specifically labelled

https://doi.org/10.1351/goldbook.S05793
An @[email protected] compound is designated as specifically labelled when a unique @[email protected] compound is formally added to the analogous @[email protected] compound. In such a case, both position(s) and number of each @[email protected] @[email protected] are defined.
Sources:
Blue Book, p. 514 [Terms] [Book]
PAC, 1981, 53, 1887. (Nomenclature of inorganic chemistry: II.1 - Isotopically modified compounds) on page 1891 [Terms] [Paper]