Gas Chromatography-atomic Emission Detection Research Articles

Morphology study of nickel and vanadium in asphaltenes via hydropyrolysis

The morphology of nickel and vanadium compounds in the asphaltenes were investigated via hydropyrolysis with the help of inductively coupled plasma mass spectrometer (ICP-MS), ultraviolet-visible (UV-Vis), high-temperature gas chromatography atomic emission detection (HT GC-AED), and positive-ion electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (+ESI FT-ICR MS). The results showed that the toluene soluble yields of products decreased from 64% to 19% as the hydropyrolysis temperature increased from 330 to 410 °C, while the abundance of nickel and vanadium compounds detected by GC-AED increased significantly. The molecular composition distribution of nickel and vanadyl porphyrins showed rhythmic changes with different temperatures in the hydropyrolysis of asphaltenes.

Characterization of metal complexes in Kuwait atmospheric residues

Four kinds of atmospheric residues (ARs) from Kuwait crudes were characterized using various analytical tools. V- and Ni petroporphyrins present in the four ARs could be analyzed by gas chromatography–atomic emission detection with high-temperature injection. All the ARs exhibited definite peaks for the vanadium and nickel species. Chromatograms of vanadium and nickel consist of a broad peak superimposed with sharp peaks corresponding to the retention times of porphyrin. Demetallation of ARs on the silica–alumina (support only) catalyst alone decreased the intensity of the sharp peaks preferentially over the broad one. ARs exhibited electron spin resonance (ESR) with the species VO, whose line profiles were different from that of VO tetraphenylporphyrin in tetrahydrofuran at room temperature. The profiles, however, resemble those of the frozen form (−150°C), indicating limited mobility of petroporphyrin in the AR at room temperature. The limited mobility, revealed by ESR, and the favorable effects of hydrogenation conditions for hydrodemetallization suggest the covalent and noncovalent binding of some petroporphyrins to the polymeric component in the as-received forms of ARs. Liberation of petroporphyrin from the gas chromatograph column at around 450°C may occur and generate monomeric forms that reach the detector.

Stability and Reactivity of Sulfur Compounds against Copper in Insulating Mineral Oil: Definition of a Corrosiveness Ranking

Corrosive sulfur is a well-known critical issue for mineral insulating oils used in power transformers. The objective of this work is to study the reactivity of different groups of sulfur containing compounds (aliphatic and aromatic mercaptans, sulfides, disulfides, thiophenes) that may be present in insulating oils. The stability of nine compounds, pertaining to the aforementioned groups, was investigated with regards to temperature and aging time, under oxidative and inert atmosphere, in order to simulate the natural aging of both hermetically sealed or free breathing type transformers. Their reactivity against copper was also investigated. A gas chromatography atomic emission detection method was optimized to quantify the consumption of each compound. The tendency of 22 sulfur compounds to react with copper and form copper sulfide was quantitatively assessed at different temperatures. The resulting corrosiveness ranking for sulfur compounds families differs from what is usually reported in the literature and was proven to be temperature dependent.

Characterization and analysis of vanadium and nickel species in atmospheric residues

Metal species (Ni and V) in as-received atmospheric residues (ARs) were characterized through conventional analysis methods as well as through gas chromatography-atomic emission detection (GC-AED) assembled with a high-temperature injector system (HT-GC-AED). The vanadium concentration in all ARs could be successfully measured by electron spin resonance (ESR) corrected with inductively coupled plasma-mass spectroscopy (ICP-MS). HT-GC-AED was attempted to confirm the characteristics of V and Ni species, from which at least five species of vanadium and six species of nickel in as-received ARs were identified, together with several shoulder peaks. In addition, HT-GC-AED analysis of product oils after hydrodemetallization (HDM) of ARs was investigated over both oxide and sulfide catalysts. This analysis provided evidence of a demetallization mechanism for the cracking of the alkyl group attached to the metal porphyrin structure over oxide catalysts. This mechanism contributes to the enhancement of HDM based on the staged reaction over the oxide (1st stage)-sulfide (2nd stage) catalytic system.

GC/AED를 이용한 의료용 액화혼합가스 중 산화에틸렌 및 프레온 가스류의 몰분율 측정

산화에틸렌(<TEX>$C_2H_4O$</TEX>, Ethylene oxide, EtO)은 에탄올아민 같은 공업적으로 중요한 물질이나 에틸렌 글리콜의 생산 원료 또는 살균제로 이용되는 물질이다. 산화에틸렌은 불화탄화수소를 분사제 또는 바탕가스로 하여 액화혼합가스로 제조되어 열에 약한 의료기기나 저장시설의 소독에 널리 사용되고 있다. 액화혼합가스의 생산 및 사용 시 품질관리 및 안전관리를 위해 각 성분의 몰분율을 정확히 측정할 필요가 있다. 휘발성 액체시료 중 각 기체성분들은 증기압이나 끓는점 등과 같이 물리 화학적 성질이 다르므로 몰분율 측정 시 실린더 내부의 상층에 평형을 이루고 있는 기체시료 또는 하층의 기화되지 않은 액체시료를 직접 측정기기에 주입하는 방법에 따라 측정 결과가 다를 수 있다. 본 연구에서는 액화혼합가스를 액체 또는 기체 상태로 주입할 수 있는 새로운 온라인 시료도입장치를 고안하고 GC/AED (gas chromatograph-atomic emission detector)를 사용하여 산화에틸렌과 불화탄화수소 액화혼합가스를 측정하였으며 AED의 검출특성, 기기에 주입 시 시료의 상태, 측정파장에 따른 측정결과의 정확성 및 반복성을 조사하였다. Ethylene oxide (<TEX>$C_2H_4O$</TEX>, EtO) is used as a raw material for the production of ethylene glycol and other industrially important material such as ethanolamines and also used as a disinfecting agent. It is applied for gas-phase sterilization of thermally sensitive medical equipment, and for processing of storage facilities as a mixture with fluorinated hydrocarbon. In this perspective, accurate determination of the mole fractions of components in the liquefied gas mixture is required for the quality control and safety of production and use. Each component of the liquefied gas mixture has different chemical and physical properties such as vapor pressure and boiling point. Therefore, we can suppose that analytical results can be different according to the introduction method for the gas phase of upper layer, or for the liquid phase of lower layer in gas cylinder. In this study, we designed a new on-line sample injection device for the liquefied gas mixture in liquid or gas state, and applied to the analysis of liquefied gas mixture of ethylene oxide and fluorinated hydrocarbons by GC/AED (gas chromatograph-atomic emission detector). We studied performance of AED, and effect of sample introduction and selected wavelength to the accuracy and repeatability of analytical results.

Determination of the volatiles from tobacco by capillary gas chromatography with atomic emission detection and mass spectrometry

A new gas chromatograph-atomic emission detector (GC-AED) coupled with Deans switching technique for analyzing volatiles from tobaccos were developed. The detector operating parameters (reagent gas pressure and make-up gas flow rate) were optimized. The detection limits for the elements carbon (193 nm), hydrogen (486 nm) and oxygen (171 nm) ranged 0.05-0.2, 0.05-0.3 and 1-11 ng, respectively, depending on the compound. The sensitivity and linearity for the elements carbon (193 nm), hydrogen (486 nm) and oxygen (171 nm) decreased in the order O>H>C. Calibration curves were obtained by plotting peak area versus concentration, and the correlation coefficients relating to linearity were at least 0.9359. Elemental response factors measured on these channels, relative to the carbon 193-nm channel, were hydrogen, 0.38-0.48 (mean %RSD=5.64), and oxygen, 0.085-0.128 (mean %RSD=14.9). The evaluation was also done for the new technique and for an established GC-MS technique for the same real samples. The results of GC-AED and GC-MS showed that there was a relatively good agreement between the two sets of data.

Application of Pyrolysis Cryogenic Trap Gas Chromatography/Atomic Emission Detection (Py-CryT-GC/AED) for the Study of Nitrogen Forms and Dynamics in a Grassland Soil

Soil organic nitrogen (N) was characterized for its chemical species and chemical transformations in a grassland soil profile by using a combination of cryogenic pyrolysis gas chromatography atomic emission detection method with soil physical size fractionation. The soils taken from 0–12, 12–25, and 25–38 cm depth layers were separated into five fractions, <2, 2–38, 38–53, 53–105, and 105–250 µm and each of which was analyzed for total organic C and N, and different N forms. Our results showed that (1) total organic carbon has a positive correlation with the total organic nitrogen (TON) with correlation coefficient increased with soil depth; (2) deep and small particle-size fraction soils yielded more volatile pyrolysate N than the surface and large particle-size fractions and the amount of volatile pyrolysate N has a linear positive correlation with TON and correlation coefficient increased with soil depth; (3) the major components of the volatile pyrolysate N include ammonia, acetonitrile, hydrogen cyanide, pyridine, and pyrrole; (4) of the total volatile pyrolysate N, ammonia accounted for more than 40%, and the sum of acetonitrile and hydrogen cyanide accounted for approximately 30–50%; and (5) the amounts of acetonitrile, hydrogen cyanide, and pyridine had increased positive correlations with TON with increasing soil depth, but the correlation between the amount of pyrrole and depth decreased in the opposite direction. Our research result sheds some light into soil organic nitrogen forms and its transformations in the processes of soil organic C aging and stabilization.

Solid phase extractive preconcentration coupled to gas chromatography–atomic emission detection for the determination of chlorophenols in water samples

Solid-phase extraction (SPE) followed by derivatization and gas chromatography-atomic emission detection (GC–AED) was evaluated for the determination of five chlorophenols (CPs) in water samples. The derivatization was based on the esterification of phenolic compounds with ferrocenecarboxylic acid. The determination of the derivatized phenols was performed by GC–AED in the iron selective detection mode at 302nm. The described method was tested on spiked water samples.The overall method gave detection limits of 1.6–3.7ngL−1 and recoveries of 90.9–104.5% for the examined mono- to trichlorophenols in 10mL water samples. The CPs extracted from a 10mL water sample with SPE were concentrated into 100μL of organic solvent, a preconcentration factor of 100. The method was applied to lake and tap water samples, and CP contents between 6 and 51ngL−1 in lake water and between below the detection limit and 8ngL−1 in tap water were found for different CPs. The method is quick, simple and gives excellent recoveries, limits of detection and standard deviations.

Concentrations, sulfur isotopic compositions and origin of organosulfur compounds in pore waters of a highly polluted raised peatland

Sulfur cycling in peatlands plays a key role in their response to atmospheric deposition of acid sulfate; however, the role of dissolved organic sulfur species has received little attention. In this study, we assess the quantitative importance of dissolved organic sulfur species in a heavily polluted peatland and their role in sulfur cycling. Surface and pore waters from a raised peat bog have been analyzed for dissolved organic and inorganic species. Except in the surface water, organically bound sulfur dominates over sulfate sulfur and the organosulfur is predominantly in the humic fraction, which is not GC amenable. Two organosulfur compounds are present in the GC amenable fraction at all depths; a compound containing a benzene ring, sulfone and amide groups dominates while a compound closely similar to either benzothiazole or 1,2-benzisothiazole is present at 100–1000 times lower concentrations. Other organosulfur species were detected in some samples by GC–AED (gas chromatography–atomic emission detection) at similar or yet lower concentrations but not identifiable with GC–MS. In the shallowest parts of the peat, sulfur isotopic data on the humic and non-humic dissolved organic sulfur fractions show a pronounced difference, implying different sources for these organosulfur compounds. Humic organosulfur is 34S enriched, indicating a source for this component from breakdown of plant materials, which have similar δ34S (0.1‰ and 4.2‰). By contrast, the non-humic organosulfur is more 34S depleted at shallow depths (−11.7‰ in surface water), indicating an origin from reaction of bacterially produced sulfide (−9.9‰ in surface water) with dissolved organic material. Deeper in the peat the non-humic organosulfur becomes more 34S enriched (up to +6.8‰), which may result from either: (i) reactions between organic material and more 34S enriched sulfide; or (less likely) (ii) a shift to production of non-humic organosulfur by breakdown of humic compounds or plant material in the peat matrix.These data highlight the importance of organosulfur species relative to inorganic species in peatland groundwaters. Organosulfur species comprise the bulk of the dissolved sulfur budget and are involved in the bacterial cycling of sulfur in the peatland ecosystem.

A Diels-Alder Reaction Between A Cigarette Mainstream Smoke Component and Benzoquinone

Abstract A notable amount of research has been placed toward understanding the roles of benzoquinone (Q) and hydroquinone (HQ) in the chemistry and toxicity of cigarette smoke. To further understanding of the roles of these compounds in cigarette smoke, a series of reactions were performed wherein the levels and chemistries of Q and HQ were monitored after having been added to selected phases of the mainstream smoke from 2R4F cigarettes. Through the application of both fundamental organic chemistry reaction mechanistic principles and qualitative analysis of smoke chemistry, a new reaction pathway for mainstream smoke components was elucidated. During the course of these investigations, the presence of a product from a Diels-Alder reaction between a 2R4F cigarette mainstream smoke component and Q was discovered. Data from carbon-13 nuclear magnetic resonance (13C NMR), gas chromatography-atomic emission detection (GC-AED), and gas chromatography-mass selective detection (GC-MSD) revealed a Diels-Alder reaction product resulting from the reaction of benzoquinone (Q), a dienophile, and 1,3-cyclopentadiene, a diene, to yield tricyclo[6.2.1.02,7] undeca-4,9-diene-3,6-dione, more commonly referred to as cyclopentadienebenzoquinone. The reaction between Q and 1,3-cyclopentadiene was observed to have occurred when fresh mainstream vapor phase smoke (MSVP) from a 2R4F cigarette, captured in acetone, was subsequently treated with Q. Other 13C containing species were detected but inadequate signal to noise values prevented structural assignments. Accompanying the Diels-Alder reaction was an additional reaction of Q to form hydroquinone (HQ). These reactions provide additional information on the complexity of cigarette smoke, particularly as it relates to possible reactions involving Q and HQ and other cigarette smoke components.

Organotin Speciation and Tissue Distribution in Rat Dams, Fetuses, and Neonates Following Oral Administration of Tributyltin Chloride

Tributyltin (TBT) is a biocide that contaminates human foodstuffs, especially shellfish. TBT is an endocrine disrupter, producing imposex in several marine gastropods. Previous studies showed that oral dosing of rat dams with TBT chloride leads to abnormal fetal and postnatal development. In this study, the tissue distribution and speciation of organotins in tissues were examined in dams, fetuses, and neonates following dosing of rat dams commencing on gestational day (GD) 8 by oral gavage with TBT in olive oil at 0, 0.25, 2.5, or 10 mg/kg body weight (BW)/d. Dams' body weights were significantly reduced by the 10-mg/kg BW/d TBT treatment. At GD20, there were no significant effects of any TBT treatment on pup weights, litter size, sex ratio, or tissue weights. However, at postnatal day (PND) 6 and 12, neonatal pup weights were reduced by the 10-mg/kg BW/d TBT treatment but tissue weights were unaffected, except for the liver weight of female pups, which was reduced by the 10-mg/kg BW/d TBT treatment. Tissues harvested on GD20 and PND6 and PND12 were extracted for determination of organotins by gas chromatography–atomic emission detection (GC-AED). In most tissues, TBT and its metabolite dibutyltin (DBT) were evident but monobutyltin (MBT) was rarely measured above the detection limit. The livers and brains of fetuses contained TBT and DBT at levels that were approximately 50% of the equivalent tissues in the dams. Furthermore, these tissues appeared to preferentially absorb/retain organotins, since the concentrations were greater than were found for the total loading in whole pups. The placenta also contained relatively large quantities of TBT and DBT. Postnatally, the TBT levels in pups decreased markedly, a probable consequence of the extremely low levels of organotins in rat milk. However, DBT levels in pups livers and brains were maintained, probably due to metabolism of TBT to DBT. Similarly, while dams' spleens contained significant quantities of organotins, the pups' spleens contained smaller quantities, and these decreased rapidly between PND6 and PND12. These results show that organotins cross the placenta and accumulate in fetal tissues but that during lactation, the pups would receive minimal organotins through the milk and during this period, the levels of TBT in pups' tissues decreases rapidly. Consequently, fetuses would be at greater risk of the adverse effects of TBT, but due to the lack of transfer through milk, the risk would be reduced during the lactational period.

The determination by gas chromatography with atomic emission detection of total sulfur in fuels used as forensic evidence

In Japan, taxed diesel fuel from non-taxed fuel oil-A is illegally produced by removing coumarin, which is added as a non-taxed marker. The coumarin is removed using concentrated sulfuric acid and this produces a high viscosity and hazardous material, called “sulfuric acid pitch”, as a by-product. This compound has a detrimental effect on the environment and is hazardous to humans. The actions have been associated with organized crime with the illegally gained taxes becoming financial bases. To discriminate legal and diesel oil from illegal product, the peak area ratio R SC, the ratio of total sulfur to carbon (>C 14), was used. R SC is calculated by the total areas of sulfur and carbon (>C 14) from the gas chromatogram obtained by gas chromatography-atomic emission detection (GC-AED). Sulfur in legal diesel fuels is strictly regulated by a maximum limit, which was 50 ppm (and is now 10 ppm), but in the preparation of illegal diesel oil, in which coumarin is eliminated, sulfur cannot be removed. Therefore, the R SC of fuel oil-A and illegal fuel oil is over 15, whereas those for legal fuel oil and diesel fuel are under 2.0. Furthermore, these ratios do not change in weathering experiments. GC-AED was applied to an actual arson case and was found to be effective for the determination of total sulfur in trace amounts of accelerants detected in fire debris at the arson scene, and hence was effective for the characterization of the ignitable liquids used.

Optimization of headspace solid-phase microextraction gas chromatography-atomic emission detection analysis of monomethylmercury

Optimum conditions for headspace solid-phase microextraction (HS-SPME) in the analysis of monomethylmercury (MeHg) have been determined. Sodium tetra( n-)propylborate (NaBPr 4) is used as derivatization reagent to promote volatility. A simple aluminium bar was used to cool the SPME fiber to about 2 °C during the equilibration phase just before extraction. HS-SPME was performed using different fibers. The 100 μm polydimethylsiloxane (PDMS) and 65 μm polydimethylsiloxane-divinylbenzene (PDMS-DVB) fibers showed the best results. Although the extraction efficiency for MeHg derivative of the polydimethylsiloxane-Carboxen (PDMS-CAR) fiber is similar to the other fibers, desorption of MeHg derivative from a PDMS-CAR fiber is poor. Factors affecting the HS-SPME process such as adsorption and desorption times, ionic strength (salting-out) and extraction temperature have been evaluated and optimized thoroughly. The highest extraction efficiency for the PDMS fiber was obtained by extraction at a low temperature (2 °C) immediately after equilibration at 30 °C. With the PDMS-DVB and PDMS-CAR fiber improvement of extraction efficiency at lower temperatures is negligible. Repeated extraction out of the same vial revealed that about 30% of MeHg derivative is extracted from the headspace with a PDMS fiber at 2 °C and about 70% with a PDMS-DVB fiber. Repeated extraction with two different fiber coatings showed that the PDMS-CAR fiber also extracts about 70% but that the desorption is incomplete. Attempts to improve the desorption failed due to degradation of the MeHg derivate at high injection temperatures. The limit of detection (3 σ) was 16 pg/L MeHg. The relative standard deviation ( n = 8) for 100 pg/L of MeHg was found to be 5%. Linearity of the HS-SPME-GC-atomic emission detection method was established over at least two orders of magnitude in the range 0–2000 pg/L. Recovery of a surface water sample spiked at 2 ng/L was 85%. The suitability of the procedure was demonstrated by analysis of a surface water sample that showed a concentration of 100 pg/L MeHg. The optimized method can be used with standard commercial equipment without further adaptations.

Feedstock recycling from plastic and thermoset fractions of used computers (I): pyrolysis

The increasing production of computers, the progress in their performance, and the shorter time between innovation and production has led to increasing numbers of obsolete products. It has thus become necessary to recover some materials from old computers and to protect the environment from a new type of pollution. Such recycling is difficult because of the diversity of polymeric materials used, e.g., thermoplastics (polystyrene or acrylonitrile-butadiene-styrene) and thermosets (epoxy resins), and the relatively high levels of flame retardants (halogen- and nitrogen-containing compounds) added during production. Pyrolysis seems to be a suitable way to recover materials and energy from such waste without component separation if an efficient method for reducing toxic compounds can be applied. In this study, the pyrolysis of plastic and thermoset fractions (keyboards, casings, printed circuit boards, and mixtures thereof) of used computers was studied by thermogravimetry and batch reactor pyrolysis. The degradation products were separated into three fractions, solid, liquid, and gaseous, each of them being characterized by suitable methods such as gas chromatography (GC-MSD, gas chromatography-mass spectrometry detection; GC-AED, gas chromatography-atomic emission detection), infrared (FT-IR) and 1H-NMR (nuclear magnetic resonanace) spectroscopy, and elemental analysis. It has been established that most of the halogens, nitrogen, and sulfur is concentrated in the residue. However, the elimination of hazardous toxic compounds, mainly those containing bromine, is necessary before being able to safely use the pyrolysis oils as fuels or in refinery or petrochemical industry flows.

ガスクロマトグラフィー質量分析法から得た硫黄分の比較によるＡ重油と軽油の簡易識別

Discrimination between fuel oils A (No. 1 and No. 2 with less than 5000 and 20000 ppm of sulfur contents, respectively) and diesel fuel with less than 50 ppm of the sulfur content was studied using a gas chromatograph-mass spectrometer (GC-MS). Mass chromatograms (MC) of m/z 184, 198, and 212 for dibenzothiophene (DBT), methyldibenzothiophenes (C1-DBT), and dimethyldibenzothiophenes and ethyldibenzo thiophenes (C2-DBT), respectively, corresponded to the chromatograms of the compounds in the oils by gas chromatography-atomic emission detection. These compounds are main sulfur compounds in the oils. The MC analysis of DBT, C1-DBT, and C2-DBT could rapidly discriminate between the diesel fuel and the fuel oils A. In the case of analysis of contaminated oil samples, the oils were cleaned-up and fractionated into two fractions on a florisil column prior to the GC-MS analysis. The first and second fractions were eluted with hexane and hexane-chloroform (2 : 1), respectively. The second fraction contained sulfur compounds together with aromatic hydrocarbons. The MC analysis of the sulfur compounds in the second fraction also discriminated the three types of oils. This method has the advantage of requiring only a sub-microliter of sample amount and a scan mode of GC-MS measurement for the discrimination of the three types of oils.

Increasing the accuracy of determination of nC/ nH ratios by gas chromatography–atomic emission detection

The influence of oxygen content in helium on the accuracy of n C/ n H ratio determination for model mixtures of aliphatic and polyaromatic hydrocarbons and polychlorinated biphenyls was studied. The best accuracy was achieved at the oxygen content ca. 9%, which was the maximal possible oxygen content in helium for this GC–atomic emission detection (helium flow rate was 25 ml min −1). Using the maximal oxygen flow in plasma the n C/ n H ratio determination accuracy improvement was accompanied by 10-fold increase in detection limit.

軽油脱硫における遊離硫黄の生成－超深度軽油脱硫触媒のパイロット性能評価における注意点－

Special precautions for evaluating ultra deep gas oil hydrodesulfurization catalysts in the pilot plant were investigated. Analysis using gas chromatograph atomic emission detector (GC-AED) and GC-MS showed free sulfur was formed in the hydrodesulfurized product gas oil, if H 2 S dissolved in the product oil contacted air. Although the precise mechanism of free sulfur formation is not clear, direct oxidation of H 2 S, Claus reaction or the oxidation of ammonium polysulfide are possible routes. Once free sulfur forms in the product gas oil, it is difficult to remove by stripping with nitrogen gas. To prevent the formation of free sulfur compound completely, H 2 S should be separated before contacting air in a pilot plant or in a sampling chamber sealed with nitrogen gas. On the other hand, no free sulfur compound was observed in commercial gas oil, as no contact with air occurs before H 2 S stripping.

Microbial Desulfurization of Gasoline in a Mycobacterium goodii X7B Immobilized-Cell System

Mycobacterium goodii X7B, which had been primarily isolated as a bacterial strain capable of desulfurizing dibenzothiophene to produce 2-hydroxybiphenyl via the 4S pathway, was also found to desulfurize benzothiophene. The desulfurization product was identified as o-hydroxystyrene by gas chromatography (GC)-mass spectrometry analysis. This strain appeared to have the ability to remove organic sulfur from a broad range of sulfur species in gasoline. When Dushanzi straight-run gasoline (DSRG227) containing various organic sulfur compounds was treated with immobilized cells of strain X7B for 24 h, the total sulfur content significantly decreased, from 227 to 71 ppm at 40 degrees C. GC flame ionization detection and GC atomic emission detection analysis were used to qualitatively evaluate the effects of M. goodii X7B treatment on the contents of gasoline. In addition, when immobilized cells were incubated at 40 degrees C with DSRG275, the sulfur content decreased from 275 to 54 ppm in two consecutive reactions. With this excellent efficiency, strain X7B is considered a good potential candidate for industrial applications for the biodesulfurization of gasoline.

Rapid Discrimination of Counterfeit Gas Oil Prepared by Mixing Fuel Oil with Sulfuric Acid Using Gas Chromatography−Mass Spectrometry and Gas Chromatography−Atomic Emission Detection

A rapid discrimination of counterfeit gas oils prepared by mixing fuel oil A with sulfuric acid (95% H2SO4) was studied by gas chromatography−atomic emission detection (GC-AED) and gas chromatography−mass spectrometry (GC-MS). Sulfuric acid is used for the removal of coumarin as an oil marker. Both the aromatic and sulfur contents in the counterfeit gas oils are reduced by sulfonation. The counterfeit gas oils gradually changed into oils with abundant paraffins. The GC-MS analysis showed no or a slight amount of the condensed polycyclic aromatic compounds in the counterfeit gas oils before the sulfuric content in the oils was reduced to 50 ppm or less on the basis of the sulfur analysis by GC-AED. These sulfur values corresponded to the sulfur content in the authentic gas oils from Japan. Therefore, the combination of GC-MS and GC-AED analyzed the composition of the aromatic compounds and the sulfur content in the oils and rapidly distinguished the counterfeit gas oils from the authentic gas oil.

Pyrolysis gas chromatography atomic emission detection method for determination of N-containing components of humic and fulvic acids

In this study, a pyrolysis gas chromatography/atomic emission detector (pyrolysis GC/AED) analytical system was established and then investigated for its utility in the chemical characterization of the N-containing components of humic and fulvic acids. Our results show that: (1) the optimal sample pyrolysis temperatures, for observing the characteristic profiles of N-containing components in soil organic matter constituents such as humic and fulvic acids, are from 300 to 500 °C; (2) the main N-containing pyrolysis products of humic and fulvic acids are acetonitrile, hydrogen cyanide, ammonia, pyridine, pyrrole and acetamide; (3) except for pyridine, each of the main N-containing fragments had more than one dominant N-containing source, with source structures being different for humic acid and fulvic acid; and (4) pyrolysis GC/AED with high selectivity and sensitivity may be a useful tool for tracking quantitatively the changes of SOM N-containing components during their decomposition in soils.