Determination Of Sulfur In Samples Research Articles

Rapid Determination of Sulfur in Sixty Geological Reference Materials by High Resolution Inductively Coupled Plasma‐Mass Spectrometry

In this study, a rapid method for the quantification of sulfur mass fractions in geological materials using high‐resolution sector field‐inductively coupled plasma‐mass spectrometry (SF‐ICP‐MS) was developed. The effects of HNO3, Lefort, aqua regia, and HCl on the recoveries of sulfur in three different geological samples were evaluated. It was found that 0.5‐1 h digestion at 90 °C was enough to completely recover sulfur from BCR‐2 (basalt rock), GSS‐25 (loess), and GSD‐7 (stream sediment) using 2 ml aqua regia in both closed and open vessels. Compared with that of traditional digestion methods (e.g., HF‐HBr‐HNO3 acid digestion method), the efficiency of this proposed aqua regia digestion is improved by a factor of approximately 20. No loss of sulfur was observed because sulfur released from geological materials is directly oxidised to sulfate, which inhibits the volatilisation of sulfur. In addition, the effect of the heating‐condensing system combined with two different skimmer cones on the analytical sensitivity of sulfur was investigated. Compared with that of the normal sampling mode, the signal intensity of sulfur is enhanced by a factor of approximately 22 and 10 at a temperature of 140 °C using the S + X cone combination and S + H cone combination, respectively. This improvement is of importance for the determination of sulfur in samples with low sulfur content. The developed method was successfully applied to the determination of sulfur in geological reference materials. Most of the measured sulfur values of sixty geological materials, using both closed and open vessel digestion, are in good agreement with reference values. Compared with closed vessel digestion, the more flexible open vessel acid digestion is simple, fast, and shows great potential for the rapid quantification of sulfur in a large batch of geological and environmental samples.

A Direct Non-destructive Method for Determination of Sulfur in Ore Samples Using EDXRF Spectrometry.

A method has been developed for direct non-destructive energy dispersive X-ray fluorescence (EDXRF) determination of sulfur in solid uranium ores and intermediates, obtained from the alkaline recovery process for uranium from its ores. The method involves thorough grinding of a few mg of solid powder samples to fine particle size and mixing the fine powder thus obtained with a few drops of 10% collodion solution in amyl acetate to make a paste. A very small amount of this paste was transferred with the help of the pestle tip, spread uniformly in the form of thin slurry on Mylar films, and dried to make very thin sample specimens on thin Mylar film supports. These specimens were presented for EDXRF measurements. A calibration plot was made by plotting the intensity ratios of S Kα and Rayliegh scattered peak of the excitation source (Ge Kα) against sulphur percent in the certified reference materials (CRMs). It was found that the precision obtained using this methodology was within 5% (±1σ) and the deviation of the EDXRF analytical results from the expected values of CRM was within 7%. The developed method was successfully applied for the determination of sulfur in the samples obtained from the different stages of the uranium ore processing using alkaline based leaching method.

Capability and limitations of the determination of sulfur in inorganic and biological matrices by total reflection X-ray fluorescence spectrometry

The capability and limitations of TXRF were explored for the determination of the light element sulfur in inorganic and biological samples. The recovery rates of sulfur were measured with tungsten L-radiation in the dry residues of various sulfates and sulfur containing amino acids with a sulfur concentration ranging from 0.5 to 20 mg/l. Furthermore, the surface topography of the dry residues of the samples was investigated by scanning electron microscopy (SEM) and their thickness profiles were recorded by an Alpha-Step. The results show that the reliable determination of sulfur in inorganic samples depends on the cation involved. Alkali sulfates tend to form bulky residues which disturb the determination of sulfur distinctly due to absorption effects of the soft sulfur K radiation. In this case the use of smoothing detergents like 1% HF, 1% malic acid and 2% hydrazine hydrate is necessary for the determinations with reasonable accuracy (tolerance range: ±10% of the recovery rate). The results for the biological samples measured agree well with the expected values. The investigations lead to the conclusion that TXRF combined with a proper sample preparation is well suited for the determination of sulfur in samples of various matrices in a wide range of concentrations.

Microdetermination of sulphate and organic sulphur: potentiometric back-titration using simple coated-wire electrodes

A method is describe for the determination of sulphate, based on precipitation with barium(II) chloride followed by potentometric back-titration of the excess of barium(II) salt sodium tetraphenylborate in the presence of polyethylene glycol. To monitor the titrations, simple ion-selective electrodes of the coated-wire type were prepared using an ordinary aluminium conductor, coating the central wire with the membrane formed by plasticized poly(vinylchloride). The determination of organic sulphur consists in burning the sample in a flask filled with oxygen. The combustion products are absorbed in alkaline hydrogen peroxide and, in an aliquot. the sulphate formed is determined. The procedure was tested on eleven organic substances and applied to the determination of sulphur in samples of asphalt. Compared with visual detection of the direct titration of sulphate with barium(II) salt, the results are of the same precision and accuracy. The use of simple potentiometric sensors of the coated-wire type allows objective end-point evaluations and makes the procedure inexpensive.

A Flame Chemiluminescence Method for the Determination of Sulfide and its Application to the Determination of Sulfur in Mild Steel, Carbon Steel, and Cast Iron

A study has been made of the determination of sulfide by generation of hydrogen sulfide from acidified sample solutions followed by measurement of the chemiluminescence of the S2 species produced on introduction of the H2S into an argon-hydrogen flame. The technique is simple to perform and results in considerable increase in the absolute detection limit for sulfur compared to that obtained on aspiration of aqueous solutions of sulfide into the flame. A method has been developed to allow application of the technique to the determination of sulfur in samples of mild steel, carbon steel, and cast iron.

29—A SEMI-MICRO METHOD OF HIGH ACCURACY FOR THE DETERMINATION OF SULPHUR IN WOOL

An accurate method, based on many hundred assays, is given for the determination of sulphur in samples of approximately 0·2 g of wool. It gives highly repeatable results, as evidenced by the small range of 3·21—3·32% sulphur with a standard error of 0·003%, for 61 determinations on a Merino top and the quantitative recovery of wool sulphur in the presence of potassium sulphate. The analytical procedure involves the wet oxidation of the sulphur to sulphuric acid by a nitric–perchloric acid mixture, and the subsequent precipitation and weighing of barium sulphate. The use of potassium dichromate as a catalyst for the oxidation, and as an indicator for its end point is discussed. The rate of the oxidation and the quantity of nitric acid required are critical as slow oxidations produce low results. Excess perchloric acid or potassium dichromate interferes with the precipitation of barium sulphate through solubility and co-precipitation effects. The methods for addition of barium chloride, aggregation and filt...