Pressurised hot-water extraction of brominated flame retardants in sediment samples

Summary A pressurised, hot-water extraction (PHWE) method was developed for brominated flame-retardants in sediments. The effect of extraction time, temperature and pressure on PHWE recovery was investigated, together with solid-phase collection parameters (trapping material, length of trapping column, eluent composition). The concentrated extracts were analysed by GC-MS. PHWE recoveries were compared with those obtained by conventional Soxhlet-extraction. In general, recoveries were much higher with PHWE than with Soxhlet.     

Magnetic nanocomposite of self‐doped polyaniline–graphene as a novel sorbent for solid‐phase extraction

This work is the first study on the extraction efficiency of self‐doped polyaniline that is immobilized on the graphene‐modified magnetic nanoparticles. The new material was used as a sorbent for the magnetic solid‐phase extraction of methyl‐, propyl‐, and butylparabens. The use of graphene provides a high surface area and prevents aggregation of the nanoparticles. The self‐doped polyaniline also provides multifunctionality, high extraction capacity, and chemical stability even in the basic medium. The parabens were acetylated for determination by gas chromatography with flame ionization detection. The effects of monomer ratio, extraction solvent, sorbent amount, sample volume, desorption solvent volume, adsorption and desorption times, and sample ionic strength were optimized. Preconcentration factors obtained were from 190 to 310. The detection limits of the method were <2.8 μg/L. Linear ranges of the method were 5–2000 μg/L for propyl and butyl parabens, and 10–2000 μg/L for methyl paraben. The method was applied for the determination of the parabens in cosmetic products and extraction recoveries were 89–101% with RSDs ≤7.9%.     

Synthesis of a graphene‐based nanocomposite for the dispersive solid‐phase extraction of vancomycin from biological samples

The approach of this work was to study the capability of graphene‐based materials in the field of biological sample preparation. A polypyrrole/graphene composite was synthesized and characterized. The potential of the nanocomposite was investigated as a sorbent in dispersive solid‐phase extraction followed by high‐performance liquid chromatography with UV detection for vancomycin as a model drug. The effect of different parameters influencing extraction efficiency such as sample pH and sample volume, ionic strength, extraction time, type, and volume of desorption solvent and desorption time were investigated. A comparison study was also conducted between polypyrrole/graphene and some different novel and classic sorbents. Under optimized conditions, the calibration curve for vancomycin showed linearity in the range of 0.05–10 μg/mL. In addition, limits of detection, and quantification were 0.003 and 0.01 μg/mL, respectively. The intraday and interday relative standard deviations at a concentration of 0.05 μg/mL (n = 3) were 1.6 and 2.1%, respectively. Furthermore, the proposed method was successfully applied for the determination of vancomycin in plasma and urine samples. The relative recoveries indicated the feasibility of graphene‐based sorbents in biological sample analysis.     

Microwave-assisted extraction for qualitative and quantitative determination of brominated flame retardants in styrenic plastic fractions from waste electrical and electronic equipment (WEEE)

A fast method for the determination of brominated flame retardants (BFRs) in styrenic polymers using microwave-assisted extraction (MAE) and liquid chromatography with UV detection (HPLC-UV) was developed. Different extraction parameters (extraction temperature and time, type of solvent, particle size) were first optimised for standard high-impact polystyrene (HIPS) samples containing known amounts of tetrabromobisphenol A (TBBPA) and decabromodiphenyl ether (Deca-BDE). Complete extraction of TBBPA was achieved using a combination of polar/non-polar solvent system (isopropanol/n-hexane) and high extraction temperatures (130 °C). Lower extraction yields were, however, obtained for Deca-BDE, due to its high molecular weight and its non-polar nature. The developed method was successfully applied to the screening of BFRs in standard plastic samples from waste electrical and electronic equipment (WEEE); TBBPA could be fully recovered, and Deca-BDE could be identified, together with minor order polybrominated diphenyl ether (PBDE) congeners.     

3‐D graphene‐supported mesoporous SiO2@Fe3O4 composites for the analysis of pesticides in aqueous samples by magnetic solid‐phase extraction with high‐performance liquid chromatography

Three‐dimensional graphene‐supported mesoporous silica@Fe₃O₄ composites (mSiO₂@Fe₃O₄‐G) were prepared by modifying mesoporous SiO₂‐coated Fe₃O₄ onto hydrophobic graphene nanosheets through a simple adsorption co‐condensation method. The obtained composites possess unique properties of large surface area (332.9 m²/g), pore volume (0.68 cm³/g), highly open pore structure with uniform pore size (31.1 nm), as well as good magnetic separation properties. The adsorbent (mSiO₂@Fe₃O₄‐G) was used for the magnetic solid‐phase extraction of seven pesticides with benzene rings in different aqueous samples before high‐performance liquid chromatography. The main parameters affecting the extraction such as adsorbent amount, volume of elution solvent, time of extraction and desorption, salt effect, oscillation rate were investigated. Under the optimal conditions, this method provided low limits of detection (S/N = 3, 0.525–3.30 μg/L) and good linearity (5.0–1000 μg/L, R² > 0.9954). Method validation proved the feasibility of the developed adsorbent, which has a high extraction efficiency and excellent enhancement performance for pesticides in this study. The proposed method was successfully applied to real aqueous samples, and satisfactory recoveries ranging from 77.5 to 113.6% with relative standard deviations within 9.7% were obtained.     

Graphene‐Fe3O4 as a magnetic solid‐phase extraction sorbent coupled to capillary electrophoresis for the determination of sulfonamides in milk

Graphene‐Fe₃O₄ nanoparticles were prepared using one‐step solvothermal method and characterized by X‐ray diffraction, FTIR spectroscopy, scanning electron microscopy, and vibrating sample magnetometry. The results demonstrated that Fe₃O₄ nanoparticles were homogeneously anchored on graphene nanosheets. The as‐synthesized graphene‐Fe₃O₄ nanoparticles were employed as sorbent for magnetic solid‐phase extraction of sulfonamides in milk prior to capillary electrophoresis analysis. The optimal capillary electrophoresis conditions were as follows: 60 mmol/L Na₂HPO₄ containing 2 mmol/L ethylenediaminetetraacetic acid disodium salt and 24% v/v methanol as running buffer, separation voltage of 14 kV, and detection wavelength of 270 nm. The parameters affecting extraction efficiency including desorption solution, the amount of graphene‐Fe₃O₄ nanoparticles, extraction time, and sample pH were investigated in detail. Under the optimal conditions, good linearity (5–200 μg/L) with correlation coefficients ≥0.9910 was obtained. The limits of detection were 0.89–2.31 μg/L. The relative standard deviations for intraday and interday analyses were 4.9–8.5 and 4.0–9.0%, respectively. The proposed method was successfully applied to the analysis of sulfonamides in milk samples with recoveries ranging from 62.7 to 104.8% and relative standard deviations less than 10.2%.     

Magnetic solid‐phase extraction based on a polydopamine‐coated Fe3O4 nanoparticles absorbent for the determination of bisphenol A,tetrabromobisphenol A, 2,4,6‐tribromophenol,and (S)‐1,1’‐bi‐2‐naphthol in environmental waters by HPLC

Polydopamine‐coated Fe₃O₄ magnetic nanoparticles synthesized through a facile solvothermal reaction and the self‐polymerization of dopamine have been employed as a magnetic solid‐phase extraction sorbent to enrich four phenolic compounds, bisphenol A, tetrabromobisphenol A, (S)‐1,1′‐bi‐2‐naphthol and 2,4,6‐tribromophenol, from environmental waters followed by high‐performance liquid chromatographic detection. Various parameters of the extraction were optimized, including the pH of the sample matrix, the amount of polydopamine‐coated Fe₃O₄ sorbent, the adsorption time, the enrichment factor of analytes, the elution solvent, and the reusability of the nanoparticles sorbent. The recoveries of these phenols in spiked water samples were 62.0–112.0% with relative standard deviations of 0.8–7.7%, indicating the good reliability of the magnetic solid‐phase extraction with high‐performance liquid chromatography method. In addition, the extraction characteristics of the magnetic polydopamine‐coated Fe₃O₄ nanoparticles were elucidated comprehensively. It is found that there are hydrophobic, π–π stacking and hydrogen bonding interactions between phenols and more dispersible polydopamine‐coated Fe₃O₄ in water, among which hydrophobic interaction dominates the magnetic solid‐phase extraction performance.     

Magnetic solid‐phase extraction of polycyclic aromatic hydrocarbons in water samples by Fe3O4@polypyrrole/carbon nanotubes

A magnetic solid‐phase extraction method coupled with gas chromatography was proposed for the determination of polycyclic aromatic hydrocarbons in the environmental water samples. The magnetic adsorbent was prepared by incorporating Fe₃O₄ nanoparticles, multi‐walled carbon nanotubes, and polypyrrole. The main factors affecting the extraction efficiency including the amount of the sorbents, desorption conditions, extraction time, salt concentration, and sample solution pH were investigated and optimized. Under the optimum conditions, good linearity was obtained within the range of 0.03?100 ng/mL for all analytes, with correlation coefficients ranging from 0.9942 to 0.9973. The method detection limits (S/N = 3) were in the range of 0.01–0.04 ng/mL and the limits of quantification (S/N = 10) were 0.03–0.1 ng/mL. Repeatability of the method was assessed through five consecutive extractions of independently prepared solutions at concentrations of 0.1, 10, and 100 ng/mL of the compounds. The observed repeatability ranged 3.4–10.9% depending of the compound considered. The proposed method was successfully applied in the analysis of PAHs in environmental samples (tap, well, river, and wastewater). The recoveries of the method ranged between 93.4 and 99.0%. The procedure proved to be efficient and environmentally friendly.     

Magnetic mixed hemimicelles solid‐phase extraction coupled with high‐performance liquid chromatography for the extraction and rapid determination of six fluoroquinolones in environmental water samples

In this study, a mixed hemimicelle solid‐phase extraction method based on Fe₃O₄ nanoparticles coated with sodium dodecyl sulfate was applied for the preconcentration and fast isolation of six fluoroquinolones in environmental water samples before high‐performance liquid chromatography determination. The main factors affecting the extraction efficiency of the analytes, such as amount of surfactant, amount of Fe₃O₄ nanoparticles, extraction time, sample volume, sample pH, ionic strength, and desorption conditions, were investigated and optimized. The method has detection limits from 0.05 to 0.1 ng/mL and good linearity (r ≥ 09948) in the range 0.1–200 ng/mL depending on the fluoroquinolone. The enrichment factor is ～200. The recoveries (at spiked levels of 1, 5, and 50 ng/mL) are in the range of 79–120%.     

Magnetic solid‐phase extraction of pyrethroid pesticides in environmental water samples with CoFe2O4‐embedded porous graphitic carbon nanocomposites

Magnetic CoFe₂O₄‐embedded porous graphitic carbon nanocomposites were prepared through a facile solid‐phase thermal reaction with NaCl as a template. The material was applied in the magnetic solid‐phase extraction process coupled with high performance liquid chromatography with a diode array detector to detect the trace fenpropathrin, cyhalothrin, S‐fenvalerate, and bifenthrin in different water samples. The synthesis conditions of nanomaterial including glucose concentration and calcination time on extraction performance for pyrethroid pesticides have been investigated. Different magnetic solid‐phase extraction parameters have been studied, such as the nanomaterial amount, solution pH, eluent types, adsorption time, and the reusability. Under the optimum conditions, good recoveries (80.2–110.9%) were achieved with relative standard deviations of 0.2–5.8%. There are probably hydrophobic interactions and dipole–dipole attractions between nanocomposites and the analytes.     

Graphene‐based solid‐phase extraction disk for fast separation and preconcentration of trace polycyclic aromatic hydrocarbons from environmental water samples

Graphene has great potentials for the use in sample preparation due to its ultra high specific surface area, superior chemical stability, and excellent thermal stability. In our work, a novel graphene‐based SPE disk was developed for separation and preconcentration of trace polycyclic aromatic hydrocarbons from environmental water samples. Based on the strong π–π stacking interaction between the analytes and graphene, the analytes extracted by graphene were eluted by cyclohexane and then determined by GC‐MS. Under the optimized conditions, high flow rate (30 mL/min) and sensitivity (0.84–13 ng/L) were achieved. The proposed method was successfully applied to the analysis of real environmental water samples with recoveries ranging from 72.8 to 106.2%. Furthermore, the property of anticlogging and reusability was also improved. This work reveals great potentials of graphene‐based SPE disk in environmental analytical.     

Rapid magnetic solid‐phase extraction of Congo Red and Basic Red 2 from aqueous solution by ZIF‐8@CoFe2O4 hybrid composites

Core–shell metal–organic framework materials have attracted considerable attention mainly due to their enhanced or new physicochemical properties compared with their single‐component counterparts. In this work, a core–shell heterostructure of CoFe₂O₄‐Zeolitic Imidazolate Framework‐8 (ZIF‐8@CoFe₂O₄) is successfully fabricated and used as an solid‐phase extraction adsorbent to efficiently extract Congo Red and Basic Red 2 dyes from contaminated aqueous solution. Vibrating sample magnetometry indicates that the saturated magnetization of ZIF‐8@CoFe₂O₄ is 3.3 emu/g, which is large enough for magnetic separation. The obtained hybrid magnetic metal‐organic framework based material ZIF‐8@CoFe₂O₄ can remove the investigated dyes very fast within 1 min of the contact time. The adsorbent ZIF‐8@CoFe₂O₄ also shows a good reusability. After regeneration, the adsorbent can still exhibit high removal efficiency (～97%) toward Congo Red for five cycles of desorption–adsorption. This work reveals the great potential of core–shell ZIF‐8@CoFe₂O₄ sorbents for the fast separation and preconcentration of organic pollutants in aqueous solution before high‐performance liquid chromatography analysis.     

Magnetic solid‐phase extraction of benzoylurea insecticides by Fe3O4 nanoparticles decorated with a hyper‐cross‐linked porous organic polymer

A magnetic polytriphenylamine porous organic polymer was prepared through simple self‐polycondensation of triphenylamine followed by coprecipitation with Fe²⁺ and Fe³⁺. It was applied as a magnetic adsorbent for the extraction of six benzoylurea insecticides from tomato, cucumber, and watermelon samples before their high‐performance liquid chromatography and mass spectral detection. Under the optimized experimental conditions, the established method gave a low limit of detection ranging from 0.05 to 0.1 ng/g and a good linear response ranging from 0.2 to 40 ng/g with coefficients of determination >0.99. The method recoveries for spiked analytes at the concentrations of 3 and 15 ng/g in real samples were in the range of 87.7–106.7% with the relative standard deviations <6.4%. The results indicated that it had a good adsorption capability toward the target analytes due to the π‐stacking and hydrogen bonding interactions. The polymer material showed great potential in the efficient extraction of organic compounds from real samples with complex matrixes.     

Magnetic solid‐phase extraction of benzoylurea insecticides in tea samples with Fe3O4‐hyperbranched polyester magnetic composite as sorbent

In this work, a method for the analysis of benzoylurea insecticides, including hexaflumuron, flufenoxuron, lufenuron and chlorfluazuron, in tea samples by high‐performance liquid chromatography with Fe₃O₄‐hyperbranched polyester nanocomposite as the adsorbent for magnetic solid‐phase extraction was developed. The magnetic nanocomposite was prepared and characterized by infrared spectroscopy, vibrating sample magnetometry, and scanning electron microscopy. The as‐prepared nanocomposite was used as a sorbent for the extraction and preconcentration of pesticide residues in tea samples. The extraction and desorption conditions, including mass ratios of raw materials, amount of sorbent, pH value, extraction time, and desorption time, were investigated. Under the final conditions chosen for the analysis, good linearity was obtained for all the tested compounds, with R² values of at least 0.9979. The limits of detection were determined in the range of 0.15–0.3 μg/L. The recovery obtained from the analysis of tea samples with various spiked concentrations was between 90.7 and 98.4%, with relative standard deviations (n = 4) lower than 4.1%. Furthermore, the present approach was successfully applied to the quantitative determination of residues of benzoylurea insecticides in real samples.     

Magnetic solid‐phase extraction based on carbon nanosphere@Fe3O4 for enantioselective determination of eight triazole fungicides in water samples

In this work, a carbon nanosphere decorated by Fe₃O₄ nanoparticles was prepared, characterized and used as the magnetic adsorbent. Eight commonly used chiral triazole fungicides, including penconazole, uniconazole, paclobutrazol, triazolone, tebuconazole, hexaconazole, triticonazole and epoxiconazole were extracted from two environmental water samples (river water and lake water) by magnetic solid‐phase extraction, followed by the enantiomeric analysis on a Chiralpark IC column coupled with a triple quadrupole mass spectrometry to evaluate their possible stereoselective degradation occurring in the water samples. The possible factors affecting the extraction performance, such as amount of used adsorbents, pH and ionic strength of water solution, types and volumes of desorption solvents were systematically investigated. Under the optimum conditions, extraction yields of eight triazole fungicides were above 80% and the concentration factors were as high as 1000. Method detection and quantification limits for the enantiomers of eight triazole fungicides were in the range of 0.56–6.95 ng/L. Satisfactory accuracy (relative recovery 77.8–93.5%), good intraday precision (RSD 4.3–9.8%) and interday precision (RSD 3.1–7.9%) were also obtained. The developed method provided the simplicity of operation, rapidity and high enrichment factor, which can be used to monitor and evaluate the behavior of the individual enantiomer of chiral triazole fungicides.     

Selective separation and determination of the synthetic colorants in beverages by magnetic solid‐phase dispersion extraction based on a Fe3O4/reduced graphene oxide nanocomposite followed by high‐performance liquid chromatography with diode array detection

A facile adsorbent, a nanocomposite of Fe₃O₄ and reduced graphene oxide, was fabricated for the selective separation and enrichment of synthetic aromatic azo colorants by magnetic solid‐phase dispersion extraction. The nanocomposite was synthesized in a one‐step reduction reaction and characterized by atomic force microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy, X‐ray diffraction and Brunauer–Emmett–Teller analysis. The colorants in beverages were quickly adsorbed onto the surface of the nanocomposite with strong π–π interactions between colorants and reduced graphene oxide, and separated with the assistance of an external magnetic field. Moreover, the four colorants in beverages were detected at different wavelengths by high performance liquid chromatography with diode array detection. A linear dependence of peak area was obtained over 0.05–10 μg/mL with the limits of detection of 10.02, 11.90, 10.41, 15.91 ng/mL for tartrazine, allure red, amaranth, and new coccine, respectively (signal to noise = 3). The recoveries for the spiked colorants were in the range of 88.95–95.89% with the relative standard deviation less than 2.66%. The results indicated that the nanocomposite of Fe₃O₄ and reduced graphene oxide could be used as an excellent selective adsorbent for aromatic compounds and has potential applications in sample pretreatment.     

Determination of trace triclosan in environmental water by microporous bamboo‐activated charcoal solid‐phase extraction combined with HPLC‐ESI‐MS

A sensitive and efficient analytical method for triclosan (TCS) determination in water, which involves enrichment with bamboo‐activated charcoal and detection with HPLC‐ESI‐MS, was developed. The influence of several operational parameters, including the eluant and its volume, the flow rate, the volume andacidity of the sample, and the amount of bamboo‐activated charcoal, were investigated and optimized. Under the optimum conditions, linearity of the method was observed in the range of 0.02–20 μg/L, with correlation coefficients (r²) >0.9990. The limit of detection was 0.002 μg/L based on the ratio of chromatographic signal to baseline noise (S/N = 3). The spiked recoveries of TCS in real water samples were achieved in the range of 97.6–112.5%. The proposed method was applied to analyze TCS in real aqueous samples. All the surface water samples collected in Xiaoqing River had detectable levels of TCS with concentrations of 42–197 ng/L.     

Zeolite/Fe3O4 as a new sorbent in magnetic solid‐phase extraction followed by gas chromatography for determining phthalates in aqueous samples

In the present study, for the first time, we successfully employed zeolite/Fe₃O₄ as a new magnetic nanoparticle sorbent in magnetic solid‐phase extraction for determining phthalates in aqueous samples. Gas chromatography with flame ionization detection was used to detect the target analytes as a powerful instrumental analysis. Affecting parameters in the extraction process, including the amount of adsorbent, adsorption and desorption time, and volume of desorption solvent, were optimized using a response surface methodology based on central composite design. Under the optimum conditions, the linear range for dibutyl phthalate and bis(2‐ethylhexyl phthalate) was varied in the interval of 10–1700 and 10–1200 μg/L, respectively. Limits of detection were 2.80 μg/L for dibutyl phthalate and 3.20 μg/L for bis(2‐ethylhexyl phthalate). The recovery value for the extraction of target analytes was between 97 and 111%. The repeatability and reproducibility of the new proposed method were obtained: 10–13% and 13–13.5%, respectively. The increased sensitivity in using the proposed method has been demonstrated. Compared with previous methods, the new proposed method is an accurate, rapid, and reliable sample‐pretreatment method.     

Aptamer‐functionalized Fe3O4 magnetic nanoparticles as a solid‐phase extraction adsorbent for the selective extraction of berberine from Cortex phellodendri

The extraction adsorbent was fabricated by immobilizing the highly specific recognition and binding of aptamer onto the surface of Fe₃O₄ magnetic nanoparticles, which not only acted as recognition elements to recognize and capture the target molecule berberine from the extract of Cortex phellodendri , but also could favor the rapid separation and purification of the bound berberine by using an external magnet. The developed solid‐phase extraction method in this work was useful for the selective extraction and determination of berberine in Cortex phellodendri extracts. Various conditions such as the amount of aptamer‐functionalized Fe₃O₄ magnetic nanoparticles, extraction time, temperature, pH value, Mg²⁺ concentration, elution time and solvent were optimized for the solid‐phase extraction of berberine. Under optimal conditions, the purity of berberine extracted from Cortex phellodendri was as high as 98.7% compared with that of 4.85% in the extract, indicating that aptamer‐functionalized Fe₃O₄ magnetic nanoparticles‐based solid‐phase extraction method was very effective for berberine enrichment and separation from a complex herb extract. The applicability and reliability of the developed solid‐phase extraction method were demonstrated by separating berberine from nine different concentrations of one Cortex phellodendri extract. The relative recoveries of the spiked solutions of all the samples were between 95.4 and 111.3%, with relative standard deviations ranging between 0.57 and 1.85%.     

Determination of organophosphate flame retardants in soil and fish using ultrasound‐assisted extraction,solid‐phase clean‐up,and liquid chromatography with tandem mass spectrometry

A solid–liquid extraction method in combination with high‐performance liquid chromatography and tandem mass spectrometry was developed and optimized for extraction and analysis of organophosphorus flame retardants in soil and fish. Methanol was chosen as the optimum extraction solvent, not only in terms of extraction efficiency, but also for its broader analyte coverage. The subsequent clean‐up by solid‐phase extraction is required to eliminate matrix coextractives and reduce matrix effects. Recoveries of the optimized method were 50–121% for soil and 47–123% for biota, both with high precision (RSDs <12% in soil and <23% in biota). The method limits of detection ranged from 0.06 to 0.20 ng/g dry weight and between 0.02 and 0.30 ng/g wet weight for soil and biota samples, respectively. However, samples with a high lipid content produce several problems as solid‐phase extraction cartridge clogging that increase variability and analysis time. The method was successfully applied for the determination of organophosphorus flame retardants in soil and fish from L'Albufera Natural Park (Valencia, Spain). Target compounds were detected in all soil and fish samples with values varying from 13.8 to 89.7 ng/g dry weight and from 3.3 to 53.0 ng/g wet weight, respectively.