重油中含硫芳烃二维液相色谱分离平台开发及应用

基于氯化钯配位交换色谱柱和氨基键合正相色谱柱，利用自动阀切换系统，构建了在线二维液相色谱分离平台。通过优化液相色谱分离条件，实现减压蜡油样品中含硫芳烃的在线富集与多环芳烃的环数分离。利用傅里叶变换离子回旋共振质谱对分离后的含硫芳烃和芳烃组分进行分子水平表征，得到更为详细的化合物类型与碳数分布信息。根据计算得到的平均结构信息，可以提供分离后组分典型的分子结构式，并对芳环结构和侧链位置进行了推测。建立的分析表征方法可以加深对重馏分油中含硫芳烃化合物的分子水平认识，为重油加工过程的原料选择与工艺条件优化提供技术支持。     

原油中芳香硫化合物形态分布的研究

建立了原油中多环芳香硫化合物形态分布的研究方法。采用氯化钯/硅胶配位交换色谱分离原油中的芳香硫化合物,并用气相色谱/质谱分析、气相色谱-硫化学发光检测法结合色谱保留指数,鉴定出原油中的100多个多环芳香硫化物,包括含烷基取代基的苯并噻吩和二苯并噻吩类硫化物。定量分析表明,二苯并噻吩类化合物的含量占芳香硫化合物总量的91%左右。该方法可用于不同来源的原油中芳香硫化合物的形态分布研究。     

Determination of polycyclic aromatic sulfur heterocycles in diesel particulate matter and diesel fuel by gas chromatography with atomic emission detection

The sulfur content of diesel fuel is of environmental concern because sulfur can facilitate the formation of diesel particulate matter (DPM) and sulfur dioxide (SO2) in the exhaust can poison catalytic converters. The US Environmental Protection Agency (EPA) has established more stringent regulations to reduce the sulfur content of diesel fuels in the near future. In this study, various types of organosulfur compounds in DPM extracts and the corresponding fuels have been determined by gas chromatography with atomic emission detection. The diesel fuels used have sulfur contents of 2284 and 433 ppm, respectively, and are labeled as high-sulfur and low-sulfur diesel fuels. The compounds identified are mainly polycyclic aromatic sulfur heterocycles (PASHs). In the fuels tested, trimethylbenzothiophenes (TMBTs), dibenzothiophenes (DBTs), and 4-methyldibenzothiophene (4-MDBT) were the most abundant sulfur compounds, while larger PASH compounds were more abundant in DPM extracts. The high-sulfur diesel fuel contained a larger proportion of PASHs with one or two rings (lighter PASHs). In DPM, the concentrations of total organic sulfur and individual PASHs are higher for the high-sulfur diesel fuel, and the relative percentage of one or two-ring PASHs is higher as well. The influence of engine load on the DPM composition was also examined. With increasing load, the PASH concentration in DPM decreased for lighter PASHs, increased for heavier PASHs, and had a bell-shaped distribution for PASHs in between.     

Polycyclic aromatic sulfur heterocycles as information carriers in environmental studies

Polycyclic aromatic hydrocarbons (PAHs) play a huge role in environmental analytical chemistry, both as pollutants and as markers for many processes. On the other hand, polycyclic aromatic sulfur heterocycles (PASHs; heterocyclic compounds related to PAHs) have been studied far less intensely, but such studies may lead to a great deal of information not available through the study of PAHs. Here we discuss analytical aspects of PASHs in environmental matrices and their use as information carriers. Since PASHs accompany PAHs in sampling and work-up, it is not necessary to expend much extra analytical effort in order to analyze them. This work reviews how they can provide information on diverse processes such as petroleum, industrial and vehicular pollution, and sources of air and marine pollution.     

Clean-up and analysis of carbazole and acridine type polycyclic aromatic nitrogen heterocyclics in complex sample matrices

A HPLC method for the analysis of polycyclic aromatic nitrogen heterocyclics (PANHs) in complex sample matrices is presented. It isolated and separated carbazole and acridine type PANHs with an absolute recovery of between 79–98%. Open column chromatography is used as an initial step to isolate a PANH fraction. By applying normal-phase liquid chromatography using a dimethylaminopropyl silica stationary phase and utilising back-flush technique it was possible to separate the PANH fraction into two fractions containing acridine type and carbazole type PANHs, respectively. The method applied on a sample of solvent refined coal heavy distillate (SRC II HD). A number of 3–5 ring acridines and carbazoles were identified with GC–electron impact MS and quantified with GC–nitrogen–phosphorous detection. Polycyclic aromatic hydrocarbons (PAHs) were determined in the SRC II HD sample by automated on-line clean-up and analysis of the obtained PAH fraction with coupled LC–GC–flame ionization detection. There was no overlap between the PANH and the PAH fractions with this method, and carbazoles and acridines were efficiently separated.     

Simultaneous determination of two serine proteinases by hydrophobic interaction chromatography

Summary An LC clean-up procedure based upon a complexation between polycyclic aromatic hydrocarbons (PAHs) and silica with chemically bonded 2,4-dinitroaniline has been combined with GC/MS. The LC pre-separation makes it possible to obtain a relatively clean fraction of PAHs free from alkanes, alkylbenzenes and naphthalenes, PCBs, chlorinated pesticides and many other interfering compounds. This fraction has been analyzed using capillary GC and mass selective detector (MSD). Substantial improvement of the MS spectra of PAHs with three or more fused benzene rings is achieved.     

多环芳香硫化合物的定量结构-气相色谱保留指数关系

应用分子电性距离矢量(MEDV)对114个多环芳香硫化合物(PASHs)进行结构表征,通过多元线性回归建立了PASHs的气相色谱保留指数与MEDV参数之间的定量结构-保留值关系模型;同时采用逐步回归分析进行变量筛选,继而以留一法交互检验对所得优化模型进行预测能力评价,所建立的模型的相关系数为0.9947,交互检验相关系数为0.9940,表明该优化模型具有良好的稳定性和预测能力。此外,通过将样本集按2:1分成校准集和测试集预测,统计分析结果显示所建的模型具有良好的相关性和稳定性。本文所建的定量结构-保留值关系(QSRR)模型为预测PASHs的气相色谱保留指数提供了一个便捷有效的新方法。     

Atmospheric pressure gas chromatography-tandem mass spectrometry analysis of fourteen emerging polycyclic aromatic sulfur heterocycles in PM_(2.5)

Research on pollution characteristics and toxicities of emerging polycyclic aromatic sulfur heterocycles(PASHs) in PM_(2.5) has not been reported due to the lack of analytical method with the needed performance.In the present study,a novel method for the determination of 14 PASHs in PM_(2.5) was developed using atmospheric pressure gas chro matography-tandem mass spectrometry(APGC-MS/MS).Atmospheric pressure chemical ionization was operated with multiple reaction monitoring in positive ionization mode.High sensitivity(method detection limit 1.673 pg/m~3),acceptable re coveries(67.6%-120.8%) and precisions(RSD of 2.2%-15.4%) were obtained.The method was successfully applied for analyzing PASHs in 10 PM_(2.5) samples collected from Taiyuan,a typical industrial city in China,in 2016,The total concentrations were from 929 pg/m~3 to 14,593 pg/m~3.The determined levels indicated that further investigations on environmental fate and toxicities of PM_(2.5)-bound PASHs may be needed.     

Determination of polycyclic aromatic hydrocarbons in fractions in asphalt mixtures using liquid chromatography coupled to mass spectrometry with atmospheric pressure chemical ionization

An analytical method using liquid chromatography coupled to mass spectrometry with atmospheric pressure chemical ionization for the determination of polycyclic aromatic hydrocarbons in asphalt fractions has been developed. The 14 compounds determined, characterized by having two or more condensed aromatic rings, are expected to be present in asphalt and are considered carcinogenic and mutagenic. The parameters of the atmospheric pressure chemical ionization interface were optimized to obtain the highest possible sensitivity for all of the compounds. The limits of detection ranged from 0.5 to 346.5 μg/L and the limits of quantification ranged from 1.7 to 1550 μg/L. The method was validated against a diesel particulate extract standard reference material (NIST SRM 1975), and the obtained concentrations agreed with the certified values. The method was applied to asphalt samples after its fractionation according to ASTM D4124 and the method of Green. The concentrations of the seven polycyclic aromatic hydrocarbons quantified in the sample ranged from 0.86 mg/kg for benzo[ghi]perylene to 98.32 mg/kg for fluorene.     

Separation of nonpolar analytes using methanol-water mixtures at elevated temperatures

Pure subcritical water has been found to be an efficient mobile phase for reversed-phase separations of both polar and moderately polar compounds. However, subcritical water must be modified with organic solvent in order to elute nonpolar analytes in an efficient manner. In this study, the separation of polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), and benzene, toluene, and p-xylene (BTX) was performed by using heated methanol-water mixtures as the mobile phase. Temperatures employed in this study ranged from 21 to 140 °C, while the percentage of methanol in the mobile phase ranged from 52 to 90%. The retention times of analytes were matched under different mobile phase conditions by increasing the temperature and decreasing the percentage of methanol in the mobile phase.     

Determination of polycyclic aromatic sulfur heterocycles (PASH) in diesel fuel by high performance liquid chromatography and photodiode-array detection

An oxidation method (sulfone method) for the determination of polycyclic aromatic sulfur heterocycles (PASH) in diesel fuel is presented. The aromatic fraction of a diesel fuel, isolated by solid phase extraction, is oxidized under controlled conditions with hydrogen peroxide. The oxidation products, mainly methylated dibenzosulfone, are determined and quantified directly, without further clean-up, by HPLC with photodiode-array detection.     

Polycyclic aromatic hydrocarbons (PAHs) in a coal tar standard reference material—SRM 1597a updated

SRM 1597 Complex Mixture of Polycyclic Aromatic Hydrocarbons from Coal Tar, originally issued in 1987, was recently reanalyzed and reissued as SRM 1597a with 34 certified, 46 reference, and 12 information concentrations (as mass fractions) for polycyclic aromatic hydrocarbons (PAHs) and polycyclic aromatic sulfur heterocycles (PASHs) including methyl-substituted PAHs and PASHs. The certified and reference concentrations (as mass fractions) were based on results of analyses of the coal tar material using multiple analytical techniques including gas chromatography/mass spectrometry on four different stationary phases and reversed-phase liquid chromatography. SRM 1597a is currently the most extensively characterized SRM for PAHs and PASHs.     

Fragmentation pathways of some benzothiophene radical cations formed by atmospheric pressure chemical ionisation

Polycyclic aromatic sulfur‐containing compounds (PASHs) are commonly found in fossil fuels and are of considerable importance in environmental studies. This work presents detailed studies on the fragmentation patterns of radical cations formed from four representative PASHs, benzo[b]thiophene, dibenzothiophene, 4‐methyldibenzothiophene and 4,6‐dimethyldibenzothiophene, using tandem atmospheric pressure chemical ionization mass spectrometry (APCI‐MS/MS). Understanding these fragmentation patterns can be a useful aid in the analysis of PASHs employing APCI or electron ionization (EI‐MS/MS), either alone or in conjunction with liquid or gas chromatography. Copyright © 2009 John Wiley & Sons, Ltd.     

Capillary electrophoretic separation of polycyclic aromatic sulfur heterocycles

Capillary electrophoresis (CE) was used to separate polycyclic aromatic sulfur heterocycles (PASHs), a class of compounds that occurs in fossil fuels and refined products of petroleum. An electric charge was introduced into the compounds through methylation or phenylation of the sulfur atom. Separations of standard PASHs that are expected to be present in industrially desulfurized fuels showed that CE possessed a higher resolution than reversed phase liquid chromatography. The CE method can separate all the monomethylbenzothiophenes; this is not achieved in capillary gas chromatography. A linear relationship was found between migration time and the calculated volume of the compounds. The PASHs in deeply desulfurized diesel were separated after preconcentration, and the electropherogram was compared with the chromatograms from GC and HPLC. Finally, derivatized PASHs are often enantiomeric and the enantiomers can be separated if a suitable cyclodextrin is added to the running buffer.     

beta-Cyclodextrin as a stationary phase for the group separation of polycyclic aromatic compounds in normal-phase liquid chromatography

The separation of highly alkylated polycyclic aromatic compounds according to the size of their aromatic system is investigated using the polycyclic aromatic sulfur heterocycles in vacuum gas oil. A large number of reference compounds containing several parent ring systems and different alkylation patterns were first investigated to characterize the retention of polycyclic aromatic compounds likely to occur in high-boiling petroleum samples. A beta-cyclodextrin phase, Merck ChiraDex, was found to be more suitable than chemically bonded aminopropanosilane and tetrachlorophthalimide in normal-phase HPLC with respect to a combination of selectivity towards the number of aromatic double bonds and degree of influence of the alkyl groups of the aromatic compounds. Finally the preseparated polycyclic aromatic sulfur heterocycles from a vacuum gas oil were fractionated according to the number of condensed aromatic rings on the ChiraDex phase and were characterized by Fourier transform ion cyclotron resonance mass spectrometry.     

Determination of mono- to tetracyclic aromatic hydrocarbons in lubricating oil

Liquid – liquid extraction with N-methyl-2-pyrrolidone, combined with solid-phase extraction on silica gel using n-pentane and dichloromethane as solvents, has been used for the isolation and concentration of the aromatic fraction from lubricating oil. The identification of individual compounds in this aromatic fraction was performed by capillary gas chromatography–mass spectrometry (CGC-MS) and by determination of retention indices. Quantitative results were obtained by flame ionization detection (CGC-FID). Eighty four compounds, predominantly naphthalenes, phenanthrenes, biphenyls, fluorenes, dibenzo-thiophenes, and their alkylated derivatives, have been identified in a commercial lubricating oil. The total amount of the aromatic fraction did not exceed 0.04 % of the oil.     

The delocalization index as an electronic aromaticity criterion: application to a series of planar polycyclic aromatic hydrocarbons

This work introduces a new local aromaticity measure, defined as the mean of Bader's electron delocalization index (DI) of para-related carbon atoms in six-membered rings. This new electronic criterion of aromaticity is based on the fact that aromaticity is related to the cyclic delocalized distribution of pi-electrons. We have found that this DI and the harmonic oscillator model of aromaticity (HOMA) index are strongly correlated for a series of six-membered rings in eleven planar polycyclic aromatic hydrocarbons. The correlation between the DI and the nucleus-independent chemical shift (NICS) values is less remarkable, although in general six-membered rings with larger DI values also have more negative NICS indices. We have shown that this index can also be applied, with some modifications, to study of the aromaticity in five-membered rings.     

含四元环的多环芳香化合物的研究进展

含四元环的多环芳香化合物通常能够表现出独特的光物理和化学性质,在很多领域具有潜在应用价值.分别针对线型、角型、螺旋型和环型含四元环多环芳香化合物的合成方法、分子堆积方式、光电性质及载流子迁移率等方面进行归纳总结.研究表明,表面合成法更利于制得规则形貌的多环芳香化合物;线型类分子表现出了较高的载流子迁移率;角型分子通常显...     

Argentation chromatography for the separation of polycyclic aromatic compounds according to ring number

Crude oils are the most complex mixtures known and every speciation method relies on a simplification of their complexity. Argentation chromatography is shown to be superior to traditional liquid chromatographic ways of separating aromatic compounds based on the number of aromatic carbon atoms. A silver(I) mercaptopropano silica gel allows an efficient group separation of polycyclic aromatic compounds to be achieved. The usefulness of this phase is demonstrated for SRM 1582 Wilmington crude oil and a diesel fuel. Furthermore, the phase can also be used for semi-preparative purposes to collect fractions for further analysis with high resolution mass spectrometry. Orbitrap mass spectra are obtained here for the polycyclic aromatic sulfur heterocycles and it is demonstrated that they can contain one to five naphtheno rings.     

Capillary Column Gas Chromatography of Environmental Polycyclic Aromatic Compounds

Abstract

The methodologies are described for isolating clean fractions of polycyclic aromatic compounds from diverse environmental samples such as air particulate matter, sediments, and fish tissue. The common step in all procedures is the separation of the polycyclic aromatic compound fraction into well-defined chemical classes by adsorption chromatography on an alumina column. These procedures greatly facilitate the detailed characterization of the polycyclic aromatic hydrocarbons, sulfur heterocycles, and nitrogen heterocycles by capillary column gas chromatography.