Selenium in environmental waters: Determination, speciation and concentration levels.

Pyrococcus furiosus is an anaerobic archaeon that grows optimally at 100 degrees C by the fermentation of carbohydrates yielding acetate, CO2, and H2 as the primary products. If elemental sulfur (S0) or polysulfide is added to the growth medium, H2S is also produced. The cytoplasmic hydrogenase of P. furiosus, which is responsible for H2 production with ferredoxin as the electron donor, has been shown to also catalyze the reduction of polysulfide to H2S (K. Ma, R. N. Schicho, R. M. Kelly, and M. W. W. Adams, Proc. Natl. Acad. Sci. USA 90:5341-5344, 1993). From the cytoplasm of this organism, we have now purified an enzyme, sulfide dehydrogenase (SuDH), which catalyzes the reduction of polysulfide to H2S with NADPH as the electron donor. SuDH is a heterodimer with subunits of 52,000 and 29,000 Da. SuDH contains flavin and approximately 11 iron and 6 acid-labile sulfide atoms per mol, but no other metals were detected. Analysis of the enzyme by electron paramagnetic resonance spectroscopy indicated the presence of four iron-sulfur centers, one of which was specifically reduced by NADPH. SuDH has a half-life at 95 degrees C of about 12 h and shows a 50% increase in activity after 12 h at 82 degrees C. The pure enzyme has a specific activity of 7 mumol of H2S produced.min-1.mg of protein-1 at 80 degrees C with polysulfide (1.2 mM) and NADPH (0.4 mM) as substrates. The apparent Km values were 1.25 mM and 11 microM, respectively. NADH was not utilized as an electron donor for polysulfide reduction. P. furiosus rubredoxin (K(m) = 1.6 microM) also functioned as an electron acceptor for SuDH, and SuDH catalyzed the reduction of NADP with reduced P. furiosus ferredoxin (K(m) = 0.7 microM) as an electron donor. The multiple activities of SuDH and its proposed role in the metabolism of S(o) and polysulfide are discussed.

Sulfide dehydrogenase from the hyperthermophilic archaeon Pyrococcus furiosus: a new multifunctional enzyme involved in the reduction of elemental sulfur.

Polysulfides formed through the breakdown of elemental sulfur or other sulfur compounds were found to be reduced to H2S by the hyperthermophilic archaebacterium Pyrococcus furiosus during growth. Metabolism of polysulfides by the organism was dissimilatory, as no incorporation of 35S-labeled elemental sulfur was detected. However, [35S]cysteine and [35S]methionine were incorporated into cellular protein. Contact between the organism and elemental sulfur is not necessary for metabolism. The sulfide generated from metabolic reduction of polysulfides dissociates to a strong nucleophile, HS−, which in turn opens up the S8 elemental sulfur ring. In addition to H2S, P. furiosus cultures produced methyl mercaptan in a growth-associated fashion.

Role of Polysulfides in Reduction of Elemental Sulfur by the Hyperthermophilic Archaebacterium Pyrococcus furiosus

Sensitive and selective fluorescence determination of trace hydrazine in aqueous solution utilizing 5-chlorosalicylaldehyde

Amperometric determination of hydrazine at manganese hexacyanoferrate modified graphite-wax composite electrode

A flow injection method for the determination of oxidizable compounds was developed by utilizing the redox reaction of iodate ion with the sample. Decrease of iodate ion concentration was monitored by measuring its reducing current at a platinum wire electrode held at +0.6 V vs. a silver tubing electrode. Furthermore, L-ascorbic acid, hydrazine and L-cysteine could be determined continuously by using only a hydrazine calibration curve in the concentration range 10−4–10−3 mol dm−3 with 20 μl samples.

Flow injection analysis with amperometric detector utilizing the redox reaction of iodate ion.

Potentiometric argentimetric method for the successive titration of sulphide and dissolved sulphur in polysulphide solutions.

Sulfide, thiosulfate, and polysulfide ions in their mixtures were determined potentiometrically with a silvernitrate standard solution. These three species can be precisely determined from two titrations for each sample with the coefficient of variation of 0.3% at the concentration level of 5×10−4 M (1 M= 1 mol dm−3). One aliquot is titrated, after making the titrand acidic with an acetate buffer (pH=4), to get the end points of the sulfide and thiosulfate ions respectively, in the presence of free sulfur. The other is titrated, after the sulfitolysis of the sample solution, to show the end points of the sulfide and thiosulfate (the original thiosulfate plus the thiosulfate which is formed from polysulfide) ions in the presence of excess sulfite. The addition of calcium nitrate is effective in making the end points clear and accurate. This method was applied to determine these species in lixiviation water of blast-furnace slag.

The Rapid Determination of Sulfide, Thiosulfate, and Polysulfide in the Lixiviation Water of Blast-furnace Slag by Means of Argentimetric Potentiometric Titration

For the rapid determination of sulfite ion, a potentiometric argentometric titrimetry using an iodide-ion selective membrane electrode was developed.The optimum conditions for the argentometric titration of iodide ion in the presence of iQdine were determined. Sulfite ion was determined by titrating the iodide ion produced by the reaction with iodine.The recommended procedure is as follows. After 10 ml of O.2N iodine-methanol solution and 1ml of 2 N sulfuric acid are mixed in a titration cell, a sulfite solution (e. g., O.1N, 10 ml) is added. The resultant solution is diluted to 100 ml with water and titrated potentiometrically with a silver nitrate solution.Sodium sulfite, at the final concentrations ranging from O. OOOO1 to O, Ol N as iOdid9 iOPA vy. aE DeVeVr fi hbie Wilh afe1-a tl Jv-e-eff6 W i-eVssny Vt 6 arf O-2. s% and a coeffiicient of variatig. n (Cr Y, ')bVre stwebeffce-V6 Mf Triaige amounts of chloride, broniide, sulfate and carbonate ions did not show anY interference(Fig.5).This meshode is applicable to the determination of suifur dioxide in chimney gases, . Analytical values obtained by this method were in good agreement with those obtained by the iodometric method previously reported.

Rapid Determination of Sulfite Ion by Potentiometric Argentometric Titration Using Iodide-ion Selective Membrane Electrode

多硫化物溶液中の硫黄化学種をノンサプレッサー型イオンクロマトグラフにより簡単に定量する方法について検討した。すなわち,多硫化物溶液中の多硫化物硫黄をシアン化物イオンにより分解(以下シアン分解という)してチオシアン酸イオンを生成させたのち,電気伝導度検出器および紫外吸収検出器(UV検出器)を用いたイオンクロマトグラフにより無機硫黄化学種を分離定量する方法である。電気伝導度検出器を使用すると多硫化物溶液中の硫化物イオン,多硫化物硫黄(チオシアン酸イオン),亜硫酸イオン,チオ硫酸イオンおよび硫酸イオンを分離定量できることがわかった。UV検出器を用いた場合には,硫化物イオン,チオシアン酸イオンおよびチオ硫酸イオンを上記より感度よく定量できた。なお,シアン分解にともなう各硫黄化学種の変動についても検討した。シアン分解は多硫化物硫黄に対して2倍当量のシアン化カリウムを添加して,90℃で10分間反応させるのが適当であった。本法は電位差滴定法などと比較して,操作が簡単であり,複雑な組成をもつ多硫化物溶液中の各硫黄化学種を迅速に検出定量できるという特徴がある。

https://www.jstage.jst.go.jp/article/nikkashi1972/1985/9/1985_9_1704/_pdf

Sanae Ikeda

Papers

Flow injection analysis with amperometric detector utilizing the redox reaction of iodate ion.

Potentiometric argentimetric method for the successive titration of sulphide and dissolved sulphur in polysulphide solutions.

The Rapid Determination of Sulfide, Thiosulfate, and Polysulfide in the Lixiviation Water of Blast-furnace Slag by Means of Argentimetric Potentiometric Titration

Rapid Determination of Sulfite Ion by Potentiometric Argentometric Titration Using Iodide-ion Selective Membrane Electrode

Ion chromatography of sulfur species in polysulfide solution utilizing cyanolysis.