Rapid magnetic solid-phase extraction based on magnetic multiwalled carbon nanotubes for the determination of polycyclic aromatic hydrocarbons in edible oils

In this study, magnetic multiwalled carbon nanotubes were fabricated by a simple method and applied to magnetic solid-phase extraction (MSPE) of eight heavy molecular weight polycyclic aromatic hydrocarbons (PAHs) including chrysene, benzo[a]anthracene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene, dibenzo[a,h]anthracene and benzo[g,h,i]perylene from edible oil samples. Several parameters affecting the extraction efficiency were investigated, including the type and volume of desorption solvent, extraction and desorption time, washing solution and the amount of sorbent. Under the optimized conditions, a simple and effective method for the determination of PAHs in edible oils was developed by coupling with gas chromatography-mass spectrometry (GC-MS). The whole pretreatment process was rapid, and it can be accomplished within 10 min. The limits of quantitation for the target PAHs were found to be 0.34-2.9 ng/g. The recoveries in oil sample were in the range 87.8-122.3% with the RSDs less than 6.8% (intraday) and 9.6% (interday). This method was successfully applied to the analysis of PAHs in seven kinds of edible oils from local markets.     

Modeling the formation of some polycyclic aromatic hydrocarbons during the roasting of Arabica coffee samples

Roasting is a critical process in coffee production, as it enables the development of flavor and aroma. At the same time, roasting may lead to the formation of nondesirable compounds, such as polycyclic aromatic hydrocarbons (PAHs). In this study, Arabica green coffee beans from Cuba were roasted under controlled conditions to monitor PAH formation during the roasting process. Roasting was performed in a pilot-spouted bed roaster, with the inlet air temperature varying from 180 to 260 degrees C, for roasting conditions ranging from 5 to 20 min. Several PAHs were determined in both roasted coffee samples and green coffee samples. Different models were tested, with more or less assumptions on the chemical phenomena, with a view to predict the system global behavior. Two kinds of models were used and compared: kinetic models (based on Arrhenius law) and statistical models (neural networks). The numbers of parameters to adjust differed for the tested models, varying from three to nine for the kinetic models and from five to 13 for the neural networks. Interesting results are presented, with satisfactory correlations between experimental and predicted concentrations for some PAHs, such as pyrene, benz[a]anthracene, chrysene, and anthracene.     

Distribution of polycyclic aromatic hydrocarbons in the soil-plant system

The content and composition of the polycyclic aromatic hydrocarbons (PAHs) in the conjugated systems of [arable soil]-[above-ground plant organs] in background (reference) and contaminated regions were studied. The coefficients of the biological uptake of PAHs by plants (K _bPAH) were determined for different PAH concentrations in the soil. Correlations of the PAH accumulation rate in plants with the physicochemical properties of the PAHs—the solubility, hydrophobicity, volatility, and chemical activity (polarizability and ionization potential)—were revealed. The high accuracy, sensitivity, and information value of the standardized parameters K _b were shown (with K _bPAH as an example) for the quantitative study of the accumulation mechanisms of substances by plants compared to the average arithmetic values of their concentrations in the plants.     

Availability of polycyclic aromatic hydrocarbons in aging soils

Purpose  

The soil contamination by hydrophobic organic contaminants (HOCs), such as polycyclic aromatic hydrocarbons (PAHs), poses great threats to human health and ecological security and attracts worldwide concerns. The total HOC concentrations overestimate its available fraction to the soil biota. Increased understanding of the availabilities of PAHs in soil environment will have considerable benefits for their risk assessment and be very instructive to food safety and remediation strategies in contaminated sites. However, the availability of PAHs in aging soils and particularly the correlations of the availabilities with their forms in soils have yet to be elucidated. In this work, the availabilities of PAHs in aging soils were evaluated using a sequential mild extraction technique.     

Polycyclic aromatic hydrocarbons in spanish olive oils: relationship between benzo(a)pyrene and total polycyclic aromatic hydrocarbon content

Samples of Spanish virgin olive oils (VOOs) from different categories, origins, varieties, and commercial brands were analyzed by HPLC with a programmable fluorescence detector to determine the content of nine heavy polycyclic aromatic hydrocarbons (PAHs): benzo(a)anthracene, chrysene, benzo(e)pyrene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, dibenzo(a,h)anthracene, benzo(g,h,i)perilene, and indeno(1,2,3-c,d)pyrene. Samples of olive pomace and crude olive pomace oils were also investigated. Benzo(a)pyrene concentrations were below the allowed limit in the European Union (2 microg/kg) in 97% of the VOO samples. Only those samples coming from contaminated olive fruits or obtained in oil mills with highly polluted environments exceeded this value. High correlation coefficients (<0.99) were obtained between the contents of benzo(a)pyrene and the sum of the nine PAHs for all of the analyzed categories, suggesting that benzo(a)pyrene could be used as a marker of the content of these nine PAHs in olive oils.     

Determination of monocyclic and polycyclic aromatic hydrocarbons in fish tissue

An analytical method is presented in which fish tissue is analyzed for neutral monocyclic and polycyclic aromatic hydrocarbons (AHs) and aromatic sulfur heterocycles (ASHs) by capillary column gas chromatography (CGC) with photoionization detection. The sample enrichment procedure includes saponification with aqueous KOH, acidification of the digestates, and extraction of the aromatic compounds into cyclopentane-dichloromethane. Adsorption chromatography on tandem segments of potassium silicate and silica gel removes 99% of the coextracted lipid. Final enrichment by gel permeation chromatography eliminates residual biogenic material and potentially interfering alkanes. Relatively volatile monoaromatics are included among the analytes by virtue of the efficiency of the complementary enrichment steps, the use of small quantities of only low-boiling solvents, and the selectivity of the detector. Most targeted compounds (AHs ranging in size from C3-alkylbenzenes through benzo[g,h,l]perylene and ASHs within the same size range) can be determined in 5 g (wet weight) samples of fish tissue at concentrations as low as 20 ng/g. Comparisons are made of recoveries of selected AHs under ordinary and gold fluorescent lighting conditions.     

Bioaccumulation of polycyclic aromatic hydrocarbons in the soil-plant systems of the northern-taiga biocenoses

Regularities in the formation of the pool of priority polycyclic aromatic hydrocarbons (PAHs) in the soil-plant systems of the northern taiga forest biocenoses were revealed. In soils and plants, PAHs mainly consisted of 3- and 4-nuclear structures. The content of polyarenes in plants on technogenically contaminated areas exceeded the background values by 2–5 times. The maximum bioconsumption of polyarenes was observed for bilberry leaves and Siberian spruce sprouts 4–5 years old. The highest mass fraction of PAHs was found in Siberian spruce plants of a mixed spruce-birch forest of the northern taiga. It was revealed that bilberry plants are hyperaccumulators of light PAHs.     

Selenium enhances Conyza canadensis phytoremediation of polycyclic aromatic hydrocarbons in soil

Journal of Soils and Sediments - To determine whether supplemental selenium (Se) enhances the tolerance of Conyza canadensis (C. canadensis) to polycyclic aromatic hydrocarbons (PAHs) and thereby...     

Liquid chromatographic determination of polycyclic aromatic hydrocarbons in fish and shellfish

A simple and accurate analytical method for determination of polycyclic aromatic hydrocarbons (PAHs) in fish and shellfish is presented, which is considered to be useful for routine analyses and for screening purposes. The procedure involves alkaline digestion, extraction with n-hexane, silica gel column chromatography, and liquid chromatographic (LC) determination with fluorometric detection. During development of the analytical method for determination of PAHs, it was found that benzo[a]pyrene, a representative PAH, was decomposed easily by the analytical procedure, and this tendency was investigated for the experimental conditions used. Benzo[a]pyrene was decomposed by the coexistence of alkaline conditions, light, and oxygen; by peroxides in aged ethyl ether; and by oxygen when absorbed on silica gel. Thus, to obtain good recoveries and precise analytical results, these decomposition conditions must be avoided. The following precautions are recommended: protection from light through all analytical steps; addition of Na2S to alkaline digestion mixture as an antioxidant; complete removal of peroxides from ethyl ether just before use; quick column chromatography on silica gel; and prevention of air from contact with adsorbent. When this simple method was applied to fish and shellfish samples, very good recoveries of PAHs from fortified fish samples were obtained, and no serious interferences were observed in fish and shellfish extracts.     

Determination of 10 carcinogenic polycyclic aromatic hydrocarbons in mainstream cigarette smoke

Polycyclic aromatic hydrocarbons (PAHs) are one class of chemical compounds that (1) are present at low to trace levels in unburned cigarette filler, and (2) are predominantly generated during combustion. According to a recent report of the International Agency for Research on Cancer, 10 carcinogenic PAHs together with 53 other known carcinogens are present in cigarette smoke. Accurate quantification of these chemicals helps assess public health risk to both smokers and nonsmokers exposed to second-hand smoke. We have developed and validated a specific and sensitive method for measuring these 10 carcinogenic PAHs in the particulate phase of mainstream tobacco smoke. Cigarette smoke particulate, produced using standard machine smoking protocols, was collected on glass fiber Cambridge filter pads. The particulate matter was solvent extracted, purified by solid-phase extraction, and analyzed by liquid chromatography/atmospheric pressure photoionization tandem mass spectrometry using isotopically labeled analogues as internal standards. Our method's limits of detection ranged from 11 to 166 pg and achieved sufficient reproducibility and accuracy to provide useful information on a range of cigarettes having dramatically different machine-smoked tar and nicotine deliveries. The identity of each PAH analyte was established from chromatographic retention time, analyte-specific fragmentation patterns, and relative peak area ratios of the product/precursor ion pairs. This new method provides higher sensitivity, specificity, and throughput than did earlier methods. We found relatively consistent PAH levels among a selection of domestic full-flavor cigarettes. The PAH levels in smoke from highly ventilated light and ultralight cigarettes were low when smoked using ISO (International Organization for Standardization) conditions. However, if highly ventilated cigarettes were smoked under more intense conditions (e.g., larger or more frequent puffs, vents blocked), their PAH levels equaled or exceeded their full-flavor counterparts under ISO conditions.     

Determination of polycyclic aromatic hydrocarbons in coffee brew using solid-phase extraction

The presence of polycyclic aromatic hydrocarbons (PAHs) in coffee has been reported and is suspected to be due to the degradation of coffee compounds during the roasting step. Due to the high toxicity of these compounds, among which benzo[a]pyrene is known to be the most carcinogenic, their presence in the coffee, especially the coffee brew that is directly ingested by the consumer, is of prime importance. However, due to the low solubility of these compounds, their concentrations are expected to be rather low. As a consequence, reliable and sensitive analytical methods are required. The aim of this study was to develop a reliable and fast analytical procedure to determine these organic micropollutants in coffee brew samples. PAHs were retained on a 0.5 g polystyrene-divinylbenzene cartridge before being eluted by a mixture of methanol/tetrahydrofuran (10:90 v/v), concentrated, and directly analyzed by reversed-phase high-performance liquid chromatography coupled to a fluorescence detector. Application to the determination of PAHs in several coffee brew samples is also given, with mean estimated concentrations in the range of 0-100 ng L(-1) for suspected benzo[b]fluoranthene and benzo[a]pyrene, whereas no fluoranthene could be detected. Tentative identification was made on the basis of UV spectra. However, identification of the suspected traces of PAHs could not be achieved due to matrix effects, so that the presence of coeluting compounds may not be excluded.     

Formation of polycyclic aromatic hydrocarbons in northern and middle taiga soils

An integrated study of the qualitative and quantitative composition of polycyclic aromatic hydrocarbons (PAHs) in the atmospheric precipitation-soil-lysimetric water system was performed using high performance liquid chromatography. It was shown that the accumulation of low-molecular PAHs (phenanthrene, anthracene, fluoranthene, pyrene, benz[a]anthracene, and chrysene) in soils is due to the transformation of organic matter and the regional transport and deposition of PAHs with atmospheric precipitation on the underlying surface. High-molecular polyarenes (benz[b]fluoranthene, benz[k]fluoranthene, benz[a]pyrene, dibenz[a,h]anthracene, benzo[ghi]perylene, and indeno[1,2,3-cd]pyrene) mainly result from the decomposition of soil organic matter.     

Determination of polycyclic aromatic hydrocarbons in fumes from fried chicken legs

The amount and variety of polycyclic aromatic hydrocarbons (PAHs) in fumes during frying of chicken legs in edible oils were determined using a modified smoke collection device and a GC-MS technique. Chicken legs were fried in soybean oil, canola oil, or sunflower oil at 163 degrees C for 1-4 h. Results showed that most smoke (99%) was collected in the condensation apparatus, whereas the rest (1%) was adsorbed onto adsorption wool. A large proportion of PAHs in the smoke were detected in adsorption wool, whereas a small portion was found in the condensation apparatus. Canola oil generated the largest content (500.9 g for a frying time of 4 h) of smoke, followed by soybean oil, and sunflower oil. A similar trend was observed for PAH formation in fumes, with the exception that soybean oil produced a higher level than canola oil.     

Contamination of soils in the urbanized areas of Belarus with polycyclic aromatic hydrocarbons

The content of polycyclic aromatic hydrocarbons (PAHs) in the soils of urbanized areas, including the impact zones of Belarus, were studied. The concentrations of 16 PAHs in the soils were determined for individual and high-rise building zones, forests, and forest parks of Belarus. The levels of the PAH accumulation in the soils of different industrial enterprises and boiler stations were analyzed. Possible sources of soil contamination with PAHs were considered, and the structure of the PAHs in the soils was shown. The levels of the soil contamination were determined from the regulated parameters for individual compounds and the sum of 16 PAHs.     

多环芳烃在土壤中的环境行为研究进展

综述了土壤环境中多环芳烃(PAHs)来源及其进入环境后的行为和归宿,并提出多环芳烃污染土壤的修复对策。     

Potential role of polycyclic aromatic hydrocarbons (PAHs) oxidation by fungal laccase in the remediation of an aged contaminated soil

The transformation of PAHs by fungal laccases has been reported but there are no published studies on the direct application of free laccase in the remediation of PAHs-contaminated soil. Here we report a study in which the transformation of PAHs by a fungal laccase was studied both in reaction mixtures and in soil. Anthracene and benzo(a)pyrene were the most degradable of the 15 US Environmental Protection Agency (EPA) priority PAHs tested. Use of a redox mediator greatly enhanced the oxidation of several PAHs in reaction mixtures and the main intermediates were identified as anthraquinone for anthracene and benzo(a)pyrenyl acetate for benzo(a)pyrene as determined by GC–MS analysis. No significant correlation was found between oxidation and ionization potentials of individual PAHs. Soil microcosms were set up to test the potential of laccase to remediate an aged PAHs-contaminated soil. The laccase transformed the PAHs immediately after it was added to the soil and significant dissimilation of benzo(a)pyrene and toxic-equivalent concentration based on benzo(a)pyrene was observed after incubation for 14 days, indicating the potential of laccase to detoxify the soil. Moreover, extractable laccase activity was completely lost and the biomass of the indigenous microorganisms remained constant in the microcosms at the end of the incubation period, suggesting that the enzyme may have potential as an agent for the efficient and safe cleanup of soil contaminated with PAHs.     

Annual rates of deposition of polycyclic aromatic hydrocarbons in different forest ecosystems

Using the flux balance of the forest canopy of a beech and a spruce stand annual rates of total deposition — divided into precipitation and interception deposition — were derived for 4 polycyclic aromatic hydrocarbons (PAH). The deposition of PAH is in general higher under spruce because of higher rates of interception deposition as compared to beech. The rate of interception deposition of the various PAH compounds (3.4-Benzopyrene, Indeno (1,2,3-cd)pyrene,1.12 Benzoperylene, Fluoranthene) are significantly different. Substantial amounts of PAH are transferred to the soil by litterfall, which indicates adsorption of PAH on leaf and needle surfaces. The storage of PAH in the soil is equivalent to 34 to 48 yr of the actual deposition for 3.4 Benzopyrene and Indeno (1,2,3-cd)pyrene and is equivalent to 14 to 26yr of actual deposition for the amount of 1.12 Benzoperylene and Fluoranthene in the soil.