Analysis Of Volatile Sulfur Compounds Research Articles

Quantification and Removal of Volatile Sulfur Compounds (VSCs) in Atmospheric Emissions in Large (Petro) Chemical Complexes in Different Countries of America and Europe

The present research was focused on the determination and removal of sulfur-containing compounds in industrial emissions of liquefied petroleum gas purification processes in petrochemical plants located in the USA, Brazil, Colombia, Spain, and Italy. For the analysis of volatile sulfur compounds (VSCs), an improved analytical methodology was implemented. The performance of the method was evaluated for eight VSCs in a linear dynamic range between 0.1 and 50 ppm. The concentrations of the eight VSCs in the deethanizer affluents ranged from 11 to 49 ppm for all the studied plants, which exceed the limits specified by institutions and administrations in occupational health and safety. The concentrations of the eight VSCs in the splitter affluents were lower than 4 ppm for all the considered plants. The emissions from each column depended upon its operating rate, with the highest concentrations estimated at 45 TM kg−1 and the lowest ones at 25 TM kg−1. A zeolite-packed prototype column was fitted at the outlet of the splitter and deethanizer columns to reduce the environmental effect of the examined VSCs. This technique was verified and put into practice on an industrial scale, obtaining VSC removal percentages of between 85 and 91%.

Effect of Ethanol on the Adsorption of Volatile Sulfur Compounds on Solid Phase Micro-Extraction Fiber Coatings and the Implication for Analysis in Wine

Complications in the analysis of volatile sulfur compounds (VSC) in wine using solid-phase microextraction (SPME) arise from sample variability. Constituents of the wine matrix, including ethanol, affect the volatility and adsorption of sulfur volatiles on SPME fiber coatings (Carboxen- polydimethylsiloxane(PDMS); DVB-Carboxen-PDMS and DVB-PDMS), which can impact sensitivity and accuracy. Here, several common wine sulfur volatiles, including hydrogen sulfide (H2S), methanethiol (MeSH), dimethyl sulfide (DMS), dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS), diethyl disulfide (DEDS), methyl thioacetate (MeSOAc), and ethyl thioacetate (EtSOAc) are analyzed, using SPME followed by gas chromatography (GC), using a system equipped with a pulsed-flame photometric detection (PFPD) system, at various ethanol concentrations in a synthetic wine matrix. Ethyl methyl sulfide (EMS), diethyl sulfide (DES), methyl isopropyl sulfide (MIS), ethyl isopropyl sulfide (EIS), and diisopropyl disulfide (DIDS) are evaluated as internal standards. The absorption of volatile compounds on the SPME fiber is greatly affected by ethanol. All compounds exhibit a stark decrease in detectability with the addition of ethanol, especially between 0.0 and 0.5% v/v. However, the ratio of interested sulfur compounds to the internal standard becomes more stable when the total alcohol concentration exceeds 2%. EMS was found to best resemble DMS. EIS and DES were found to best resemble DMDS, MeSOAc, and EtSOAc. DIDS was found to best resemble DEDS, DMTS, H2S, and MeSH.

Effect of Wine Matrix Composition on the Quantification of Volatile Sulfur Compounds by Headspace Solid-Phase Microextraction-Gas Chromatography-Pulsed Flame Photometric Detection.

The analysis of volatile sulfur compounds using headspace solid-phase microextraction (HS-SPME) is heavily influenced by matrix effects. The effects of a wine matrix, both non-volatile and volatile components (other than ethanol) were studied on the analysis of several common sulfur volatiles found in wine, including hydrogen sulfide (H2S), methanethiol (MeSH), dimethyl sulfide (DMS), dimethyl disulfide (DMDS), dimethyl trisulfide (DMTS), diethyl disulfide (DEDS), methyl thioacetate (MeSOAc), and ethyl thioacetate (EtSOAc). Varying levels of devolatilized wine and common wine volatiles (acids, esters, alcohols) were added to synthetic wine samples to act as matrices. Sulfur standards were added and analyzed using gas chromatography with pulsed-flame photometric detection (GC-PFPD). Five internal standards were used to find best representatives of each compound despite matrix effects. Sensitivity remained stable with the addition of devolatilized wine, while addition of volatile components decreased sensitivity. DMS was found to be best measured against EMS; DMDS and the thioacetates were best measured against DES; H2S, MeSH, DEDS, and DMTS were best measured against DIDS. The method was used to quantitate the volatile sulfur compounds in 21 wines with various ethanol contents and volatile profiles.

Immediate results of photodynamic therapy for the treatment of halitosis in adolescents: a randomized, controlled, clinical trial.

Light with or without chemical agents has been used to induce therapeutic and antimicrobial effects. With photodynamic therapy, the antimicrobial effect is confined to areas covered by a photosensitive dye and irradiated with light. The aim of the present study was to evaluate the effect of photodynamic therapy for the treatment of halitosis in adolescents through the analysis of volatile sulfur compounds, especially sulfide. A controlled, clinical trial was conducted with 45 adolescents randomly allocated to three groups: group 1, photodynamic therapy administered to the dorsum of the tongue; group 2, treatment with a tongue scraper; and group 3, treatment with a tongue scraper combined with photodynamic therapy. The diagnosis of halitosis was performed using gas chromatography before and after treatment. Comparisons were made using the Kruskal-Wallis test followed by the Student-Newman-Keuls test, with the level of significance set at 5% (p < 0.05). After treatment, a statistically significant reduction in halitosis was found in all groups (p < 0.001). The greatest reduction in total sulfides (median = 0) occurred with the combination of tongue scraper and photodynamic therapy. The present study describes a novel option for the treatment of halitosis in adolescents with an immediate effect that does not involve the mechanical aggression of the lingual papillae that occurs with conventional treatment. Photodynamic Therapy in Adolescents Halitosis ( https://clinicaltrials.gov/ct2/show/NCT02007993?term=NCT02007993&rank=1 )Number: NCT02007993FUNDING:FAPESPNumber: 2013/13032-8.

Investigation of volatile low molecular weight compounds formed during continuous reclaiming of ground tire rubber

Ground tire rubber was thermo-mechanically reclaimed at different temperature conditions (80, 120, 160 °C) using a co-rotating twin screw extruder. The progress of ground tire rubber reclaiming was evaluated with specific mechanical energy, sol fraction and thermogravimetric analysis. Volatile organic compounds (VOCs) including volatile sulfur compounds (VCSs) released from ground tire rubber and ground tire rubber after reclaiming were investigated. The quality of VOCs was studied using dynamic headspace and gas chromatography-mass spectrometry (DHS-GC-MS). Total amount of VOCs was evaluated with static headspace and gas chromatography with flame ionization detector (SHS-GC-FID). Analysis of volatile sulfur compounds was performed using a static headspace and gas chromatography with flame photometric detector (SHS-GC-FPD). Studies of total VOCs content by SHS-GC-FID revealed that, depending on sample, the determined concentration in the headspace phase at 150 °C varied in the range of 17.5–31.4 μg/ml. A large number of individual VOCs, including BTEX compounds, ketones and aldehydes as well as volatile sulfur compounds (VSCs), has been identified by DHS-GC-MS technique. In the VSCs group hydrogen sulfide, benzothiazole, 3-methylthiophene, 2-methylthiophene were determined. Benzothiazole was the most abundant sulfur compound due to degradation of vulcanization accelerators residue present in GTR.The highest concentration of VOCs was found for sample processed at the highest temperature – 160 °C. The study revealed that, during extrusion, degradation products interacted with each other and formed new chemical structures which affected the total amount of volatile organic compounds.

Analysis of volatile sulphur compounds in healthy individuals and those with periodontal disease

Analysis of volatile sulphur compounds in healthy individuals and those with periodontal disease

Quantitative analysis of free and bonded forms of volatile sulfur compouds in wine. Basic methodologies and evidences showing the existence of reversible cation-complexed forms

This paper examines first some basic aspects critical to the analysis of Volatile Sulfur Compounds (VSCs), such as the analytical characteristics of the GC-pFPD system and the stability of the different standard solutions required for a proper calibration. Following, a direct static headspace analytical method for the determination of exclusively free forms of VSCs has been developed. Method repeatability is better than 4%, detection limits for main analytes are below 0.5μgL−1, and the method dynamic linear range (r2>0.99) is expanded by controlling the split ratio in the chromatographic inlet to cover the natural range of occurrence of these compounds in wines. The method gives reliable estimates of headspace concentrations but, as expected, suffers from strong matrix effects with recoveries ranging from 0 to 100% or from 60 to 100 in the cases of H2S and the other mercaptans, respectively. This demonstrates the existence of strong interactions of these compounds with different matrix components. The complexing ability of Cu2+ and to a lower extent Fe2+ and Zn2+ has been experimentally checked. A previously developed method in which the wine is strongly diluted with brine and the volatiles are preconcentrated by HS-SPME, was found to give a reliable estimation of the total amount (free+complexed) of mercaptans, demonstrating that metal-mercaptan complexes are reversible. The comparative analysis of different wines by the two procedures reveals that in normal wines H2S and methanethiol can be complexed at levels above 99%, with averages around 97% for H2S and 75% for methanethiol, while thioethers such as dimethyl sulfide (DMS) are not complexed. Overall, the proposed strategy may be generalized to understand problems caused by VSCs in different matrices.

ChemInform Abstract: Challenges and Artifact Concerns in Analysis of Volatile Sulfur Compounds

AbstractReview: 102 refs.

Exploration of sulfur metabolism in the yeast Kluyveromyces lactis

Hemiascomycetes are separated by considerable evolutionary distances and, as a consequence, the mechanisms involved in sulfur metabolism in the extensively studied yeast, Saccharomyces cerevisiae, could be different from those of other species of the phylum. This is the first time that a global view of sulfur metabolism is reported in the biotechnological yeast Kluyveromyces lactis. We used combined approaches based on transcriptome analysis, metabolome profiling, and analysis of volatile sulfur compounds (VSCs). A comparison between high and low sulfur source supplies, i.e., sulfate, methionine, or cystine, was carried out in order to identify key steps in the biosynthetic and catabolic pathways of the sulfur metabolism. We found that sulfur metabolism of K. lactis is mainly modulated by methionine. Furthermore, since sulfur assimilation is highly regulated, genes coding for numerous transporters, key enzymes involved in sulfate assimilation and the interconversion of cysteine to methionine pathways are repressed under conditions of high sulfur supply. Consequently, as highlighted by metabolomic results, intracellular pools of homocysteine and cysteine are maintained at very low concentrations, while the cystathionine pool is highly expandable. Moreover, our results suggest a new catabolic pathway for methionine to VSCs in this yeast: methionine is transaminated by the ARO8 gene product into 4-methylthio-oxobutyric acid (KMBA), which could be exported outside of the cell by the transporter encoded by PDR12 and demethiolated by a spontaneous reaction into methanethiol and its derivatives.

Rapid Determination of Low-Level Sulfur Compounds in Beer by Headspace Gas Chromatography with a Pulsed Flame Photometric Detector

Off-flavors in beer are frequently due to the presence of sulfur compounds. A simple and sensitive method for the analysis of volatile sulfur compounds in beer at trace levels was developed using headspace gas chromatography with a pulsed flame photometric detector. Different capillary columns were tested, and a 60-m nonpolar DB-1 capillary column was found to be the most appropriate. Four sulfur compounds, including hydrogen sulfide, methanethiol, ethanethiol, and dimethyl sulfide, could be quantified simultaneously using ethyl methyl sulfide as the internal standard. Calibration curves were established in a 4% (vol/vol) ethanolic solution with pH adjusted to 4.0; linear correlation coefficients (r) were greater than 0.99 for all target compounds. This method enables four sulfur compounds in beer to be determined at trace levels, with recoveries greater than 96%, a repeatability error of less than 5%, and limits of detection between 0.1 and 2 μg/L. The overall method was successfully applied to the determination of sulfur compounds studied in several beers.

Volatile sulfur compounds in Cheddar cheese determined by headspace solid-phase microextraction and gas chromatograph-pulsed flame photometric detection

The aim of this study was to develop a methodology for the analysis of volatile sulfur compounds (VSCs) in Cheddar cheese. Solid-phase microextraction (SPME) was employed to extract VSCs from the cheese matrix using a CAR-PDMS fiber. This extraction method was combined with gas chromatography–pulsed flame photometric detection (GC–PFPD) to achieve high sensitivity for sulfur compounds. The impact of extraction parameters, including time, temperature and sample size, was evaluated to determine the best conditions to analyze sulfur compounds in Cheddar cheese. Hydrogen sulfide, methanethiol, and dimethyl sulfide were found to constitute the majority of the overall sulfur profile while dimethyl disulfide and dimethyl trisulfide were present in lesser amounts. Artifact formation of volatile sulfur compounds was found to be minimal. Two commercial cheese samples were analyzed and differences in sulfur content were observed. Overall, SPME–GC–PFPD was found to be a highly sensitive technique for the analysis of sulfur compounds in Cheddar cheese.

Investigation of Artefact Formation During Analysis of Volatile Sulphur Compounds Using Solid Phase Microextraction (SPME)

The occurrence and origin of artefact formation during the analysis of volatile sulphur compounds in air by PDMS/Carboxen fibre were investigated. Among the studied compounds (hydrogen sulphide, carbon disulphide, diethyl sulphide, methyl ethyl sulphide, isopropanethiol, methanethiol, dimethyl sulphide, dimethyl disulphide, carbonyl sulphide), essentially mercaptans were shown to react to form the corresponding dimers. However, in the presence of several oxygenated and amines compounds which are common components of industrial effluents, no further artefact formation or reaction was noticed. Artefact formation was therefore considered to be independent of the sample matrix. Thermal oxidation occurring during the desorption step in the GC injection port was assessed. As metallic elements were previously suspected to catalyse the reaction, a specially deactivated SPME needle was tested, but no significant difference was noticed compared to the original needle. It was therefore assumed that metallic elements naturally present on Carboxen may act as catalysts. Similar results were obtained by using Carboxen in adsorbent tubes, as artefacts were increased by comparison with Tenax TA and molecular sieve 5A.

Analysis of volatile sulphur compounds in breath by gas chromatography–mass spectrometry using a three-stage cryogenic trapping preconcentration system

A method for the determination of trace volatile sulphur compounds (VSCs) including methanethiol, dimethyl sulfide (DMS) and dimethyl disulfide (DMDS) at low ppbv (volume/volume) in breath has been developed using a large volume preconcentration technique prior to capillary GC–MS analysis. The breath sample was collected in a 6-l fused-silica-lined stainless steel canister and introduced into the three-stage cryogenic trapping preconcentration system by GC–MS in the total ion monitoring (scan) mode. The water condensation effect of breath sample inside the canister, which is due to the difference between human body temperature and laboratory temperature, was examined. The condensed water in the fused-silica-lined canister at 24°C did not affect the recoveries of VSCs within 12 h. As this three-stage cryogenic trapping preconcentration technique made it possible to remove excess water {relative humidity (RH) >95%} and carbon dioxide (3.8%) without loss of the VSCs, more than 400 ml of the breath sample could be concentrated. The detection limits of methanethiol, DMS and DMDS in a breath sample using this method were 0.13, 0.09 and 0.15 ppbv, respectively.

Analysis of odorous sulfur compounds in air from a petroleum company by gas chromatography with flame photometric detection

The programmed‐temperature‐vaporizing (PTV) injector has been used as a thermal desorption chamber for analysis of volatile sulfur compounds. A trap employing the solid adsorbent Tenax‐TA was used to enrich ambient levels of volatile sulfur compounds, then the sulfur gases were thermally released according to programmed temperature from the adsorbent trap and directly transferred to the system of PLOT‐column gas chromatography/flame‐photometric detector for analysis. The sulfur compounds known to cause nuisance odors in the air from various sewerage treatment tanks of a chemical petroleum company are determined.

Chromatographic analysis of volatile sulphur compounds in wines using the static headspace technique with flame photometric detection

This study describes the development of a method for determining eleven sulphur compounds in wine, which takes into account that thiols are easily oxidizable. The equilibria of the analytes between air and aqueous ethanol were studied and optimised using static headspace gas chromatography in order to obtain the best sensitivities. The influences of parameters such as temperature, time, ionic strength, headspace volume and the volume of headspace injected were determined. A cryogenic trap was used to concentrate the headspace analytes and they were chromatographically analysed using GC temperature programming on a poly(ethylene glycol) capillary column with FPD detection at 394 nm. The power relationship was observed between the chromatographic response and a concentration of sulphur compounds in the range 2–150 μg l−1 in the sample. Recoveries were determined by the standard addition technique and were higher than 90% for sulphides and disulphides and close to 80% for thiols. The overall method was succesfully used to determine the sulphur compounds in white and red wines.

Influence of Complex Media Composition, Cognac's Brandy, or Cognac, on the Gas Chromatography Analysis of Volatile Sulfur Compounds — Preliminary Results of the Matrix Effect

Some of the constituents of Cognac9s brandy or Cognac media indeed interact with volatile sulfur compounds: among these constituents, transition metals (particularly copper ions) chelate thiols reversibly. This thiol complexation diminishes considerably their concentration in the analyzed static headspace of the solutions. In the case of cognacs media, the caramel addition decrease the concentrations of volatile sulfur compounds; hydrogen sulfide and thiols are especially well bounded.

Quantitative Analysis of Volatile Sulfur Compounds in Beer Using a Membrane Extraction Interface

Improved quantitation of volatile sulfur compounds in beer using membrane extraction is demonstrated. The membrane consists of a silicone tube (300 mm × 0.29 mm i.d. × 0.6 mm o.d.). The tube, purge...

Quantitative Analysis of Volatile Sulfur Compounds in Beer Using a Membrane Extraction Interface

Quantitative Analysis of Volatile Sulfur Compounds in Beer Using a Membrane Extraction Interface

Improved chromatographic analysis of volatile sulfur compounds by the static headspace technique on water-alcohol solutions and brandies with chemiluminescence detection

Volatile sulfur compounds are renowned for their nauseous character in alcoholic beverages at an extremely low concentration. In this work, quantitative analytical method was developed for their detection with the static headspace technique using a Sievers chemiluminescence detector (SCD 355). It gives a linear response over the concentration range 10–100 μg/l with a repeatability or reproducibility error of less than 5%. It was found that the headspace concentration of sulfur compounds in water-alcohol solutions or brandies rises with increasing ratio between the gas and liquid phase volumes and proportional to the temperature. However, it diminishes with increasing ethanol content and is barely sensitive to the liquid-phase salt concentration.

ChemInform Abstract: Comparison of Gas Chromatographic Detectors for the Analysis of Volatile Sulfur Compounds in Foods.

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