releaser

in analytical flame spectroscopy
https://doi.org/10.1351/goldbook.R05288
A substance which reduces solute-volatilization interferences by forming a compound preferentially with the interferent, thus preventing the reaction of the analyte or interferent from entering a thermally stable compound.
Source:
Orange Book, 2nd ed., p. 172 (http://media.iupac.org/publications/analytical_compendium/)