Radioactive Tracers (use of radio–isotopes)
A radioactive isotope can be easily identified by its radioactivity. The radioactivity can, therefore act as a tag or label that allows studying the behaviour of the element or compounding which contains this isotope. An isotope added for this purpose is known as isotopic tracer. The radioactive tracer is also known as an isotopic tracer. The radioactive tracer is also known as an indicator because it indicates the reaction. Radioisotopes of moderate half-life periods are used for tracer work. The activity of radioisotopes can be detected by means of electroscope, the electrometer or the Geiger-Muller counter. Tracers have been used in the following fields,
(i) To diagnose many diseases: For example, Arsenic – 74 tracer is used to detect the presence of tumours, Sodium – 24 tracer is used to detect the presence of blood clots and Iodine –131 tracer is used to study the activity of the thyroid gland. It should be noted that the radioactive isotopes used in medicine have very short half-life periods.
(ii) In agriculture:The use of radioactive phosphorus in fertilizers has revealed how phosphorus is absorbed by plants. This study has led to an improvement in the preparation of fertilizers. is used to study the kinetics of photo synthesis.
(iii) In industry:Radioisotopes are used in industry to detect the leakage in underground oil pipelines, gas pipelines and water pipes. Radioactive carbon has been used as a tracer in studying mechanisms involved in many reactions of industrial importance such as alkylation, polymerization, catalytic synthesis etc.
(iv) In analysis: Several analytical procedures can be used employing radioisotopes as tracers.
(a) A small amount of radioactive isotope is mixed with the inactive substance and the activity is studied before and after adsorption. Fall in activity gives the amount of substance adsorbed.
(b) The solubility of lead sulphate in water may be estimated by mixing a known amount of radioactive lead with ordinary lead.
(c) Ion exchange process of separation is readily followed by measuring activity of successive fractions eluted from the column.
(d) By labelling oxygen of the water, mechanism of ester hydrolysis has been studied.
(e) The efficiency of analytical procedures may be measured by adding a known amount of radio-isotopes to the sample before analysis begins. After the completion, the activity is again determined. The comparison of activity tells about the efficiency of separation.
(3) Use of rays: rays are used for disinfecting food grains and for preserving food stuffs. Onions, potatoes, fruits and fish etc., when irradiated with rays, can be preserved for long periods. High yielding disease resistant varieties of wheat, rice, groundnut, jute etc., can be developed by the application of nuclear radiations. The rays radiations are used in the treatment of cancer. The radiations emitted by cobalt –60 can burn cancerous cells. The radiations are used to sterilize medical instruments like syringes, blood transfusion sets. etc. These radiations make the rubber and plastics objects heat resistant.