Detection Limit For Sulfur Research Articles

Determination of sulfur in Soils and Stream Sediments by Wavelength Dispersive X-ray Fluorescence Spectrometry

A simple, rapid and nondestructive wavelength dispersive X-ray fluorescence spectrometry (WD-XRF) was developed for the determination of sulfur in soils and stream sediments. WD-XRF was used to study the spectral line shifts and matrix effects of different inorganic species such as sulfide, elemental sulfur, thiosulfate, sulfite and sulfate. Analysis of the spectral lines in the S Kα wavelength range confirmed that Mo Lα (2θ = 111.799 °) lines interfered with S Kα (2θ=110.683°) lines. Twenty-seven soils and stream sediments reference samples were used to calibrate and evaluate the analytical method and the detection limit for sulfur was 5.43 mg/kg. The relative error (%RE) of the reference samples was −8.3–6.4%, showing good accuracy. However, the single form of sulfur (sulfide, sulfite and sulfate) had a significant matrix enhancement effect in the sodium carbonate matrix, especially for sulfides, and its relative error was 11.9 ~ 26.9%. The results of WD-XRF, inductively coupled plasma emission spectroscopy (ICP-OES) and elemental infrared analyzer were compared. The fitness for purpose of the results was also evaluated by the quality criteria test proposed by the International Geological Correlation Programme (IGCP), from which it can be deduced that the method was adequate considering geochemical mapping application.

Measurement of gold and sulfur mass fractions in l-cysteine-modified gold nanoparticles by ICP-DRC-MS after acid digestion: validation and uncertainty of results

Measurement of mass fractions of trace element sulfur and main element gold in L-cysteine-modified gold nanoparticles was performed by inductively coupled plasma mass spectrometry with dynamic reaction cell (DRC) technology after aqua regia digestion. Sulfur concentration was measured at m/z 48 as 32S16O+ in a reaction cell with O2 to reduce the effect of polyatomic interferences at m/z 32. Following a study of the main interferences affecting the signal from 32S16O+, optimization of instrument parameters by an experimental design along with an investigation of the effect of aqua regia in matrix on the signal-to-background ratio of 32S16O+ were carried out to improve the detection limit for sulfur. Under the optimum experimental conditions the detection limits were 1.43 μg L−1 for S and 0.033 μg L−1 for Au. 45Sc was selected as the internal standard for measurement of 32S16O+. The presence of Au at high concentrations showed a negligible effect on the intensity of 32S16O+ and 45Sc+ under DRC mode. The method was in-house validated and the combined uncertainty was estimated according to the Guide to the Expression of Uncertainty in Measurement. Preliminary studies show that the method may be transferred to other ICP-MS systems by re-optimizing cell gas flow (e.g. 1.8 mL min−1 used for NexION 300D). X-ray photoelectron spectroscopy confirmed that a self-assembled monolayer of cysteine was formed on the surface of colloidal gold nanoparticles via sulfur-to-gold bonding.

Sulfur determination in coal using molecular absorption in graphite filter vaporizer

The vaporization of sulfur containing samples in graphite vaporizers for atomic absorption spectrometry is accompanied by modification of sulfur by carbon and, respectively, appearance at high temperature of structured molecular absorption in 200–210nm wavelength range. It has been proposed to employ the spectrum for direct determination of sulfur in coal; soundness of the suggestion is evaluated by analysis of coal slurry using low resolution CCD spectrometer with continuum light source coupled to platform or filter furnace vaporizers. For coal in platform furnace losses of the analyte at low temperature and strong spectral background from the coal matrix hinder the determination. Both negative effects are significantly reduced in filter furnace, in which sample vapor efficiently interacts with carbon when transferred through the heated graphite filter. The method is verified by analysis of coals with sulfur content within 0.13–1.5% (m/m) range. The use of coal certified reference material for sulfur analyte addition to coal slurry permitted determination with random error 5–12%. Absolute and relative detection limits for sulfur in coal are 0.16μg and 0.02mass%, respectively.

Complementary molecular and elemental detection of speciated thioarsenicals using ESI-MS in combination with a xenon-based collision-cell ICP-MS with application to fortified NIST freeze-dried urine

The simultaneous detection of arsenic and sulfur in thioarsenicals was achieved using xenon-based collision-cell inductively coupled plasma (ICP) mass spectrometry (MS) in combination with high-performance liquid chromatography. In an attempt to minimize the (16)O(16)O(+) interference at m/z 32, both sample introduction and collision-cell experimental parameters were optimized. Low flow rates (0.25 mL/min) and a high methanol concentration (8%) in the mobile phase produced a fourfold decrease in the m/z 32 background. A plasma sampling depth change from 3 to 7 mm produced a twofold decrease in background at m/z 32, with a corresponding fourfold increase in the signal associated with a high ionization surrogate for sulfur. The quadrupole bias and the octopole bias were used as a kinetic energy discriminator between background and analyte ions, but a variety of tuning conditions produced similar (less than twofold change) detection limits for sulfur ((32)S). A 34-fold improvement in the (32)S detection limit was achieved using xenon instead of helium as a collision gas. The optimized xenon-based collision cell ICP mass spectrometer was then used with electrospray ionization MS to provide elemental and molecular-based information for the analysis of a fortified sample of NIST freeze-dried urine. The 3sigma detection limits, based on peak height for dimethylthioarsinic acid (DMTA) and trimethylarsine sulfide (TMAS), were 15 and 12 ng/g, respectively. Finally, the peak area reproducibilities (percentage relative standard deviation) of a 5-ppm fortified sample of NIST freeze dried urine for DMTA and TMAS were 7.4 and 5.4%, respectively.

Precolumn Isotope Dilution Analysis in nanoHPLC−ICPMS for Absolute Quantification of Sulfur-Containing Peptides

A novel generic approach based on precolumn isotope dilution nanoHPLC-ICPMS analysis was developed for the accurate absolute quantification of sulfur-containing peptides. A 34S-labeled, species-unspecific sulfur spike (sulfate), noninteracting with analyte peptides under the optimized HPLC condition, was added directly to the chromatographic eluents. Thus a generic sulfur standard permanently present during analysis was used for peptide quantification. Interference-free detection of the 32S and 34S isotopes in ICPMS was achieved by eliminating O2+ ions in a collision cell using Xe gas at 130 microL min-1. The detection limit for sulfur was 45 microg L-1 which corresponded to 1-2 pmol of individual peptides. The method was validated by the analysis of a standard peptide solution showing high accuracy (recovery 103%) and good precision (RSD 2.1%). The combination of nanoHPLC-ICP IDMS with nanoHPLC-ESI MS/MS allowed the precise quantification and identification of sulfur-containing peptides in tryptic digests of human serum albumin and salt-induced yeast protein (SIP18) at the picomole level.

Optimization of LC-DRC-ICP-MS for the speciation of selenotrisulfides with simultaneous detection of sulfur and selenium as oxides combined with determination of elemental and isotope ratios

A LC-DRC-ICP-MS method for the simultaneous detection of selenium and sulfur in the selenotrisulfides selenocysteineglutathione (Cys-Se-SG) and selenodiglutathione (GS-Se-SG) is described. Both sulfur and selenium are reacted with oxygen in the dynamic reaction cell (DRC) and detected as oxides. The selenotrisulfides were separated applying a 30 min gradient liquid chromatographic (LC) method with a formic acid/methanol eluent. The detection limits for sulfur (as 32S16O+) and selenium (as 80Se16O+) in the chromatographic system were 4.0 and 0.2 μg L−1 (100 and 5 ng in absolute mass units), respectively. S/Se elemental ratios in the 1.9–2.1 range, close to the theoretical value of 2.0, was found for both selenotrisulfides along with accurate (<2.5% deviation) and precise (∼1% RSD) sulfur and selenium isotope ratios. This emphasises the potential of the developed method for the speciation of sulfur and/or selenium compounds combined with measurement of elemental and isotope ratios in the characterisation and quantification of biomolecules and drug metabolites.

Isotope dilution ICP-MS with laser-assisted sample introduction for direct determination of sulfur in petroleum products

Inductively coupled plasma isotope dilution mass spectrometry (ICP-IDMS) with direct laser-assisted introduction of isotope-diluted samples into the plasma, using a laser ablation system with high ablation rates, was developed for accurate sulfur determinations in different petroleum products such as 'sulfur-free' premium gasoline, diesel fuel, and heating oil. Two certified gas oil reference materials were analyzed for method validation. Two different 34S-enriched spike compounds, namely, elementary sulfur dissolved in xylene and dibenzothiophene in hexane, were synthesized and tested for their usefulness in this isotope dilution technique. The isotope-diluted sample was adsorbed on a filter-paper-like material, which was fixed in a special holder for irradiation by the laser beam. Under these conditions no time-dependent spike/analyte fractionation was only observed for the dibenzothiophene spike during the laser ablation process, which means that the measured 34S/32S isotope ratio of the isotope-diluted sample remained constant-a necessary precondition for accurate results with the isotope dilution technique. A comparison of LA-ICP-IDMS results with the certified values of the gas oil reference materials and with results obtained from ICP-IDMS analyses with wet sample digestion demonstrated the accuracy of the new LA-ICP-IDMS method in the concentration range of 9.2 microg g(-1) ('sulfur-free' premium gasoline) to 10.4 mg g(-1) (gas oil reference material BCR 107). The detection limit for sulfur by LA-ICP-IDMS is 0.04 microg g(-1) and the analysis time is only about 10 min, which therefore also qualifies this method for accurate determinations of low sulfur contents in petroleum products on a routine level.

Microanalysis by laser-induced plasma spectroscopy in the vacuum ultraviolet.

A new setup for microanalysis by laser-induced plasma spectroscopy in the VUV range is presented and described in detail. The system features an integrated ablation and detection module with a newly designed VUV echelle system. The echelle permits a full spectral coverage between 150 and 300 nm with a resolving power lambda/Deltalambda between 11,000 and 15,000. At present, the ablation module permits a microanalysis with a crater size of 25 microm and a nominal depth resolution with an ablation rate of 150 nm/pulse. The VUV performance was demonstrated for bulk analysis of steel; detection limits for sulfur, carbon, and phosphorus were in the lower milligram per kilogram range. The VUV scanning and mapping performance for heterogeneous matrixes was illustrated for mineral bottom ash samples from a waste incineration process.

In-gel screening of phosphorus and copper, zinc and iron in proteins of yeast mitochondria by LA-ICP-MS and identification of phosphorylated protein structures by MALDI-FT-ICR-MS after separation with two-dimensional gel electrophoresis

A new screening technique using two-dimensional gels was developed in order to rapidly identify various elements in well-separated protein spots. Yeast mitochondrial proteins were separated using two-dimensional gel electrophoresis (blue native/SDS 2D-PAGE) and marked by silver staining. The 2D gels were systematically analyzed by laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) using a double-focusing sector field instrument. From more than 60 mitochondrial protein spots in two-dimensional gels, phosphorus, sulfur and selected metals (Cu, Zn and Fe) were detected in a short analysis time by screening 2D gel with LA-ICP-MS using a focused laser beam. In selected protein spots a quantitative element determination was performed. Ion intensities of phosphorus and metals in single protein spots in the gels were measured at medium mass resolution using an optimized microanalytical method by LA-ICP-MS and in a solution of the gel (blank) after HNO3 digestion by ICP-MS. For quantification purposes sulfur was used as the internal standard element. The detection limits for phosphorus, sulfur, copper, zinc and iron in protein spots, determined in the gel blank (Coomassie staining), were 0.18 µg g−1, 1.3 mg g−1, 6.4 µg g−1, 17.6 µg g−1 and 9.5 µg g−1, respectively. In silver staining gel a detection limit for sulfur of 137 µg g−1 was measured. Matrix-assisted laser desorption ionization Fourier transform ion cyclotron resonance mass spectrometry (MALDI-FTICR-MS) was applied for structure analysis and determination of phosphorylation sites of phosphorylated proteins. Results of the structure analysis of separated mitochondrial proteins obtained by MALDI-FTICR-MS were combined with those of the direct determination of phosphorus, sulfur and metal concentrations in protein spots in two-dimensional gels with LA-ICP-MS.

Flame photometric detection inside of a capillary gas chromatography column.

A novel micro-flame photometric detector (FPD) employing a miniature counter-current flame is described. The micro-FPD flame, encompassing a volume of about 30 nL, is operated inside the end of a capillary gas chromatography column (i.e. on-column) or inside of a quartz capillary after the column (i.e. post-column). Either air or oxygen can support a hydrogen flame in the device, although oxygen is far preferable. The detector can be operated for several hours without any observed degradation in performance or flame stability. The optimal gas flows established for the detection of sulfur and phosphorus are in the range of 4 mL min(-1) of oxygen and 9 to 13 mL min(-1) of hydrogen. The fuel-rich micro-FPD flame generates chemiluminescent blue S2* emission for sulfur and green HPO* emission for phosphorus, similar to a conventional FPD. Sulfur response in the micro-FPD is quadratic over nearly 3 orders of magnitude while that of phosphorus is linear over nearly 5 orders of magnitude. The micro-FPD detection limit for sulfur is 1 x 10(-9) g S s(-1), and that of phosphorus is 2 x 10(-10) g P s(-1). The properties established for the initial prototype of the micro-FPD make this counter-current flame method potentially suitable for integration with on-chip gas chromatography or other micro-analytical devices where flame-based detection methods are desirable.

Nonmetals in the argon-inductively coupled plasma-optical emission spectrometry: I. Phosphorus, sulfur and carbon.

The behavior of phosphorus, sulfur and carbon in the argon-ICP-OES was systematically investigated for a wide range of nebulizer gas flows and observation heights. Five lines of phosphorus, four lines of sulfur and three lines of carbon, which have analytical usable detection limits, were taken into consideration. The further parameter set was inspired by the needs of every-day-analysis in the laboratory, especially the low integration time that is necessary for analysis of large amounts of samples. For each element line a signal-to-noise plot was obtained with a method described earlier. The optimum conditions for the combined analysis were determined from signal-to-noise plots of those element lines with the lowest detection limits. The lowest detection limits for phosphorus (0.13 mg/L) and carbon (0.01 mg/L) are useful for solving many analytical problems. However, even the best detection limit for sulfur (2.97 mg/L) is only of limited use without further preconcentration. A major problem was the background of carbon, most probably from carbon dioxide, which increased the available detection limit to about 0.04 mg/L. Surprisingly, the best detection limits were obtained at very low observation heights, which were only a couple of millimeters above the load coil. Fortunately, all elements showed a similar behavior and so the detection limits at compromise conditions were only slightly higher compared with the single-element detection limits.

Studies on type-inversion of sulfide-treated p-InP

The effects of various sulfide treatments on n- and p-InP and the stability of the sulfide-passivated surfaces have been studied by x-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). When the sulfide treatments were performed at room temperature, a reduction of donor-type surface states was induced as indicated by a decrease of surface band bending on p-InP. However, such surface passivation deteriorated when annealed at 200–300 °C in vacuum, and a strong type inversion with band bending reaching 1.3 eV was observed on p-InP. XPS data from the annealed samples suggest that the presence of polysulfides plays an important role in the cause of the observed strong type inversion. However, SIMS analysis of the type-inverted samples indicated that the sulfur concentration at a depth of 7.5 nm from the surface was less than the SIMS detection limit for sulfur in InP (5×1016 atoms/cm3). In addition, XPS studies of the type-inverted samples showed that reversal of the type inversion occurred when the samples were immersed into water and/or a HF solution. Therefore, the observed type inversion of p-InP is probably caused either by the formation of surface sulfur-containing species, which contribute surface donor states near the conduction-band edge of InP, or by very shallow sulfur doping.

Near Infrared Atomic Emissions of Sulfur and Carbon in the Argon Inductively Coupled Plasma

Inductively coupled plasma (ICP) excitation of the 9212.91 Å nonresonant line of atomic sulfur is reported and is found to yield a detection limit more than 20-fold better than any visible or “air path” ultraviolet sulfur lines produced by the argon ICP. The ICP excited spectrum reported here for the element sulfur is markedly different from that reported for atmospheric pressure microwave-induced helium plasmas. Partial Grotrian diagrams and tables of relative intensities, detection limits, and corresponding wavelengths of 30 ICP excited, nonresonant atomic sulfur emission lines and 20 ICP excited, nonresonant atomic carbon lines are presented for the air path, photomultiplier accessible region 2000 to 9900 Å. No lines of ionized sulfur were observed in the 27-MHz, 1.75-kW argon ICP. Vertical emission intensity profiles of near infrared S(I) and C(I) lines are presented for both conventional and extended ICP torches. The present near infrared (S(I) 9212.91 Å and C(I) 9094.83 Å) detection limits for sulfur and carbon are 0.006 μg and 0.13 μg, respectively, using 8 μL gas sampling loop injections of H2S and CH4 into a low-volume transfer line leading directly into the ICP.

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.