Methylmercury Species

Formation constants for MeHg -pyridine complexes decrease as the 

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Kato, T., Uehiro, T., Yasuhara, A. and Morita, M. (1992) Determination of methylmercury species by capillary column gas chromatography with axially viewed inductively coupled plasma atomic emission spectrometric detection./. Anal. At. Spectrom., 7, 15-18. 

With respect to distribution in the body, the methylmercury species behave more like mercury metal, Hg(0), than inorganic mercury(II), Hg2+. Like elemental mercury, methylmercury compounds traverse the blood-brain barrier and affect the central nervous system. However, the psychopatho-logical effects of methylmercury compounds (laughing, crying, impaired intellectual abilities) are different from those of elemental mercury (irritability, shyness). 

Describe one chemical and one biochemical means of synthesis of (CH3)2Hg. In what sense was the discovery of biosynthesis of methylmercury species an unpleasant surprise in environmental... 

Methylmercury species in sediment samples were speciated in a study by Hintelman et al. [89]. Detection limits were 1 pg (as Hg) in dry sediment samples. Organomercury compounds, along with organotin and organolead compounds, were also separated in another study by Prange and Jantzen [90]. Detection limits were three orders of magnitude lower than those reported previously in the literature. A quartz transfer line was used in this study. 

Methylmercury species (or other metal alkyls) may be produced at a rate fastother organisms. They may accumulate in organisms. Metals and metalloids that have been reported to be biomethylated in minor amounts include Ge, Sn, As, Se, Te, Pd, Pt, Au, Hg, T1 and probably Pb. Anthropogenic pollution by alkylated metal ions is certainly more significant than biomethylation. Methylated tin species have been observed in near-shore polluted waters. For data on As, Sb, Se, and Te see the recent review by Andreae (1986a). 

Methylmercury Species Because of the role of metal and metalloid alkyls in the toxicity of certain elements and the importance of such forms in the movement, bioaccumulation, and transformation of these elements, we briefly... 

Gardfeldt K, Sommar J, Stromberg D and Feng X (2001) Oxidation of atomic mercury by hydroxyl radicals and photoinduced decomposition of methylmercury species in the aqueous phase. Atmos Environ 35 3039-3047. 

For organometallic species, the analytical challenge involves quantitative extraction of the species from the solid phase without appreciable transformation to other forms. Various liquid extractants have been used such as methanolic hydrochloric acid (extraction of organotins). Strong alkali digests (KOFI or tetramethylammonium hydroxide) will dissolve most tissue without breakdown or transformation of arsenic species. As an alternative to liquid extraction, methylmercury species may be extracted from solids using steam distillation. Specific reaction conditions will affect the recovery of various species and rigorous validation of extraction procedures is therefore recommended. 

The method has been used for the determination of methylmercury species in fish and in drinking water. 

As speciation analysis slowly enters authority s regulations (already the case for chromium, organotin and methylmercury species) and routine analysis becomes required, precise and accurate quantitative species determination, as well as access to certified reference materials, is becoming imperative. 

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