Optimization of a microwave-assisted extraction method for the analysis of polycyclic aromatic hydrocarbons from fish samples

Microwave-assisted extraction in closed vessel in food analysis

Microwave-assisted extraction (MAE) is an important technique in analytical chemistry. It offers several advantages over traditional extraction methods, such as improved extraction efficiency, shorter extraction times, reduced solvent consumption, and enhanced analyte recovery. Using microwaves, heat is directly applied to the sample, leading to rapid and efficient extraction of target compounds by enhancing the solubility and diffusion of the target compounds, thus requiring lower solvent volume. Therefore, MAE can be considered a more environmentally friendly and cost-effective option facilitating the transition toward greener and more sustainable analytical chemistry workflows. This contribution systematically reviews the application of MAE to a selection of target compounds/compounds classes of relevance for food quality and safety assessment. As inclusion criteria, MAE active temperature control and molecularly-resolved characterization of the extracts were considered. Contents include a brief introduction of the principles of operation, available systems characteristics, and key parameters influencing extraction efficiency and selectivity. The application section covers functional food components (e.g., phenols, diterpenes, and carotenoids), lipids, contaminants (e.g., polycyclic aromatic hydrocarbons and mineral oil hydrocarbons), pesticides, veterinary drug residues, and a selection of process contaminants and xenobiotics of relevance for food safety.

Preparation of Novel Solid Phase Extraction Sorbents for Polycyclic Aromatic Hydrocarbons (PAHs) in Aqueous Media

In this study, functionalized mesoporous silica was prepared and characterized as a stationary phase using various analytical and solid-state techniques, including a Fourier-transform infrared (FTIR) spectrometer, thermogravimetric analysis, and nitrogen sorption. The results confirmed the successful synthesis of the hybrid stationary phase. The potential of the prepared hybrid mesoporous silica as a solid-phase extraction (SPE) stationary phase for separating and enriching polycyclic aromatic hydrocarbons (PAHs) in both spiked water samples and real water samples was evaluated. The analysis involved extracting the PAHs from the water samples using solid-phase extraction and analyzing the extracts using a two-dimensional gas chromatograph coupled to a time-of-flight mass spectrometer (GC × GC-TOFMS). The synthesized sorbent exhibited outstanding performance in extracting PAHs from both spiked water samples and real water samples. In the spiked water samples, the recoveries of the PAHs ranged from 79.87% to 95.67%, with relative standard deviations (RSDs) ranging from 1.85% to 8.83%. The limits of detection (LOD) for the PAHs were in the range of 0.03 µg/L to 0.04 µg/L, while the limits of quantification (LOQ) ranged from 0.05 µg/L to 3.14 µg/L. Furthermore, all the calibration curves showed linearity, with correlation coefficients (r) above 0.98. Additionally, the results from real water samples indicated that the levels of individual PAH detected ranged from 0.57 to 12.31 µg/L with a total of 44.67 µg/L. These findings demonstrate the effectiveness of the hybrid mesoporous silica as a promising stationary phase for solid-phase extraction and sensitive detection of PAHs in water samples.

In-vial solid-phase extraction of polycyclic aromatic hydrocarbons in drug formulations stored in packaging containing rubber

Polycyclic aromatic hydrocarbons (PAHs) are a class of ubiquitous and persistent organic compounds that are significantly teratogenic, carcinogenic and mutagenic. Rubber stoppers commonly used in sterile formulation packaging materials often contain carbon black as the additive to enhance mechanical strength. However, PAHs may be formed during the production of carbon black, which could cause the drug formulations to be contaminated when contacting with the rubber stopper, and then enter the patient's body. The determination of PAHs in drug formulations is challenging, due to their trace amounts and matrix interference. Therefore, sample pretreatment is necessary and important. In this work, a novel technique, named in-vial solid-phase extraction (IVSPE), was developed for the selective extraction and enrichment of 16 PAHs in pharmaceuticals. The coated sample vial was directly used as the container for the whole process of sample pretreatment. As the solid-phase adsorbent, the coating was prepared by successively modifying the inner surface of a sample vial with polydopamine film and octadecylamine. PAHs could be selectively extracted through π-π stacking interaction and hydrophobic interaction, and then desorbed and enriched by a small amount of organic solvent. After systematic optimization of the coating preparation and the extraction process, the limits of detection and quantification of 16 PAHs were in the range of 0.002-0.60 ng mL^-1 and 0.007-2.00 ng mL^-1, respectively. Good linearities and precision of six repeated injections were obtained. The recoveries at three spiked concentration levels in normal saline were in the range of 62.72-106.90% with the relative standard deviation between 0.83% and 6.78%. Finally, PAHs in normal saline and powders for injection were extracted by established IVSPE, followed by separation and detection with high-performance liquid chromatography with a fluorescence detector and diode array detector (HPLC-FLD/DAD). It is worth noting that the preparation conditions of the adsorbent in the IVSPE method are mild, simple and green. Moreover, IVSPE has the advantages of having few work steps and avoiding the risk of contamination, because no special instrumentation or sample transfer is required. IVSPE could also be used for the pretreatment of multiple samples at the same time, which is beneficial to practical applications.

Levels and risk assessment of polycyclic aromatic hydrocarbons in wood vinegars from pyrolysis of biomass

A method quantifying 16 polycyclic aromatic hydrocarbons (PAHs) in wood vinegars (WVs) obtained from slow pyrolysis of biomass with ultrasonic-assisted liquid-liquid extraction/gas chromatography-mass spectrometry (USALLE/GC-MS) was established. The recovery range was 83-128%, and the relative standard deviations (RSD%) were less than 15% except naphthalene, acenaphthylene and acenaphthene. Acenaphthylene, acenaphthene, fluorene, anthracene, phenanthrene, fluoranthene, and pyrene were observed in all samples and the other 9 compounds, including benzopyrene (B[a]P), were not detected. The concentration of ∑PAHs referred to the sum total of 7 PAHs mentioned above was 22.0-498.3 μg L^-1. The PAHs concentration increased with the increasing pyrolysis temperature in bamboo willow WV, pinus sylvestris WV, and corncob WV, while it increased initially, and then decreased with a maximum at 550 °C in rice husk WV. The ∑PAHs concentration increased with a higher heating rate in the white pine WV, while rice husk WV and cornstalk WV showed the opposite trend. The varied condensed aromatic ring number showed that 3-ring PAHs relatively were the main component in all kind WVs. 3-ring PAHs increased with increasing temperatures, while 4-ring PAHs showed an opposite trend in sawdust WV and corncob WVs. A higher cellulose content in sawdust enhanced the reaction of lignin leading to a higher concentration of PAHs than that in straws and leaves. Calculations of the toxicity equivalents of PAHs in WVs indicated that anthracene was the most toxic among the PAHs, and the pinus sylvestris WV had the highest risk of ∑PAHs toxicity in all WVs.

Microwave-Assisted Saponification Method Followed by Solid-Phase Extraction for the Characterization of Sterols and Dialkyl Ketones in Fats

Unlike other fields, the methods routinely applied for fats and oils are still tied to traditional, time- and solvent-consuming procedures, such as saponification, column chromatography and thin-layer chromatography. In this paper, microwave-assisted saponification followed by a lab-made solid-phase extraction was optimized for the characterization of either dialkyl ketones (DAK) or sterols or both simultaneously. The instrumental determination was performed by gas chromatography- flame ionization detector (GC-FID) for quantification and gas chromatography-mass spectrometry (GC-MS) for confirmation purposes. The proposed method showed good recoveries (>80%) and limit of quantification (0.04–0.07 μg/g for the 4 DAK and of 0.07 μg/g for α-cholestanol). Repeatabilities (n = 3) were below 15% for DAKs and generally lower than 6% for sterols. Accuracy on the entire sterol profile was confirmed in comparison to the International Olive Council reference method. The method was finally applied to real-world samples before and after chemical interesterification.

Comparison of Polyaromatic Hydrocarbon Residue Concentrations in Clarias gariepinus Smoked with Traditional and Mechanical Kilns

BACKGROUND

Wood, a common fueling material for fish smoking in Nigeria, contains polycyclic aromatic hydrocarbons (PAHs) which have been found to be carcinogenic and pose a human health hazard.

OBJECTIVES

The present study investigated the interactions and effects of kiln types on levels of PAHs in smoked fish.

METHODS

Twenty fresh samples of Clarias gariepinus with an average size of 800 g were eviscerated, washed and salted for smoking. Sixteen (16) of the fish were randomly and equally allotted to each of the two kilns (treatments) and replicated three times in a completely randomized design. Each kiln was loaded and heated up with hard wood charcoal and the effects were evaluated on the resulting smoked fish. The remaining four fish samples were kept under refrigeration (controls). Samples of the smoke-dried fish from each kiln were homogenized using a porcelain mortar and pestle, sieved through a 250-μm² sieve, and packaged in labeled airtight containers prior to extraction. Pure extracts from the samples were subjected to gas chromatography.

RESULTS

The results showed that the PAH concentration in non-smoked catfish was 1.0 mg/kg, the PAH concentration in fish samples smoked with a traditional kiln was 2.0 mg/kg, and no PAHs were detected in samples smoked with a mechanical kiln.

CONCLUSIONS

The level of PAH contamination of smoked fish is dependent on the type of kiln used, as demonstrated by the differences between fished smoked with traditional and mechanical kilns in the present study.

COMPETING INTERESTS

The authors declare no competing financial interests.

Microwave-Based Technique for Fast and Reliable Extraction of Organic Contaminants from Food, with a Special Focus on Hydrocarbon Contaminants

Due to food complexity and the low amount at which contaminants are usually present in food, their analytical determination can be particularly challenging. Conventional sample preparation methods making use of large solvent volumes and involving intensive sample manipulation can lead to sample contamination or losses of analytes. To overcome the disadvantages of conventional sample preparation, many researchers put their efforts toward the development of rapid and environmental-friendly methods, minimizing solvent consumption. In this context, microwave-assisted-extraction (MAE) has obtained, over the last years, increasing attention from analytical chemists and it has been successfully utilized for the extraction of various contaminants from different foods. In the first part of this review, an updated overview of the microwave-based extraction technique used for rapid and efficient extraction of organic contaminants from food is given. The principle of the technique, a description of available instrumentation, optimization of parameters affecting the extraction yield, as well as integrated techniques for further purification/enrichment prior to the analytical determination, are illustrated. In the second part of the review, the latest applications concerning the use of microwave energy for the determination of hydrocarbon contaminants-namely polycyclic aromatic hydrocarbons (PAHs) and mineral oil hydrocarbons (MOH)-are reported and critically overviewed and future trends are delineated.

Bioaccumulation of Polycyclic Aromatic Hydrocarbon (PAH) in a bivalve (Arca senilis- blood cockles) and health risk assessment

Concentration of PAH in bivalves (Arca senilis) and human health risks due to consumption was examined in samples collected from southern Nigeria and analysed using gas chromatography. Mean PAH concentration (ngkg-1) ranged from 12.0 ± 5.0-5500.0 ± 1000 with a significant difference (p < 0.001) while total PAH ranged from 3000.0-16,000.0. Concentrations (ngkg-1) of PAH4 varied from 250 to 15268.0 while concentrations of PAH8 ranged from 542.0 to 15620.7 with significant difference (p < 0.001). Diagnostic ratios for PAH source distinction suggested mixture of petrogenic and pyrogenic sources. Dietary daily intake-DDI (ng/kg/day) of individual PAHs ranged from 1.04 to 9.86 while DDI for PAH4 and PAH8 were 340.8 and 379.8 respectively. Carcinogenic potencies (ngkg-1) varied from 0.012 to 900.0 for individual PAH while carcinogenic toxic equivalent (TEQs) values were 1916.2, 572.49 and 1914.4 for total PAH, PAH4 and PAH8 respectively. The Excess cancer risk (ECR) for individual PAHs, PAH4 and PAH8 were all <10-6. DDI and ECR values obtained were below USEPA threshold concentration/limits indicating minimal health risk concerns while PAH4 and PAH8 concentrations were also below the EU regulatory limits (30 μg kg-1) for PAH4. The margin of exposures were above the 10,000 critical limit proposed by EFSA while incremental life cancer risk (ILCR) value (10-5 - 10-9) also suggests low potential health risk for consumers of the sea food. The screening value (SV) was 0.095 but lower than observed TEQs values indicating potential health concerns. The study concluded that consumers of bivalves (Arca senilis) in southern Nigeria generally have minimal health risk concern via consumption but regular monitoring is required to detect changes.

Bioaccumulation of Polycyclic Aromatic Hydrocarbons for Forensic Assessment Using Gas Chromatography-Mass Spectrometry

Polycyclic aromatic hydrocarbons (PAHs) are considered xenobiotics of a potentially carcinogenic nature, being accumulated in the fatty tissue of the body. The objective of this work was the development and validation of a new analytical method to check the bioaccumulation of these toxic compounds in human organs obtained from autopsies. The contaminants were first isolated from the tissues by salt-assisted liquid-liquid extraction in acetonitrile. Because of the low concentrations of these compounds in the human body, a dispersive liquid-liquid microextraction procedure was included. The preconcentrated samples were analyzed by gas chromatography-mass spectrometry to identify the compounds. Principal component analysis was applied to show the natural clustering of forensic samples and orthogonal partial least-squares discriminant analysis to develop a multivariate regression method, which permitted the classification of samples. The quantification limits for the 13 PAHs (acenaphthylene, fluorene, phenanthrene, anthracene, pyrene, benzo(a)anthracene, chrysene, benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(a)pyrene, dibenz(a,h)anthracene, benzo(g,h,i)perylene, and indeno(1,2,3-cd)pyrene) analyzed were in the 0.06-0.44 ng g^-1 range, depending on the compound, while the mean intraday relative standard deviation of about 7% demonstrated the high precision of the method. Linearity was verified in the 0.5-200 ng g^-1 range, and the enrichment factors were between 55 and 122. The results provided by the analysis of seven different human organs (brain, liver, kidney, lung, heart, spleen, and abdominal fat) from eight autopsies confirmed the PAH-bioaccumulation capacity of human body, fat showing the highest degree of bioaccumulation. The present work is the first study on PAH contamination in different organs obtained from autopsies, being PAH detected in most human samples at values ranged from 0 to 19 ng g^-1.

Human health risk assessment of polycyclic aromatic hydrocarbons (PAHs) in smoked fish species from markets in Southern Nigeria

Polycyclic Aromatic Hydrocarbons (PAHs) levels in four commonly consumed smoked fish species from markets in Southern Nigeria were assessed to evaluate possible human health risks associated with consumption. Varying levels of PAH congeners were observed in the fish tissues with the highest total concentration of PAHs in Scomber scombrus. High concentrations of benzo(a)pyrene was observed in Clarias gariepinus and Ethmalosa fimbriata with values above the guideline value of 0.05 mg/kg. The Dietary Daily Intake (DDI) value for total PAHs (∑PAHs) was highest for S. scombrus while the DDI value for the total carcinogenic PAHs (∑CPAHs) was highest for E. fimbriata. Carcinogenic human health risk assessment using carcinogenic toxic equivalents (TEQ), indicated that consumption of E. fimbriata has a higher potential to cause carcinogenic risks. TEQ values for all the fish species were however, below the estimated screening value (SV) of 3.556 mg/kg, while the estimated cumulative excess cancer risk (ECR) for E. fimbriata and C. gariepinus and PAH4 index for all the assessed fish species exceeded threshold values indicating potential carcinogenic risk from consumption.

Simultaneous analysis of phthalates, adipate and polycyclic aromatic hydrocarbons in edible oils using isotope dilution-gas chromatography-mass spectrometry

A method for simultaneous determination of 12 priority phthalates, adipate and polycyclic aromatic hydrocarbons (PAHs) in edible oils by isotope dilution-gas chromatography-mass spectrometry (ID-GC-MS) was developed for fast, accurate and trace analysis. The extraction and clean-up procedures were optimised, and using stable isotope-labelled internal standards for each analyte, relative standard deviations (RSDs) of 0.92-10.6% and spiked sample recoveries of 80.6-97.8% were obtained. Limits of detection for PAHs were in the range of 0.15-0.77 µg/kg and those for phthalates were in the range of 4.6-10.0 µg/kg. The calibration curves exhibited good linearities with regression coefficients of R(2) ≥ 0.99. Twelve edible oils were examined to evaluate the efficiency of this method. Among the 12 analytes, dibutyl phthalates (DBP), diethylhexyl phthalates (DEHP), diethylhexyl adipate (DEHA), benzo[a]anthracene (B[a]A), chrysene (Chry) and benzo[b]fluoranthene (B[b]F) were detected in the range of 1.17-806 µg/kg.

Microwave assisted extraction combined with solvent bar microextraction for one-step solvent-minimized extraction, cleanup and preconcentration of polycyclic aromatic hydrocarbons in soil samples

For the first time, a novel one-step sample preparation method that combines microwave assisted extraction and solvent bar microextraction (MAE-SBME) with analysis by gas chromatography-mass spectrometry (GC-MS), was developed for the fast and efficient determination of polycyclic aromatic hydrocarbons (PAHs) in environmental soil samples. An interesting feature of the new procedure is that SBME was conducted simultaneously with MAE. Thus, the extract from the SBME could be directly and immediately analyzed by GC-MS. A separate clean up and/or preconcentration process, such as time-consuming and tedious gel permeation chromatography, solid-phase extraction, filtration, or adsorption chromatography, normally associated with conventional MAE, was not necessary. It is also notable that the procedure was environmentally benign since water was used as the extraction solvent in MAE, and only several microliters of organic solvent were used in SBME. Some factors affecting the extraction were studied and optimized. Under the most favorable conditions, the method showed good linearities (between 0.2 and 500, 0.5 and 500, 1 and 500, and 2 and 500 ng/g, depending on the analytes), low limits of detection (from 0.03 to 0.25 ng/g), and satisfactory precision (with relative standard deviations below 9.8%). The MAE-SBME procedure provides a fast and simple sample preparation approach for the processing of environmental soil samples.

Overview on polycyclic aromatic hydrocarbons: occurrence, legislation and innovative determination in foods

Polycyclic aromatic hydrocarbons are ubiquitous compounds, well-known to be carcinogenic, which can reach the food in different ways. Thus the analysis of such compounds has always been of great importance. The aim of the present review, is not only to give an overview of the most recent sample preparation and analytical approaches (such as pressurized liquid extraction, solid-phase microextraction, supercritical fluid extraction, etc.), but also to introduce such a topic to researchers who want to approach it for the first time; therefore, the most significant references related to general aspects, such as formation, toxicity, risk assessment, occurrence in food, are reported and briefly discussed.

A cost effective, sensitive, and environmentally friendly sample preparation method for determination of polycyclic aromatic hydrocarbons in solid samples

A simple, cost effective, and yet sensitive sample preparation technique was investigated for determining Polycyclic Aromatic Hydrocarbons (PAHs) in solid samples. The method comprises ultrasonic extraction, Stir Bar Sorptive Extraction (SBSE), and thermal desorption-gas chromatography-mass spectrometry to increase analytical capacity in laboratories. This method required no clean-up, satisfied PAHs recovery, and significantly advances cost performance over conventional extraction methods, such as Soxhlet and Microwave Assisted Extraction (MAE). This study evaluated three operational parameters for ultrasonic extraction: solvent composition, extraction time, and sample load. A standard material, SRM 1649 a (urban dust), was used as the solid sample matrix, and 12 priority PAHs on the US Environmental Protection Agency (US EPA) list were analyzed. Combination of non-polar and polar solvents ameliorated extraction efficiency. Acetone/hexane mixtures of 2:3 and 1:1 (v/v) gave the most satisfactory results: recoveries ranged from 63.3% to 122%. Single composition solvents (methanol, hexane, and dichloromethane) showed fewer recoveries. Comparing 20 min with 60 min sonication, longer sonication diminished extraction efficiencies in general. Furthermore, sample load became a critical factor in certain solvent systems, particularly MeOH. MAE was also compared to the ultrasonic extraction, and results determined that the 20-min ultrasonic extraction using acetone/hexane (2:3, v/v) was as potent as MAE. The SBSE method using 20 mL of 30% alcohol-fortified solution rendered a limit of detection ranging from 1.7 to 32 ng L(-1) and a limit of quantitation ranging from 5.8 to 110 ng L(-1) for the 16 US EPA PAHs.

Polycyclic aromatic hydrocarbons concentrations and biomarker responses in the clam Ruditapes decussatus transplanted in the Ria Formosa lagoon

Clams Ruditapes decussatus were transplanted in the Ria Formosa lagoon and the variation of PAH concentrations in the whole soft tissues measured, along with a suite of biomarkers, including the following: (a) phase I and phase II metabolism of xenobiotics enzymes: benzo[a]pyrene hydroxylase (BPH) and glutathione S-transferase (GST); (b) antioxidant enzymes: superoxide dismutase, catalase and glutathione peroxidases and (c) lipid peroxidation (LPO) levels. Individual PAHs were differently accumulated and eliminated by R. decussatus. During the metabolisation of PAHs by R. decussatus BPH was clearly induced in the digestive gland. Moreover, ROS lead to the induction of protective antioxidant enzymes still causing oxidative damage to membranes. Therefore, BPH seems to be a relevant indicator of PAHs in R. decussatus.

A reliable analytical approach based on gas chromatography coupled to triple quadrupole and time-of-flight mass analyzers for the determination and confirmation of polycyclic aromatic hydrocarbons in complex matrices from aquaculture activities

The potential of gas chromatography coupled to tandem mass spectrometry (GC/MS/MS) with a triple quadrupole analyzer (QqQ) has been investigated for the quantification and reliable identification of sixteen polycyclic aromatic hydrocarbons (PAHs) from the EPA priority list in animal and vegetable samples from aquaculture activities, whose fat content ranged from 5 to 100%. Matrices analyzed included fish fillet, fish feed, fish oil and linseed oil. Combining optimized saponification and solid-phase extraction led to high efficiency in the elimination of interfering compounds, mainly fat, from the extracts. The developed procedure minimized the presence of these interfering compounds in the extracts and provided satisfactory recoveries of PAHs. The excellent sensitivity and selectivity of GC/(QqQ)MS/MS in selected reaction monitoring (SRM) allowed to reach limits of detection at pg/g levels. Two SRM transitions were acquired for each analyte to ensure reliable identification of compounds detected in samples. Confirmation of positive findings was performed by GC coupled to high-resolution time-of-flight mass spectrometry (GC/TOFMS). The accurate mass information provided by GC/TOFMS in full acquisition mode together with its high mass resolution makes it a powerful analytical tool for the unequivocal confirmation of PAHs in the matrices tested. The method developed was applied to the analysis of real-world samples of each matrix studied with the result of detecting and confirming the majority of analytes at the microg/kg level by both QqQ and TOF mass spectrometers.

Evaluation of solid-phase microextraction conditions for the determination of polycyclic aromatic hydrocarbons in aquatic species using gas chromatography

This paper describes a headspace solid-phase microextraction (HS-SPME) procedure coupled to gas chromatography with mass spectrometric detection (GC-MS) for the determination of eight PAHs in aquatic species. The influence of various parameters on the PAH extraction efficiency was carefully examined. At 75 degrees C and for an extraction time of 60 min, a polydimethylsiloxane-divinylbenzene (PDMS/DVB) fiber coating was found to be most suitable. Under the optimized conditions, detection limits ranged from 8 to 450 pg g(-1), depending on the compound and the sample matrix. The repeatability varied between 7 and 15% (RSD). Accuracy was tested using the NIST SRM 1974b reference material. The method was successfully applied to different samples, and the studied PAHs were detected in several of the samples.