Mixtures Of Aromatic Hydrocarbons Research Articles

Analysis of Multivariable Sensor Responses to Multi-Analyte Gas Samples in the Presence of Interferents and Humidity.

This work presents an adaptive sensor signal-processing approach to enable quantification, using a single gas sensor or a small sensor array, of multianalyte mixtures of aromatic hydrocarbons in the presence of various interferents and humidity for environmental-monitoring applications. Dynamic sensor responses are analyzed by extracting multivariable sensing parameters to provide necessary sensitivity and selectivity. This is achieved by integrating the Levenberg-Marquardt-modified, exponentially weighted, recursive-least-squares-estimation (LM-modified EW-RLSE) algorithm and principal-component analysis (PCA). Achieving measured detection limits as low as 3 μg/L (≤1 ppm by volume) for 6 target analytes, the system exhibits excellent PCA cluster separation for all analytes in the mixtures, with reliable identification and accurate quantification, even in the presence of various interferents. Concentration errors of approximately ±5% are obtained for mixtures containing up to 6 BTEX compounds (including chemical isomers) and up to 4 interferents. Additionally, the study investigates the impact of humidity on the polymer/plasticizer-coated shear-horizontal surface acoustic wave (SH-SAW) sensors, demonstrating accurate concentration estimation in a relative humidity range from dry nitrogen to 65%. This sensing-and-multivariate-signal-processing approach is a promising candidate for reliable environmental monitoring in real-world applications.

Fractionation of complex aromatic hydrocarbon mixtures using membrane cascades hybridized with distillation

Membrane-based separations are a promising technology to enable reductions in process intensity in chemical processing industries. However, membrane-based complex mixture fractionation is a nascent process, and these systems may require several membrane stages to achieve product specifications. Here, we highlight an example multi-stage fractionation process for complex aromatic hydrocarbon mixtures. Three separate hollow fiber membrane modules with varying hydrocarbon molecular weight cut offs were used for this experimental demonstration of a multi-stage membrane separation of a synthetic crude oil that is loosely based on the actual composition of light Permian oil. Moreover, the potential energy benefit of a traditional distillation combined with membrane cascade systems was investigated by combining a transport model based on the dry glass reference perturbation theory (DGRPT) and a process simulator. The work highlights that the heat energy duty of a distillation column can be reduced by more than 50 % when hybridized with a membrane cascade.

Assessment of the influence of production factors on physiological parameters, behavioral reactions and accelerated aging of laboratory animals in a chronic experiment

In solving problems in the state of health of workers under the influence of occupational hazards, laboratory animals are used as an accessible experimental model to establish the risks of occupational diseases and the mechanisms of premature aging. Laboratory animals are of great importance for registering physiological indicators and behavioral reactions, revealing the mechanisms of the occurrence of diseases associated with the profession. Objective: to assess the isolated effects of production factors on physiological parameters, behavioral reactions and accelerated aging of laboratory animals in a chronic experiment characterizing the stages of the adaptation process. Object of the study: white laboratory rats of the Wistar line (n=120), grouped into four groups: three experimental rats contained in conditions of periodic isolated exposure to vibration, noise and a 4‑component mixture of aromatic hydrocarbons at the level of 1.5 MPC, MPC, and one control (intact animals) — in comfortable conditions (normal photoperiodism and the temperature is +22–24 °C). The indicators of body weight and temperature and functional activity of the nervous system were studied using the «Open Field» method. Statistical analysis was performed using standard Statistica 10.0 application programs with calculation of median (Me) and percentile interval. The acceptable level of reliability of the results was considered to be the probability of differences of 95 % or higher (p≤0.05). Animals of all groups showed a constant temperature balance, and an increase in body weight by the 180th day of the experiment. Indicators of motor, emotional and research activity statistically significantly decreased on the 180th day of the experiment in animals of the experimental groups, and indicators of vertical and horizontal activity significantly decreased in rats in the chemical exposure group compared with the control group. Further study of the influence of production factors on changes in body weight, temperature balance, anxiety, emotional state and cognitive activity in model animals as biological (living) systems will contribute to the disclosure of the mechanisms of premature aging and occupational diseases in workers under conditions of occupational hazards.

Adverse impact of phthalate and polycyclic aromatic hydrocarbon mixtures on birth outcomes: A metabolome Exposome-Wide association study

It has been well-investigating that individual phthalates (PAEs) or polycyclic aromatic hydrocarbons (PAHs) affect public health. However, there is still a gap that the mixture of PAEs and PAHs impacts birth outcomes. Through innovative methods for mixtures in epidemiology, we used a metabolome Exposome-Wide Association Study (mExWAS) to evaluate and explain the association between exposure to PAEs and PAHs mixtures and birth outcomes. Exposure to a higher level of PAEs and PAHs mixture was associated with lower birth weight (maximum cumulative effect: 143.5 g) rather than gestational age. Mono(2-ethlyhexyl) phthalate (MEHP) (posterior inclusion probability, PIP = 0.51), 9-hydroxyphenanthrene (9-OHPHE) (PIP = 0.53), and 1-hydroxypyrene (1-OHPYR) (PIP = 0.28) were identified as the most important compounds in the mixture. In mExWAS, we successfully annotated four overlapping metabolites associated with both MEHP/9-OHPHE/1-OHPYR and birth weight, including arginine, stearamide, Arg-Gln, and valine. Moreover, several lipid-related metabolism pathways, including fatty acid biosynthesis and degradation, alpha-linolenic acid, and linoleic acid metabolism, were disturbed. In summary, these findings may provide new insights into the underlying mechanisms by which PAE and PAHs affect fetal growth.

Exploring the endocrine disrupting potential of a complex mixture of PAHs in the estrogen pathway in Oreochromis niloticus hepatocytes

This study aimed to investigate the toxicity and endocrine disrupting potential of a complex mixture of polycyclic aromatic hydrocarbons (PAHs) in the estrogen pathway using hepatocytes of Nile tilapia Oreochromis niloticus, the hepatocytes were exposed to various concentrations of the PAH mixture, and multiple endpoints were evaluated to assess their effects on cell viability, gene expression, oxidative stress markers, and efflux activity. The results revealed that the PAH mixture had limited effects on hepatocyte metabolism and cell adhesion, as indicated by the non-significant changes observed in MTT metabolism, neutral red retention, and crystal violet staining. However, significant alterations were observed in the expression of genes related to the estrogen pathway. Specifically, vitellogenin (vtg) exhibited a substantial increase of approximately 120% compared to the control group. Similarly, estrogen receptor 2 (esr2) showed a significant upregulation of approximately 90%. In contrast, no significant differences were observed in the expression of estrogen receptor 1 (esr1) and the G protein-coupled estrogen receptor 1 (gper1). Furthermore, the PAH mixture elicited complex responses in oxidative stress markers. While reactive oxygen species (ROS) and reactive nitrogen species (RNS) levels remained unchanged, the activity of catalase (Cat) was significantly reduced, whereas superoxide dismutase (Sod) activity, glutathione S-transferase (Gst) activity, and non-protein thiols levels were significantly elevated. In addition, the PAH mixture significantly influenced efflux activity, as evidenced by the increased efflux of rhodamine and calcein, indicating alterations in multixenobiotic resistance (MXR)-associated proteins. Overall, these findings, associated with bioinformatic analysis, highlight the potential of the PAH mixture to modulate the estrogen pathway and induce oxidative stress in O. niloticus hepatocytes. Understanding the mechanisms underlying these effects is crucial for assessing the ecological risks of PAH exposure and developing appropriate strategies to mitigate their adverse impacts on aquatic organisms.

Assessment of genotoxic damage induced by exposure to binary mixtures of polycyclic aromatic hydrocarbons and three heavy metals in male mice

Introduction Heavy metals (HM) and polycyclic aromatic hydrocarbons (PAHs) exposition has been associated with health problems. Therefore, this research evaluated genotoxicity induced in male mice strain CD-1 exposed to benzo[a]anthracene (B[a]A) and benzo[a]pyrene (B[a]P) and their interaction with Fe, Pb, and Al. Methods Groups of animals were exposed intraperitoneally to HM, PAHs, and mixtures of both. Peripheral blood samples were taken from 0 to 96 h at 24 h intervals; genotoxicity was determined by micronucleus tests and comet assay. Additionally, toxicity and viability were evaluated. Results HM and PAHs individually were genotoxic. About toxicity, only Al altered polychromatic erythrocytes number and did not change leukocytes viability. Concerning mixtures, Fe + B[a]P, Fe + B[a]A, Pb + B[a]P increased genotoxicity. There were no changes with Pb + B[a]A. Finally, Al mixtures with both PAHs damage was decreased. Conclusions Exposure to HM and PAH caused genetic damage. Fe, Al, and B[a]A, established a genotoxic potential. Every metal can interact with PAHs in different ways. Also, the micronucleus test and the comet assay demonstrated their high capacity and reliability to determine the genotoxic potential of the compounds evaluated in this work.

Transformation of aromatic hydrocarbons in the process of hydrogenation of a concentrated mixture to produce clean fuels

The process of hydrogenation of a modeling mixture of aromatic hydrocarbons was studied in order to develop regulated approaches for producing environmentally friendly fuels. The process was carried out on a trimetallic PdNiCr catalyst deposited on aluminum oxide. The optimal conditions for carrying out the reaction were determined. The influence of the structure of substituted substrates on the formation of by-products of the ring-opening reaction has been established.

Preparation of N and O doped coal tar pitch based porous carbon for supercapacitor electrode

Coal tar pitch (CTP) is mainly composed of a mixture of polycyclic aromatic hydrocarbons, is almost hydrophobic, and has a low heteroatom content, which limits its surface function. During carbonization, it is prone to condensation and difficult to form pore structures, resulting in poor electrochemical performance for carbon electrode materials. Herein, nitrogen (N) and oxygen (O) doped hierarchical porous carbon (C-ANOCTP) was prepared by HNO3 oxidation and KOH activation using CTP as carbon precursor. The oxidation of HNO3 remarkably increases the hydrophilic functional groups containing N and O on the surface of CTP, improves the hydrophilicity of CTP surface, facilitates the activation process of KOH, promotes the development of carbon material pore structure and the generation of active sites, as well as the formation of defect structures. The specific surface area of C-ANOCTP obtained is 1130 m2/g, with O content of 10.29 at% and N content of 2.37 at%. The specific capacitance of C-ANOCTP in a three-electrode system with 6 M KOH electrolyte is as high as 410.51 F/g at 0.5 A/g. A symmetric supercapacitor is assembled in a 6 M KOH electrolyte using C-ANOCTP as electrode. When the power density is 25 W/kg, the energy density is 10.24 Wh/kg. After 10,000 cycles, the capacitance retention rate is still 90.03% and the coulomb efficiency is 100%. The high N and O content of porous carbon is prepared by simple HNO3 oxidation synergistic KOH activation and low temperature carbonization, which shows excellent electrochemical properties in supercapacitors, making CTP an ideal candidate material for high energy density supercapacitors.

Associations of polycyclic aromatic hydrocarbons mixtures with cardiovascular diseases mortality and all-cause mortality and the mediation role of phenotypic ageing: A time-to-event analysis

The associations of polycyclic aromatic hydrocarbons (PAHs) with cardiovascular diseases (CVDs) and all-cause mortality are unclear, especially the joint effects of PAHs exposure. Meanwhile, no studies have examined the effect of phenotypic ageing on the relationship between PAHs and mortality. Therefore, this study aimed to investigate the independent and joint associations between PAHs and CVDs, all-cause mortality, and assess whether phenotypic age acceleration (PhenoAgeAccel) mediate this relationship. We retrospectively collected data of 11,983 adults from the National Health and Nutrition Examination Survey database. Firstly, Cox proportional hazards regression and restricted cubic splines were applied to evaluate the independent association of single PAH on mortality. Further, time-dependent Probit extension of Bayesian Kernel Machine Regression and quantile-based g-computation models were conducted to test the joint effect of PAHs on mortality. Then, difference method was used to calculate the mediation proportion of PhenoAgeAccel in the association between PAHs and mortality. Our results revealed that joint exposure to PAHs showed positive association with CVDs and all-cause mortality. By controlling potential confounders, 1-Hydroxynapthalene (1-NAP) (HR = 1.24, P = 0.035) and 2-Hydroxyfluorene (2-FLU) (HR = 1.25, P < 0.001) showed positive association with CVDs mortality, and they were the top 2 predictors (weight: 0.82 for 1-NAP, 0.14 for 2-FLU) of CVDs mortality. 1-NAP (HR = 1.15, P < 0.001) and 2-FLU (HR = 1.13, P < 0.001) also showed positive association with all-cause mortality, and they were also the top 2 predictors of all-cause mortality (weight: 0.66 for 1-NAP, 0.34 for 2-FLU). PhenoAgeAccel mediated the relationship between 1-NAP, 2-FLU and CVDs, all-cause mortality, with a mediation proportion of 10.00 % to 24.90 % (P < 0.05). Specifically, the components of PhenoAgeAccel including C-reactive protein, lymphocyte percent, white blood cell count, red cell distribution width, and mean cell volume were the main contributors of mediation effects. Our study highlights the hazards of joint exposure of PAHs and the importance of phenotypic ageing on the relationship between PAHs and mortality.

Design and evaluation of semicarbazide-embeddedd stationary phases for liquid chromatography

Semicarbazide, as a derivative of urea, constitutes a great variety of functional molecules for different needs. Herein, novel stationary phases with an incorporated semicarbazide group were proposed. Using aliphatic (docosanoyl, C22) and aromatic (benzoyl, Bz) hydrazides, the semicarbazide-embedded ligands were synthesized before chemical modification of the silica gel, allowing for an accurate interpretation of the chromatographic properties of the corresponding packings. The new stationary phases were water-wettable, due to the presence of highly polar groups. In particular, Bz-semicarbazide (Bz-SCD) stationary phase was sufficiently hydrophilic to run in hydrophilic interaction (HILIC) mode, whilst the C22 (C22-SCD) equivalent, in spite of its reversed-phase nature, was markedly less hydrophobic than the referenced polar-embedded ones. The versatility of C22-SCD was demonstrated with a large selection of analytes, including geometric isomers and standard mixtures of polycyclic aromatic hydrocarbons, sulfonamides, sulfonylurea, substituted ureas, pyridines and carbamates, fat-soluble colorants, antifungal metabolites, angiotensin II receptor blockers and calcium channel blockers.

Differences in phytoplankton population vulnerability in response to chemical activity of mixtures.

Hydrophobic organic contaminants (HOCs) affect phytoplankton at cellular to population levels, ultimately impacting communities and ecosystems. Baseline toxicants, such as some HOCs, predominantly partition to biological membranes and storage lipids. Predicting their toxic effects on phytoplankton populations therefore requires consideration beyond cell uptake and diffusion. Functional traits like lipid content and profile can offer insights into the diverse responses of phytoplankton populations exposed to HOCs. Our study investigated the vulnerability of five phytoplankton species populations to varying chemical activities of a mixture of polycyclic aromatic hydrocarbons (PAHs). Population vulnerability was assessed based on intrinsic sensitivities (toxicokinetic and toxicodynamic), and demography. Despite similar chemical activities in biota within the exposed algae, effects varied significantly. According to the chemical activity causing 50% of the growth inhibition (Ea50), we found that the diatom Phaeodactylum tricornutum (Ea50 = 0.203) was the least affected by the chemical exposure and was also a species with low lipid content. In contrast, Prymnesium parvum (Ea50 = 0.072) and Rhodomonas salina (Ea50 = 0.08), both with high lipid content and high diversity of fatty acids in non-exposed samples, were more vulnerable to the chemical mixture. Moreover, the species P. parvum, P. tricornutum, and Nannochloris sp., displayed increased lipid production, evidenced as 5-10% increase in lipid fluorescence, after exposure to the chemical mixture. This lipid increase has the potential to alter the intrinsic sensitivity of the populations because storage lipids facilitate membrane repair, reconstitution and may, in the short-term, dilute contaminants within cells. Our study integrated principles of thermodynamics through the assessment of membrane saturation (i.e. chemical activity), and a lipid trait-based assessment to elucidate the differences in population vulnerability among phytoplankton species exposed to HOC mixtures.

Evidence of transboundary movement of chemicals from Mexico to the U.S. in Tijuana River Estuary sediments

The Tijuana River Estuary (TRE) has been a public health hazard and point of contention between the United States and Mexico for decades, with sources of pollution on both sides of the border. The goal of our study is to determine the presence and dynamics of chemical contamination in the TRE. We sampled sediment from four TRE locations in the U.S. during stable dry conditions and immediately after a wet weather period. Organic chemicals were initially screened with non-targeted analysis using gas chromatography high-resolution mass spectrometry (GC/HRMS) that tentatively identified 6978 chemicals in the NIST 20 database. These tentative identifications were filtered using the USEPA CompTox database to guide quantitative targeted analysis at detection limits below 1 ng/g dry weight sediment. Quantitative targeted analysis of 152 organic pollutants and 18 inorganic elements via GC/HRMS revealed generally higher concentrations of contaminants in dry weather sediments compared to wet weather sediments. The highest concentrations of all chemical classes were detected at the site closest to the U.S.-Mexico border, followed by an urban area near Imperial Beach, California, U.S. All sites exhibited a mixture of petrogenic and pyrogenic polycyclic aromatic hydrocarbons (PAHs). Current-use pesticides were dominated by pyrethroid insecticides and the thiocarbamate herbicide s-Ethyl dipropylthiocarbamate (EPTC), while the U.S.-banned organochlorine pesticides were dominated by chlordanes, dieldrin, and dichlorodiphenyltrichloroethane (DDT) and its degradation byproducts. Polychlorinated biphenyl (PCB) concentrations were greatest at the site closest to the U.S.-Mexico border but in the low nanogram-per-gram range. Phthalates were only found at the same site, with relatively high concentrations of bis(2-ethylhexyl) phthalate. This study provides positive identification and quantitative concentrations for organic pollutants in TRE sediments. Our data suggest that there are multiple sources of chemical contamination in the estuary, including possible transboundary movement of pollutants from Mexico.

Halogenated polymers as a problematic component in the pyrolysis of waste plastics

The study deals with the complications associated with the pyrolysis of a polymer releasing highly corrosive compounds and other products that are difficult to be utilized in practice. Poly(vinyl chloride-vinyl acetate) was chosen as a sample material. This copolymer was subjected to slow pyrolysis up to a temperature of 650 °C, which was achieved with a temperature ramp of 10 °C min‒1. Thermal decomposition took place in a batch apparatus in nitrogen atmosphere. The evaluation of the experiments included a mass balance using an online recording of gas and condensate formation, which was followed by an analysis of the obtained products. The tests showed very small yields of condensates (pyrolysis tar) in the range of 3.0 – 5.5% compared to gas production reaching 71.1 – 72.1% of the raw material weight. Within the discussion, the problem with the production of non-flammable gas consisting mainly of HCl in the initial stages of pyrolysis was highlighted. Under the given conditions, the release of acid gases, in which HCl was gradually replaced by also non-flammable CO2, continued up to about 400 °C. Only gases collected from this temperature above and having a calorific value of 33.5 MJ m‒3 (20 °C / 101.32 kPa) can be considered energetically usable. Condensates mainly represented by a mixture of aromatic hydrocarbons, acetic acid and chlorobenzene were also evaluated as problematic for possible use. The possibilities of physical activation of solid pyrolysis residues by steam at temperatures of 850 and 900 °C were also tested. All experiments led to obtaining products with very small specific surface areas in the range of 1 – 6 m2 g–1. The process loss during activation reached 25 – 33% of the pyrolysis residue weight, depending on the applied temperature and contact time with steam. These values show that the reaction of the activation medium with the sample took place more or less only on the outer surface of the particles and did not lead to the development of an internal porous structure. The achieved results were compared with the identically processed samples of waste tires, which were evaluated as promising in tests carried out in the past. The contrast be-tween the two materials clearly spoke against the discussed copolymer. The results of the experiments can be interpreted, among other things, as a certain warning against attempts at industrial pyrolysis processing of this type of plastic.

Gender-specific associations between mixture of polycyclic aromatic hydrocarbons and telomere length.

Evidence shows the relationships of individual environmental PAHs by their urinary metabolites with relative telomere length (RTL), which may be affected by biological gender differences. Since plasma parent PAHs are not metabolized, it may reflect human exposure to PAHs more realistically in daily life. Thus, exploring joint associations between plasma parent PAHs and RTL is urgent, which may identify the major contributor to its adverse effect. In this study,2577 participants were obtained from the Henan Rural Cohort. The level of PAHs in blood samples was detected by gas chromatography coupled with tandem mass spectrometry. RTL in blood samples was detected by quantitative polymerase chain reaction. Generalized linear models or quantile g-computation were performed to evaluate the associations between the individual or a mixture of PAHs and RTL. Results from generalized linear models showed that each unit increment in BghiP value corresponded to a 0.098 (95%CI: 0.067, 0.129) increment in RTL for men; each unit increment in BaP, BghiP and Flu value corresponded to a 0.041 (95%CI: 0.014, 0.068), 0.081 (95%CI: 0.055, 0.107) and 0.016 (95%CI: 0.005, 0.027) increment in RTL for women. Results from quantile-g computation revealed that each one-quantile increment in the mixture of 10 PAHs corresponded to a 0.057 (95%CI: 0.021, 0.094) and 0.047 (95%CI: 0.003, 0.091) increment in RTL valuesof women and men, but these associations were mainly ascribed to three PAHs for women (BaP, Flu and BghiP) and men (BaP, BghiP and Pyr), respectively. Similar results were found in smoking men and cooking women without smoking. Our study foundthat exposure to 10 PAHs mixture was positively associated with RTL across gender, mainly attributed to Flu, BaP and BghiP, implicating that gender-specific associations may be ascribed to tobacco and cooking smoke pollution. The findings provided clues for effective measures to control PAHs pollutants-related aging disease.Clinical trial registration The Henan Rural Cohort Study has been registered at the Chinese Clinical Trial Register (Registration number: ChiCTR-OOC-15006699). Date of registration: 06 July 2015. http://www.chictr.org.cn/showproj.aspx?proj=11375 .

Mechanistic study of ultrasound-assisted chromatography using plastic and stainless steel columns

Based on the previous ultrasound-assisted chromatography (UAC) studies on plastic and stainless steel (SS) columns, this study explores the UAC mechanism by comparatively analyzing ultrasound effects on plastic and SS columns with C18 stationary phase when separating a mixture of polycyclic aromatic hydrocarbons (PAHs) under various ultrasound intensities. The results showed a substantial difference in H values between the PEEK and SS columns under the influence of ultrasound agitation. Specifically, for the pyrene peak, as the ultrasonic intensity increased from 0% to 100% of 900 W, the H values of the SS column slightly rose from 8.82 μm to 9.86 μm. Conversely, the corresponding values for the PEEK column exhibited a significant 12-fold increase from 11.5 μm to 134 μm. The findings demonstrated poor penetration of ultrasound energy through the SS column, and the temperature rise of the medium induced by the ultrasound was the primary contributing factor to PAH separation. However, ultrasound easily penetrated through the plastic column, resulting in acoustic cavitation within the C18 polyether ether ketone (PEEK) column. Cavitation induced heat generation and contributed to a decrease in retention time and the magnitude of peak broadening or distortion, depending on the specific ultrasonic energy. Based on the estimated change in inlet temperature of the PEEK column due to an acoustic effect, the comparison with temperature effects under non-sonic conditions consistently demonstrated a stronger acoustic effect in reducing the retention time, by 2–9%, depending on specific peaks and pairs. We revisited the previously described separation mechanism of ultrasound-assisted ion chromatography and conjoined with our findings to infer and establish a thorough explanation for the previously unexplained separation mechanism of chiral separation and size exclusion chromatography by UAC using SS columns.

Calculated cancer risks for polycyclic aromatic hydrocarbon mixtures in mainstream smoke of cigarettes sold in China

China is the world's largest consumer of cigarettes. However, the potential cancer risk posed by polycyclic aromatic hydrocarbons (PAHs) in mainstream cigarette smoke, especially species other than benzo[a]pyrene (BaP) remains unclear. In this study, we collected yield data on multiple PAH species from a variety of cigarettes in the China market and calculated their smoking-related incremental lifetime cancer risk (ILCR) values. The computed ILCRs of the total PAHs (ILCRΣPAHs) for ≥95% of the brands were one order of magnitude higher than the acceptable level. ILCRBaP accounted for only 5.0%–37.7% of ILCRΣPAHs among brands, indicating that using single analyte BaP to represent ΣPAHs would significantly underestimate ILCRΣPAHs. No clear trend of changes in ILCRΣPAHs was found for Chinese cigarettes over multiple years, suggesting that smoking cessation is still the best option to minimize the cancer risk of PAHs. The comparison study showed that rarely reported PAHs from Chinese cigarettes can contribute over half of ILCRΣPAHs for several American cigarettes, highlighting the imperativeness to improve the diversity of analytes for Chinese cigarettes. Adults would need to inhale the air-borne PAHs with a BaP equivalent concentration of at least 53.1 ng/m3 to reach the ILCR value comparable to that obtained from smoking.

Water-Soluble Pd6L3 Molecular Bowl for Separation of Phenanthrene from a Mixture of Isomeric Aromatic Hydrocarbons.

Phenanthrene is a high-value raw material in chemical industries. Separation of phenanthrene from isomeric anthracene continues to be a big challenge in the industry due to their very similar physical properties. Herein, we report the self-assembly of a water-soluble molecular bowl (TB) from a phenothiazine-based unsymmetrical terapyridyl ligand (L) and a cis-blocked 90° Pd(II) acceptor. TB featured an unusual bowl-like topology, with a wide rim diameter and a hydrophobic inner cavity fenced by the aromatic rings of the ligand. The above-mentioned features of TB allow it to bind polyaromatic hydrocarbons in its confined cavity. TB shows a higher affinity for phenanthrene over its isomer anthracene in water, which enables it to separate phenanthrene with ∼93% purity from an equimolar mixture of phenanthrene and anthracene. TB is also able to extract pyrene with around ∼90% purity from an equimolar mixture of coronene, perylene, and pyrene. Moreover, TB can be reused for several cycles without significant degradation in its performance as an extracting agent. This clean strategy of separation of phenanthrene and pyrene from a mixture of hydrophobic hydrocarbons by aqueous extraction is noteworthy.

Solid–liquid equilibria of binary mixtures of alcohols and aromatic hydrocarbons: experimental methods and modeling analysis

Solid–liquid equilibria of binary mixtures of alcohols and aromatic hydrocarbons: experimental methods and modeling analysis

Evaluation of the cancer risk from PAHs by inhalation: Are current methods fit for purpose?

There is ample evidence from occupational studies that exposure to a mixture of Polycyclic Aromatic Hydrocarbons (PAHs) is causally associated with an increased incidence of lung cancers. In both occupational atmospheres and ambient air, PAHs are present as a mixture of many compounds, but the composition of the mixture in ambient air differs from that in the occupational atmosphere, and varies in time and space in ambient air. Estimates of cancer risk for PAH mixtures are based upon unit risks which derive from extrapolation of occupational exposure data or animal model data, and in the case of the WHO use one compound, benzo[a]pyrene as a marker for the entire mixture, irrespective of composition. The U.S. EPA has used an animal exposure study to derive a unit risk for inhalation exposure to benzo[a]pyrene alone, and there have been a number of rankings of relative carcinogenic potency for other PAHs which many studies have used to calculate a cancer risk from the PAHs mixture, frequently incorrectly by adding the estimated relative risks of individual compounds, and applying the total “B[a]P equivalent” to the WHO unit risk, which already applies to the entire mixture. Such studies are often based upon data solely for the historic US EPA group of 16 compounds which do not include many of the apparently more potent carcinogens. There are no data for human cancer risk of individual PAHs, and conflicting evidence of additivity of PAH carcinogenicity in mixtures. This paper finds large divergences between risk estimates deriving from the WHO and U.S. EPA methods, as well as considerable sensitivity to the mixture composition, and assumed PAH relative potencies. Of the two methods, the WHO approach appears more likely to provide reliable risk estimates, but recently proposed mixture-based approaches using in vitro toxicity data may offer some advantages.

Simple Preparation Method of Silica Core–Shell Spheres for HPLC in Undergraduate Chemistry

High-performance liquid chromatography (HPLC) experiments are an important part of the undergraduate analytical instrumentation laboratory courses and usually use commercial C18 silica-packed reversed-phase columns. In this experiment, a simple method of preparing SiO2 core–shell packed columns was developed to enable students to master the whole process of HPLC experiment from stationary phase preparation and column packing to separation experiments, just as they do for gas chromatography. Nonporous SiO2 particles with a particle size of approximately 2.2 μm were prepared by a three-step dilution reaction using the sol–gel method. The product yield was 92.1%. Monodisperse and spherical SiO2 core–shell particles (SiO2@dSiO2) with a particle size of about 2.4 μm were prepared by a one-step hydrothermal method using the prepared SiO2 spheres as the core. The product yield was 83.3%. The prepared SiO2@dSiO2 particles were derivatized with n-octadecyldimethylchlorosilane and then packed into a stainless steel chromatography column. A high column efficiency of 83,188 theoretical plates per meter was obtained for fluorene in reversed-phase mode for the separation of a mixture of polycyclic aromatic hydrocarbons. The column efficiency obtained with this method is the same as that of a commercial column packed with fully porous particles of the same particle size. The SiO2 core–shell stationary phase preparation method developed in this experiment has the advantages of simple process, high yield, and good repeatability. The experiment can be designed to be completed over a period of 1–3 weeks. Inorganic material synthesis is another important aspect of this experiment.