ABSTRACT
The basic unit of radioactivity is the number of decay events per unit of time. This is expressed as disintegrations per second (dps) or disintegrations per minute (dpm). Other units of radioactivity are derived from the dps or dpm value. The specific activity of a radiolabeled compound is expressed in units of radioactivity per mole or weight of compound. Radioactivity therefore, offers a universal quantification method with standard curves and authentic chemical standards being unnecessary. The energy from emitted radioactivity can lead to the formation of highly reactive radicals, which then react with the test chemical. Because the use of radiotracers offers a universal quantification method, the limits of detection (LOD) can be calculated on a generic basis, irrespective of the chemical structure of the analyte. For biological samples, the LOD is expressed as an amount of drug per weight of sample. Isotopes that undergo nuclear decay and emit radioactivity are known as radioisotopes.
