Radioactive isotopes 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. 

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... 

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. 

Peters B. (1959) Cosmic-ray produced radioactive isotopes as tracers for studying large-scale atmospheric circulation. J. Atmos. Terr. Phys. 13, 351-370. 

A major advantage of using radioactive isotopes as tracers is that they are easy to detect. Their presence even in very small amounts can be detected by photographic techniques or by devices known as counters. Figure 23.19 is a diagram of a Geiger counter, an instrument widely used in scientific work and medical laboratories to detect radiation. 

In 1911 Ernest Rutherford asked a student, George de Hevesy, to separate a lead impurity from a decay product of uranium, radium-D. De Hevesy did not succeed in this task (we now know that radium-D is the radioactive isotope °Pb), but this failure gave rise to the idea of using radioactive isotopes as tracers of chemical processes. With Friedrich Paneth in Vieima in 1913, de Hevesy used °Pb to measure the solubifity of lead salts—the first appfication of an isotopic tracer technique. De Hevesy went... 

Very recently a few experiments (48) have been carried out which point the way to a new technique that can be used in studjdng ordinary catalytic reactions, and in studying reactions by use of radioactive isotopes as tracers. This technique has been referred to as a microcatalytic-chromatographic technique. 

A valuable technique for research is the use of both radioactive and non-radioactive isotopes as tracers. By the use of these isotopes an element can be observed in the presence of large quantities of the same element. 

In an industrial context, we often use radioactive isotopes as tracers. These do break down, but the breakdown process is well known, defined, and easy to take into account. The isotopes can be introduced into the system in several ways, which makes it significantly easier to attain the correspondence mentioned above. Keeping in mind the radiation risks, we generally choose isotopes with a relatively short half-life. Species other than radioactive ones with other measurable properties can also be utilized as tracers. 

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