SOP determination of MeHg in water with no isotope dilution

Standard Operating Procedure for the Determination of Methyl Mercury in Water and Suspended Solids by Aqueous Phase Ethylation, Followed by Gas Chromatography Separation with Cold Vapor Atomic Fluorescence Detection.

Water samples are distilled to remove potential interferences. The pH of the distillate is adjusted to 4.9 using acetate buffer. The distillate is then ethylated using sodium tetraethyl borate (NaTEB) and allowed to react for 15 minutes. Following reaction with NaTEB the distillate is purged with grade 5 nitrogen gas (N2) for 20 minutes and the ethylated mercury species are collected on a Carbotrap. The ethylated mercury species are thermally desorbed from the Carbotrap, separated using a gas chromatography (GC) column, reduced using a pyrolytic column, and detected using a cold vapor atomic fluorescence spectrometry (CVAFS).

Mercury Research Laboratory, 2010, revision 4