioisotopes in analysis (see also Section 16.3) includes determinations of solubilities of sparingly soluble salts and vapour pressures of rather involatile substances, and investigations of solid solution formation and adsorption of precipitates. 

Lambie, D. a. Techniques for the Use of Radioisotopes in Analysis. Princeton, Toronto, New York, London D. van Nostrand Company, Inc. 1964. 

A mixture is being assayed by radioisotope dilution analysis. 10 mg of the labelled analyte (0.51 pCi mg-1) was added. 1.5 mg of the pure analyte was separated and its specific activity measured and found to be 0.042 pCi mg1. What was the amount of analyte in the original sample ... 

C4. Carr-Brion, E. G., The selection of exciting energy in radioisotope fluorescence analysis. Analyst London) 94, 177-181 (1969). 

These include the use of the beta emitter ti/2 = 432 yr) in smoke detectors, the sterilization of food using nuclear radiation, the use of gamma sources to estimate the thickness of metal pipes, and the use of radioisotopes in an analytical technique called neutron activation analysis (see Box 21.1). 

Other applications of photochemistry include the development of sensitive fluorescent chemosensors for analysis of dilute solutions of inorganic cations and anions and the study of the diffusion of individual molecules in solution at room temperature. Fluorescent compoimds have been used as replacements for radioisotopes in the analysis of biological compoimds and the study of biologically active compounds and living systems. Photochemical reactions also offer alternative probes for the characterization of the microenvironments in diverse solid and liquid media, including crystals, zeolites, alumina, silica and clay surfaces, semiconductor surfaces, liquid crystals and host-guest inclusion complexes, polymer films, monolayers and supported multilayers of surfactant molecules, mi-celles, and dendrimers. ... 

Antibodies have been used in analysis for over 60 years, and offer an unexpectedly wide range of techniques and applications. In some cases, the specific combination of an antibody with the corresponding antigen or hapten can be detected directly (e.g., by nephelometry), but more often such reactions are monitored by a characteristic label such as a radioisotope, fluorophore, etc. Since antibody reactions do not have a built-in amplification effect, these labels are frequently necessary to provide sufficient analytical sensitivity. Antibodies of different classes vary greatly in stability, but some are relatively robust proteins, and this contributes significantly to the range of methods available. 

Crossley, D. A., Jr., and D. E. Reichle. 1969. Analysis of transient behavior of radioisotopes in insect food chains. BioScience 19(4) 341-343. 

Dedek, V. W. 1975. Radioisotopes in pesticide research. Part VI. Review papers, general methods of analysis, insecticides. Isotopenpraxis ll(ll) 378-385 (in German). 

Perhaps the simplest of all applications of radioisotopes in chemical analysis is the use of a yield monitor . The element to be measured is labelled by the addition of a known amount of carrier-free radioisotope, in the same chemical form, to the sample. After chemical separation of the element, a comparison of the activity of the recovered material with the original activity gives the chemical yield. The method is used frequently to correct for the chemical losses of carrier separations in activation analysis and is, of course, a standard procedure for checking gravimetric analytical methods. Considerable amounts of time can be saved in certain gravimetric analyses if less than quantitative recovery is accepted and radiometric yield correction is used. 

Ba solutions using radioisotope dilution analysis. A discussion of the trend when quartz or TiO are used as adsorbents appears in Chem.. Ind. (1975)704. 

It is not necessary that there be two isotopes in both the sample and the spike. One isotope in the sample needs to be measured, but the spike can have one isotope of the same element that has been produced artificially. The latter is often a long-lived radioisotope. For example, and are radioactive and all occur naturally. The radioactive isotope does not occur naturally but is made artificially by irradiation of Th with neutrons. Since it is commercially available, this last isotope is often used as a spike for isotope-dilution analysis of natural uranium materials by comparison with the most abundant isotope ( U). 

The neutrons in a research reactor can be used for many types of scientific studies, including basic physics, radiological effects, fundamental biology, analysis of trace elements, material damage, and treatment of disease. Neutrons can also be dedicated to the production of nuclear weapons materials such as plutonium-239 from uranium-238 and tritium, H, from lithium-6. Alternatively, neutrons can be used to produce radioisotopes for medical diagnosis and treatment, for gamma irradiation sources, or for heat energy sources in space. 

A large number of radiometric techniques have been developed for Pu analysis on tracer, biochemical, and environmental samples (119,120). In general the a-particles of most Pu isotopes are detected by gas-proportional, surface-barrier, or scintillation detectors. When the level of Pu is lower than 10 g/g sample, radiometric techniques must be enhanced by preliminary extraction of the Pu to concentrate the Pu and separate it from other radioisotopes (121,122). Alternatively, fission—fragment track detection can detect Pu at a level of 10 g/g sample or better (123). Chemical concentration of Pu from urine, neutron irradiation in a research reactor, followed by fission track detection, can achieve a sensitivity for Pu of better than 1 mBq/L (4 X 10 g/g sample) (124). 

Radiochemical tracers, compounds labeled with radioisotopes (qv), have become one of the most powerful tools for detection and analysis in research, and to a limited extent in clinical diagnosis (see Medical IMAGING TECHNOLOGY). A molecule or chemical is labeled using a radioisotope either by substituting a radioactive atom for a corresponding stable atom in the compound, such as substituting for H, for or for P, and for for... 

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