Principle and Equation:

It is primarily based on the principle that the specific activity of a mixture of stable and radioisotope remains unchanged during chemical processing. Accurately known amount of specific activity of a radiotracer is added to an aliquot of analyte mixture containing the sought component. After addition, the resultant specific activity decreases. Chemical separation procedure is carried out where the component need not be recovered quantitatively but it must be in chemically pure form with well defined composition and in sufficient amount so that it can be weighed. Separation may be carried out by any of the following separation procedures:

• Solvent extraction of chelate complexes formed with specific reagent
• Precipitation using specific reagent
• Ion-exchange separation
• Electrodeposition or sorption process