High‐yield synthesis of milligram amounts of isotopically enriched methylmercury (CH₃¹⁹⁸HgCl)

Isotopically enriched CH 3 198 HgCl (MeHgCl) has been synthesized from commercially available elemental 198 Hg (96% isotopic purity). Elemental mercury is first converted to HgCl 2 and subsequently reacted with methylcobalamin to produce MeHgCl. The resulting MeHgCl is isolated from the reaction mixture by successive extractions with toluene and dried over Na 2 SO 4 . The product structure was verified using gas chromatography–mass spectrometry (GC–MS) and the isotopic composition was determined by GC–inductively coupled plasma MS. The yield obtained is 99%. The proposed method allows preparation of milligram quantities of MeHgCl in one step, minimizing the cost of this synthesis.