Severe changes in speciation information were observed during volatile species generation (VSG) due to de-alkylation of generated Hg species as proven by cryogenic trapping with inductively coupled plasma mass spectrometric detection (CT-ICP-MS). Methyl mercury hydride is de-methylated to Hg0 by 45% and 6%, respectively, in HCl and TRIS buffer media. Ethylmercury hydride is de-ethylated to Hg0 by 71% and 28%, respectively in HCl and TRIS buffer media. Only Hg0 as a volatile product was observed when generating from phenylmercury regardless of the reaction medium employed. These findings limit significantly the application of VSG to Hg speciation analysis, especially the possibility of generation of alkyl-substituted mercury hydrides for cryogenic trapping/separation or gas chromatography. On the contrary, post-column VSG of Hg species prior to spectrometric detection can be employed to enhance sensitivity without any negative effects on accuracy and precision of the results.
Keywords: Cryogenic trapping; De-alkylation; Hydride generation; Mechanistic study; Mercury; Speciation analysis.
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