Number Of Polycyclic Aromatic Hydrocarbons Research Articles

Revealing the backbone structures of land-based fulvic acids derived from river and soil through n-butylsilane reduction.

While ultra-high-resolution mass spectrometry has enabled the identification of the molecular composition of dissolved organic matter (DOM), elucidating its molecular structure remains a challenging endeavor. Here, two fulvic acids (FAs), one from river and the other from forest soil, were subjected to reduction using an optimized n-butylsilane (n-BS) reduction method. The reduction products were purified through a combination of liquid-liquid extraction and silica gel column chromatography, resulting in the separation into saturates, aromatics, and polar products. The polar products were analyzed by high-resolution mass spectrometry (HRMS), and the saturates and aromatics were analyzed using gas chromatography-mass spectrometry (GC-MS). HRMS results showed that the number of oxygen atoms and double-bond equivalent (DBE) values of FA decreased after reduction. GC-MS results revealed that a total of 270 hydrocarbon monomers were identified from the reduction products of a single sample, with the highest carbon number of cycloalkanes reaching C33. For the first time, steranes and hopanes were detected in the reduction products, potentially serving as evidence for the existence of carboxyl-rich alicyclic molecule (CRAM) precursors. Additionally, a significant number of polycyclic aromatic hydrocarbons were identified, and the potential sources of various compounds were preliminarily inferred based on their isomers. This study extends the knowledge of the possible backbone structure of the DOM and provides a new potential tool for investigating the origin and transformation mechanisms of DOM.

Assessment of Bee Honey in some Districts in South-Western Nigeria for Agricultural Pesticide Residues and Polycyclic Aromatic Hydrocarbons (PAHs)

Purpose: Honey are produced by honeybees which are expected to be free from contaminants or pollutants in the environment. But different degrees of anthropogenic activities in regions where apiaries domiciles have raised issues of primary health importance because of the increasing contents of pesticide residues, polycyclic aromatic hydrocarbons (PAHs), and other related hydrocarbon compounds in honey. Osun State is an agrarian state where agricultural herbicides and insecticides are used. The study focused on organophosphate and organochlorine compounds and PAHs. Research Method: Honey samples sourced from selected zones in Osun State, were screened for organophosphate, organochlorine compounds, PAHs as well as other related hydrocarbon compounds using Gas Chromatography-Mass Spectrometry (GC-MS). Finding: There were no traces of highlighted pesticide residues except for PAHs and other related compounds. Ninety-two PAHs and other related hydrocarbon compounds were identified. The number of PAHs and related compounds per sample ranged from 9 to 35. While Cyclohexane, Decodane and Naphthalene were the most common with higher concentrations in all the samples. The Mn±S.D values of Cyclohexane, Naphthalene and Decodane obtained were 0.2976±0.1253µgkg-1, 0.471±0.119µgkg-1, and 12.516±3.120µgkg-1 respectively. Other PAHs and other related hydrocarbon compounds identified had insignificant concentrations. Originality/value: The study recommends that bee farmers should locate their apiaries 3km to 5km away from regions where there are serious hazardous anthropogenic activities including industrial areas. Also, there is need for strong understanding between the bee farmers and crop farmers on tolerable uses of agricultural pesticides, and herbicides on field crops during the flower bloom period where there are no options. Lastly, harvested honey should undergo quality assurance and control for safety reasons. All packaged honey for retail should bear labels including the compositions after quality analysis.

Evolution of carbon deposits during ethylene aromatization over Zn/ZSM-5

Zn/ZSM-5 catalysts exhibit remarkable catalytic activity in the ethylene aromatization process. Nonetheless, they frequently suffer from rapid deactivation owing to coke deposition. This study investigated the coking process of Zn/ZSM-5 catalyst during the ethylene aromatization, as well as the evolution of carbon deposits and their impact on the catalyst's structure and surface properties. The results showed that, despite ethylene conversion remaining at 100 % during the initial high-activity stable phase (0–24 h), even small amounts of carbon deposition resulted in significant decrease in microporosity and strong acid sites of the catalyst. Methyl-substituted benzene was identified as the primary deposit on the catalyst in the initial reaction stage, as confirmed by infrared (IR) spectroscopy, ultraviolet-Raman (UV-Raman), thermogravimetry-mass spectrometer (TG-MS), gas chromatography-mass spectrometry (GC–MS), and electron paramagnetic resonance (EPR), which can act as an active hydrocarbon pool species for ethylene oligomerization. Thus, the catalyst was able to maintain high ethylene conversion activity despite the loss of some acid sites. However, during the decline in activity period (24–72 h), the composition and location of carbon deposits underwent significant changes. A large number of polycyclic aromatic hydrocarbons formed on the catalyst surface, which resulted in the weakening of the interaction between Zn species and the zeolite, ultimately leading to the transformation into large grain ZnO and decrease in aromatics selectivity. Additionally, the bulky carbon deposits covered the pores of the zeolite, leading consequently to a decrease in ethylene conversion and ultimately catalyst deactivation.

Emission characteristics of particulate matter emitted from 4- and 2-stroke marine diesel engines under the background of sulfur emission reduction.

With the implementation of sulfur emission regulations, influences of particulate matter (PM) emitted by marine diesel engines on nearshore atmospheric environment and human health are of increasingly concern. Whatever measures are chosen to meet sulfur emission regulations, the emission characteristic and influencing factors of PM should also be determined. In this study, number and mass emissions, volatility, main composition, and toxicity of PM from marine 4- and 2-stroke diesel engines were investigated. It was found that the size distribution curves of particle number are multiple peaks. Fuels and engines types influence the modal distribution of particles number concentration. For light diesel oil and low-sulfur heavy fuel oil (HFO), particle number was dominated by nucleation and accumulation mode respectively, and particle mass was dominated by accumulation mode. Reduction of fuel sulfur content (FSC) could reduce the particles mass, number and fraction of volatile substance emissions, and small-size particles had the most volatility. Particulate organic carbon (OC) was the main substance, especially for marine 2-stroke diesel engine burning HFO (high- or low-sulfur), while particulate OC contained a large number of polycyclic aromatic hydrocarbons (PAHs) and n-alkanes. The PAHs also had very high toxicity when the engine was burning HFO. The use of low-sulfur HFO cannot make the marine diesel engine meet the current and upcoming PM regulations, and after-treatment technologies or cleaning fuel should be needed.

Influence of Miscanthus Rhizome Pyrolysis Operating Conditions on Products Properties

Waste from the Miscanthus production cycle may be a promising source of material for the pyrolysis and biochar production. The biochar can be used to enrich the soil on which the crop grows, thus increasing productivity. A sample of Miscanthus rhizomes was used as a raw material in a series of experiments in order to find the most suitable conditions for the preparation of biochar. Miscanthus biochar was prepared in a laboratory unit using four different temperatures (i.e., 400, 500, 600 and 700 °C). All pyrolysis products were subsequently evaluated in terms of their quality and product yields were determined. For a temperature of 600 °C and a residence time of 2 h, the appropriate properties of biochar were achieved and the process was still economical. The biochar contained a minimal number of polycyclic aromatic hydrocarbons and a high percentage of carbon. Surface area was measured to be 217 m2/g. The aqueous extract of biochar was alkaline.

ВРАЩАТЕЛЬНЫЕ СПЕКТРЫ РЯДА ПОЛИЦИКЛИЧЕСКИХ АРОМАТИЧЕСКИХ УГЛЕВОДОРОДОВ

A theoretical study of the rotational spectra of a number of polycyclic aromatic hydrocarbons (PAHs) was carried out on the basis of quantum-chemical calculations by PRIRODA program in the PBE/3ζ approximation. Calculations are given for neutral molecules, their radical anions and radical cations in the rigid top approximation. Twelve neutral PAHs under study have no dipole moment and are not of interest for rotational spectroscopy. Thirteen neutral PAHs have a dipole moment not exceeding 0.09 Debye and, under certain conditions, can be studied in the microwave region. The remaining six compounds are PAHs with methyl and phenyl substituents, their dipole moments are 0.32-0.65 Debye, which makes it possible to study their microwave spectrum. For radical ions, the situation with the dipole moment is as follows: if a neutral molecule does not have a dipole moment, then the corresponding radical ion does not have it either; if the dipole moment of a neutral molecule is nonzero, then for radical ions it increases at least several times. For example, in the benzo [b] chrysene radical anion, the μa-component component of the dipole moment increases by 250 times, the μb-component by 7 times, and the total dipole moment by about 100 times. This effect is more pronounced for radical anions than for radical cations. In this case, it becomes possible to detect the spectrum of if not a neutral molecule, then at least one of its charge states. For a number of compounds, the patterns of various spectroscopic parameters depending on the number of carbon atoms in PAHs were found. In the B3LYP/6-31G(d,p) approximation, quartic centrifugal distortion constants were calculated for five compounds, and their effect on the rotational spectrum was estimated: for many compounds under study, they can have a significant effect on the microwave spectrum. With an increase in PAHs, the centrifugal constants decrease indicating an increase in the rigidity of the molecules. Thus, substituted neutral PAHs, as well as a number of radical ions, may be of interest for experimental studies in laboratory conditions and in space.

Calculating vibrational excitation energies using tensor-decomposed vibrational coupled-cluster response theory.

The first implementation of tensor-decomposed vibrational coupled cluster (CP-VCC) response theory for calculating vibrational excitation energies is presented. The CP-VCC algorithm, which has previously been applied to solving the vibrational coupled cluster (VCC) ground-state equations without explicitly constructing any tensors of order three or higher, has been generalized to allow transformations with the Jacobian matrix necessary for computation of response excitation energies by iterative algorithms. A new eigenvalue solver for computing CP-VCC excitation energies is introduced, and the different numerical thresholds used for controlling the accuracy of the obtained eigenvalues are discussed. Numerical results are presented for calculations of the 20 lowest eigenvalues on a set of 10 four-atomic molecules, as well as for a number of polycyclic aromatic hydrocarbons (PAHs) of increasing size, up to PAH8 with 120 modes. It is shown that the errors introduced by the tensor decomposition can be controlled by the choice of numerical thresholds. Furthermore, all thresholds can be defined relative to the requested convergence threshold of the equation solver, which allows black-box calculations with minimal user input to be performed. Eigenstates of PAHs were efficiently computed without any explicitly constructed tensors, showing improvements in both memory and central processing unit time compared to the existing full-tensor versions.

Metallic Barium: A Versatile and Efficient Hydrogenation Catalyst

AbstractBa metal was activated by evaporation and cocondensation with heptane. This black powder is a highly active hydrogenation catalyst for the reduction of a variety of unactivated (non‐conjugated) mono‐, di‐ and tri‐substituted alkenes, tetraphenylethylene, benzene, a number of polycyclic aromatic hydrocarbons, aldimines, ketimines and various pyridines. The performance of metallic Ba in hydrogenation catalysis tops that of the hitherto most active molecular group 2 metal catalysts. Depending on the substrate, two different catalytic cycles are proposed. A: a classical metal hydride cycle and B: the Ba metal cycle. The latter is proposed for substrates that are easily reduced by Ba0, that is, conjugated alkenes, alkynes, annulated rings, imines and pyridines. In addition, a mechanism in which Ba0 and BaH2 are both essential is discussed. DFT calculations on benzene hydrogenation with a simple model system (Ba/BaH2) confirm that the presence of metallic Ba has an accelerating effect.

Metallic Barium: A Versatile and Efficient Hydrogenation Catalyst.

Ba metal was activated by evaporation and cocondensation with heptane. This black powder is a highly active hydrogenation catalyst for the reduction of a variety of unactivated (non‐conjugated) mono‐, di‐ and tri‐substituted alkenes, tetraphenylethylene, benzene, a number of polycyclic aromatic hydrocarbons, aldimines, ketimines and various pyridines. The performance of metallic Ba in hydrogenation catalysis tops that of the hitherto most active molecular group 2 metal catalysts. Depending on the substrate, two different catalytic cycles are proposed. A: a classical metal hydride cycle and B: the Ba metal cycle. The latter is proposed for substrates that are easily reduced by Ba0, that is, conjugated alkenes, alkynes, annulated rings, imines and pyridines. In addition, a mechanism in which Ba0 and BaH2 are both essential is discussed. DFT calculations on benzene hydrogenation with a simple model system (Ba/BaH2) confirm that the presence of metallic Ba has an accelerating effect.

Chemometric tools applied to optimize a fast solid-phase microextraction method for analysis of polycyclic aromatic hydrocarbons in produced water.

Chemometric tools are powerful strategies to efficiently optimize many processes. These tools were employed to optimize a fast-solid phase microextraction procedure, which was used for the analysis of polycyclic aromatic hydrocarbons (PAHs) in oil-based produced water using a Headspace-Solid Phase Microextraction technique (HS-SPME/GC-MS). This optimization was achieved with a 24 factorial design approach, where the final conditions for this extraction procedure were 10 μg L-1, 1 h, 92 °C (at headspace), and 0.62 mol L-1 for PAHs concentration, fiber exposition to headspace, temperature, and NaCl concentration, respectively. The limit of detection (LOD) in this protocol ranged from 0.2 to 41.4 ng L-1, while recovery values from 67.65 to 113.10%. Besides that, relative standard deviation (RSD) were lower than 8.39% considering high molecular weight compounds. Moreover, the proposed methodology in this work does not require any previous treatment of the sample and allows to quantify a higher number of PAHs. Notably, naphthalene was the major PAHs compound quantified in all samples of the produced water at 99.99 μg L-1. Altogether, these results supported this methodology as a suitable analytical strategy for fast determination of PAHs in produced water from oil-based industry.

Tütsülenmiş Balıklarda Gıda Toksikantı Olarak Polisiklik Aromatik Hidrokarbonlar

Fish plays important role in human nutrition and health due to its nutritional value. On the other hand, fresh fish is perishable material because of its high moisture content. Therefore, various methods are used to maintain and extend the shelf life of fish. Smoking is one of the most common food preservation methods in fish processing. However, wood smoke used in the smoking process contains hazardous chemical compounds like polycyclic aromatic hydrocarbons. Polycyclic aromatic hydrocarbons (PAHs) are organic compounds consisting of two or more fused aromatic rings. Epidemiological studies have shown that a number of PAHs are mutagenic and/or carcinogenic. Therefore, it is needed more information about PAHs found and/or formed in smoked fishes. In the present review, the structure and toxicity of PAHs, the factors that affect PAH concentration and the studies conducted in this context, and legal limits about PAHs in smoked fishes were reviewed.

High-pressure elastic properties of polycyclic aromatic hydrocarbons obtained by first-principles calculations

Crystal structure and compressibility parameters of benzene and a number of polycyclic aromatic hydrocarbons (PAHs) were calculated by first-principles methods of the density functional theory with a gradient approximation of the exchange-correlation potential in the form of PBE, taking into account the van der Waals interactions optPBE-vdW in a pressure interval of 0–20 GPa. A comparison with the experimental data for benzene, naphthalene, tetracene, and pentacene shows a high accuracy of the calculations. All studied materials have a close compressibility with the bulk modulus from 8 to 12 GPa and its pressure derivative 6.9–7.5, which consistent with a decrease in the intermolecular distances and a weak deformation of the molecules and benzene rings themselves. There is a weak dependence of the compressibility on the number of atoms (benzene rings) in the molecule or on the type of crystal structure (most PAHs have a space group P 21/a). Compounds with a large number of benzene rings, as well as a denser ring structure – cyclic (pyrene, coronene) have lower compressibility with respect to less dense PAHs (tetracene, hexacene). Some PAHs, benzene, phenanthrene, pyrene and coronene, have high-pressure modifications, but a correct description of their structures, which allows to obtain elastic modules, has not yet been made. The obtained data on PAH compressibility can be used in the development of high-temperature equations of state and calculation of the equilibrium composition of the liquid and solid components of the C-O-H system.

Modelling soot formation in a benchmark ethylene stagnation flame with a new detailed population balance model

Numerical simulation of soot formation in a laminar premixed burner-stabilised benchmark ethylene stagnation flame was performed with a new detailed population balance model employing a two-step simulation methodology. In this model, soot particles are represented as aggregates composed of overlapping primary particles, where each primary particle is composed of a number of polycyclic aromatic hydrocarbons (PAHs). Coordinates of primary particles are tracked, which enables simulation of particle morphology and provides more quantities that are directly comparable to experimental observations. Parametric sensitivity study on the computed particle size distributions (PSDs) shows that the rate of production of pyrene and the collision efficiency have the most significant effect on the computed PSDs. Sensitivity of aggregate morphology to the sintering rate is studied by analysing the simulated primary particle size distributions (PPSDs) and transmission electron microscopy (TEM) images. The capability of the new model to predict PSDs in a premixed stagnation flame is investigated. Excellent agreement between the computed and measured PSDs is obtained for large burner-stagnation plate separation ( ≥ 0.7 cm) and for particles with mobility diameter larger than 6 nm, demonstrating the ability of this new model to describe the coagulation process of aggregate particles.

Analysis of emission profiles from charcoal produced from selected tree species by different pyrolysis methods

The use of charcoal is associated with indoor air pollution where users are continually exposed to combustion pollutants with detrimental effects to their health. This study analyzed the emission profiles of selected domestically used charcoal produced by different pyrolysis methods. Charcoal samples from three tree species Acacia polyacantha, Acacia xanthophloea and Eucalyptus grandis, produced by both efficient and traditional pyrolysis were collected from charcoal producers in rural Kenya. The volatile organic compounds were collected using a fabricated chimney placed on clay cook stove such that smoke was vented to a glass cannula and condensed. Extracted volatiles were analyzed by gas chromatography-linked mass spectrometry. Twenty-two polycyclic aromatic hydrocarbons were identified together with other hydrocarbons. Polycyclic aromatic hydrocarbons found in the smoke extracts with known health effects included naphthalene, 1-methylnaphthalene, 2-methylnaphthalene, fluorene, phenanthrene, anthracene, 1-methylphenanthrene, fluoranthene, benzo(a)anthracene and chrysene. There were significant differences in the concentrations of fluorine, naphthalene and pyrene emitted from Acacia polyacantha and Acacia xanthophloea prepared by traditional pyrolysis. From Acacia polyacantha, concentrations were naphthalene (110 µg/g), fluorine (72 µg/g) and pyrene (60 µg/g), while from Acacia xanthophloea, concentrations were naphthalene (140.42 µg/g), fluorene (97.35 µg/g) and pyrene (71.82 µg/g). Charcoal prepared by traditional pyrolysis emitted the highest number of polycyclic aromatic hydrocarbons and also had higher concentration of polycyclic aromatic hydrocarbons relative to the accepted 0.1–0.2 mg/m3 levels, while those prepared by efficient pyrolysis produced the lowest concentration. Therefore, there is need to use efficient pyrolysis methods of charcoal production.

“Risk is in the air”: Polycyclic aromatic hydrocarbons, metals and mutagenicity of atmospheric particulate matter in a town of Northern Italy (Respira study)

Air pollution has well-known harmful effects on human beings, causing both acute and chronic diseases. Some data suggest that genetic damage occurring early in life may influence the risk of having cancer and other chronic diseases in adulthood. Therefore, there is a growing interest in studying the genotoxic activity of air pollution, and especially particulate matter. The aim of this study was to analyze airborne particulate matter (PM10) collected in an industrialized town of Northern Italy. PM10 was sampled in six areas of the town, divided in three distinct dimensional classes (<0.5 μm; 0.5–3 μm and 3–10 μm), and analyzed for the quantification of polynuclear aromatic hydrocarbons and metals contents. A model-based approach using diagnostic ratios and toxic equivalency factor was also followed. Concurrently, biological assays were performed for the assessment of mutagenicity and genotoxicity in bacteria, human and plant cells. Mutagenicity was observed in bacteria and human cells, with a clear dose-response relationship, induced above all by the finest PM samples (PM0.5 and PM0.5-3), which contained the largest number of polycyclic aromatic hydrocarbons. DNA damage, such as chromosomal aberrations and micronuclei, was also found in Allium cepa root cells, but without a clear relationship with the tested doses. The in-vitro models utilized showed to be good indicators of air quality for mutagenicity. Chemical analyses evidenced high content of polycyclic aromatic hydrocarbons, metals and semi-metals in PM extracts. Polycyclic aromatic hydrocarbons, metals and mutagenicity can be ascribed mainly to vehicular traffic (in terms of both exhausted gases emission and mechanical losses), which represents a constant and ubiquitous source of human exposure, and to steel working, carried out within the urban area.

Terahertz Spectral Properties of Coal Tar

Coal tar is a complex mixture of a large number of polycyclic aromatic hydrocarbons (PAHs) and heterocyclic compounds. The terahertz (THz) spectral properties of coal tar are studied by terahertz time-domain spectroscopy (THz-TDS). The absorption coefficient, refractive index, and relative permittivity of coal tar in the range of 0.2–2.5 THz are determined. Compared with pure cyclic hydrocarbons such as benzene, quinolone, and carbazole that are able to be extracted from coal tar, it is surprising to find that coal tar has a higher transmittance to THz waves than its pure components.

Accumulation of Polycyclic Aromatic Hydrocarbons in Soils and Mosses of Southern Tundra at Different Distances from the Thermal Power Plant

A number of polycyclic aromatic hydrocarbon (PAH) structures have been identified in organic horizons of surface-gley tundra soils (Stagnic Cambisols) and the moss Pleurozium schreberi. The total content of polyarenes in soils and P. schreberi exceeds the background values in 3.5–5 times. A tendency of increasing content of polyarenes with the distance from the source to 1 km has been revealed. High coefficients of variation have been found between the contents of PAHs in snow cover, organic soil horizons, and mosses. Light hydrocarbons dominate in the composition of PAHs from the snow and ground covers and mosses. Naphthalene dominates on the surface of mosses in all of the studied plots, which is largely related to its intensive uptake by mosses under pollution conditions. It has been found that when the input of polyarenes onto the surface of tundra phytocenoses increases, the bioaccumulation of PAHs by P. schreberi is intensified, and PAHs begin to penetrate into moss. The increase in the concentration of high-molecularweight polyarenes in the environment plays the key role in the activation of PAH bioaccumulation by moss. It has been shown that P. schreberi can be used as an indicator species for monitoring the contamination of tundra phytocenoses by polyarenes. Both living and dead parts of P. schreberi are suitable for the environmental monitoring of PAH contamination.

Antibody Development and Immunoassays for Polycyclic Aromatic Hydrocarbons (PAHs)

Polycyclic aromatic hydrocarbons (PAHs) are a class of ubiquitous contaminants produced by natural or anthropogenic processes and found in various environment and food samples. A number of PAHs are carcinogenic and listed as priority pollutants in a variety of regulations. For a long time, much public attention has been drawn on PAHs due to the sensitive issue of environmental risks and food safety. In recent years, immunoassay methods have been applied in environmental and food analysis of PAHs and employed as highly sensitive, selective and cost-effective alternative to complement traditional chromatographic analysis. In this article, the rapid progress in the immunoassays for analysis of PAHs in food and environmental samples, such as selecting haptens, producing antibodies and developing immunoanalytical methods, has been reviewed. Since there was a comprehensive review published in 2002, this article is mainly focusing on the achievements since 2002 in this field. Some significant works before 2002 are also included. Although there have been quite a few antibodies and immunoassays for PAHs available, more novel antibodies and immunoanalytical methods are still welcome. Moreover, class-selective determinations and quantitative structure-activity relationship (QSAR) techniques are likely to play an important role in PAHs immunoassays in the future. Keywords: Immunoassay, ELISA, PAHs, benzo[a]pyrene, hapten, antibody.

Biodegradation potentials of polyaromatic hydrocarbon (pyrene and phenanthrene) by Proteus mirabilis isolated from an animal charcoal polluted site

Indiscriminate disposal of animal charcoal from skin and hides cottage industries often impact the environments with toxic hydrocarbon components and thus require eco-friendly remedial strategies. A bacterial strain isolated from a site polluted with animal charcoal was characterized, identified as Proteus mirabilis 10c, and studied for ability to degrade pyrene and phenanthrene. The bacterium resisted 30 µg chloramphenicol, 10 µg ampicillin, 30 µg amoxicillin and 10 µg perfloxacin; while it utilized a number of polycyclic aromatic hydrocarbons and cinnamic acid. Specific growth rate on pyrene and phenanthrene were 0.281 d−1 and 0.276 d−1, respectively. Kinetics of degradation of pyrene was 87.92 mg l−1 in 30 days at the rate of 2.93 mg l−1 d−1, biodegradation constant at 0.073 d−1 and half-life of 9.50 d. The corresponding values for phenanthrene degradation kinetics by the bacterium were 90.12 mg l−1, 3.02 mg l−1 d−1, 0.079 d−1 and 8.77 d, respectively. Efficient degradation of crude oil (92.3%) in chemically defined medium was evident with near-disappearance of most aromatic spectra in 30 days. Considering its unique physiologies and broad specificities for aromatic and aliphatic hydrocarbons, the bacterium has potentials for decommissioning environments contaminated with toxic components of animal charcoal.

Impacts of Extraction Methods and Solvent Systems in the Assessment of Toxic Organic Compounds in a Solid Matrix

Polycyclic Aromatic Hydrocarbons (PAHs) are among the listed persistent organic compounds (POP) which are pollutants of environmental concern due to their toxicity. This study evaluated soxhlet and ultrasonic extraction methods using a three-solvent system (acetone+dichloromethane+n-hexane) in order to compare the ability of the techniques to extract selected PAHs in raw coals collected from a coal mine in Okobo-Enjema, Nigeria. Then, binary solvent mixtures consisting of acetone+dichloromethane; dichloromethane+n-hexane; and acetone+n-hexane, were compared with the ternary solvent system for their ability to extract the target PAHs by soxhlet extraction method. The extracts were quantitatively analysed for sixteen PAHs using Gas Chromatography-Mass Spectrometer (GC-MS). Sonication extraction method extracted higher number of PAHs, required fewer amount of solvents, shorter time of extraction and less energy consumption compared to soxhlet extraction, which extracted higher amount of the target PAHs. The total amount of PAHs determined ranged from 0.02 mg/kg to 0.20 mg/kg in the various solvents' mixtures. The ternary mixture extracted larger quantities of the target toxic PAHs. This report will assist in the choice of analytical methods and solvent systems for environmental studies.