Polycyclic Aromatic Sulfur Heterocycles Research Articles

Sorption of Polycyclic Aromatic Sulfur Heterocycles (PASH) on Nylon Microplastics at Environmentally Relevant Concentrations.

Microplastics have garnered an infamous reputation as a sorbate for many concerning environmental pollutants and as a delivery vehicle for the aquatic food chain through the ingestion of these contaminated small particulates. While sorption mechanisms have been extensively studied for polycyclic aromatic hydrocarbons, polycyclic aromatic sulfur heterocycles (PASHs) have not been investigated, partly due to their low concentrations in aquatic ecosystems. Herein, an analytical methodology is presented for the analysis of dibenzothiophene, benzo[b]naphtho[1,2-b]thiophene, benzo[b]naphtho[2,1-b]thiophene, benzo[b]naphtho[2,3-b]thiophene, chryseno[4,5-bcd]thiophene and dinaphtho[1,2-b:1',2'-d]thiophene at relevant environmental concentrations based on solid phase extraction and high-performance liquid chromatography. The sorption uptake behavior and the sorption kinetics of the three benzo[b]napthothiophene isomers were then investigated on nylon microplastics to provide original information on their environmental fate and avoid human contamination through the food chain. The obtained information might also prove relevant to the development of successful remediation approaches for aquatic ecosystems.

Method Development for Quantitative Analysis of Polycyclic Aromatic Hydrocarbons, Nitrogen Heterocycles and Sulfur Heterocycles in Crude Oils Using Quadrupole Time-of-Flight Mass Spectrometry

An oil spill is a catastrophic event that results in various toxic polycyclic aromatic hydrocarbons (PAHs) entering the environment. Polycyclic aromatic nitrogen heterocycles (PANHs) are more toxic to the environment than their parent PAHs. The high cost and paucity of available PANH standards, the lower abundance of PANHs relative to PAHs, and the difficult separation due to co-elution with PAHs have all contributed to the scarcity of related published literature on the determination of these compounds. To overcome these challenges, a new quantitative method has been successfully developed and validated for the inclusion of 113 polycyclic aromatic carbon (PAC) compounds in a single injection. The 113 compounds consist of PAHs, nitrogen heterocycles, sulfur heterocycles, and alkylated equivalents. Distinct separation of the PANHs and their alkylated counterparts (APANHs) from PAHs was achieved using a gas chromatography quadrupole time-of-flight (GC-QToF) mass spectrometer. The instrument resolved compounds by the high-resolution extraction of monoisotopic masses, allowing response correction factors (RCFs) to be determined from available PANH standards and to calculate concentrations from PAH calibration standards. The developed method was applicable to crude oil samples, generating concentrations of PANHs and relevant information on compound stability for use in oil spill forensics investigation. Development of this practical PAC method provides a powerful tool for screening toxic contaminants, assessing environmental impact, and monitoring recovery following an oil spill.

Utilizing polycyclic aromatic sulphur heterocycles to develop hypercrosslinked microporous polymeric adsorbents for deep desulphurization of fuels

Adsorptive desulphurization is a well-known method for removing polycyclic aromatic sulphur heterocycles (PASHs) from petroleum fractions. Nevertheless, due to the non-destructive adsorption mechanism, managing the adsorbed carcinogenic PASHs remains a major challenge. In the present research, a prototype is presented to manage three PASHs (thiophene, benzothiophene and dibenzothiophene) by using them to develop hypercrosslinked microporous polymeric adsorbents (yield > 90%) within 60 min via microwave assisted synthesis. Textural properties including specific surface area (401–628 m2 g−1), controlled pore size (1.1–1.7 nm) and pore volume (0.24–0.29 cm3 g−1) have been estimated. The developed adsorbents are used for desulphurizing diesel fuels. Batch adsorption studies result in the sulphur adsorption capacities of 6.7 and 6.4 mgS g−1, for 100 ppm and 10 ppm-dosed simulated fuels respectively. Thermodynamic, kinetics and adsorption isotherm studies are performed using the batch adsorption studies. Column adsorption studies exhibit sulphur breakthrough capacities of 7.2 and 0.62 mgS g−1 for 100 ppm and 10 ppm-dosed simulated fuels respectively. The combine effect of textural properties and π electron density on the adsorption capacity is discussed. The present work not only demonstrates a sustainable management cycle of PASHs but also utilized them for deep desulphurization of fuels.

Comparative analysis of organic chemical compositions in airborne particulate matter from Ulaanbaatar, Beijing, and Seoul using UPLC-FT-ICR-MS and artificial neural network

This paper presents comparative study on the composition and sources of PM2.5 in Ulaanbaatar, Beijing, and Seoul. Ultrahigh performance liquid chromatography (UPLC) combined with ultrahigh resolution mass spectrometry (UHR-MS) were employed to analyze 85 samples collected in winter. The obtained 340 spectra were interpreted with artificial neural network (ANN). PM2.5 mass concentrations in Ulaanbaatar were significantly higher than those in Beijing and Seoul. ANN based interpretation of UPLC UHR-MS data showed that aliphatic/lipid derived organo‑sulfur compounds, polycyclic aromatic and organo‑oxygen compounds were characteristic to Ulaanbaatar. Whereas, aliphatic/lipid-derived organo‑oxygen compounds were major components in Beijing and Seoul. Aromatic organo‑nitrogen compounds were the main contributors to differentiating the spectra obtained from Beijing from the other cities. Based on two-dimensional gas chromatography/high resolution mass spectrometric (GCxGC/HRMS) data, it was determined that the concentrations of the polycyclic aromatic hydrocarbon (PAH) and polycyclic aromatic sulfur heterocycle (PASH) containing sulfur were highest in Ulaanbaatar, followed by Beijing and Seoul. Coal/biomass combustion was identified as the primary source of contamination in Ulaanbaatar, while petroleum combustion was the main contributor to PM2.5 in Beijing and Seoul. The conclusion that diesel-powered heavy-duty trucks and buses are the main contributors to NOx emissions in Beijing is consistent with previous reports. This study provides a more comprehensive understanding of the composition and sources of PM2.5 in the three cities, with a focus on the differences in their atmospheric pollution profiles based on the UPLC UHR-MS and ANN analysis. It is notable that this study is the first to utilize this method on a large-scale sample set, providing a more detailed and molecular-level understanding of the compositional differences among PM2.5. Overall, the study contributes to a better understanding of the sources and composition of PM2.5 in Northeast Asia, which is essential for developing effective strategies to reduce air pollution and improve public health.

Adsorptive desulphurization of fuels by hypercrosslinked nanoporous polymers derived from polycyclic aromatic hydrocarbons

A sustainable method is employed to remove polycyclic aromatic sulphur heterocycles (PASHs) from fuels by using a series of high surface area nanoporous adsorbents synthesized from polycyclic aromatic hydrocarbons (PAHs). The hypercrosslinking of PAHs has been used to synthesize high surface area (SABET of 620–1565 m2 g−1) nanoporous polymeric materials via a microwave assisted method. The adsorbent poly-naph (highest SABET, i.e., 1565 m2 g−1) display best performance for desulphurization of fuels from batch to fixed bed column mode. In batch mode, the adsorption capacity of 12.1 (up to 9 ppm sulphur) and 8.9 mgS g−1 (up to 43 ppm sulphur), has been estimated for model (100 ppm sulphur) and real fuels (110 ppm sulphur), respectively. Furthermore, from ultra-low sulphur model (10 ppm sulphur) and real fuel (9 ppm sulphur), the adsorption capacity of 16.1 (up to 0.3 ppm sulphur) and 10 mgS g−1 (up to 3 ppm sulphur) has been estimated. In fixed-bed column mode, the high concentrated model and real fuel have been desulphurized to final concentration of 1 and 12 ppm, respectively. While, at low concentrations, the final concentration of 100 ppb and 1 ppm is achieved for model and real fuels, respectively. The adsorption mechanism revealed that π-electron density in the polymeric framework plays prominent role in the adsorption process apart from high surface area. This approach to control carcinogenic aromatic pollutants like PAHs and PASHs can be sustained over time through technological advancement, financial assistance and governmental regulation.

Quantification of polycyclic aromatic sulfur heterocycles in fine airborne urban particles (PM2.5) after multivariate optimization of a green procedure

Polycyclic aromatic sulfur heterocycles (PASHs), such as benzothiophenes (BT), dibenzothiophenes (DBT) and benzonapthothiophenes (BNT), can be emitted from vehicular traffic and deposited in fine particles matter (PM2.5). The presence of these compounds in PM2.5 is an environmental concern due to air pollution and its toxic properties. In this study, a green microscale solid–liquid extraction method was developed to determine twenty-three PASHs in PM2.5. A simplex-centroid mixture design was applied to optimize the extraction solvent. A full factorial design was used for preliminary evaluation of the factors that influence the extraction process (extraction time, sample size, and solvent volume) and then a Doehlert design for the significant parameters. The optimal extraction conditions based on the experimental design were: sample size, 4.15 cm2; 450 μL of toluene:dichloromethane (80:20,v/v); and extraction duration, 24 min. High sensitivity (LOD < 0.66pg m−3 and LOQ < 2.21 pg m−3) and acceptable recovery (82.8–120 %), and precision (RSD 3.6–14.0 %) were obtained. The greenness of the method was demonstrated using the Analytical GREEnness (AGREE) tool. The method was applied for analyzing PASHs in PM2.5 samples collected in three time intervals per day from years with different sulfur contents in the diesel: S-500 (≤500 ppm sulfur) and S-50 (≤50 ppm sulfur). Fourteen PASHs were quantified with the highest concentrations observed for 2,8-DMDBT and 4,6-DMDBT, which are recalcitrant compounds. The ANOVA test indicated significant differences between sampling periods during the day. The reduction of diesel S-500 to S-50 corresponded to a 28 % decrease in the total sum of PASHs (∑PASHs) evaluated. Spearman's rank correlations allowed for verifying that BTs and DBTs were highly correlated, suggesting that they were derived from similar sources. A weak correlation of 2,1-BNT and 2,3-BNT with BTs and DBTs indicates that these compounds are a chemical proxy for the emission of diesel engines during the combustion process.

Overcoming shielding in mass detection via isolation of sulfur heterocycles using green silver nanoparticles

AbstractSilver nanoparticles (nano‐Ag0) fixed on supports or in colloidal solution exhibit surface plasmon resonance, but there have been few attempts at surface plasmon resonance‐based liquid chromatographic separation. Here, for the first time, a capped Ag(I) green tea colloidal solution was used as a precursor to anchor nano‐Ag0 on silica. Nano‐Ag0 supported on silica was confirmed by spectroscopy and microscopy, and nano‐Ag0 particles (average diameter 20 nm) were scattered on the silica surface. This ecologically friendly approach for doping nanoparticles on solid supports was as efficient as chemical methods and could be used to separate polycyclic aromatic sulfur heterocycles from a heavy aromatic fraction. Using a nano‐Ag‐silica ligand exchanger, parts‐per‐million concentrations of sulfur heterocycles were probed by surface plasmon resonance nano‐Ag0 on a solid substrate. Using this approach, mass detection shielding can be eliminated to isolate polycyclic aromatic sulfur heterocycles from aromatic fractions. This study presents an innovative approach to producing dispersed silver nanoparticles on a solid substrate.

A sustainable management of polycyclic aromatic hydrocarbons to synthesize microporous organic polymers for adsorptive desulphurization of fuels

A sustainable management of carcinogenic polycyclic aromatic hydrocarbons (PAHs) to synthesize a series of high surface area (SABET of 563–1553 m2 g−1) microporous polymeric adsorbents is reported. The products with high yield (>90%) were obtained within only 30 min at a low temperature of 50 °C using a microwave-assisted approach with 400 W microwave power followed by 30 min of ageing by raising the temperature to 80 °C. The synthesized adsorbents are used for removing another category of carcinogenic pollutants i.e., polycyclic aromatic sulphur heterocycles (PASHs) from model and real fuels. Adsorptive desulphurization experiment in batch mode could reduce the sulphur from high concentrated model (100 ppm) and real (102 ppm) fuels to 8 ppm and 45 ppm respectively. Similarly, desulphurization of model and real fuels with ultralow sulphur concentrations of 10 and 9 ppm, respectively, reduced the final concentration of sulphur to 0.2 and 3 ppm, respectively. Adsorption isotherms, kinetics, and thermodynamic studies have been conducted using batch mode experiments. Adsorptive desulphurization using fixed bed column studies show the breakthrough capacities of 18.6 and 8.2 mgS g−1, for the same high concentrated model and real fuels, respectively. The breakthrough capacities of 1.1 and 0.6 mgS g−1 are estimated for the ultralow sulphur model and real fuels, respectively. The adsorption mechanism, based on the spectroscopic analysis (FTIR and XPS) demonstrates the role of π-π interactions between the adsorbate and adsorbent. The adsorptive desulphurization studies of model and real fuels from batch to fixed bed column mode would offer an in-depth understanding to demonstrate the lab-scale findings for industrial applications. Thus, the present sustainable strategy could manage two classes of carcinogenic petrochemical pollutants, PAHs and PASHs, simultaneously.

Excited State Dynamics of Dibenzothiophene Derivatives.

Polycyclic aromatic sulfur heterocycles are environmental pollutants formed from incomplete combustion processes and crude oil spills. Their excited state dynamics are not understood. Herein, femtosecond transient absorption is combined with steady-state spectroscopy and computational methods to elucidate the relaxation mechanisms of three dibenzothiophene derivatives. The low-energy singlet and triplet states all have ππ* character in the Franck-Condon region, and two minima were located in the S1 surface. Excitation at 320 nm populates their S1 state directly, which relaxes with lifetimes ranging from 4 to 13 ps. Most of the S1 population undergoes efficient intersystem crossing to the triplet state with lifetimes ranging from 820 ± 50 to 900 ± 30 ps. The compounds exhibit negligible nonradiative internal conversion, low fluorescence yields of 1.2 to 1.6%, and triplet yields of ca. 98%. Linear interpolation of internal coordinates reveals the chemical basis for relaxing the spin-forbidden intersystem crossing in these π-aromatic systems.

Polycyclic aromatic sulfur heterocycles used as molecular markers in crude oils and source rocks

Polycyclic aromatic sulfur heterocycles (PASHs), such as benzothiophenes (BTs), dibenzothiophenes (DBTs), and benzonaphthothiophenes (BNTs), are found in crude oil and source rocks and have been extensively studied in the last decades. PASHs play a significant role in organic geochemistry as molecular markers (S-markers) because they are common in a variety of both oils and source rocks and mainly due to their thermal stability. Furthermore, relative to other hydrocarbon groups such as alkanes and many aromatic compounds, S-markers are highly stable and degradation-resistant. Thus, S-markers have been studied to obtain important information about thermal evolution, depositional environment, maturity as well as about petroleum migration and biodegradation. DBT-related markers, such as 4-MDBT/1-MDBT, 4,6-DMDBT/1,4-DMDBT, and benzonaphtho[2,1-d]thiophene/benzonaphtho[1,2-d]thiophene ([2,1]BNT/[1,2]BNT) are good maturity indicators, particularly for high to over-mature oil. The application of these S-markers overcomes the limitation of hopane and sterane maturity indicators which are restricted to a relatively low maturation range. S-markers are also related to the type of source rock where oils derived from siliceous rocks are rich in BT, DBT, DMDBT, and TMDBT and their relative concentrations are lower than those in carbonate-sourced oils. Individual DBTs are used to indicate susceptibility to biodegradation in the following order: DBT > 4-MDBT > 2-+3-MDBT > 1-MDBT. In this study, PASHs used as S-markers individually or through diagnostic ratios in crude oils and source rocks were reviewed. Different analytical techniques (including classical and innovative approaches) used to quantify and characterize S-markers, are discussed. According to our knowledge, this article is the first overview of PASHs employed as geochemical markers and provides an overview of the different alternatives for sample preparation, instrumental analysis, identification, and quantification of these compounds.

Characterization of chemical fingerprints of ultralow sulfur fuel oils using gas chromatography-quadrupole time-of-flight mass spectrometry

With the implementation of stringent environmental regulations, high sulfur fuel oils (HSFO) are shifted to very low (VLSFOs) and ultralow sulfur fuel oils (ULSFOs). The current understanding of these fuels is far from sufficient. The chemical fingerprints of these oils are significantly altered by desulfurization processes, and sulfur-containing compounds present in these oils are in low or extremely low concentrations. These changes pose challenges for petroleum analysis. The ULSFOs studied were limited to distillates. Like conventional fuel oils, ULSFOs are diverse. ULSFOs do not just include distillates but can be a mixture of multiple oil products. The present work measured and compared the physical and chemical properties of ULSFOs with conventional fuels. Gas chromatography-quadrupole time-of-flight mass spectrometry (GC-QTOF-MS) was applied to characterize the chemical fingerprints of ULSFOs. Polycyclic aromatic sulfur heterocycles (PASHs) and their alkylated homologues were determined in considerable abundance in the oils with ≤ 1,000 ppm and ≤ 500 ppm of total sulfur. The chromatographic profiles of ULSFOs were obviously different from that of crude oil and high sulfur fuel oil. Most of PASHs are barely detectable in ≤ 10 ppm S ultralow sulfur diesel fuels (ULSDs), which were subject to deep desulfurization. Some dibenzothiophene isomers such as 4-methyldibenzothiophene,4,6-dimethyldibenzothiophene and 2,4,6-trimethyldibenzothiophene naturally occur in relatively high abundance and are the most refractory to the refinery process due to the methyl steric hindrance. These refractory species were clearly detected in ≤ 10 ppm S ULSDs while other PASHs are barely detectable. Certain compounds with special chemical fingerprints in ULSFOs and ULSDs have potential suitability as diagnostic molecular markers for associated oil spill characterization and identification.

Foraging Honeybees (Apis mellifera ligustica) as Biocenosis Monitors of Pollution in Areas Affected by Cement Industry Emissions

Two areas affected by cement plant emissions, in an industrial district of Central Italy, were investigated by foraging honeybees (Apis mellifera ligustica) on the return to their hives, as an in situ biomonitor. The contamination was compared with that of a background reference area on the Central Apennine Mountains, quite far from the contamination sources. At all the sites, the bee colonies were stationary. One hundred seventy-seven compounds belonging to the class of polycyclic aromatic compounds (PACs) were positively identified by gas chromatographic and mass spectrometric techniques. For the first time, the presence of several unusual compounds on bee samples is highlighted. These include polycyclic aromatic sulfur heterocycles (PASHs), 1.55–35.63 ng/g d.w., compounds that, like polycyclic aromatic hydrocarbons (PAHs), 67.50–129.95 ng d.w., are classified as carcinogenic and/or mutagenic. In an attempt to identify the contribution of different and specific sources of these pollutants to the total pollution profile, the composition of aliphatic linear hydrocarbons was also examined.

Determination of polycyclic aromatic sulfur heterocycles in ascidians (Phallusia nigra) using a green procedure

Ascidians as a pollution bioindicator are well reported based on metal analysis, but little is known about organic compounds accumulation in these marine organisms. In this study, a miniaturized solid–liquid extraction method, combined with dispersive micro-solid-phase extraction (MSLE-DµSPE) cleanup was applied to the determination of fourteen polycyclic aromatic sulfur heterocycles (PASH) from petrochemical sources in ascidian Phallusia nigra. The alumina amount in DµSPE step was optimized and the method was validated in terms of linearity, accuracy and precision using matrix-matched calibration. The ascidians were collected in Todos os Santos Bay, in a region close to a floating gas station. In the laboratory, samples were dissected in two parts (branchial basket and tunic), lyophilized, weighed and extracted by MSLE-DµSDE. Analytes were determined by gas chromatography coupled to mass spectrometry in selective ion monitoring (GC–MS/SIM). Under optimum conditions, the limit of detection ranged from 0.17 µg L−1 (4,6-dimethyldibenzothiophene) to 1.99 µg L−1 (2,3-dimethylbenzothiophene) and the limit of quantification the values were in the range from 0.57 µg L−1 to 6.65 µg L−1 for the same compounds. Determination coefficients (R2) ≥ 0.99 were obtained for all analytical curves. The recoveries of the PASH were between 76 and 119 % with intraday and interday precisions lower than 20 %. The method was successfully applied to ascidian samples and ten PASHs were quantified with highest concentrations in the branchial basket. This study represents the first application of a green miniaturized procedure to the determination of PASH from petrochemical source in marine organisms.

Advancement in oil forensics through the addition of polycyclic aromatic sulfur heterocycles as biomarkers in diagnostic ratios

In current oil spill forensics, diagnostic ratios of hydrocarbon biomarker responses are commonly used to compare oil spill samples to source materials in order to determine the identity of the oil. This well recognized procedure was developed by the European Committee for Standardization (CEN) with corresponding published EN 15522–2 Oil Spill Identification guidelines. However, it is further recognized that weathering can have a negative effect on some of the biomarkers used in the analysis, leading to decreased confidence in the result. In this study, polycyclic aromatic sulfur heterocycles (PASHs) and their alkylated forms (APASHs) were assessed for their potential as additional biomarkers. With the aim of identifying stable PASHs and APASHs useful as weathered oil biomarkers, the superior specificity of gas chromatography with high resolution mass spectrometry was exploited to determine chromatographic peak responses for sixteen petroleum oil samples. Extensive study, involving microcosm extreme weathering and spreadsheet development, led to the identification of 19 new diagnostic ratios based on newly discovered stable PASH and APASH biomarkers. Application of the extended diagnostic ratio suite showed high potential to improve the forensic attribution of post-spill weathered oil back to its original source.

Investigating the fate of polycyclic aromatic sulfur heterocycle compounds in spilled oils with a microcosm weathering experiment

One of the common toxic compound groups in crude oils are the polycyclic aromatic sulfur heterocycles (PASHs) and their related alkylated forms (APASHs). Unlike commonly investigated polycyclic aromatic hydrocarbons (PAHs) and their alkylated forms (APAHs), these sulfur containing compounds have not been extensively studied due to the lack of practical analytical methodology as well as expense and limited availability of chemical standards. In the current study, a newly developed polycyclic aromatic carbon (PAC) method was applied to analyze the various PASHs/APASHs in crude oil samples using PAHs as surrogate standards. To investigate the fate of PASHs/APASHs in spilled oils in the environment, microcosm systems containing various crude oils were prepared and exposed to the environment for two months, simulating the summer weather conditions of Canada’s west coast. The artificially weathered crude oil samples were analyzed for both PAH/APAH and PASH/APASH composition, and the results were compared to un-weathered counterparts of the oils. PASHs/APASHs were found to be affected by the microcosm weathering in similar ways to PAHs/APAHs. Fifteen PASHs and APASHs were found to be resistant to weathering and be potential candidates as biomarkers in oil spill forensic investigation.

A rapid gas chromatography quadrupole time-of-flight mass spectrometry method for the determination of polycyclic aromatic hydrocarbons and sulfur heterocycles in spilled crude oils.

Spilled crude oil samples contain various toxic compounds including polycyclic aromatic hydrocarbons (PAHs) as well as sulfur heterocycles (PASHs) and their related alkylated forms (APAHs and APASHs). In this study, a method was successfully developed employing a gas chromatography quadrupole time-of-flight (GC-QToF) mass spectrometer to quantitatively analyze both PAHs/APAHs and PASHs/APASHs in these samples. With GC-QToF, the monoisotopic mass of the compounds is distinguished, allowing the PASHs/APASHs to be extracted separately from the PAHs/APAHs in crude oil. A gas chromatography triple quadrupole (GC-MS/MS) mass spectrometer was also used to confirm that a GC-QToF is the preferred instrument for analyzing these compounds. With the use of PASH/APASH standards to determine response correction factors (RCFs) in relation to PAH standards, the developed method is capable of analyzing PAHs, APAHs, PASHs, and APASHs in a single injection. The use of RCFs allowed for the development of a practical polycyclic aromatic carbon (PAC) method for analyzing a total of 77 compounds of the 2 groups in crude oil. This newly developed method was applied to spilled crude oils, demonstrating its potential in toxicological study as well as oil spill forensic investigation.

Unraveling the molecular-level structures and distribution of refractory sulfur compounds during residue hydrotreating process

Molecular-level structures and distribution of refractory polycyclic aromatic sulfur heterocycles (PASHs) during residue hydrotreating process (RHT) are investigated. A prior atmospheric pressure photoionization (APPI) FT-ICR MS was used to obtain the distribution of refractory PASHs. Then the key refractory PASHs were further dissociated by collision-induced dissociation (CID) to identify the isomers and gain their fragment ions. During deep hydrodesulfurization (HDS), S1 class compounds detected in the RHT products was identified as the major refractory sulfur compounds. Moreover, an increase in the aromatic structure of S1 class species is present during RHT. The key refractory PASHs are these with DBE = 9–12, which also determine HDS depth during RHT process. From the CID experiments, as indicated by an increase of abundance of fragmentation of alkyl(C1-C4)-substituted DBT, alkyl(C2)-substituted DBT in particular, these key refractory PASHs have a structure of alkyl(C2)-substituted DBT, such as 4,6-DMDBT. In addition, the molecular chemical formula and molecular structure for these key refractory PASHs were proposed, shedding a light on the development of industrial HDS catalysts and optimization of RHT process

Microscale extraction combined with gas chromatography/mass spectrometry for the simultaneous determination of polycyclic aromatic hydrocarbons and polycyclic aromatic sulfur heterocycles in marine sediments

This paper describes a novel method based on an ultrasound-assisted extraction microscale device (UAE-MSD) for the rapid and simultaneous determination of polycyclic aromatic hydrocarbons (PAH) and polycyclic aromatic sulfur heterocycles (PASH) in marine sediments. Solvent extraction conditions were optimized by applying a simplex-centroid mixture design. Optimum conditions were used to validate and determine the concentrations of 17 PAH and 7 PASH. The best conditions were obtained by extracting sediments with 500 µL of DCM:MeOH (65:35, v:v) over 23 min of sonication. Analytes were determined by gas chromatography/mass spectrometry in selective ion monitoring (GC-MS/SIM). Matrix effects were evaluated, and matrix-matched calibration was used for quantitation. Analytical method validation was carried out using the certified reference material NIST SRM 1941b, as well as sediment spiked with PASH at three concentration levels. Recoveries ranged between 70.0 ± 3.5% and 119 ± 9.1% for PAH and 80.6 ± 10.4% and 120 ± 10% for PASH. Linearity (R2) was ≥0.99 for all compounds. Method detection limits ranged from 8.8 to 30.2 ng g−1, while limits of quantification ranged from 29.4 to 1011 ng g−1. UAE-MSD was applied to marine sediments exposed to different anthropogenic impacts collected in Todos os Santos Bay, Brazil. PAH concentrations ranged from <LOQ to 667 ng g−1, while PASH levels were <LOQ to 1152 ng g−1. Dibenzothiophene was the compound presented in the highest concentration in all samples, with values up to 249 ng g−1. The results indicated contributions of pyrogenic sources from all compounds. The developed method can potentially be applied to extract trace levels of compounds in different solid matrices to minimize extraction time and solvent consumption.

Discovery of emerging sulfur-containing PAHs in PM2.5: Contamination profiles and potential health risks

We reported the discovery and identification of emerging sulfur-containing polycyclic aromatic hydrocarbons, namely polycyclic aromatic sulfur heterocycles (PASHs), in PM2.5 collected from two typical regions of China, Taiyuan and Guangzhou. Until now, there is no research on contamination status, sources and potential health risks of this unexpected group of organic contaminants in PM2.5. High atmospheric concentrations (ngm−3) and significant time-dependent variations were determined in PM2.5 of Taiyuan from 2017 to 2018. Coal combustion/secondary formation and traffic emission/secondary formation were apportioned as possible pollution sources for the PM2.5-bound PASHs in Taiyuan and Guangzhou, respectively. Dithiothreitol and cell viability assays were applied for evaluations of PASH-induced reactive oxygen species (ROS) production and cell toxicity based on the determined real exposure levels for adults. The results illustrated that PASHs in PM2.5 possibly caused oxidative stress and inhibition of human bronchial epithelial cells in seriously polluted regions such as Taiyuan, suggesting that the pollutant-induced health concerns may need more investigations. This study provides new insights into PM2.5 pollution, and is beneficial for the development of effective contamination control strategies and reduction of risks on public health.

Dual-Purpose SERS Sensor for Selective Determination of Polycyclic Aromatic Compounds via Electron Donor-Acceptor Traps.

Toxic, carcinogenic, and mutagenic properties of polycyclic aromatic hydrocarbons (PAHs) and environmental pollution caused by polycyclic aromatic sulfur heterocycles (PASHs) postulate the importance of their selective and sensitive determination in environmental and oil fuel samples. Surface-enhanced Raman spectroscopy (SERS) opens up an avenue toward multiplex analysis of complex mixtures, however not every molecule gives high enhancement factors and, thus, cannot be reliably detected via SERS. However, the sensitivity can be drastically increased by additional resonant enhancement as a result of the analyte absorption band overlapping with the surface plasmon band of nanoparticles (NPs) and the laser excitation wavelength. Using this idea, we developed a dual-purpose SERS sensor based on trapping the target PAHs and PASHs into colored charge-transfer complexes (CTCs) with selected organic π-acceptor molecules on the surface of AgNPs. Studying, computing, and then comparing stability constants of the formed CTC served as a powerful explanation and prediction tool for a wise choice of π-acceptor indicator systems for the further silver surface modification. Moreover, we show that CTC formation can be effectively utilized for increasing both selectivity and sensitivity by simple liquid-liquid extraction prior to SERS measurements. For the first time, the dual-purpose SERS sensor allowed determination of two different classes of polycyclic aromatic fuel components down to 10 nM concentration, lower than that restricted by the ASTM regulation, and demonstrated multi-purpose capabilities of the developed approach.