isotopically modified compound
isotopically modified compound
Any molecular entity in which the isotopic ratio of nuclides for at least one element deviates measurably from that occurring in nature. The term includes both <em>isotopically substituted</em> compounds (in which essentially all the molecules of the compound have only the indicated nuclide(s) at each designated position) and <em>isotopically labeled</em> compounds (a formal mixture of an isotopically unmodified compound with one or more analogous isotopically substituted compound(s).