Simultaneous determination of PAHS, nitro-PAHS and quinones in surface and groundwater samples using SDME/GC-MS

Chemodynamics of Polycyclic Aromatic Hydrocarbons and Their Alkylated and Nitrated Derivatives in the Yellow Sea and East China Sea

The occurrence of continuously released polycyclic aromatic hydrocarbons (PAHs) in marginal seas is regulated by hydrological and biogeochemical processes; however, scarce knowledge is about their derivatives in marine environments. In this study, the dissolved and particulate PAHs and their alkylated/nitrated derivatives (A-PAHs/N-PAHs) in surface seawater of the southwestern Yellow Sea (YS) and northwestern East China Sea (ECS) during September 2022 were comprehensively discussed. Results confirm higher levels of Σ26PAHs (9.3-70 ng/L) and Σ43A-PAHs (13-76 ng/L) than Σ20N-PAHs (0.80-6.6 ng/L). The spatial heterogeneity of contaminants was regulated by substantial riverine runoff and ocean currents. Lagrangian Coherent Structure analysis further revealed the existence of a transport barrier at the shelf break of the southwestern YS where contaminants hardly crossed and tended to accumulate. The relationship between dissolved compounds and chlorophyll a indicated both biodegradation and the biological pump contributed to the depletion of PAHs and A-PAHs from surface seawater while the biological pump was the major driver for N-PAHs, despite their complicated water-particle partition behavior due to variations in physicochemical properties in the presence of nitro groups. Source identification demonstrated that pyrogenic and petrogenic sources dominated the YS and ECS, respectively, while photochemical transformations appeared more active in the YS.

Fluoranthene determination based on a rapid and sensitive syringe extraction and solid-phase fluorescence technique

A rapid and sensitive strategy was proposed for the detection of fluoranthene (FL), which is a polycyclic aromatic hydrocarbon (PAH), in water samples. In this work, syringe solid-phase extraction (SPE) combined with solid-phase fluorescence spectrometry was used to determine FL in PAHs polluted environmental samples. The fluorescence signals were directly monitored on the membrane surface after FL was enriched by syringe SPE. Under the optimal conditions, the proposed method showed a linear relationship in the concentration range 2-50 μg/L with a correlation coefficient (R2 ) of 0.998, and the limit of detection was 0.143 μg/L. The recoveries varied from 93.47% to 109.81% in the actual samples, with the relative standard deviations (n = 3) ranging from 2.06% to 6.32%. According to the results, the established method can be applied in the field of rapid detection as it is fast, simple, portable, and highly sensitive, and has strong anti-interference.

Multivariate optimization of a green procedure for determination of emerging polycyclic aromatic nitrogen heterocycles in PM2.5 from sites with different characteristics

Emerging polycyclic aromatic nitrogen heterocycles (PANHs) contributes significantly to the health risk associated with inhaling polluted air. However, there is a lack of analytical methods with the needed performance to their determination. This study presents the optimization and validation for the first time of a green microscale extraction procedure for the determination of twenty-one PANHs, including carbazole, indole, and quinolone classes, in particulate matter (PM2.5) samples by gas chromatography-mass spectrometry. A simplex-centroid mixture design and full factorial design (23) were employed to optimize the following extraction parameters: type and volume of solvent, sample size, extraction time, and necessity of a cleanup step. Low limits of detection and quantification (LOD < 0.97 pg m-3 and LOQ < 3.24 pg m-3, respectively) were obtained in terms of matrix-matched calibration. The accuracy and precision of the method were adequate, with recoveries in three levels between 73 to 120% and intraday and interday relative standard deviations from 2.0 to 12.9% and 7.3 to 18.9%, respectively. The green character of the method was evaluated using the Analytical Greenness (AGREE) tool, where a score of 0.69 was obtained, indicating a great green procedure. The method was applied to PM2.5 samples collected from sites with different characteristics; the concentrations ranged from 69.3 pg m-3 (2-methylcarbazole) to 11,874 pg m-3 (carbazole) for individual PANHs and from 2306 to 24,530 pg m-3 for ∑21PANHs. Principal component analysis (PCA) and hierarchical clustering enabled discrimination of the sampling sites according to the PANHs concentrations. The score plots formed two distinct groups, one with samples containing higher concentrations of PANHs, corresponding to sites with a major influence from diesel emissions, and another group with minor PANH contents, corresponding to sites impacted by emissions from urban traffic and industrial activities.

Distribution, sources, and health risk of polycyclic aromatic hydrocarbons and their derivatives in the watershed: the case of Yitong River, China

Polycyclic aromatic hydrocarbons (PAHs) and substituted PAHs (SPAHs) are persistent organic pollutants prevalent globally, and SPAHs have received widespread attention in recent years due to their stronger toxicity and carcinogenicity compared to PAHs. There is a lack of systematic examination of PAHs and their derivatives in watersheds. Thus, to clarify the current status, possible sources, and potential risks of PAHs and their derivatives in watersheds, a study was conducted on Yitong River in China. The results showed that the concentrations of ∑PAHs, ∑OPAHs, and ∑NPAHs ranged from 297.9-1158.3 ng/L, 281.1-587.2 ng/L, and 65.7-269.1 ng/L, respectively. Diagnostic ratio analysis showed that the PAHs were mainly derived from petroleum sources, agricultural waste, and coal combustion. Nitrated PAHs (NPAHs) were mainly derived from liquid combustion sources, and oxygenated PAHs (OPAHs) were derived mainly from petroleum source emissions and atmospheric deposition. The exposure risk model of PAHs revealed that 86% of the studied sites would pose carcinogenic risks after dermal contact. The contaminant causing a major carcinogenic risk was DahA, and none of the sites produced non-carcinogenic risks. The lifetime carcinogenic risk of NPAHs was 8.85 × 10^-10-1.44 × 10^-4, and some surface waters presented with potential carcinogenic risks.

Occurrence, partition behavior, source and ecological risk assessment of nitro-PAHs in the sediment and water of Taige Canal, China

Nitrated polycyclic aromatic hydrocarbons (NPAHs) are widespread organic pollutants that possess carcinogenic and mutagenic properties, so they may pose a risk to the environment and human health. In this study, the concentrations of 15 NPAHs and 16 polycyclic aromatic hydrocarbons (PAHs) in 30 surface water samples and 26 sediment samples were measured in 2018 from the Taige Canal, one of the main rivers flowing into Taihu Lake, China. The total NPAH concentrations in water and sediment ranged from 14.7 to 235 ng/L and 22.9 to 96.5 ng/g dw, respectively. 9-nitrophenanthrene (nd-76.3 ng/L) was the dominant compound in surface water, while 2+3-nitrofluoranthene (1.73-18.1 ng/g dw) dominated in sediment. Among PAHs, concentration ranging from 1,097 to 2,981 ng/L and 1,089 to 4,489 ng/g dw in surface water and sediment, respectively. There was a strong positive correlation between the log octanol-water partition coefficient (K_ow) and log sediment-water partition coefficient due to hydrophobic interaction. The fugacity fraction value increased with the decrease of log K_ow, and chrysene was transferred from water into sediment. The residual NPAHs in surface water and sediment of the Taige Canal have partial correlation. Diesel engine and coal combustion emissions were probably the principal sources of NPAHs in surface water and sediment. The results of ecological risk assessment showed that some NPAHs in water (e.g, 1-nitropyrene and 6-nitrochrysene) and sediment (e.g., 2-nitrobiphenyl, 5-nitroacenaphthene, 9-nitrophenanthrene and 2+3-nitrofluoranthene) had moderate ecological risks, which should be of concern.

Facile synthesis of hollow microtubular COF as enrichment probe for quantitative detection of ultratrace quinones in mice plasma with APGC-MS/MS

A hollow microtubular covalent organic framework (denoted as TatDha-COF) was synthesized by solvothermal method for the enrichment and determination of quinones. The TatDha-COF showed large specific surface area (2057 m² g^-1), good crystal structure, ordered pore size distribution (2.3 nm), stable chemical properties and good reusability. Accordingly, a simple and efficient method based on dispersive solid-phase extraction (d-SPE) and atmospheric pressure gas chromatography tandem mass spectrometry (APGC-MS/MS) was developed for the determination of quinones in complex samples. The established method demonstrated a wide liner range, good linearity (r>0.9990), high enrichment factors (EFs, 24-69-folds) and low detection limits (LODs, 0.200-30.0 pg L^-1, S/N≥3). On this basis, the suggested method was successfully applied to sensitively detect the eight ultratrace quinones in mice plasma. Overall, the established method has provided a powerful tool for the enrichment and detection of ultratrace quinones in complex samples, presenting the promising application of TatDha-COF in sample pretreatment.

Adsorption of p-benzoquinone at low concentrations from aqueous media using biosolid-based activated carbon

The toxic oxidation intermediate p-benzoquinone exists in aqueous environments at dilute concentrations above the fish-toxicity limit of 0.045 mg/L, affecting aquatic life. The reduction of this compound to the concentrations required to achieve safe discharge limits is challenging. In this study, the adsorptive removal of p-benzoquinone by a biosolid-based activated carbon (SBAC) was systematically investigated in batch experiments. The adsorption rate was rapid, and the bulk of p-benzoquinone adsorption occurred within 30 min. The maximum adsorption capacity of SBAC was estimated at 19.6 mg/g using the Langmuir isotherm model. Its adsorptivity was independent of temperature from 6 to 40 °C. The presence of 6 g/L of chloride and 500 mg/L of sulphate did not affect the removal of 1 mg/L p-benzoquinone, whereas 15 mg/L of humic acid media slightly decreased the p-benzoquinone removal from 87.0% to 83.2%. Diffusion, hydrophilic, and electrostatic interactions (i.e., dipole-dipole) govern the adsorption of p-benzoquinone and are influenced by the SBAC surface chemistry. Biosolid-based activated carbon can lower the residual p-benzoquinone to below the fish-toxicity limit of 0.045 mg/L within 1 h of sequential adsorption. Thus, biosolid-based activated carbon can effectively remove p-benzoquinone from aqueous environments; this is a waste-to-resource approach that addresses sustainability (waste disposal) and environmental protection (pollutant removal).

Development and validation of dispersive liquid-liquid microextraction method for the determination of 15 polycyclic aromatic hydrocarbons in 200 Antarctica samples by gas chromatography mass spectrometry

Antarctica has seen an increase in scientific research and tourism, and anthropogenic activities such as incineration of waste products and fuel combustion for energy and transportation are potential contamination sources to the ecosystem. Polycyclic aromatic hydrocarbons are common products of incomplete combustion of organic compounds and could be among accumulating contaminants in Antarctica. Thus, this study sought to develop a sensitive dispersive liquid-liquid microextraction method for the determination of 15 polycyclic aromatic hydrocarbons by gas chromatography mass spectrometry. Parameters that were relevant to the extraction method were carefully optimized and validated using aqueous standard solutions. The optimum method recorded detection limits in the range of 0.20-6.1 µg/L for the analytes. Spike recovery experiments were carried out on artificial seawater, rock-soil, and moss samples, using matrix matching calibration to mitigate effects of the sample matrices. The samples analyzed included seawater, lake, rock-soil, moss, seaweed, and feces samples all collected from the Horseshoe and Faure Islands in Antarctica. The percent recovery results obtained for the samples spiked at different concentrations ranged between 86 and 115%.

1,2-Naphthoquinone-4-sulfonic acid salts in organic synthesis

Several low molecular weight naphthoquinones are very useful in organic synthesis. These compounds have given rise to thousands of other naphthoquinones that have been tested against various microorganisms and pharmacological targets, including being used in the preparation of several drugs that are on the pharmaceutical market. Among these naphthoquinones, the series of compounds prepared from 1,2-naphthoquinone-4-sulfonic acid salts (β-NQS) stands out. In addition to being used in organic synthesis, they are excellent analytical derivatization reagents to spectrophotometrically determine drugs containing primary and secondary amino groups. This review summarizes the literature involving β-NQS.

Synthesis of hypercrosslinked polymers for efficient solid-phase microextraction of polycyclic aromatic hydrocarbons and their derivatives followed by gas chromatography-mass spectrometry determination

Three novel hypercrosslinked polymers (HCPs) were synthesized via Friedel-Crafts reaction employing 1,3,5-tris(bromomethyl)-2,4,6-trimethylbenzene as alkylating agent, and triphenylbenzene, tetraphenylethylene and p-quaterphenyl as the aromatic units, respectively. The prepared HCPs were applied as solid-phase microextraction coatings for direct immersion extraction of polycyclic aromatic hydrocarbons (PAHs) and their oxygenated and nitrated derivatives in environmental water samples. The key factors affecting the extraction efficiency including extraction time, extraction temperature, stirring rate, ionic strength and desorption conditions, were carefully studied. Coupled with gas chromatography mass spectrometry analysis, a new method for determining PAHs and their derivatives was developed. Under the optimized conditions, the limits of detection (S/N=3) and limits of quantitation (the lowest concentration for quantification) of the method were in the range of 2.5-25.0 and 7.5-75.0 ng L^-1, respectively. The recoveries of spiked samples were in the range of 73.1-118.3% with relative standard deviations less than 13.0%. The developed method was applied for the simultaneous determination of nine PAHs and their derivatives in environmental water samples, showing good accuracy and reliability.

Combined effects of polyethylene and organic contaminant on zebrafish (Danio rerio): Accumulation of 9-Nitroanthracene, biomarkers and intestinal microbiota

Microplastics, as emerging pollutant, are predicted to act as carriers for organic pollutants, but the carrier role and bio-toxic effects with other pollutants in environments are poorly acknowledged. In this study, both the single and combined effects of polyethylene (PE, 10 and 40 mg/L) with the particle size of 100-150 μm and 9-Nitroanthracene (9-NAnt, 5 and 500 μg/L) on zebrafish (Danio rerio) had been investigated. The results illustrated that PE could be as 9-NAnt carrier to enter into zebrafish body, but significantly reduced the bioaccumulation of 9-NAnt, due to the occurrence of adsorption interactions between the simultaneous presence of both PE and 9-NAnt. After 4 days, the enzymes activity of cytochrome P4501A, acetylcholinesterase (AChE), superoxide dismutase (SOD), catalase (CAT), lactate dehydrogenase (LDH), and the abundance of malondialdehyde (MDA), lipid peroxide (LPO) responded strongly to low-dose PE exposure (10 mg/L). After 7 days exposure to PE-9-NAnt (40 mg/L), the P4501A activity increased significantly, but the activities of AChE and LDH were inhibited clearly, causing certain neurotoxicity and disorders of energy metabolism to zebrafish. The analysis of integrated biomarker response index (IBR) suggested that PE had greater bio-toxicity to zebrafish in all exposure groups after short-term exposure, but the PE-9-NAnt complex showed greater bio-toxicity after 7 days, which indicated that complex exposure of PE-9-NAnt had a delayed effect on the bio-toxicity of zebrafish. Furthermore, analysis of the intestinal microbiota exhibited that under the conditions of the exposure group with 9-NAnt, the relative abundance of the five dominant bacterial phyla (Proteobacteria, Firmicutes, Fusobacteriota, Bacteroidota and Verrucomicrobiota) changed greatly. Overall, this study confirmed that PE could carry 9-NAnt into fish causing bioaccumulation, but in the case of coexisting exposures, PE reduced 9-NAnt bioaccumulation, suggesting that microplastics with other emerging pollutants in chronic toxicity are probably next objects in future works.

Nitrated and parent PAHs in the surface water of Lake Taihu, China: Occurrence, distribution, source, and human health risk assessment

Nitrated polycyclic aromatic hydrocarbons (NPAHs) have toxic potentials that are higher than those of their corresponding parent polycyclic aromatic hydrocarbons (PAHs) and thus have received increasing attention in recent years. In this study, the occurrence, distribution, source, and human health risk assessment of 15 NPAHs and 16 PAHs were investigated in the surface water from 20 sampling sites of Lake Taihu during the dry, normal, and flood seasons of 2018. The ΣPAH concentrations ranged from 255 to 7298 ng/L and the ΣNPAH concentrations ranged from not-detected (ND) to 212 ng/L. Among the target analytes, 2-nitrofluorene (2-nFlu) was the predominant NPAH, with a detection frequency ranging from 85% to 90% and a maximum concentration of 56.2 ng/L. The three-ringed and four-ringed NPAHs and PAHs comprised the majority of the detected compounds. In terms of seasonal variation, the highest levels of the ΣNPAHs and ΣPAHs were in the dry season and flood season, respectively. Diagnostic ratio analysis indicated that the prime source of NPAHs was direct combustion, whereas in the case of PAHs the contribution was predominantly from a mixed pattern including pollution from unburned petroleum and petroleum combustion. The human health risk of NPAHs and PAHs was evaluated using a lifetime carcinogenic risk assessment model. The carcinogenic risk level of the targets ranged from 2.09 × 10^-7 to 5.75 × 10^-5 and some surface water samples posed a potential health risk.

An accurate and sensitive effervescence-assisted liquid phase microextraction method for the determination of cobalt after a Schiff base complexation by slotted quartz tube-flame atomic absorption spectrophotometry in urine samples

In this study, an accurate analytical method development for cobalt determination in urine samples was described. The method is based on the mass transfer of the target analytes to the organic phase from the aqueous phase by the dispersing extractant throughout the solution with the aid of CO₂ bubbles prior to sample measurement by using a slotted quartz tube flame atomic absorption spectrophotometer. An extractor (1-decanol) dropped effervescent tablet (anhydrous sodium carbonate and sodium dihydrogen phosphate dihydrate mixture) was used in order to separate/preconcentrate cobalt after complexation of cobalt ions in aqueous solution with the Schiff base ligand. The parameters affecting the extraction output such as complexing conditions (pH, ligand concentration, and volume) and extraction conditions (extraction solvent type and volume, extraction temperature, and heating duration, NaOH volume and mixing period) were optimized to lower the detection limit. The limit of detection and quantification values under optimized experimental and instrumental conditions were determined as 3.7 μg L^-1 and 12 μg L^-1, respectively with high linearity with respect to the dynamic range between 15 and 300 μg L^-1. The enhancement factor obtained with the developed method was calculated as 83 fold. The pretreatment process was applied to urine samples in order to test the convenience of the developed method in urine samples for the determination of cobalt at low levels. The high percentage recovery results of 96-97% for four different concentrations of spiked urine samples indicated the proposed method's sufficient sensitivity for analyte determination in such a complex matrix.

Quantitation of ultra-trace nitrated polycyclic aromatic hydrocarbons isomers in water by online solid-phase extraction coupled-liquid chromatography-mass spectrometry

An online solid-phase extraction (SPE)-coupled liquid chromatography-mass spectrometry (LC-MS) method was established for the determination of 10 nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) in water. Water samples were mixed with methanol to generate 40% methanol solutions (v/v), and filtered by 0.45 μm membrane. The filtration with polytetrafluoroethylene(PTFE) membrane got higher recovery rates than nylon membrane, especially for 4-ring and 5-ring nitro-PAHs. 2.5 mL solution was directly injected into online SPE flow path to allow for online purification and enrichment of target analytes in the SPE column. The nitro-PAHs eluted from the SPE column were automatically transferred to the analytical flow path by a well-designed valve-switching system. With the optimization of LC and MS condition, ten nitro-PAH isomers was separated and detected from each other by LC-MS/MS with negative atmospheric pressure chemical ionization (APCI). It was firstly found that nitro-PAHs could produce strong [M-H]^- precursor ions in the primary MS besides [M+e]^- and [M+15]^-. In the secondary MS, the precursor ions mainly lose NO neutral molecule (30 Daltons) to produce daughter ions. The online SPE and LC-MS analysis process was completed in 15.5 min. The linear correlation coefficients of 10 nitro-PAH standard curves were higher than 0.99. The detection limits of nitro-PAHs were about 1.2~22.2 ng/L (S/N=3). The intra-day and inter-day reproducibility (RSD, n=6) were 1.6%~8.4% and 5.3%~16.9%, respectively. The recoveries of 10, 40 and 200 ng/L in tap water were 71.7%~106.4%, 79.7%~100.9% and 73.0%~105.5%, with the corresponding RSD of 2.4%~10.5%, 2.1%~8.6% and 2.7%~6.2%, respectively.

Polycyclic Aromatic Hydrocarbons: Occurrence, Electroanalysis, Challenges, and Future Outlooks

The past several decades have seen increasing concern regarding the wide distribution of polycyclic aromatic hydrocarbons (PAHs) in environmental matrices. Primary toxicological data show PAHs' persistent characteristics and possible toxicity effects. Because of this pressing global issue, electroanalytical methods have been introduced. These methods are effective for PAH determination in environmental waters, even outclassing sophisticated analytical techniques such as chromatography, conventional spectrophotometry, fluorescence, and capillary electrophoresis. Herein, the literature published on PAHs is reviewed and discussed with special regard to PAH occurrence. Moreover, the recent developments in electrochemical sensors for PAH determination and the challenges and future outlooks in this field, are also presented.

Solid-Phase Extraction Combined with Ultra-High-Performance Liquid Chromatography-Tandem Mass Spectrometry for the Determination of 5 Trace Nitro-Polycyclic Aromatic Hydrocarbons in Barbecued Foods

BACKGROUND

Nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) are the derivatives of polycyclic aromatic hydrocarbon which are direct mutagens and carcinogens to human. Nitro-PAHs can be produced in the process of food barbecuing/grilling. At present, there are few studies for the determination of nitro-PAHs in food.

OBJECTIVE

To assess the effect of barbecued food to human health, we have established a method for the determination of 5 nitro-PAHs in barbecued foods.

METHODS

The target nitro-PAHs were extracted with the mixture of methanol/acetone and then purified with an HLB SPE cartridge and finally analyzed by ultra-high-performance liquid chromatography-tandem mass spectrometry. Two pairs of target multiple reaction monitoring (MRM) ion pairs have been successfully identified for the target nitro-PAHs, and confirmed by high-resolution mass spectrometry to explore their formation mechanism.

RESULTS

The method had linear ranges of 2.0-500 µg/L (except 1-nitronaphthalene 20-5000 µg/L) with the correlation coefficients greater than 0.995. The extraction recoveries were between 70.1% and 85.6% with the relative standard deviations less than 10.0%. The limits of detection of the method were less than 0.60 µg/L (except 1-nitronaphthalene 6.0 µg/L).

CONCLUSIONS

The method has been successfully applied to the analysis of 5 nitro-PAHs in barbecued foods. 1-nitronaphthalene, 1,8-dinitropyrene , 1-nitropyrene were detected in some charcoal grilled samples with the contents of 1.35-12.9 µg/kg. 1,8-Dinitropyrene was detected in some oil-fried samples with the contents of 2.12-5.12 µg/kg.

HIGHLIGHTS

This work presents an ultra-high-performance liquid chromatography-tandem mass spectrometry method for the determination of 5 nitro-PAHs in barbecued foods for the first time. The method has been successfully applied to the analysis of 5 nitro-PAHs in various barbecued foods and the nitro-PAHs were detected in some barbecued food samples. The mechanism of mass spectrometric decomposition of nitro-PAHs was investigated as well.

Application of an agitation-assisted dispersed solvent microextraction for analysis of naphthalene and its derivatives from aqueous matrices

Agitation-assisted dispersive liquid-liquid extraction without a dispersing solvent is lately receiving considerable attention owing to the low to no solvent loss relative to its predecessor, which suffers severe extracting solvent loss. Herein, we report the application of a simple agitation-assisted dispersive liquid-liquid microextraction method, without a disperser solvent, for the extraction of naphthalene and its derivatives from aqueous solutions. Under the optimised conditions, namely, 25 μL 3:1 mixture of dichloroethane and ethylacetate with 20 s agitation, in 2-mL aqueous solutions containing 10% NaCl, the method demonstrated acceptable figures of merit: linearity-R² ≥ 0.9914 in the concentration range 0.5-50 ng/mL, repeatability (%RSD ≤ 12.9 for n = 15) and limits of detection (0.034-0.081 ng/mL). The recoveries obtained from the spiked dam water sample were also satisfactory (94-103%). These parameters are comparable with those reported in literature, especially for dispersive liquid-liquid microextraction techniques albeit for different analytes. Despite only naphthol being detected in one of the three sampled sites, the method shows considerable promise for routine monitoring of river and dam water quality subject to accuracy validation using certified reference materials.

Recent Advances in the Extraction of Polycyclic Aromatic Hydrocarbons from Environmental Samples

Polycyclic aromatic hydrocarbons (PAHs) comprise a group of chemical compounds consisting of two or more fused benzene rings. PAHs exhibit hydrophobicity and low water solubility, while some of their members are toxic substances resistant to degradation. Due to their low levels in environmental matrices, a preconcentration step is usually required for their determination. Nowadays, there is a wide variety of sample preparation techniques, including micro-extraction techniques (e.g., solid-phase microextraction and liquid phase microextraction) and miniaturized extraction techniques (e.g., dispersive solid-phase extraction, magnetic solid-phase extraction, stir bar sorptive extraction, fabric phase sorptive extraction etc.). Compared to the conventional sample preparation techniques, these novel techniques show some benefits, including reduced organic solvent consumption, while they are time and cost efficient. A plethora of adsorbents, such as metal-organic frameworks, carbon-based materials and molecularly imprinted polymers, have been successfully coupled with a wide variety of extraction techniques. This review focuses on the recent advances in the extraction techniques of PAHs from environmental matrices, utilizing novel sample preparation approaches and adsorbents.

Critical review of micro-extraction techniques used in the determination of polycyclic aromatic hydrocarbons in biological, environmental and food samples

Polycyclic Aromatic Hydrocarbons (PAHs) are ubiquitous environmental contaminants and their accurate determination is very important to human health and environment safety. In this review, sorptive-based micro-extraction techniques [such as Solid-Phase Micro-extraction (SPME), Stir Bar Sorptive Extraction (SBSE), Micro-extraction in Packed Sorbent (MEPS)] and solvent-based micro-extraction [Membrane-Mediated Liquid-Phase Micro-extraction (MM-LPME), Dispersive Liquid-Liquid Micro-extraction (DLLME), and Single Drop Micro-extraction (SDME)] developed for quantification of PAHs in environmental, biological and food samples are reviewed. Moreover, recent micro-extraction techniques that have been coupled with other sample extraction strategies are also briefly discussed. The main objectives of these micro-extraction techniques are to perform extraction, pre-concentration and clean up together as one step, and the reduction of the analysis time, cost and solvent following the green chemistry guidelines.

Method development for simultaneous analyses of polycyclic aromatic hydrocarbons and their nitro-, oxy-, hydroxy- derivatives in sediments

It is important to establish an available analytical method for polycyclic aromatic hydrocarbons (PAHs), nitrated PAHs (nitro-PAHs), oxygenated forms of PAHs (oxy-PAHs), and hydroxy-PAHs (OH-PAHs) in sediment samples due to the fact that they co-exist in various environmental mediates, particularly in sediment. In this study, an analytical method has been developed and validated for the quantification of PAHs, nitro-PAHs, oxy-PAHs, and OH-PAHs in sediment samples. The sediment samples were extracted by accelerated solvent extraction and cleaned up with SPE alumina-n combining with aminopropyl cartridges. The extracts were further fractionated by using different solvents. The fractionated extracts were analyzed via gas chromatography of single and triple quadrupole mass spectrometry in the electron ionization and negative ion chemical ionization with selective ion monitoring and selective reaction monitoring mode and liquid chromatography-triple quadrupole mass spectrometry. Each group of analytes was determined by different instrument modes such as GC-EI-SIM for PAHs, GC-NICI-SRM for nitro-PAHs, GC-EI-SRM for the oxy-PAHs and LC-ESI-MS/MS for OH-PAHs. A total of 44 analytes (16 PAHs, 14 nitro-PAHs, 9 oxy-PAHs, and 5 OH-PAHs) and 6 deuterated surrogates were performed. Most of recovery percentage varied from 52.8% up to 114.1% for the targeted analytes verified at three concentration levels (100 ng/g, 400 ng/g and 1000 ng/g for PAHs and 10 ng/g, 50 ng/g and 400 ng/g for their derivatives). The repeatability determined by the relative standard deviation percentage of triplicate trials was less than 10% for most analytes. The limit of detection ranged from 0.01 to 0.02 ng/g for PAHs, 0.002-0.067 ng/g for nitro-PAHs, 0.01-0.1 ng/g for oxy-PAHs, and 0.003-0.006 ng/g for OH-PAHs. Most of the compounds were detectable in the sediments collected from a local River, which illustrates the developed method could be a practical and suitable technique for detection of PAHs and their derivatives in real sediment samples.

The presence of nitroarenes formed by secondary atmospheric processes in the Japanese freshwater environment

In this study, the concentrations and distributions of nitrated polycyclic aromatic hydrocarbons (NPAHs) were characterized in the freshwater environment of a Japanese city. While the NPAHs were few in number, they were found in pg/L concentrations and the specific isomers suggested the deposition of NPAHs formed via the atmospheric transformation of PAHs. The absence of NPAHs formed via primary combustion processes such as automobile exhaust, suggests that improvements in emission standards are being reflected in the environment, though the NPAHs formed by secondary atmospheric processes are still a significant ecotoxicological threat. The stability of the NPAHs was also examined in spiked freshwater matrices. There was a significant decrease in spiked NPAHs over this period, suggesting that they were either being sorbed or transformed and are therefore not long lived in the freshwater environment. This indicates that the NPAHs found in freshwater samples are from recent deposition.

Current trends on microextraction by packed sorbent – fundamentals, application fields, innovative improvements and future applications

MEPS, the acronym of microextraction by packed sorbent, is a simple, fast and user- and environmentally-friendly miniaturization of the popular solid-phase extraction technique (SPE).

Methodology to examine polycyclic aromatic hydrocarbons (PAHs) nitrated PAHs and oxygenated PAHs in sediments of the Paraguaçu River (Bahia, Brazil)

Conventional methods for determination of polycyclic aromatic compounds (PACs) in sediments usually require large sample sizes (grams) and solvent volumes (at least 100 mL) through the employment of Soxhlet extraction, which is both time (hours) and energy consuming, among other disadvantages. We developed a new analytical protocol for the determination of PACs in sediments using microextraction, which requires small sample masses (25 mg), 500 μL of acetonitrile-dichloromethane mix and sonication for 23 min, followed by GC-MS analysis. The method was validated using the certified reference material SRM 1941b - NIST organic marine sediment, as well as internal deuterated standards. Seventeen PAHs, seven nitro-PAHs and one quinone were detected and quantified. The mean concentrations were 90.4 ng g^-1 for PAHs, 179.2 ng g^-1 for nitro-PAHs and 822.5 ng g^-1 for quinones. The proposed method showed good sensitivity, linearity, precision and accuracy for the determination of PAC in sediments samples.

A green chemometrics-assisted fluorimetric detection method for the direct and simultaneous determination of six polycyclic aromatic hydrocarbons in oil-field wastewaters

Oil-field wastewaters contain high level of polycyclic aromatic hydrocarbons (PAHs), which have to be analyzed to assess the environmental effects before discharge. In this work, a green fluorimetric detection method that combines excitation-emission matrix (EEM) fluorescence with parallel factor analysis (PARAFAC) algorithm was firstly developed to achieve the direct and simultaneous determination of six U.S. EPA PAHs in two different kinds of complex oil-field wastewaters. Due to the distinctive "second-order advantage", neither time-consuming sample pretreatments nor toxic organic reagents were involved in the determination. By using the environment-friendly "mathematical separation" of PARAFAC, satisfactory quantitative results and reasonable spectral profiles for six PAHs were successfully extracted from the total EEM signals of oil-field wastewaters without need of chromatographic separation. The limits of detection of six PAHs were in the range of 0.09-0.72ngmL^-1, and the average spiked recoveries were between (89.4±4.8)% and (109.1±5.8)%, with average relative predictive errors <2.93%. In order to further confirm the accuracy of the proposed method, the same batch oil-field wastewater samples were analyzed by the recognized GC-MS method. t-test demonstrated that no significant differences exist between the quantitative results of the two methods. Given the advantages of green, fast, low-cost and high-sensitivity, the proposed method is expected to be broadened as an appealing alternative method for multi-residue analysis of overlapped PAHs in complex wastewater samples.

Magnetic halloysite nanotube/polyaniline/copper composite coupled with gas chromatography-mass spectrometry: A rapid approach for determination of nitro-phenanthrenes in water and soil samples

A fast, sensitive and reliable ultrasound-assisted magnetic dispersive solid-phase microextraction (UAMDSPME) setup was developed and evaluated for the enrichment of nitro- phenanthrenes compound in environmental samples prior to GC-MS determination. A new type of nanocomposite sorbent was made based on halloysite nanotubes (HNTs). HNTs is a type of natural material, have attracted great interest because of their large surface area and high chemical and thermal stability. The hybrid nanocomposite (magnetic HNT@PANI@Cu) was obtained by coating the magnetic HNTs by polyaniline (PANI) and afterwards decorating with metalic copper. Its morphology and surface properties were characterized using Fourier transform infrared spectroscopy, field-emission scanning electron microscopy, energy dispersive spectroscopy and vibrating sample magnetometry. In this work several factors that may affect the extraction efficiencies such as desorption solvent type and its volume, sonication times for extraction and desorption, sorbent amount, organic modifier content, salt concentration and matrix effect were investigated in detail. Under the optimal conditions, the limit of detection (S/N = 3) was 0.25 ng L^-1 and the linearity was in the range of 0.01-100 μg L^-1. The method precision expressed as relative standard deviations (RSDs%) were 4.6-6.1% (intra-day), and 7.2-9.6% (inter-day). Finally, the presented method was successfully applied to the rapid determination of trace levels of nitro-phenanthrenes in spiked water and soil samples.

Hollow fiber microextraction: a new hybrid microextraction technique for trace analysis

A new hybrid microextraction technique (hollow fiber microextraction) is presented that uses the main concepts and advantages of the modern miniaturized devices used for trace analysis. This novel analytical approach uses devices made of polypropylene membranes (10.0 mm long and 0.6 mm internal diameter) in which convenient organic solvents are embedded that promote fast kinetics during the enrichment process, using the floating sampling technology concept. An innovative analytical cycle is also proposed by use of low-cost disposable devices during the microextraction stage together with a user-friendly ("single liquid desorption step") back-extraction stage in compliance with green analytical chemistry principles. To evaluate the performance of the proposed technique, 18 polycyclic aromatic hydrocarbons (PAHs) were used as model compounds and were monitored by gas chromatography coupled with mass spectrometry. Under optimized experimental conditions, assays performed on 25 mL aqueous samples spiked with the PAHs at trace level yielded average recoveries between (14.5 ± 8.2)% (dibenzo[a,h]anthracene) and (90.4 ± 8.4)% (benzo[a]anthracene) with use of a device in which n-nonane had been embedded. Low detection limits were also achieved (2.50-6.00 ng L^-1), as well as good linear dynamic ranges (20.00-2000.00 ng L^-1), with suitable coefficients of determination (r² > 0.9905) and appropriate precision (relative standard deviation below 15%). By use of the standard addition method, the proposed hybrid microextraction technique had remarkable performance to monitor PAHs at the ultratrace level in several types of matrices, including surface water, wastewater, soil, tea, and fish liver samples. From the data obtained, the new hybrid hollow fiber microextraction technique proved to be user-friendly, eco-friendly, cost-effective, and very competitive for routine work. In short, the novel microextraction technique proposed herein is a remarkable alternative to other well-established microextraction techniques for ultratrace analysis of emerging compounds in real matrices. Graphical abstract Innovative analytical procedure for hollow fiber microextraction (HFμE). GC gas chromatography, LD liquid desorption.

Low-cost and convenient ballpoint tip-protected liquid-phase microextraction for sensitive analysis of organic molecules in water samples

Simplification and miniaturization in analytical procedures are highly preferred by analysts and other researchers. In this study, a low-cost, convenient and efficient liquid-phase microextraction method, termed ballpoint tip-protected liquid-phase microextraction (BT-LPME), was established. The bullet-shaped BT possessed a hollow cavity of several microliters for solvent storage and an opening tail for solute extraction. Magnetic field-induced BT spinning significantly accelerated the extraction process. By virtue of the adhesion between a stainless steel sheath and an organic solvent, along with cave protection, finely stable storage of extractant was achieved even under high spinning speeds (>1000 rpm). The BT-LPME performance was evaluated by extracting five polycyclic aromatic hydrocarbons (PAHs) from aqueous solution, followed by gas chromatography-mass spectrometry (GCMS) analysis. Compared to static single drop microextraction (SDME), the BT-LPME method provided higher enrichments (128-173-fold) for the five PAHs. Good linearities (from 0.01∼0.05 μg L^-1 to 50 μg L^-1) with a regression coefficient (r²) ≥0.9993, as well as low limits of detection (LODs, 0.002-0.011 μg L^-1) and limits of quantification (LOQs, 0.007-0.023 μg L^-1), were obtained. Relative recoveries varied from 92.3% to 103.4% at three spiked levels of 0.1, 1 and 10 μg L^-1. The BT-LPME technique was also successfully applied to the enrichment of other organic compounds, such as organophosphorus compounds, organochlorines and triazines.