Protocol for Quantitative Detection of Elemental Sulfur and Polysulfide Zero‐Valent Sulfur Distribution in Natural Aquatic Samples

Abstract

A HPLC‐based protocol has been developed for the determination of zero‐valent sulfur (ZVS) speciation, including solid, colloidal elemental sulfur and individual inorganic polysulfides in natural aquatic samples. The protocol includes four experimental procedures: (1) determination of polysulfide speciation by rapid single‐phase derivatisation with methyl trifluoromethanesulfonate; (2) determination of the sum of polysulfide and colloidal sulfur by reaction with hydrogen cyanide (cyanolysis); (3) determination of total zero‐valent sulfur by treatment with zinc chloride followed by extraction with chloroform; and (4) chromatographic determination of polythionates without sample pre‐treatment. With proper sampling and preservation techniques in the field or on board ship, this combination of methods allowed the quantitative determination of: (a) individual polysulfide species; (b) dispersed colloidal sulfur; (c) dispersed solid elemental sulfur; and (d) tetra‐, penta‐ and hexathionates. With minor modification, the method could be expanded to include other polythionates. Sixteen various wet chemical and liquid chromatographic methods were tested on nine synthetic reference samples (including solid elemental sulfur, colloidal elemental sulfur, inorganic polysulfides and polythionates) to establish the optimal protocol. The protocol was further evaluated by analysing the zero‐valent sulfur content in microbially‐produced sulfur and in sulfur from two natural samples of sulfide‐rich seawater from tidal flats pools of the Wadden Sea (Germany).

Improved cyanolysis protocol for detection of zero‐valent sulfur in natural aquatic systems

“…It provides the major improvement of the method performance compared with cyanolysis with ion-chromatography finishing (detection limit 2 µmol L -1 , as reported by Kamyshny et al [2008]), photometric finishing (detection limit 10 µmol L -1 , as reported by Kamyshny et al [in press ]), and cyanolysis in organic solvents (150 µmol kg -1 sediment, as reported by Troelsen and Jørgensen [1982] and 100 nmol L -1 , as reported by Jacobs and Emerson [1982]). …”

“…The final pH value of the colloidal ZVS was 2.3. At this pH value, more than 99.97% of ZVS was in the form of colloidal sulfur and only 0.027% in the form of polysulfides (calculated from the set of thermodynamic constants from Kamyshny et al [2007]). Polysulfide ZVS standards and colloidal ZVS standards were used for not more than 4 h after preparation.…”

“…Final composition and concentration of the polysulfide solution Stock 1 can be described as 21.5 mmol L -1 Na 2 S 2.86 . At standard conditions and infinite dilution, the solution of such composition is undersaturated with respect to sulfur at pH > 9.0 (calculated from the set of thermodynamic constants from Kamyshny et al [2007]). …”

“…Solubility of elemental solid S 8 in pure water is low (19 ± 6 nmol L -1 S 8 ) (Boulegue 1978). Polysulfides and elemental sulfur are produced by biological and abiotic hydrogen sulfide oxidation in various natural systems (Zopfi et al 2004 and references therein; Kamyshny et al 2008). Sulfur-oxidizing bacteria can produce and store sulfur intra-or extra-cellularly (Van Gemerden and Mas 1995).…”

Hydrogen Cyanide Accumulation and Transformations in Non-polluted Salt Marsh Sediments

“…Sulfide oxidation intermediates, which have sulfur-sulfur bonds, are known to be reactive toward free cyanide (Kelly et al 1969;Szekeres 1974;Luthy and Bruce 1979;Kamyshny 2009;Kamyshny et al 2009). Polysulfides, polythionates with four or more sulfur atoms, and soluble and colloidal elemental sulfur react with cyanide faster than trithionate and thiosulfate (Kelly et al 1969;Luthy and Bruce 1979;Kamyshny et al 2009). Polysulfides are known to react rapidly with hydrogen cyanide via:…”