Determination of methylmercury in sediment and cyanobacteria samples : method validation and application to methylation investigation.
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2018
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The aim of this work was to validate two methods for methylmercury (CH3Hg+) determination in sediments
and cyanobacteria and their application to the Hg methylation study of planktonic organisms in water from
a contaminated site in Brazil. Analytical methods for the determination of CH3Hg+ include many steps, and
the necessity of adaptation to different matrices is very common and not always easy. In addition, these
adaptations require new optimization and validation, which are found in a few articles using the matrix
sediments but in none with planktonic organisms. The methods presented here were based on the
extraction of CH3Hg+ from these matrices, derivatization, trapping, thermal desorption, GC separation,
pyrolysis and detection by AFS (GC-pyro-AFS). The results showed good linearity (0.994) in the range of
0 to 400 pg CH3Hg+ with a repeatability of 3%, an intermediate precision of 8%, a recovery in spiked
sample tests in the range of 93 to 129%, and detection limits of 0.04 mg kg 1 for sediments and 1.3 mg
kg 1 for cyanobacteria. Certified reference materials showed good recoveries. The method for the
cyanobacteria matrix was used for the Hg2+ methylation assay with cultures of cyanobacteria and
microalgae isolated from water samples collected in an ancient Hg-contaminated gold mining area in
Brazil. The production of CH3Hg+ was detected only in the culture of the microalga Stichococcus
species (0.23% of total Hg), indicating its participation in the biotransformation of Hg. The methods can
be used as important tools in routine analysis and/or studies of the biogeochemical cycle of Hg.
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MENDES, L. A. et al. Determination of methylmercury in sediment and cyanobacteria samples : method validation and application to methylation investigation. Analytical Methods, v. 10, p. 91-100, 2018. Disponível em: <https://pubs.rsc.org/en/content/articlelanding/2018/ay/c7ay02415k#!divAbstract>. Acesso em: 08 fev. 2019.