Determination Of Sulphur In Organic Compounds Research Articles

Extraction and determination of organosulfur compounds in water samples by using homogeneous liquid-liquid micro-extraction via flotation assistance-gas chromatography-flame ionization detection

A new method was developed for the preconcentration and determination of organosulfur compounds (OSCs) in water samples using homogeneous liquid-liquid microextraction via flotation assistance (HLLME-FA) and gas chromatography (GC) with flame ionization detection (FID). Toluene at microliter volume level and acetone were used as an extraction and a homogeneous solvent, respectively. In this research, a special extraction cell was designed to facilitate collection of the low-density solvent extraction. No centrifugation was required in this procedure. Using air flotation, extraction solvent was collected at the conical part of the designed cell. The effects of the different variables on the efficiency of the extraction such as kind and the volume of extraction and homogeneous solvents, ionic strength and extraction time were studied and optimized. Under the optimum conditions, linearity of the method were in the range from 0.25 to 200 µg L-1 with limit of detections (LODs) (S/N = 3) were in the range from 0.05 to 0.4 µg L-1. HLLME-FA is a fast, simple and efficient method for the determination of organic sulfur compounds in aquatic samples. KEY WORDS: Homogeneous liquid-liquid microextraction, Flotation assistance, Organosulfur compounds, Gas chromatography, Water samples Bull. Chem. Soc. Ethiop. 2014, 28(2), 195-204DOI: http://dx.doi.org/10.4314/bcse.v28i2.4

Identification of organic sulfur compounds in coal bitumen obtained by different extraction techniques using comprehensive two-dimensional gas chromatography coupled to time-of-flight mass spectrometric detection

The determination of organic sulfur compounds (OSC) in coal is of great interest. Technically and operationally these compounds are not easily removed and promote corrosion of equipment. Environmentally, the burning of sulfur compounds leads to the emission of SO(x) gases, which are major contributors to acid rain. Health-wise, it is well known that these compounds have mutagenic and carcinogenic properties. Bitumen can be extracted from coal by different techniques, and use of gas chromatography coupled to mass spectrometric detection enables identification of compounds present in coal extracts. The OSC from three different bitumens were tentatively identified by use of three different extraction techniques: accelerated solvent extraction (ASE), ultrasonic extraction (UE), and supercritical-fluid extraction (SFE). Results obtained from one-dimensional gas chromatography (1D GC) coupled to quadrupole mass spectrometric detection (GC-qMS) and from two-dimensional gas chromatography with time-of-flight mass spectrometric detection (GC × GC-TOFMS) were compared. By use of 2D GC, a greater number of OSC were found in ASE bitumen than in SFE and UE bitumens. No OSC were identified with 1D GC-qMS, although some benzothiophenes and dibenzothiophenes were detected by use of EIM and SIM modes. GC × GC-TOFMS applied to investigation of OSC in bitumens resulted in analytical improvement, as more OSC classes and compounds were identified (thiols, sulfides, thiophenes, naphthothiophenes, benzothiophenes, and benzonaphthothiophenes). The roof-tile effect was observed for OSC and PAH in all bitumens. Several co-elutions among analytes and with matrix interferents were solved by use of GC × GC.

Dispersive liquid-liquid microextraction for the preconcentration and determination of some organic sulfur compounds in aqueous samples

In this study, dispersive liquid-liquid microextraction was developed for preconcentration of some organic sulfur compounds in aqueous samples. In this extraction method, 1.0 cm3 acetonitrile (as dispersive solvent) containing 12.0 mm3 chlorobenzene (as extraction solvent) was rapidly injected into the water sample containing analytes, and a cloudy solution was formed. The cloudy state resulted from the formation of fine droplets of chlorobenzene, which have been dispersed in bulk aqueous sample. After centrifugation (2 min at 5,000 rpm), these droplets were sedimented in the bottom of the conical test tube (5 ± 0.2 mm3). Then 2.0 mm3 of sedimented phase containing preconcentrated analytes was injected into the gas chromatograph with flame ionization detector. The parameters affecting the extraction efficiency have been evaluated and optimized. Under the optimum conditions, the limits of detection and preconcentration factors were obtained in the range of 0.1–0.9 μg dm−3 and 564–768, respectively. The calibration graphs were linear in the range of 1–200 μg dm−3. The relative standard deviations at 100 μg dm−3 concentration levels of analytes were found to be less than 10%. Finally, the accuracy of the proposed method was evaluated by extraction and determination of organic sulfur compounds from different water samples such as river, tap, and sea waters, and satisfactory results were obtained.

Preparation of sol–gel polyethylene glycol–polydimethylsiloxane–poly(vinyl alcohol)-coated sorptive bar for the determination of organic sulfur compounds in water

A novel headspace sorptive extraction (HSSE) using a glass bar coated with carbowax (polyethylene glycol)–polydimethylsiloxane–poly(vinyl alcohol) (CW/PDMS/PVA) prepared by sol–gel technology method was proposed for the determination of volatile organic sulfur compounds (VOSs) in water. After the extraction, the sorptive bar was desorbed with 60 μL of ethanol and 30 μL of the extract was analysed by large volume injection (LVI) into a gas chromatography-flame photometric detector (GC-FPD). The parameters affecting the headspace sorptive extraction of VOSs such as extraction and desorption time, extraction temperature, stirring speed, desorption solvent, headspace phase ratio, salt and pH were carefully investigated and the optimized experimental conditions were established. The limits of detection (LODs) for the studied VOSs ranged from 0.04 to 4.8 μg/L with the relative standard deviations (RSDs) ranging from 4.5 to 10.2% ( n = 6). The reproducibility for the preparation of CW/PDMS/PVA-coated sorptive bar ranged from 3.2 to 9.2% in one batch, and from 2.8 to 18.5% in batch-to-batch, and more than 50 extractions can be achieved without apparent loss. The proposed method was compared with polydimethylsiloxane-HSSE and carboxen/PDMS-headspace-solid phase microextraction (CAR/PDMS-HS-SPME) under their optimum conditions, CW/PDMS/PVA-HSSE shows the highest adsorption capacity (larger surface area and more active sites), the highest sensitivity (about 10 times) and the best polarity matching for VOSs.

Analytical methods and quality assurance

The method for speciation and quantitative analysis of inorganic sulphur form, sulphate and organic sulphur compounds by using high performance ion chromatography (IC) with inductively coupled plasma atomic emission spectrophotometry (ICP‐AES) has been developed. An ICP‐AES was operated as a detector of IC. To achieve a lower detection limit a hydraulic high‐pressure nebulizer was used for connection between IC and ICP. This hyphenated system was used for the separation and determination of organic sulphur compounds and sulphate ions. By using an anion exchange column, with 2.5 mM phthalic acid, adjusted with TRIS to pH=4.2, all of the organic sulphur forms were measured together as a first (pseudo) peak (Nieto and Frankenberger, 1985) at 2.0 min., while the sulphate ion was retained on the column and its peak appeared with retention time at 4.2 min. Other inorganic sulphur forms (sulphide, sulphite, thiosulphate etc.) were not detectable in the water extracts from the examined plants. The sulphide and sulphite peaks were observed between the organic sulphur and sulphate peaks, but the developed method was not optimised for their separation. The sulphur was detected on the polychromator of ICP‐AES on 180.734 nm. The detection limits were 0.023 mg L‐1 and 0.085 mg L‐1 of sulphate‐sulphur and of organic‐sulphur respectively. Water extracts of standard wheat straw and grain samples were analysed.

Isolation and determination of dissolved organic sulphur compounds — development of the organic group parameter DOS

A procedure has been worked out for the determination of organic sulphur compounds (OSCs) in aqueous solution. They are isolated from water by solid phase extraction on macroporous resins and reversed-phase sorbents. The total sulphur content of the extracts is determined via a process of thermal cracking and hydrogenation (pyrohydrogenolysis) of small amounts of extract in a heated quartz tube (1100°C) flushed with hydrogen. Sulphur is detected at a wavelength of 394 nm in the hydrogen flame of a flame photometer. The flame photometric detector (FPD) is calibrated with a coulometric H2S-generator. The procedure of solid phase extraction and subsequent pyrohydrogenolysis/flame photometry of the extracts can be used to determine the organic group parameter DOS (Dissolved Organic Sulphur) in the range of 20–1000 μg/1.

Determination of organic sulphur compounds in sediments of the river Elbe using gas chromatography with flame photometric detection

Sediment samples from different reference sites representing typical situations on the river Elbe were analyzed for organo-sulphur compounds (OSC). Gas chromatography with sulphur specific flame-photometric detection was used for the identification and quantification of individual OSC. Chromatographic retention data for 42 standard heterocycles were determined and compared with the composition of sediment extracts. An extraction scheme used for the OSC determination is described. Dibenzothiophene (DBT), its alkylated homologues, phenanthro[4,5-bcd]thiophene, benzo[b]naphtho[2,1-d]thiophene and in some cases still unidentified compounds were the predominant OSC. Depending on sampling site and date the qualitative composition of sulphur heterocycles detected by the described method varied, and the total concentrations of all OSC ranged from 0.3 to 21 mg/kg.

Determination of organic sulphur compounds in garlic extracts by gas chromatography and mass spectrometry

Gas chromatography and mass spectrometry were used to study organic sulphur compounds present in extracts of Allium sativum (garlic) plants. The limits of detection were between 1.76 and 9.40 ng for allyl methyl sulphide and dimethyl disulphide, respectively. Extraction of aqueous solutions with diethyl ether yielded percentage recovery rates ranging from 74.4% (allyl methyl sulphide) to 90.3% (dipropyl disulphide). The composition and yield of organic sulphur compounds present in extracts of garlic were studied using gas chromatography and mass spectrometry.

Application of catalytic stripping voltammetry for the determination of organic sulfur compounds at a hanging mercury drop electrode: behaviour of cysteine, cystine and N-acetylcysteine in the presence of nickel ion

The differential-pulse cathodic stripping voltammetry of cysteine (CysH), cystine (Cys) and N-acetylcysteine (Ac-CysH) was studied at a hanging mercury drop electrode at pH 7 in the presence of nickel ion, 3-(N-Morpholino)propanesulfonic acid (MOPS) and phosphate–acetate buffer were used as supporting electrolytes. In the presence of CysH, after accumulation at potentials ranging between 0.0 and –0.4 V, the catalytic reduction of nickel ion gives a peak at –0.6 V versus the Ag—AgCl reference electrode. An additional effect of nickel ion is the suppression of the cathodic stripping peak due to mercury cysteinate reduction, thus permitting the simultaneous determination of another thiol with no catalytic activity (e. g., Ac-CysH), Consequently, CysH (or Cys) and Ac-CysH can be determined simultaneously or independently in the same sample. Cys is reduced at potentials preceding the catalytic peak, which is actually due to the CysH thus produced. Some differences between the behaviour of Cys and CysH are due to different accumulation mechanisms. The catalytic stripping voltammetry of CysH or Cys exhibits good sensitivity (detection limit about 1 nmol dm–3 for 3 min accumulation). The stripping voltammetric method described appears to be the first involving adsorptive accumulation of a metal complex in which the organic ligand is determined catalytically. Further, this particular method affords some selectivity in the determination of sulfur compounds, which are normally determined by cathodic stripping, voltammetry of their anodically accumulated mercury complexes.

Gas chromatographic and capillary gas chromatographic/mass spectrometric determination of organic sulfur compounds (OSCs) in sediment from ports: Significance of these compounds as an oil pollution index

Oil pollution arises in waters near petroleum industrial districts. In oily odor fish caught in the coast near petroleum industries, toluene, other aromatic hydrocarbons and olefinic hydrocarbons have been detected. The authors also reported the presence of organic sulfur compounds (OSCs), probably originating from polluting oil, in fish caught in the Seto Inland Sea after an accidental oil spilling from a tank. In a previous study, the authors detected OSCs in the oyster and mussel caught in the Seto Inland Sea. However, the presence of OSCs and polyaromatic hydrocarbons (PAHs) in sea sediments has not been described. In the present report, OSCs and PAHs in the sea sediments collected in several ports facing Seto Inland Sea were analyzed by a gas chromatographic/mass spectrometric (GC-MS) system.

Automated determination of organic sulfur compounds: I. Spectrophotometric measurement of inorganic sulfate by low-pressure exchange chromatography

A method for determination of inorganic sulfate is described which represents the terminal step of an automated assay of organic sulfur compounds in biological fluids. Nanomole quantities of inorganic sulfate were applied to a barium chloranilate column. Corresponding amounts of chloranilate ion, released as a result of an exchange reaction, were then measured by uv absorption at 313 nm. The reproducibility and sensitivity of the method and a calibration curve are reported.

Capillary GC/MS determination of organic sulfur compounds detected in oyster and mussel caught in the sea as an oil pollution index.

The organic sulfur compounds usually contained in crude oil were used as a marker of oil pollution in shellfish. The oyster (Crassostrea gigas) and mussel (Mytilus edulis) were caught in the Seto Inland Sea of Japan. Capillary-column gas chromatography/mass spectrometry (GC/MS) of extracts showed the presence of organic sulfur compounds of dibenzothiophene and alkyl dibenzothiophenes (C1-C3). The concentration factor of organic sulfur compounds in the oyster and mussel was determined by gas chromatography using a flame photometric detector.

Cathodic stripping voltammetry Part I. Determination of organic sulfur compounds, flavins and porphyrins at the sub-micromolar level

The experimental parameters of cathodic stripping voltammetry have been studied and optimised, and the use of a cell with a mercury pool electrode has been proposed. The technique is valuable for the determination of several classes of organic compounds, including thiols, disulfides, flavins, flavones, pterins and porphyrins at concentrations as low as 1×10−8 M. In most cases the measurement precision at the 2×10−7 M level is ±3–5%, which is similar to that of anodic stripping voltammetry. Detailed investigations were made of the electrode reaction mechanisms of cysteine, cystine, riboflavin and hemoglobin. All thiol compounds were found to adsorb strongly on mercury and chemically react with it to form a film of a mercury-thiol compound. Some closely-related thiols, e.g. 2- and 6-mercaptopurine, produced stripping peaks at well-separated potentials. Selectivity could be achieved with some thiol mixtures by adjustment of the deposition potential.

Cathodic stripping voltammetry: Part I. Determination of organic sulfur compounds, flavins and porphyrins at the sub-micromolar level

The experimental parameters of cathodic stripping voltammetry have been studied and optimised, and the use of a cell with a mercury pool electrode has been proposed. The technique is valuable for the determination of several classes of organic compounds, including thiols, disulfides, flavins, flavones, pterins and porphyrins at concentrations as low as 1×10 −8 M. In most cases the measurement precision at the 2×10 −7 M level is ±3–5%, which is similar to that of anodic stripping voltammetry. Detailed investigations were made of the electrode reaction mechanisms of cysteine, cystine, riboflavin and hemoglobin. All thiol compounds were found to adsorb strongly on mercury and chemically react with it to form a film of a mercury-thiol compound. Some closely-related thiols, e.g. 2- and 6-mercaptopurine, produced stripping peaks at well-separated potentials. Selectivity could be achieved with some thiol mixtures by adjustment of the deposition potential.

Potentiometric determination of organic sulphur compounds in cracked gasolines

W H ~ developing methods for the control of alcohol production by oxo-synthesis it became necessary to determine the content of organic sulphur compounds in low boiling cracked gasoline fractions, the raw material of oxosynthesis. There are now several methods of determining these compounds which are, however, only intended for straight-run petroleum products [1-6]. According to the ~conclusion derived by Luk'yanltsa [5], who made a detailed critical review of methods of determining sulphur compounds, potentiometric titration is the most effective method, we have used this to determine mercaptan, disulphide and sulphide sulphur in products containing olefins. Mercaptan sulphur. Direct potentiometric titration with an ammonlacal silver nitrate solution in an electrode cell with a calomel electrode and a silver sulphide electrode (silver coated with a silver sulphide layer) was used to determine mercaptan sulphur. This method has been specified as standard for fuels (GOST 9558-60). To prevent loss of volatile components, samples were taken by a special pipette with two taps and the solution cooled during titration. Tests showed that changing the temperature of the ~olution titrated from 5 to 20 ° had no effect on analysis. Results obtained by determining mercaptan sulphur content in standard amylmercaptan solutions in heptane in the presence of heptene and di-isobutylene differed by not more than 4 × 10 -4 % abs. from calculated results, i.e. did not exceed the standard error (Table 1). The sulphide silver electrode retained activity over a long period. Disulphide sulphur. To determine disulphide sulphur a method proposed by Hubbard [4] and later Rubinshtein [6, 7] was used, which is based on accelerated reduction of disulphides to mercaptans and determination of the latter by potentiometric titration.