1.1 This test covers the determination of total mercury in natural gas at concentrations down to 1 ng/m3. It includes separate procedures for both sampling and atomic absorption spectrophotometric determination of mercury. The procedure detects both inorganic and organic forms of mercury.1.2 The values stated in SI units are to be regarded as the standard.This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the r