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Validation of a simplified field-adapted procedure for routine determinations of methyl mercury at trace levels in natural water samples using species-specific isotope dilution mass spectrometry
Umeå University, Faculty of Science and Technology, Chemistry.
Umeå University, Faculty of Science and Technology, Chemistry.
2004 (English)In: Analytical and Bioanalytical Chemistry, ISSN 1618-2642 (Print) 1618-2650 (Online), Vol. 380, no 7-8, 871-5 p.Article in journal (Refereed) Published
Abstract [en]

A field-adapted procedure based on species-specific isotope dilution (SSID) methodology for trace-level determinations of methyl mercury (CH3Hg+) in mire, fresh and sea water samples was developed, validated and applied in a field study. In the field study, mire water samples were filtered, standardised volumetrically with isotopically enriched CH3200Hg+, and frozen on dry ice. The samples were derivatised in the laboratory without further pre-treatment using sodium tetraethyl borate (NaB(C2H5)4) and the ethylated methyl mercury was purge-trapped on Tenax columns. The analyte was thermo-desorbed onto a GC-ICP-MS system for analysis. Investigations preceding field application of the method showed that when using SSID, for all tested matrices, identical results were obtained between samples that were freeze-preserved or analysed unpreserved. For DOC-rich samples (mire water) additional experiments showed no difference in CH3Hg+ concentration between samples that were derivatised without pre-treatment or after liquid extraction. Extractions of samples for matrix–analyte separation prior to derivatisation are therefore not necessary. No formation of CH3Hg+ was observed during sample storage and treatment when spiking samples with 198Hg2+. Total uncertainty budgets for the field application of the method showed that for analyte concentrations higher than 1.5 pg g–1 (as Hg) the relative expanded uncertainty (REU) was approximately 5% and dominated by the uncertainty in the isotope standard concentration. Below 0.5 pg g–1 (as Hg), the REU was >10% and dominated by variations in the field blank. The uncertainty of the method is sufficiently low to accurately determine CH3Hg+ concentrations at trace levels. The detection limit was determined to be 4 fg g–1 (as Hg) based on replicate analyses of laboratory blanks. The described procedure is reliable, considerably faster and simplified compared to non-SSID methods and thereby very suitable for routine applications of CH3Hg+ speciation analysis in a wide range of water samples.

Place, publisher, year, edition, pages
2004. Vol. 380, no 7-8, 871-5 p.
Keyword [en]
Methyl mercury, Speciation, SSID, Species-specific isotope dilution mass spectrometry
URN: urn:nbn:se:umu:diva-14327DOI: doi:10.1007/s00216-004-2863-zOAI: diva2:153998
Available from: 2007-05-28 Created: 2007-05-28 Last updated: 2011-01-12Bibliographically approved
In thesis
1. Mercury species transformations in marine and biological systems studied by isotope dilution mass spectrometry and stable isotope tracers
Open this publication in new window or tab >>Mercury species transformations in marine and biological systems studied by isotope dilution mass spectrometry and stable isotope tracers
2005 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis focuses on the implementation of species-specific isotope dilution (SSID) methodology and stable isotope tracers to determine mercury species occurrence and transformation processes in-situ and during sample treatment. Isotope enriched tracers of methyl-, ethyl- and inorganic mercury were synthesised and applied in different combinations to marine and biological samples. Experimental results were obtained using gas chromatography-inductively coupled plasma-mass spectrometry (GC-ICP-MS).

Mercury methylation and methylmercury demethylation processes in surface sediments were studied in the brackish Öre River estuary, Bothnian Bay. Uni- and multivariate data evaluation identified the organic material content and mercury methylation potential in the sediments as important factors controlling incipient methylmercury levels. Mercury species distribution in mice treated with the pharmaceutical preservative Thimerosal (ethylmercurithiosalicylate) was studied. The ethylmercury moiety of Thimerosal was observed to rapidly convert to inorganic mercury in the mice during the treatment period as well as during sample treatment, hence necessitating SSID methodology for accurate ethylmercury determinations in biological samples.

To facilitate the introduction of SSID as a routine quantitative method in mercury speciation, a methylmercury isotopic certified reference material (ICRM) was produced. Prior to certification, the stability of the material was examined in conventional and isochronous stability studies spanning 12 months, which permitted uncertainty estimation of the methylmercury amount content for two years of shelf-life.

Finally, a field-adapted SSID method for methylmercury determinations in natural water samples was developed. The proposed analytical protocol significantly simplified sample storage- and treatment procedures without sacrifices in analytical accuracy.

Place, publisher, year, edition, pages
Umeå: Kemi, 2005. 38 p.
Analytical chemistry, Mercury, methylmercury, ethylmercury, Thimerosal, speciation, methylation, demethylation, brackish water sediment, natural waters, GC-ICP-MS, species-specific isotope dilution, isotope enriched tracers, Analytisk kemi
National Category
Analytical Chemistry
Research subject
Analytical Chemistry
urn:nbn:se:umu:diva-467 (URN)91-7305-838-6 (ISBN)
Public defence
2005-04-01, KB3A9, Kemiskt Biologiskt Centrum (KBC), Umeå Universitet 90187, Umeå, 10:00 (English)
Available from: 2005-03-09 Created: 2005-03-09 Last updated: 2009-05-25Bibliographically approved

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