Radioactivity

So far in this course you have learnt about several electroanalytical techniques and thermal methods of analysis whereas electrical properties and decomposition behaviour were measured in chemical systems and the resultant information was used to determine the concentration of an analyte. There is a whole a new branch of analytical methods known as radioanalytical methods that are based on the measurement of radiations emitted through radioactive substances within the analyte sample. Radioactivity is a unique phenomenon of spontaneous emission of radiations like as α,β, γ and others from the nucleus of an atom. The radionuclide emitting radiations might be already present in a sample, it might be added from outside or might be made radioactive through bombardment in a nuclear reactor. Radioactivity so present and measured is associated along with the concentration of element and used for quantitative analysis. Within essence radioanalytical methods could be employed for the analysis of minor, major, trace and ultra trace amounts in small size samples of various matrices along with greater accuracy and precision compared to other chemical and instrumental methods. Many methods have been hugely employed for the analysis of geological, biological (plant as well as human tissue), environmental, archaeological, industrial and forensic samples.

Since radioactivity is a nuclear phenomenon while other analytical methods are based on atomic or electronic properties, and radiations could be measured more efficiently, radio analytical methods are considered as more sensitive and yield better results. Therefore, these methods cannot be employed unless an appropriate radiotracer (radionuclide) or nuclear radiation measurement facilities involving a specially equipped laboratory are available.

Objectives

After studying this unit, you should be able to:

•  Distinguish among radioactive and stable or non-radioactive substances,
•  Define the simple laws of radioactivity, its units and correlation of mass and energy,
•  Distinguish between natural and artificial radioactivity,
•  Discuss decay laws and classification of nuclides,
•  Distinguish among radioactive and chemical equilibrium,
•  Define the nuclear reactions and the preparation of radioisotopes,
•  List several category of detectors used to measure radioactivity,
•  Explain the statistical behaviour of radioactivity, and
•  Discuss background correction within radioactivity measurements.