Assignation of inorganic mercury and methylmercury mass fractions in a soil matrix certified reference material by two analytical methodologies based on species-specific isotope dilution mass spectrometry and chromatographic separation

Assignment of inorganic mercury and methyl mercury mass fractions at an ultratrace level in soil certified reference material EnvCRM 03 with a complex matrix composition was undertaken. Inorganic mercury and methyl mercury contents by species-specific isotope dilution inductively coupled plasma mass spectrometry with on-line high-performance liquid chromatography or with classical off-line chromatography were established. Different extraction protocols: sequential extraction ((1) H2SO4/KBr/CuSO4; (2) dichloromethane; (3) Na2S2O3) or one-step extraction (diluted HCl) in solid-liquid systems were verified. Sequential extraction allowed quantification and separation of inorganic mercury and methyl mercury on HPLC column in one chromatographic run and were found to be (316 +/- 10) mu g/kg (U = 3.2%, k = 2) and (0.53 +/- 0.02) mu g/kg (U = 3.8%, k = 2), respectively. Extraction by diluted HCl and application of classical off-line chromatography led to the separation of methyl mercury from predominant inorganic mercury form and was found to be (0.54 +/- 0.03) mu g/kg (U = 5.4%, k = 2). To the best-obtained literature knowledge, there was no available soil material aimed for speciation analysis of inorganic mercury and methyl mercury so far. Both developed analytical methodologies were found to be equally sensitive and could be successfully applied for mercury species determination in samples with the complex matrix.