Turbidimetric determination of some sulphur compounds in ethanol from fermentation

A simple method is described which can be used for the determination of certain sulphur compounds found in industrial ethanol obtained from fermentation of molasses. The method is based on the turbidimetric determination of sulphate after the sample has been treated with dilute hydrogen peroxide solution, by precipitation of the sulphate with barium chloride under appropriate conditions. Several samples of fermentation ethanol have been analysed by this method and the sulphur contents found compared with the total acidity.     

Indirect polarographic microdetermination of sulphur in organic compounds

A polarographic method for the microdetermination of sulphur in organic compounds is described; it is based on oxygen-flask combustion to yield sulphate, which is then reacted with excess of barium dichromate solution in hydrochloric acid, followed by adjustment to pH 12, collection of the combined barium chromate and sulphate precipitate, and polarographic determination of the free chromate (equivalent to the sulphate originally present).     

Sulphur speciation of PM10 samples by XANES spectroscopy

Sulphur K-edge X-ray absorption near edge structure (XANES) spectroscopy was used to identify sulphur compounds in PM10 samples collected simultaneously at two sites with different environmental situations in the province of Trieste (NE of Italy), during summer and winter seasons respectively. The first site is an industrial site located near a steel mill plant and the second is a coastal site. The sulphur speciation at the industrial site has shown the presence of the following sulphur compounds in both seasons: organic compounds (thiophenes or Polycyclic Aromatic Sulphur Heterocycles — PAHs) and sulphates while in the winter season sulphites were also present. In the coastal site organic compounds (thiophenes or PASHs) and sulphate were found during winter season, moreover bisulphates were found during summer season. Relative percentages of the different sulphur compounds have shown that sulphate is the most abundant form of sulphur in the industrial site samples during both seasons and in the coastal site sample collected during the winter season (> 98%); in the coastal site sample collected during the summer season the relative percentages of bisulphate and sulphate were around 40% and 60% respectively.      

Determination and fractionation of sulphur in a contaminated dredged sediment

Conversion of sulphur compounds in reduced, contaminated sediments that are brought in upland conditions may largely affect the potential mobility of heavy metal contaminants. We applied selected methods for the determination of total sulphur and sulphur fractions in a contaminated sediment in the reduced state and after gradual drying and oxidation during 1 month. Dry ashing, followed by ion chromatographic detection, was reliable for the determination of total sulphur. Good recoveries were obtained in both reference samples and spiked samples. Total sulphur was 14.5±0.6 g kg⁻¹ relative to dry sediment. Wet chemical methods that involve the determination of acid-volatile, Zn–HCl-reducible, chromium-reducible, acetone-soluble and HI-reducible sulphur were used to estimate specific sulphur forms. Results for acetone-soluble sulphur were to high and not consistent with results for other fractions. Major part of sulphur in the sediment (90%) was inorganic. Sulphides were converted partially to sulphate and to intermediary oxidised sulphur compounds upon oxidation of the sediment. The results suggested that the intermediary oxidised sulphur pool in the reduced sediment (2.5 g kg⁻¹) mainly consisted of pyrite, that was not converted during drying and oxidation. No significant changes in organic sulphur were detected.     

Determination and fractionation of sulphur in a contaminated dredged sediment

Conversion of sulphur compounds in reduced, contaminated sediments that are brought in upland conditions may largely affect the potential mobility of heavy metal contaminants. We applied selected methods for the determination of total sulphur and sulphur fractions in a contaminated sediment in the reduced state and after gradual drying and oxidation during 1 month. Dry ashing, followed by ion chromatographic detection, was reliable for the determination of total sulphur. Good recoveries were obtained in both reference samples and spiked samples. Total sulphur was 14.5±0.6 g kg⁻¹ relative to dry sediment. Wet chemical methods that involve the determination of acid-volatile, Zn–HCl-reducible, chromium-reducible, acetone-soluble and HI-reducible sulphur were used to estimate specific sulphur forms. Results for acetone-soluble sulphur were to high and not consistent with results for other fractions. Major part of sulphur in the sediment (90%) was inorganic. Sulphides were converted partially to sulphate and to intermediary oxidised sulphur compounds upon oxidation of the sediment. The results suggested that the intermediary oxidised sulphur pool in the reduced sediment (2.5 g kg⁻¹) mainly consisted of pyrite, that was not converted during drying and oxidation. No significant changes in organic sulphur were detected.     

Die bestimmung des gesamtschwefels in vulkanisierten gummimischungen

A method is described in which by means of a resin ion-exchanger the interference of foreign cations, particularly iron and chromium, can be prevented in the determination of total sulphur in vulcanized rubbers. The procedure allows the use of rapid volumetric methods for determining sulphate even when analyzing mixtures containing iron oxide or chromium oxide pigments. Here, the sulphate is precipitated with benzidine and determined by titration with sodium hydroxide solution. The method is quicker and more certain than the usual barium sulphate gravimetric procedure.     

A rapid turbidimetric method for the determination of total sulphur in zinc concentrate

A rapid, simple and reliable routine method for the determination of total sulphur in zinc concentrates, roasted products and leached residues from zinc smelters is described. The method involves the fusion of the ample with sodium peroxide and sodium carbonate or routine acid decomposition and dissolution to give soluble compounds. The absorbance of the barium sulphate suspension produced by the addition of barium chloride powder to a dilute hydrochloric acid solution of the sample, containing cetyltrimethylammonium bromide solution as a dispersing agent, is measured at 420 nm. The results obtained for some zinc concentrates and other products are compared with those obtained by the conventional gravimetric barium sulphate method. Results for a reference zinc concentrate and other samples with various matrices and the results obtained with standard additions to the samples are good.     

型煤中硫的还原热解MS和GC/MS分析(英文)

以煤和生物质为主要原料的商用型煤为研究对象，采用还原热解（AP-TPR）在线质谱（MS）联用，以及离线色谱/质谱（GC/MS）分析法，定性和定量研究了家用型煤释放的含硫化合物。不同组成的型煤表现出各自不同的硫释放特性。对于生物型煤来说，仅检测到少量二烷基硫醚和脂肪硫醇的存在。褐煤型煤检测到种类最多的有机硫化物。在高阶煤制成的型煤中没有检测到氧化态的硫化物，其典型特征是存在一些噻吩类硫化物。     

The spectrophotometric determination of sulphate after its extraction with methyltricaprylammonium chloride into cyclohexane

Improvements are described to Flynn's procedure for the extraction of sulphate with Aliquat-336 and its subsequent determination as sulphuric acid. A single-point photometric measurement with sodium 2,4-dinitrophenate is applied to the determination of sulphate (ca. 10 mg kg^?1) in soils, and also in sulphur in organic compounds after oxygen flask combustion.     

The direct micro determination of oxygen in organic material

A procedure is described in which interferences caused by hydrogen and sulphur are eliminated. These occur when petroleum hydrocarbons or sulphur containing materials are analysed. Copper oxide, in conjunction with the gravimetric determination of carbon dioxide, has been found preferable to the iodine pentoxide procedure. The replacement of iodine pentoxide by copper oxide has also simplified the maintenance of the apparatus without any loss of applicability to organic compounds in general. Activated copper is used to absorb sulphur compounds. Details of the modified procedure are included.     

A new procedure, based on combustion to sulphate and ion chromatography for the analysis of elemental sulphur in sediments

Summary A procedure exploiting the bomb preparation method for the analysis of total sulphur in organic materials has been developed for the determination of zero-valent sulphur (S^o) in sediments. Sediment samples were dried over magnesium oxide and sonicated in the presence of toluene to extract S^o. Toluene solutions were directly oxidized by combustion in a bomb containing sodium carbonate-bicarbonate buffer, which trapped sulphur species generated from S^o as sulphate ions. These were in turn analysed by suppressed anion chromatography with ion-conductivity detection. The method was used to determine the distribution of S^o in saltmarsh sediment cores.     

Investigation of sulphur compounds in coal tar using monodimensional and comprehensive two-dimensional gas chromatography

Coal is a non renewable fossil fuel, used mainly as a source of electrical energy and in the production of coke. It is subjected to thermal treatment, pyrolysis, which produces coke as a main product, in addition to a condensed liquid by-product, called tar. Tar is a complex mixture of organic compounds which contains different chemical classes, presenting aromatic and sulphur heterocyclic compounds. In general, identification of these compounds requires steps of isolation and fractionation, mainly due to co-elution of these compounds with polyaromatic hydrocarbons (PAH). The objective of this work is to characterize the sulphur compounds present in the coal tar obtained via pyrolysis, using comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry detector (GC×GC/TOFMS). Coal samples from the State of Paraná, Brazil were subjected to laboratorial scale pyrolysis. Several experimental conditions were tested, such as sample weight (5, 10 and 15g), heating ramp (10, 25 and 100°C/min) and final temperature (500, 700 and 900°C). Samples were analyzed by one dimensional gas chromatography (1D-GC) coupled to a quadrupole mass spectrometry detector (GC/qMS) and two-dimensional gas chromatography with time-of-flight mass spectrometry detector (GC×GC/TOFMS). The higher amount of sulphur compounds was obtained at a final temperature of 700°C and a heating ramp of 100°C/min. The main classes observed in the color plot were thiophenes, benzothiophenes and alkylated dibenzothiophenes. GC×GC/TOFMS allowed the identification of the greater number of compounds and the separation of several sulphur compounds from one another. Moreover, separation of sulphur compounds from polyaromatic hydrocarbons and phenols was achieved, which was not possible by 1D-GC. Comparing GC×GC/TOFMS and 1D-GC (SIM mode) also showed that 1D-GC, one of the most employed quantification tools for sulphur compounds, can be misleading for detection, identification and quantification, as the number of isomers of sulphur compounds found was greater than theoretically possible.     

An analytical scheme for determining forms of sulphur in oil shales and associated rocks

An analytical scheme for determining various forms of sulphur in oil shales and associated rocks is presented. Acid-soluble sulphate, sulphur contained in monosulphide and in disulphide minerals, and organically-bound sulphur are all quantitatively recovered as separate fractions. Finely-ground oil-shale samples are treated in an inert atmosphere with 6M hydrochloric acid to dissolve the acid-soluble sulphate minerals and form H₂S from the decomposition of monosulphide minerals. The acid-soluble sulphate is precipitated as barium sulphate and the H₂S is collected and weighed as silver sulphide. Disulphide minerals in the solid residue from the acid treatment are reduced by an acidified Cr(II) solution in an inert atmosphere, releasing the sulphide as H₂S. The H₂S is collected as silver sulphide. An Eschka fusion oxidizes and solubilizes all sulphur remaining within the Cr(II)-treated residue. This sulphate represents organically-bound sulphur and is collected as barium sulphate. The analytical procedures have been verified by using ⁵⁷Fe Mössbauer spectroscopy. Good agreement between the chemical and Mössbauer data substantiated the sequential removal of the forms of sulphur and also demonstrated the ability of Mössbauer spectroscopy to determine the absolute quantities of iron present in specific minerals.     

New iodometric methods for the microdetermination of arsenic in organic compounds

New methods are described for the iodometric microdetermination of arsenic in organic compounds after wet digestion or oxygen flask combustion. After evaporation of the arsenic solution to dryness and dissolution of the residue in water, acetone is added and the solution is treated with iodide-iodate and the iodine liberated (by the interfering acids and the first dissociation step of arsenic acid) is reduced with thiosulphate. The KH(2)AsO(4) left is then reacted with zinc sulphate in presence of excess of KI and KIO(3). Acetone is added and the liberated iodine is titrated with thiosulphate. This titration corresponds to the second and third dissociation steps of arsenic acid and is used to calculate the arsenic content of the compound. When arsenicals not containing sulphur are decomposed by the oxygen flask method, the arsenic acid solution obtained is reacted directly with zinc sulphate in presence of KI and KIO(3) and the iodine released is titrated with thiosulphate. In this case, the titration corresponds to all three dissociation steps of arsenic acid. The average recoveries obtained by the two methods are 99.5 and 99.9%, respectively.     

Substoichiometric isotope-dilution determination of sulphur after conversion to methylene blue and ion-pair extraction with dodecyl sulphate

The proposed substoichiometric determination of sulphur includes two key steps: conversion of sulphur to methylene blue and ion-pair extraction of methylene blue into chloroform with a substoichiometric amount of dodecyl sulphate. The method, combined with isotope dilution is applied to the determination of total sulphur in NBS SRM Citrus Leaves and in a seaweed sample (Laminaria religiosa Miyabe). The mean values obtained were 0.401±0.008% S (RSD 2%; n=9; certified value 0.407±0.009%) for the SRM, and 0.756±0.012% S (RSD 1.6%; n=5) for the seaweed. A sample of 0.5–1 g containing ca. 100 μg of sulphur can be analysed.     

A new reagent for the detection and determination of small amounts of the sulphate Ion

An aqueous solution of 2-aminoperimidine hydrochloride is proposed as a new reagent for the detection and determination of the sulphate ion. As little as 0.05 p.p.m. can be detected by precipitation of the corresponding amine sulphate. Suspensions of the precipitate show remarkable stability and no colloidal stabilizers are needed. The reagent is applied to the nephelometric determination of 0.1–5 p.p.m. of sulphate ion; at the 0.5 p.p.m. level, the relative standard deviation is 4.5%. Although many ions form precipitates with the reagent at high concentrations, very few of the common anions provide significant interference in the nephelometric determination. The reagent seems promising for the determination of sulphate in natural waters, and for traces of sulphur in organic compounds after oxygen flask combustion.     

Determination of inorganic sulphur in aqueous solutions. An application for cyanide extracts of gold ore and plating solutions

Summary The method described for the determination of total sulphur in aqueous solutions known to contain no organic sulphur is based on quantitative conversion of sulphur species to sulphate by hydrogen peroxide at room temperature. The oxidation is first carried out under basic conditions for 1 h and then under acidic conditions for a further hour. The conversion of S^2–, S₂O ₅ ^2– , S²O ₃ ^2– , S₂O ₈ ^2– , SCN^– and SO ₃ ^2– to sulphate is quantitative. The sulphate is then determined turbidimetrically. The method is suitable for a wide range of inorganic solutions containing greater than 2 ppm sulphur. It was applied to determine the total sulphur content in several cyanide extracts of gold ore and plating solutions of zinc and nickel.

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Bestimmung von anorganischem Schwefel in wäßrigen Lösungen. Anwendung auf Cyanideextrakte von Golderzen und galvanische Bäder

     

Surface activity and fluorite flotation with myristic acid derivatives containing oxygen and sulphur atoms

Surface tension isotherms and fluorite flotation were studied in systems containing myristic acid derivatives in which carbon atoms in the hydrocarbon skeleton were partly replaced by oxygen and/or sulphur atoms. The location of the oxygen and sulphur atoms affects significantly compound hydrophobicity, adsorption at the air/water interface and fluorite flotation. The most effective collectors were the compounds with one oxygen or sulphur atom close to the carboxylic group.     

Assay of sulphur compounds with 1-chlorobenzotriazole

A simple but accurate potentiometric method for the estimation of certain sulphur containing organic compounds has been developed, based on their oxidation with 1-chlorobenzotriazole. A back-titration procedure can also be used. The nature of oxidation in different media is discussed and the oxidation products have been identified.     

Accurate determination of sulphur in steels and certain heat-resisting alloys by isotope dilution mass spectrometry

A mass spectrometric isotope dilution method for the determination of sulphur in steels and certain alloys has been investigated. Addition of bromine in the dissolution of carbon steels was necessary for the complete conversion of sulphur into sulphate. The relative standard deviation was better than 1.5% for sulphur contents in the range 40-3,000 ppm. The results on standard materials were in good agreement with the certified values for samples of BCS, but lower than those for JSS and NBS.