DETERMINATION OF METHYLMERCURY IN BIOLOGICAL CERTIFIED REFERENCE MATERIALS

Various isolation techniques (ion - exchange, extraction, volatilization, distillation) were used to separate organic Hg, followed by cold vapor atomic absorption spectrophotometry (CV AAS) for determination of total organic Hg, and/or gas chromatography (electron capture detector) for determination of MeHg and EtHg if present. Some currently available CRMs with certified total Hg values, including NBS Oyster Tissue 1566, NBS Horse Kidney H-9, IAEA Fish Flesh Homogenate MA-A-2/TM, IAEA Fish Tissue Lyophilized MA-B-3/TM, IAEA Mussel Tissue MA-M-2/TM, IAEA Copepod Homogenate MA-A-1/TM, IAEA Shrimp Tissue Homogenate MA(S)-MEDPOL-86/TM, NIES No. 5 Human Hair, and NIES No. 9 Sargasso were investigated. CRMs from the National Research Council of Canada (TORT-1, DORM-1, DOLT-1) which have recently been certified for MeHg, were also analyzed. Results obtained by different approaches show good agreement. The advantage of GC which permits different organic compounds to be determined was demonstrated in the case of some IAEA CRMs where both MeHg and EtHg was found; indirect CV AAS gives the results for total organic Hg. Therefore it can be suggested that various currently available CRMs for total Hg can also be used for establishment of recommended values for MeHg (and EtHg if present) and organic Hg. However, additional intercalibration exercises or data from other laboratories are necessary to obtain a consensus.