Isotopic tracer

An isotopic tracer, or Isotopic marker, is used in chemistry and biochemistry to help understand chemical reactions and interactions. In this technique, one or more of the atoms of the molecule of interest is substituted for an atom of the same element, but of a different (often radioactive) isotope. Because the atom is of a different isotope, it will behave in exactly the same way chemically, but is different from other atoms of the same element that may be present in the molecule. This difference means that it can be seen as separate from the other atoms of the same element, but will not interfere with the reaction under investigation.

Techniques such as NMR typically use this type of technique to investigate the mechanisms of chemical reactions (basically trying to find out which starting atom ends up where after a reaction), because NMR cannot only detect isotopic differences, but gives and indication of the position of the atom.