Method 1630: is for determination of methyl mercury (CH3Hg) in filtered and unfiltered water by distillation, aqueous ethylation, purge and trap, desorption, and cold vapor atomic fluorescence spectrometry (CVAFS). Method 1631: allows determination of mercury at a minimum level (ML) of 0.5 ng/L (parts-per-trillion; ppt), approximately 400 times lower than the level achieved by other mercury methods previously approved at 40 CFR Part 136. Method 245.1: This method describes the instrumental analytical procedures for mercury by cold vapor atomic absorption (CVAA). Method 7470 A: is a cold-vapor atomic absorption procedure approved for determining the concentration of mercury in mobility-procedure extracts, aqueous wastes, and ground waters. Method 7471 A: is approved for measuring total mercury (organic and inorganic) in soils, sediments, bottom deposits, and sludge-type materials. Method 7473: is designated for the determination of mercury in solids, aqueous samples, and digested solutions in both the laboratory and field environments.