The amount of suitable PAC isotopes required for a measurement is between about 10 to 1000 billion atoms (10-10). The right amount depends on the particular properties of the isotope. 10 billion atoms are a very small amount of substance. For comparison, one mol contains about 6.22x10 particles. 10 atoms in one cubic centimeter of beryllium give a concentration of about 8 nmol/L (nanomol=10 mol). The radioactive samples each have an activity of 0.1-5 MBq, which is in the order of the exemption limit for the respective isotope.
How the PAC isotopes are brought into the sample to be examined is up to the experimenter and the technical possibilities. The following methods are usual: