A method and system are provided for creating a mercury halide standard, and for using that standard to test a mercury analyzer system. Gaseous elemental mercury of a known concentration from a gas cylinder and a halogen donor are fed to a reaction chamber where they react to form mercury halide. The mercury halide is fed to a mercury analyzer system where it is converted to reform gaseous elemental mercury which is then measured by a mercury analyzer. By comparing either the amount of elemental mercury supplied to the reaction chamber or the amount of mercury halide formed in the reaction chamber with the amount of elemental mercury converted from the mercury halide, the ability of the mercury analyzer system to convert mercury halide to gaseous elemental mercury can be evaluated.