Radioisotopes of hydrogen, carbon, phosphorus, sulfur, and iodine have been used extensively to trace the path of biochemical reactions.
The proton are accelerated to high energy either in a cyclotron or a linear accelerator. The electrons produced have an average energy of 5.7 ke V.Because the emitted electrons have relatively low energy, the detection efficiency by scintillation counting is rather low.A radioactive tracer, radiotracer, or radioactive label, is a chemical compound in which one or more atoms have been replaced by a radionuclide so by virtue of its radioactive decay it can be used to explore the mechanism of chemical reactions by tracing the path that the radioisotope follows from reactants to products.Radiolabeling or radiotracing is thus the radioactive form of isotopic labeling.Therefore, the radioactive isotope can be present in low concentration and its presence detected by sensitive radiation detectors such as Geiger counters and scintillation counters.
George de Hevesy won the 1943 Nobel Prize for Chemistry "for his work on the use of isotopes as tracers in the study of chemical processes".Radiocarbon dating uses the naturally occurring carbon-14 isotope as an isotopic label. When the atomic nucleus of an isotope is unstable, compounds containing this isotope are radioactive. The principle behind the use of radioactive tracers is that an atom in a chemical compound is replaced by another atom, of the same chemical element.The substituting atom, however, is a radioactive isotope. The power of the technique is due to the fact that radioactive decay is much more energetic than chemical reactions.Substances which emits radiation is known as radioactive substances and this property of substances to emit radiation is called as radioactivity.C was mostly incorporated into the seawater from the atmosphere.It is continuously produced in the upper atmosphere of the earth so it occurs at a trace level in the environment.