Asetof20commerciallyavailablenanodiamondsamplesofeightmanufacturersofvariouscountries,whichare mostfrequentlyusedinbasicandappliedstudies,wasanalyzedfortheconcentrationofHg.Conditionsofmercurydeterminationbyflamelessatomicabsorptionspectroscopywiththermalsampledecomposition(pyrolysis) at800°Cwereproposedandconfirmedbywavelength-dispersiveX-rayfluorescenceanalysis.Itwasfoundthat nanodiamondshaveasignificantdiversityofamountsofmercury,from20μg/kgtohigherthan0.7g/kg.Thus, theneedtocontrolHgimpurityinnanodiamonds,especiallyforbiologicalandmedicalresearch,wasdemonstrated.Theprecisionofflamelesspyrolysisatomicabsorptiondeterminationofmercuryinnanodiamondsis discussed. ©