Radioactive isotopes applications

Three common quantitative applications of radiochemical methods of analysis are considered in this section the direct analysis of radioactive isotopes by measuring their rate of disintegration, neutron activation, and the use of radioactive isotopes as tracers in isotope dilution. 

One example of a characterization application is the determination of a sample s age based on the kinetics for the decay of a radioactive isotope present in the sample. The most common example is carbon-14 dating, which is used to determine the age of natural organic materials. 

Many artificial (likely radioactive) isotopes can be created through nuclear reactions. Radioactive isotopes of iodine are used in medicine, while isotopes of plutonium are used in making atomic bombs. In many analytical applications, the ratio of occurrence of the isotopes is important. For example, it may be important to know the exact ratio of the abundances (relative amounts) of the isotopes 1, 2, and 3 in hydrogen. Such knowledge can be obtained through a mass spectrometric measurement of the isotope abundance ratio. 

The diffusion coefficients of cations in metal oxides are usually measured through the use of radioactive isotopes. Because of the friable nature of oxides it is exU emely difficult to use the sectioning technique employed for metal samples. The need for this can be avoided by the application of radioisotopes which emit radiation having a well established absorption law in matter. Isotopes which emit y radiation are very useful when the cation has a relatively high diffusion coefficient because of the long-range peneU ation of y rays. The absorption law is... 

C02-0008. The following radioactive isotopes have medical applications. Determine the number of... 

Until the advent of modem physical methods for surface studies and computer control of experiments, our knowledge of electrode processes was derived mostly from electrochemical measurements (Chapter 12). By clever use of these measurements, together with electrocapillary studies, it was possible to derive considerable information on processes in the inner Helmholtz plane. Other important tools were the use of radioactive isotopes to study adsorption processes and the derivation of mechanisms for hydrogen evolution from isotope separation factors. Early on, extensive use was made of optical microscopy and X-ray diffraction (XRD) in the study of electrocrystallization of metals. In the past 30 years enormous progress has been made in the development and application of new physical methods for study of electrode processes at the molecular and atomic level. 

Tracer materials are defined as any product included in the test substance that can be recovered analytically for determining the drift from the application. This may be the active ingredient in an actual tank mix, or it may be a material added to the tank mix for subsequent detection. The selection of an appropriate tracer for assessing deposition rates in the field is critical to the success of a field study. Tracer materials such as low-level active ingredient products, colored dyes, fluorescent dyes, metallic salts, rare earth elements and radioactive isotopes have been used with varying degrees of success in the field. An appropriate tracer should have the following characteristics ... 

The uranium and thorium decay-series contain radioactive isotopes of many elements (in particular, U, Th, Pa, Ra and Rn). The varied geochemical properties of these elements cause nuclides within the chain to be fractionated in different geological environments, while the varied half-lives of the nuclides allows investigation of processes occurring on time scales from days to 10 years. U-series measurements have therefore revolutionized the Earth Sciences by offering some of the only quantitative constraints on time scales applicable to the physical processes that take place on the Earth. 

There has been great interest in Cu(II) as a result of its role in biology, and the versatility in its available radioactive isotopes. The chemistry of bis(thiosemicarbazonato) metal complexes has received much interest over the last decade with particular interest in the copper complexes that are known blood perfusion tracers and also display hypoxic selectivity. Biomedical applications revolve around its redox chemistry (12,83-88,98-104). 

Even nowadays the application of radioactive isotopes is the most sensitive method for the analysis of biomolecules or their reaction products. Besides the low detection limits, the replacement of a naturally overbalancing stable isotope by its radioactive analogue does not interfere with the physical or chemical properties of the enzyme (with some exceptions for hydrogens). Figure 6 lists some frequently used radioactive isotopes and their half-life periods. 

Radioactive isotopes provide a very convenient way of monitoring the fate or metabolism of compounds that contain the isotopes. When used in this way, the isotope is described as a tracer and compounds into which the radioactive atom has been introduced are said to be labelled or tagged. The labelled molecules need only comprise a very small proportion of the total amount of the unlabelled radioactive substance because they act in the same way as the non-radioactive substance but can be detected very much more easily. The varied applications of tracers in biochemistry range from studies of metabolism in whole animals or isolated organs to sensitive quantitative analytical techniques, such as radioimmunoassay. Phosphorus-32 is used in work with nucleic acids, particularly in DNA sequencing and hybridization techniques. In these instances the isotope is used as a means of visualizing DNA separations by autoradiographic techniques. 

We have considered typical examples of lanthanide and actinide solvent extraction by chelate formation, involving complexes with citric acid and with TTA, to prove that the labelling of a stable element by one of its radioactive isotopes can help to produce accurate data on the stability constants for complex formation. The method is applicable to elements with radioisotopes having a half-life allowing an ion concentration of 10 6m or less. Other methods of partition such as radiopolarography and radio-coulometry also result in accurate thermodynamical data when the same procedure of labelling is used (29). 

Wolfe has presented an excellent description of the systematic application of stable and radioactive isotope tracers in determining the kinetics of leucine metabolism and other amino acids in living systems. 

Wolfe has presented an excellent description of the systematic application of stable and radioactive isotope tracers in determining the kinetics of substrate oxidation, carbon dioxide formation (including C02 breath tests), glucose oxidation, and fat oxidation in normal and diseased states. Quantification of the rate and extent of substrate oxidation can be achieved by using a specific or C-substrate which upon oxidation releases radioactive carbon dioxide. 

I.6.I. Radioactive Isotopes. The administration of isotopically labeled drugs is now commonplace in the experimental pharmacology of every new therapeutic agent (K18, M4) but has little or no clinical application. It often provides much of the initial information about the pharmacokinetics upon which subsequent clinical practice depends, but... 

The most important use of barium is as a scavenger in electronic tubes. The metal, often in powder form or as an alloy with aluminum, is employed to remove the last traces of gases from vacuum and television picture tubes. Alloys of barium have numerous applications. It is incorporated to lead alloy grids of acid batteries for better performance and added to molten steel and metals in deoxidizing alloys to lower the oxygen content. Thin films of barium are used as lubricant suitable at high temperatures on the rotors of anodes in vacuum X-ray tubes and on alloys used for spark plugs. A few radioactive isotopes of this element find applications in nuclear reactions and spectrometry. 

The metal has very little commercial use. In elemental form it is a laser source, a portable x-ray source, and as a dopant in garnets. When added to stainless steel, it improves grain refinement, strength, and other properties. Some other applications, particularly in oxides mixed with other rare earths, are as carbon rods for industrial hghting, in titanate insulated capacitors, and as additives to glass. The radioactive isotope ytterbium-169 is used in portable devices to examine defects in thin steel and aluminum. The metal and its compounds are used in fundamental research. 

KAL con s thermal units are applicable to treatment of hydrocarbon-contaminated soils but may not be used to remediate soils contaminated with polychlorinated biphenyls (PCBs), radioactive isotopes, or dioxins. Pesticides and herbicides can be treated by low-temperature thermal desorption, but special permitting is required and may be difficult to obtain. 

Studying these isotopes provides fertile ground for physicists and chemists to gain a better understanding of the properties and behavior of nuclei. This field of research also has important applications. For example, radioisotopes—radioactive isotopes—that emit certain particles are critical in some medical treatments such as radiation therapy, which is used to kill cancer cells, and positron emission tomography (PET), which is extremely useful in imaging parts of the body. 

Short reviews appeared on the various MS techniques for quantitation of stable isotopes and long-lived radioisotopes and the application of Mg stable isotopes as tracers in biology and medicine. The radioactive isotope Mg is not usually available and has a short half-life (21.3 h), hence its hmited usefulness as a tracer. The sensitivities and interference problems encountered in activation analysis for Al, Mg, Mo, P, Si and Zr were discussed. Much higher sensitivities were found for cyclotron-produced than for reactor-produced fast neutrons or 14 MeV neutrons. ... 

The most widely used radioactive isotopes in medical and industrial applications are cobalt 60 ( C), cesium 137 ( Cs), and iridium 192 ( lr). The half-life of is 5.3 years, that of Cs is 30 years, and the half-life of Ir is 74 days. When used for irradiation the isotope is generally in the form of a pellet size, 1.5 x 1.5 mm, loaded into a stainless steel capsule and sealed. Unlike electron beam or x-rays, gamma rays cannot be turned off. 

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