Abstract
Electroanalytical (voltammetric, polarographic, chronoamperometric) methods on an Hg electrode were applied for studying of different sulfur compounds in model and natural water systems (anoxic lakes, waste water, rain precipitation, sea-aerosols). In all investigated samples typical HgS reduction voltammetric peak, characteristic for many different reduced sulfur species (RSS: sulfide, elemental sulfur, polysulfide, labile metal sulfide and organosulfur species) was recorded at about -0.6 V vs. Ag/AgCl reference electrode. In addition, in anoxic waters which are enriched with sulfide and iron species, voltammetric peaks characteristic for the presence of free Fe(II) and FeS nanoparticles (NPs) were recorded at -1.4 V and around -0.45 V, respectively. Depending on the used electroanalytical method and experimental conditions (varying deposition potential, varying time of oxidative and/or reductive accumulation, sample pretreatment i.e. acidification followed by purging) it is possible to distinguish between different sulfur species. This work clearly shows a large potential of the electrochemistry as a powerful analytical technique for screening water quality regarding presence of different reduced sulfur species and their speciation between dissolved and colloidal/nanoparticle phases.
Highlights
Electrochemical measurements are along with Inductively Coupled Plasma Mass Spectrometry (ICP-metal sulfide (MS)), the most used but challenging approaches in essential elements analysis and speciation in complex natural samples
EU water quality guidelines are searching for new innovative methods for water quality monitoring, and electrochemistry in comparison with Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and/or Inductively coupled plasma/optical emission spectrometry (ICP-OES) and diffusive gradients in thin-films (DGT) approach was found as preferable choice
This peak usually is taken as a measure for “free” and labile sulfur species content (H2S/HS-/S2, S0, SnS2, thiols, labile metal sulfide complexes and nanoparticles)
Summary
Electrochemical measurements are along with ICP-MS, the most used but challenging approaches in essential elements analysis and speciation in complex natural samples. Keywords Voltammetry; chronoamperometry; speciation; reduced sulfur species; metal sulfide nanoparticles; Hg electrode; anoxic water samples
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