A substance in appreciable amount which, when associated with a trace of a specified substance, will carry the trace with it through a chemical or physical process.
See also:
support (of a catalyst)
PAC, 1982, 54, 1533. (Glossary of terms used in nuclear analytical chemistry (Provisional)) on page 1537 [Terms] [Paper]
See also:
PAC, 1976, 46, 71. (Manual of Symbols and Terminology for Physicochemical Quantities and Units - Appendix II. Definitions, Terminology and Symbols in Colloid and Surface Chemistry. Part II: Heterogeneous Catalysis) on page 79 [Terms] [Paper]