Isotope as tracers

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. 

G. Hevesy (Stockholm) use of isotopes as tracers in the study of chemical processes. 

Some aspects of the biochemistry of metabolic processes affecting nutrients appear to have significant consequences for the expected behavior of stable carbon isotopes as tracers of diet. Specifically, we have seen that the simple model of a total scrambling of carbon atoms during endogenous biosynthesis is inconsistent with the expected pathways of some nutrients, whereas other isotopic records in ancient human tissues can be adequately accounted for by this model. 

The use of natural abundance variations in stable isotopes as tracers relies on the fractionations that occur during chemical, physical and biological processes (Ambrose 1993). Differences in fractionation during these processes lead to distinct isotopic signatures for biological materials, such as in foods exploited by humans in antiquity. 

The concept of the atom as the smallest particle of matter (from the Greek word for indivisible) was promulgated by John Dalton about 1803. Within about a century and a quarter of scientific investigation which will be briefly described in this chapter, this concept yielded the idea of the periodic table and the understanding of the periodic table including the nuclear atom, the concept of isotopes, and the discovery of the majority of the isotopes which are used in the studies of the isotope effects. It is appropriate to point out that this book deals with the study of the effect of isotopic substitution on the physical and chemical properties of molecular (or atomic) systems. The book does not deal with the use of isotopes as tracers, a use which usually depends on the assumption that isotope effects are small and can be ignored in tracer studies. 

Stable Isotopes as Tracers in Biological, Agricultural, Nutritional and Medical Research... 

The title indicates the scope of the text. The term isotope effects is used rather than applications of isotopes to indicate clearly that it deals with differences in the properties of isotopically substituted molecules, for example differences in the chemical and physical properties of water and the heavy waters (H2O, HDO, D2O, HTO, etc.). Thus H20, HDO and D2O have different thermodynamic properties. Also reactions in solvent mixtures of light and heavy water proceed at different rates than they do in pure H2O. On the other hand, the differences are not large and consequently, to the extent the difference in properties can be ignored, HDO or HTO can be used as tracers for H2O. An important point, however, is that this book does not deal with isotopes as tracers in spite of the widespread importance of tracer studies, particularly in the bio and medical sciences. Also the title specifically does not mention physics which would necessarily have been included if the term Physical Sciences had been used. Thus the text does not deal with differences in the nuclear properties of isotopic atoms. Such differences are in the realm of nuclear physics and will not be discussed. 

Cary EE, Wood RJ, Schwartz R (1990) Stable Mg isotopes as tracers using ICP-MS. J Micronutrient Anal 8(l) 13-22... 

Isotopes as Tracers of the Source and Fate of Marine Organic Compounds... 

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. ... 

Peck, G. A., Szymcak, R. and Jeffree, R. A., in IAPSO-IAEA Workshop WS01 Isotopes as Tracers in Marine Environmental Studies. Monaco (2006). 

The principal disadvantage to the use of radioactive isotopes as tracers 0 is the hazard involved in handling radioactive materials. To reduce this hazard to a minimum, Shell has de- vised a procedure for injecting the tracer by remote control. 4... 

HEVESY, GEORG de (1885-1966). A Hungarian chemist who won the Nobel prize in chemistry in 1943, for his work on (he use of isotopes as tracers in the study of chemical processes. He discovered the element hafnium in 192.7. One of his interesting projects involved the calculation of ihc percentages of chemical elements in the universe. He also was involved in research using radioactive lead and phosphorus traces. His work included the separation of isotopes by physical means. His Ph D was granted ai Freiburg in 1908. 

Carbon Isotopes as Tracers of Biogenic and Fossil-Fuel-Derived Carbon Transport in the Atmosphere... 

Peterson, B.J., Howarth, R.W., and Garritt, R.H. (1986) Sulfur and carbon isotopes as tracers of salt-marsh organic matter flow. Ecology 67, 865-874. 

Hansmann, W., and Koppel, V. (2000). Lead isotopes as tracers of pollutants in soils. Chem. Geol. 171, 123-144. 

Tritium, Dissolved Ions, and Stable Isotopes as Tracers for Rapid Discharge Along Fractures ... 

The aim of this study was to further explore the potential and limitations of using stable iron isotopes as tracers and EI-MS in absorption studies. Procedures were developed for preparing iron acetylacetonate from both blood and fecal samples for mass spectrometric analysis. The precision and accuracy of ion abundance measurements were evaluated. In vivo use of stable iron isotope tracers was tested with a human study in which 54pe and 57pe were given orally and absorption was estimated with the fecal monitoring and hemoglobin incorporation methods. 

Peterson, B. J. (1999). Stable isotopes as tracers of organic matter input and transfer in benthic food webs A review. Acta Oecologica 20(4), 479-487. 

Nuclear chemistry (radiochemistry) has now become a large and very important branch of science. Over four hundred radioactive isotopes have been made in the laboratory, whereas only about three hundred stable isotopes have been detected in nature. Three elements —technetium (43), astatine (85), and promethium (61), as well as some trans-uranium elements, seem not to occur in nature, and are available only as products of artificial transmutation. The use of radioactive isotopes as tracers has become a valuable technique in scientific and medical research. The controlled release of nuclear energy promises to lead us into a new world, in which the achievement of man is no longer limited by the supply of energy available to him. 

An extremely valuable technique for research that has been developed in recent years is the use of both radioactive and nonradioactive isotopes as. tracers. By the use of these isotopes an element can be observed in the presence of large quantities of the same element. For example, one of the earliest uses of tracers was the experimental determination of the rate at which lead atoms move around through a crystalline sample of the metal lead. This phenomenon is called self-diffusion. If some radioactive lead is placed as a surface layer on a sheet of lead, and the sample is allowed to stand for a while, it can then be cut up into thin sections parallel to the original surface layer, and the radioactivity present in each section can be measured. The presence of radioactivity in layers other than the original surface layer shows that lead atoms from the surface layer have diffused through the metal. 

In the discussion of chemical equilibrium in Chapter 19 it was pointed out that a system in chemical equilibrium is not static, btit that instead chemical reactions may be proceeding in the forward direction and the reverse direction at equal rates, so that the amounts of different substances present remain constant. At first thought it would seem to be impossible to determine experimentally the rates at, which different chemical reactions are proceeding at equilibrium. It was mentioned in Chapter 19 that it has now been found possible to make experiments of this sort, however, with the use of isotopes as tracers. 

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