US EPA has posted two draft mercury (Hg) reference methods:
Draft Method 30A—Determination of Total Vapor Phase Mercury Emissions from Stationary Sources (Instrumental Analyzer Procedure) (pdf, 49pp., 1221kB) and- Draft Method 30B—Determination of Total Vapor Phase Mercury Emissions from Coal-Fired Combustion Sources Using Carbon Sorbent Traps (pdf, 37pp., 1036kB).
The draft versions are for information purposes only. US EPA is considering approving them later this year.