Mercury speciation in biological marine materials by gas chromatography with atomic emission detection

A method was developed for the quantification of alkylmercury species in complex matrix, biological marine materials. The extraction procedure consists of sample acidification followed by extraction into toluene. Copper powder is added to the extraction vessel to eliminate sulfur interferences. High molecular weight pigments and lipid materials are removed from the sample extracts by preparative gel permeation chromatography prior to gas chromatographic analysis. Separation of the extracted alkylmercury bromides is achieved with a poly(14%-cyanopropylphenyl-86%-dimethylsiloxane) stationary phase capillary column. The organomercury species are detected with a commercial microwave-induced plasma atomic emission detector using atomic emission detector (GC-AED) using the mercury 253.652 nm emission line. Chromatographic and detection parameters were optimized for the quantification of alkylmercury halides. The method was validated with four certified biological tissue reference materials. The methylmercury contents of 19 reference materials of various matrix compositions were determined, including 9 marine standard reference materials from the National Institute of Standards and Technology. Multiple subsamples of each material were analyzed to demonstrate method reproducibility and evaluate material homogeneity. Relative standard deviations below 10% were found for most materials. Trends in methylmercury content and percentage of methylmercury with respect to total mercury were observed for species at differing levels in the marine food web. Agreement among results obtained using the GC-AED method and those obtained using cold vapor atomic absorbtion spectrometry and gas chromatography with atomic fluorescence detection was observed. Beluga whale livers from the Alaskan Marine Mammal Tissue Archival Project were analyzed for methylmercury content. Methylmercury levels increased with whale length, but not with approximate age. Trends were observed in methylmercury content and percentage of methylmercury with respect to total mercury for different whale populations. No relationship between sex and methylmercury content was observed