A methodology for the determination of reductive sulphur in optical and technical glass

This paper describes an analytical method for the determination of reductive sulphur (S(IV), S(-II)) in glass. The glass sample is dissolved in hydrofluoric/hydrochloric acid mixture and the sulphur is separated via distillation in an apparatus made of polyfluoralkoxyethylene (PFA). The distilled hydrogen sulphide is trapped in buffered boric acid-zinc acetate solution and subsequently determined after conversion to an ethylene blue dye. The range of the method lies within a range of 2-1200 μg g⁻¹ reductive sulphur. The quantification limit for reductive sulphur is 2 μg g⁻¹.Different analysed glass types show either no detectable reductive sulphur or up to 30% of the total sulphur content reductive sulphur. The inter-laboratory standard deviation shown by a round robin test performed is excellent (±4 μg g⁻¹; average 59 μg g⁻¹). Sources of error of the methodology are discussed.     

In Process Citation

The method for the determination of sulphur in organic compounds (E. Debal and R. Levy, Bull. Soc. Chim. France, 1968, 426; 1971, 3374) by combustion in oxygen at 1310-1320 degrees C and coulometric titration of the sulphur dioxide formed is improved. Silver and 8-hydroxy-quinoline are successfully used to remove halogens (fluorine included) from combustion products. A new glass cell for the acidimetric titration of sulphur dioxide with an automatic coulometer is devised, with a water-jacket for its cathodic and reference compartments. The constant-temperature water-flow makes this determination easy to carry out with no drawbacks, even in varying ambient temperature.     

Dynamic vulcanization of reclaimed tire rubber and high density polyethylene blends

Dynamic vulcanization of reclaimed tire rubber (RTR) and HDPE blends was reported. The effect of blend ratio, methods of vulcanization, i.e. sulphur, peroxide, and mixed system and the addition of compatibilizer on mechanical, thermal, and rheological properties were investigated. The blend with highest impact strength was obtained from 50/50 RTR/HDPE vulcanized by sulphur. Increasing the RTR content to more than 50% resulted in a decrease in the impact strength of blend, most likely due to the increasing carbon black content. For tensile strength, the presence of rubber and carbon black, however, unavoidably caused a drop in this property. Comparing among three methods of vulcanization, sulphur system seems to be the most effective method. Results from solvent swelling ratio, glass transition temperatures and viscosity indicated that the sulphur vulcanization created the highest degree of cross-link and filler-matrix interaction in the RTR/HDPE blend. Morphology of the blends was also assessed by scanning electron microscopy (SEM).     

Determination of sulphur and total sulphur dioxide in wines by an ICP-AES method

Sulphur contents of the original sample and the sample free from sulphur dioxide were determined by ICP-AES following nitric acid digestion under high pressure (using PAAR HPA equipment), and the total sulphur content was calculated from the difference between the results obtained. With the aim of preparing a sample free from sulphur dioxide, bound sulphur dioxide was released by sodium hydroxide, then after acidifying by phosphoric acid, boiling was carried out. Relative standard deviations of the results obtained for total sulphur, the sulphur without S(IV) and total sulphur dioxide were lower than 2.5, 3.5 and 5% respectively. Various amounts of sulphur (in the form of Na₂SO₄), added to wine samples, were successfully recovered between 95.5 and 104.9%. Based on comparative analyses performed by a widely accepted classic method, the indirect method developed was found to be adequate for the determination of total sulphur dioxide. The procedure is suitable for serial tests.     

The fluorimetric determination of phosphate with thiamine

A method for the microdetermination of sulphur in organic compounds by means of combustion in a flow of oxygen is described. The oxides of sulphur are absorbed and stored on a small silver layer. After completion of the combustion, the oxygen is replaced first by nitrogen and secondly by hydrogen which liberates the sulphur as sulphur dioxide and regenerates the silver layer. The sulphur dioxide can be easily absorbed by dilute hydrogen peroxide and determined by any convenient method.     

Application of microwave heating to the determination of free, combined and total sulphur in rubber

An atomic absorption spectrometry (AAS) method for the determination of total and combined sulphur in rubber and a catalytic method for the determination of free sulphur in rubber are described. The catalytic method is based on the iodine-azide reaction and is followed by an extraction of free sulphur with benzene, toluene or acetone. The catalytic determination, with the aid of gas chromatography, was performed in N,N-dimethylformamide after expelling the more volatile solvents used in the extraction. The calibration is linear over the range 2 × 10⁻⁶ – 3 × 10⁻⁴ M. Before the determination of total and combined sulphur, the rubber samples were decomposed by microwave assisted heating (5 min, 110 W) in a Teflon closed vessel. After microwave heating the solution was clear and homogenous and all sulphur compounds contained in the rubber were quantitatively oxidized to sulphate. The sulphates were then precipitated as BaSO₄ and an excess of barium was determined by AAS. From the difference in the results of the determinations of total and free sulphur the amount of combined sulphur can be calculated, and from the difference in the determinations of total and combined sulphur the amount of free sulphur can be calculated. In the latter case the catalytic analysis is not needed.     

Determination of sulphur content in drill core samples by backscattered beta-particles and gamma-ray absorption

A relatively simple method of sulphur determination in drill cores of calcium carbonate matrix is described. The method is based on the combination of measurements of backscattered beta-particles and transmitted low energy gamma-radiation intensities. The transmitted gamma-radiation measurement corrects the errors of sulphur determination caused by the varying strontium sulphate and silicon dioxide content. The method has been tested on 170 samples. It was estimated that the standard deviation of sulphur determination does not exceed 2.5% of sulphur. The apparatus for routine absorption measurement is also described.     

A new indirect spectrophotometric procedure for determination of sulphur dioxide

An operationally inexpensive and sensitive spectrophotometric procedure for sulphur dioxide is proposed. The reagent 5,5-dimethyl-1,2,3-cyclohexanetrione-1,2-dioxime-3-thiosemicarbaz one is used to determine trace amounts of sulphur dioxide indirectly by means of the reduction of Fe(III) to Fe(II). The method can determine down to 0.032 microg/ml of sulphur dioxide in the final solution and recoveries are better than 98%. The method can be applied to the determination of atmospheric SO(2) provided that interfering gases such as nitrogen dioxide and hydrogen sulphide are eliminated.     

A gravimetric procedure for the determination of wet precipitated sulphur, dissolved sulphur, soluble sulphides and hydrogen sulphide

Elemental sulphur (in wet precipitated form or dissolved in organic solvents) and hydrogen sulphide have been determined gravimetrically at room temperature by conversion into copper sulphide by elemental copper in presence of an organic solvent such as benzene or acetonitrile. Any solvent in which sulphur is soluble can be used. The black copper sulphide formed can be weighed or determined iodometrically. Analysis indicates the black compound to be Cu(1.8)S. This room temperature method is a versatile one-step procedure sensitive to microgram or macro amounts of sulphur. It has been used for determining the solubility of sulphur in tetrahydrofuran and dioxan. The apparent heat of solution indicates that sulphur dissolves in these solvents without any marked solute-solvent interactions.     

SEMIEMPIRICAL CALCULATION OF THE INNER SHELL BINDING ENERGY SHIFTS IN MOLECULES INVOLVING SULPHUR ATOM

Abstract

The inner core binding energy shifts of sulphur atom in various chemical environments were studied by the semiempirical self-consistent charge molecular orbital method. The relaxation energy was taken into account by using two distinct approaches:(a) reorganizatinoo potential method and (b) transition potential method. The changes in ESCA chemical shifts of sulphur are satisfactorily accounted for by the latter method, the s tandard deviation from the experimental data being 0.2 eV. It appears that the reorganization energy plays an important role in rationlizing inner core binding energy shifts of sulphur.     

Method for analysis of heavy sulphur compounds using gas chromatography with flame photometric detection

A method for analysis of heavy sulphur compounds in wines, based on gas chromatography (GC) with flame photometric detection, is reported. Wine samples preparation includes a dichloromethane liquid-liquid extraction followed by concentration under a nitrogen atmosphere. The extracted fraction was also analysed by GC-mass spectrometry. The method enables high recovery of sulphur compounds in wine and satisfies the requirements of repeatability and sensitivity. Applications of the method to red, white and Port wines are reported.     

Determination of sulphur in petroleum products after sulphur dioxide generation and of sulphur dioxide in air by chemiluminescent flame emission

The determination of sulphur in petroleum products by combustion, concentration of the sulphur dioxide in sodium tetrachtoromercurate solutions and cool flame molecular emission is described. Improvements in burner design and optimization of analytical conditions result in a minimum detectable amount of 6 ng of sulphur. The absorption of sulphur dioxide from air samples and its determination by a similar method gives a detection limit of 1.3 μg SO₂ m^-3.     

Determination of acid volatile sulphur in river sediments by ICP-OES coupled with purge and trap method

The developed and tested method is based on the acid volatile sulphur (AVS) releasing from a sample of sediment by acidification with hydrochloric acid and sequential absorption of released hydrogen sulphide into the absorption solution of sodium hydroxide. Total sulphur absorbed in the absorption solution is subsequently determined by inductively coupled plasma optical emission spectrometry (ICP-OES) technique. The method was tested using both model and real samples of the river sediment. Obtained results were compared with the results of iodometric determination as the method routinely used for the AVS determination. In case of using ICP-OES with purge and trap, there is no spectral interference of calcium; therefore for the determination of sulphur, it is possible to use atomic emission line of sulphur S I 180.7 nm. The tested method provides the results comparable with the iodometric method within the range of tested concentrations. The detection limit (LOD) of this method is 0.09 mg· S^2? ? L^?1 in the absorption solution which corresponds to 0.23 mg S^2?·kg^?1 in a sediment. Value of LOD is comparable with the iodometric determination.     

Determination of trace amounts of sulphur in selenium

Determination of trace amounts of sulphur as Methylene Blue after reduction of sulphate to sulphide by hydriodic and hypophosphorous acids in acetic acid solution is applied to the determination of trace amounts of sulphur in selenium after removal of the selenium by evaporation with hydrobromic acid. Samples of 100 mg or less of selenium are chosen if the sulphur content is greater than 5-10 ppm; the time required for the separation is about 1.5 hr; 100 ppm of sulphur has been determined with a coeffident of variation of 5.2%. If the sulphur content is less than 5 ppm, 1-g samples must be taken and the time required is then about 3 hr; 0.4 ppm of sulphur has been determined with a standard deviation of 0.13 ppm. The accuracy of the method seems to be well within the random error.     

Determination of free elemental sulphur in some petroleum products

Uncombined elemental sulphur in petroleum products such as kerosene, diesel, furnace and gear oil has been determined by conversion into copper(I) sulphide at 150-170 degrees . The copper(I) sulphide can be weighed, or its sulphur content determined by the iodimetric method.     

Determination of total sulphur in fuel oils by ion chromatography

A method is described for the determination of total sulphur in fuel oils. The oils are burnt in an oxygen flask and the resulting sulphur dioxide is oxidised with hydrogen peroxide to sulphate which is subsequently determined by ion chromatography. With a 50-mg oil sample the limit of detection is 0.007% sulphur. The procedure is simple and has a r.s.d. of 2.7%. Blanks are negligible and the only interferences can be from metal ions that form insoluble sulphates. The method is compared with m.e.c.a, x.r.f. and titrimetric procedures.     

Study of sulphur in oxidised coals by atmospheric pressure-temperature programmed reduction

The influence of oxidation of coal, performed with different oxidising agents, on the sulphur species was studied. Conversions of the sulphur species were investigated by the Atmospheric Pressure-Temperature Programmed Reduction method (AP-TPR). The removal of pyrite proved to be advantageous for AP-TPR analysis. It was found that non-thiophene sulphur species undergo easier oxidation by different agent then thiophenic structures.This revised version was published online in November 2005 with corrections to the Cover Date.     

Electrochemical behaviour of silver and gold single-crystal surfaces covered with a monolayer of adsorbed sulphur

The behaviour of sulphur adsorbed at a silver and gold/electrolyte interface has been studied by a combination of radiotracer and classical electrochemical methods. Sulphur forms stable monolayers on single-crystal silver surfaces in aqueous NaF between ?0.4 and ?1.0 V (MSE). The double-layer capacity is substantially lowered and the pzc shfted. The sulphur can be removed by cathodic treatment, but the silver surface cannot be returned to its original clean condition by this method.     

Direct analysis of thiophene-containing compounds In Tagetes (Asteraceae) leaf secretory cavities by tandem mass spectrometry

The direct analysis of thiophene-containing compounds present in the leaf secretory cavities of Tagetes (Asteraceae) was obtained by tandem mass spectrometry (MS—MS). In contrast to the usual extraction and chromatographic procedures, leaf glands were pricked with a column injection syringe and the sample was collected directly in a glass capillary. Direct electron impact mass spectrometric analysis of such secretions led to the identification of sulphur containing ionic species, as determined by both isotopic cluster analysis and accurate mass measurements. The molecular ions were easily identifies by parent ion scans and their further structural characterization was achieved by MS—MS.     

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.