Methylmercury determination in sub-ppb level by cold vapor analysis: facts, mechanisms and optimization

Abstract

Recent reports, according to international organizations, on the highly toxic presence of methyl-mercury (MeHg) in the environment, classify it among the major/priority environmental pollutants. Understanding the need to find new, but also safe, sources of usable water and to monitor the current ones, regarding water quality, the aim of this study is to investigate the determination of MeHg by the application of cold vapor analysis, providing useful facts, considering the method's optimization, in order to be adopted also from other researchers. During the cold vapor analysis organic or/and inorganic mercury atomization takes place chemically by the addition of an appropriate reducing agent. The most known relevant agent is SnCl2, which however is able to reduce only the inorganic Hg. Instead, NaBH4 is capable to reduce both Hg forms, but a pre-treatment of the sample is required, namely the addition of KMnO4. Therefore, in this work, the reagents' concentration was studied, and their role was clarified in every step of the proposed method analysis. According to the results, the addition of at least 0.0005% w/v KMnO4 and 0.005% w/v NaBH4 is needed in the aquatic sample for a reliable MeHg measurement. In fact, the formed MnO2, that produced by the reduction of residual KMnO4 from NaBH4, was found to catalyze the MeHg atomization reaction.

Thiol-Functionalization Carbonaceous Adsorbents for the Removal of Methyl-Mercury from Water in the ppb Levels

“…The residual MeHg concentrations in the filtrate were determined by a Bacharach Coleman-Model 50B cold vapor mercury analyzer system (Figure S1), following a method that was optimized in previously published research [14]. In brief, the aquatic samples were pre-treated by adding 0.005% w/v KMnO 4 and 0.05% w/v NaBH 4 ; the latter was needed for the reliable MeHg measurement as a reducing agent for the atomization of mercury.…”