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Packed cartridges have been widely used in solid-phase extraction. However, there are still some drawbacks, such as they are blocked easily and the method is time-consuming. In view of the advantages of monoliths, a monolithic extraction material has been directly synthesized in a glass syringe without any gap between the monolith and syringe inner wall. The monolithic syringe was modified with graphene oxide by loading graphene oxide dispersion onto it. The content of graphene oxide and the surface topography of the monolith have been evaluated by elemental analysis and scanning electron microscopy, respectively, which confirmed the successful modification. This prepared graphene oxide-modified monolithic syringe was directly used as a traditional solid-phase extraction cartridge. As expected, it shows good permeability and excellent capability for the extraction of quaternary ammonium alkaloids. The sample loading velocity (1-6 mL/min) does not affect the recovery. Under the optimal conditions, good linearities ( R = 0.9992-0.9998) were obtained for five quaternary ammonium alkaloids, and the limits of detection and quantification were 0.5-1 and 1-2 μg/L, respectively. The proposed method was successfully applied for the analysis of quaternary ammonium alkaloids in Chinese patent medicine. [ABSTRACT FROM AUTHOR]

As a novel solid-phase extraction material, zinc oxide crystal whiskers were used to extract flavonoid compounds and showed good extraction abilities. X-ray diffraction, scanning electron microscopy with energy dispersive X-ray spectroscopy and surface area/pore volume characterized the sorbent. The zinc oxide was packed into a solid-phase extraction micro-column and its extraction ability was evaluated by four model flavonoid compounds. The sample loading and elution parameters were optimized and the zinc oxide based analytical method for flavonoids was established. It showed that the method has wide linearities from 1 to 150 μg/L and low limits of detection at 0.25 μg/L. The relative standard deviations of a single column repeatability and column to column reproducibility were less than 6.8% and 10.6%. Several real samples were analyzed by the established method and satisfactory results were obtained. The interactions between flavonoids and zinc oxide were calculated and proved to be from the Van der Waals’ forces between the 4p and 5d orbitals from zinc atom and the neighboring π orbitals from flavonoid phenyl groups. Moreover, the zinc oxide crystal whiskers showed good stability and could be reused more than 50 times under the operation conditions. This work proves that the zinc oxide crystal whiskers are a good candidate for flavonoids enrichment. [ABSTRACT FROM AUTHOR]

• A hydrophobic NH 2 -UiO-66@H COF hybrid was successfully fabricated and explored as a promising SPE sorbent. • The NH 2 -UiO-66@H COF hybrid exhibited better extraction performance than NH 2 -UiO-66 and H COF via synergistic effects. • A sensitive detection method was established for analysis of flavonoids in food samples. Metal-organic framework (MOF) and covalent organic framework (COF) exhibit excellent extraction performance in sample pretreatment, but their wider application is hindered by some inherent drawbacks. Herein, we successfully synthesized a novel MOF@COF hybrid material with large specific surface area, good chemical stability and reusability, which is suitable as a solid phase extraction (SPE) sorbent for the efficient extraction of flavonoids. Importantly, due to the synergistic effect, the obtained MOF@COF hybrid material showing a higher extraction efficiency than individual MOF and COF. This is mainly due to the obtained MOF@COF hybrid material combines the high specific surface area of MOF and multiple interactions (hydrophobic interaction, hydrogen bonding and π-π stacking interaction) with flavonoids conferred by the COF structure. Then, a sensitive analytical method for flavonoids with ideal linear range (1–500 ng mL−1), low detection limit (0.15–0.41 ng mL−1) and good repeatability (2.64–6.20%) was developed under optimized conditions. In addition, the MOF@COF hybrid sorbent has better selectivity for hydrophobic targets containing multiple hydrogen bond acceptors/donors. Finally, the established method was applied to the determination of flavonoids in different food samples, and satisfactory recoveries (81.4–102.1%) were obtained, which initially confirmed its applicability. [ABSTRACT FROM AUTHOR]

As a novel solid-phase extraction material, zinc sulfide nanosheets were prepared by a simple method and were used to extract flavonoids. We used scanning electron microscopy to show its nanosheet morphology and energy dispersive X-ray spectroscopy and powder X-ray diffraction to confirm its chemical and phase compositions. Coupled to a high-performance liquid chromatography, the zinc sulfide nanosheets were packed into a microcolumn and were used to extract four model flavonoids to examine their extraction ability. The parameters of sample loading and elution were investigated. Under optimized conditions, the analytical method for flavonoids was established. For the method, wide linearities from 1 to 250 μg/L and low limits of detection from 0.25 to 0.5 μg/L were obtained. The relative standard deviations for single column repeatability and column to column reproducibility were less than 7.7 and 10.4%, respectively. The established method was also used to analyze two real samples and the recoveries from 88.7 to 98.2% further proved the reliability of the method. Moreover, the zinc sulfide nanosheets have good stability and that in one column can be reused for more than 50 times. This work proves that the prepared zinc sulfide nanosheets are a good candidate as the flavonoids sorbent. [ABSTRACT FROM AUTHOR]

A new β-cyclodextrin/graphene oxide hybrid material prepared via a chemical covalent interaction and layer-to-layer assembly was developed as a sorbent for the solid-phase microextraction of fragrance allergens. As a result of its ultra-large surface area, large delocalized π-electron system and abundant hydroxyls, the β-cyclodextrin/graphene oxide-coated fiber could be used to extract particular compounds via strong π–π interactions, van der Waals forces and hydrogen bonding interactions. β-Cyclodextrin with a hydrophobic interior cavity and hydrophilic peripheral face was conducive in extracting the fragrances with hydrophobic and hydrophilic groups. Under the optimized extraction and desorption conditions, the β-cyclodextrin/graphene oxide-coated fiber showed acceptable extraction efficiency for hydrophilic and hydrogen-bonding-donating alcohols. Compared with other methods based on different coating fibers, the proposed fiber obtained wide linear ranges for fragrances with correlation coefficients ranging from 0.9921 to 0.9970, and low limits of detection in the range of 0.050–0.150 μg L−1. The obtained results indicated that the newly developed fiber was a selective, feasible and cost-effective microextraction medium and could be successfully applied for the determination of several fragrances in personal products. [ABSTRACT FROM AUTHOR]

A novel graphene oxide decorated with silver nanoparticles coating on a stainless-steel fiber for solid-phase microextraction was prepared. Scanning electron microscopy and X-ray photoelectron spectroscopy were used to characterize the coating surface and showed that silver nanoparticles were dispersed on the wrinkled graphene oxide surface. Coupled to gas chromatography with flame ionization detection, the extraction abilities of the fiber for polycyclic aromatic hydrocarbons were examined in the headspace solid-phase microextraction mode. The extraction parameters including adsorption time, adsorption temperature, salt concentration, desorption time and desorption temperature were investigated. Under the optimized condition, wide linearity with low limits of detection from 2 to 10 ng/L was obtained. The relative standard deviations for single-fiber repeatability and fiber-to-fiber reproducibility were less than 10.6 and 17.5%, respectively. The enrichment factors were from 1712.5 to 4503.7, showing the fiber has good extraction abilities. Moreover, the fiber exhibited a good stability and could be reused for more than 120 times. The established method was also applied for determination of polycyclic aromatic hydrocarbons in two real water samples and the recoveries of analytes ranged from 84.4-116.3% with relative standard deviations less than 16.2%. [ABSTRACT FROM AUTHOR]

CdS nanoparticles coated on a stainless-steel wire for solid-phase microextraction was prepared. Scanning electron microscopy showed that the CdS nanoparticles clustered together to form a porous structure and X-ray diffraction confirmed that the CdS nanoparticles were the wurtzite phase. Coupled to gas chromatography with flame ionization detection, the extraction abilities of the fiber for polycyclic aromatic hydrocarbons were examined by the headspace method. The parameters of adsorption time, adsorption temperature, salt concentration, desorption time, and desorption temperature were investigated and optimized. For the method, wide linearity and low limits of detection from 5 to 15 ng/L were obtained. The relative standard deviations for single-fiber repeatability and fiber-to-fiber reproducibility were less than 10.2 and 12.6%, respectively. The enrichment factors were from 1155.6 to 3905.4, showing the fiber has good extraction capacity for polycyclic aromatic hydrocarbons. Moreover, the fiber can be used more than 50 times, exhibiting good stability. The established method was also used to analyze the polycyclic aromatic hydrocarbons in two real samples, and the recoveries from 82.7 to 114.2% further proved the reliability of the method. [ABSTRACT FROM AUTHOR]

A novel mosaic structure Silica@C/Co@ZIF-67 composite was synthesized by successfully embedding Co nanoparticles on the surface of silica spheres with the help of thermoplastic polyethyleneimine by carbon-reduction. The ZIF-67 half-shell layer structure was synthesized by the in-situ growth of ZIF-67 on the surface of silica spheres through the coordination of 2-methylimidazole with Co metal nodes. The composite was used as a magnetic solid-phase extraction adsorbent combined with high performance liquid chromatography-ultraviolet detector (HPLC–UV) for the extraction and determination of benzoylurea insecticides (BUs) in vegetables and tea. Based on the presence of π-π, hydrophobic and hydrogen bonding interactions between Silica@C/Co@ZIF-67 and BUs, the BUs were rapidly captured by the composites resulting in high adsorption performance. Under the optimal extraction parameters, the linear ranges were 0.3–200 µg L−1 for diflubenzuron, 0.6–200 µg L−1 for chlorbenzuron, and 1.0–200 µg L−1 for triflumuron, teflubenzuron, and flufenoxuron, with correlation coefficients (R2) greater than 0.9991. The limits of detection (LODs) of the method were 0.1–0.3 μg L−1, and the relative standard deviations (RSDs) were 1.2–3.0% for intra-day and 2.6–4.6% for inter-day. In the spiked recovery experiments of vegetables and tea, the recoveries of the five kinds of BUs ranged from 75.8 to 112.9%. In addition, after 10 repetitions using Silica@C/Co@ZIF-67, the recoveries of the five kinds of BUs were still as high as 78.4 to 83.9%. [ABSTRACT FROM AUTHOR]

• A stable core-shell MOF@COF composite was synthesized and utilized as SPE adsorbent. • The covalent integration of hydrophobic COF shell successfully enhanced the hydrophobicity of MOF core. • The excellent extraction efficiency was attributed to the presence of multiple interactions. • A sensitive method for the quantification of flavonoids in grape juice and honey samples was developed. Hydrophobization and stability is crucial for the practical application of most metal-organic frameworks (MOFs) in extraction technique. In this study, a stable core-shell MOF@COF composite (NH 2 -MIL-101(Fe)@TAPB-FPBA-COF) was successfully prepared by Schiff base reaction and applied to solid-phase extraction (SPE) of hydrophobic flavonoids. Notably, the TAPB-FPBA-COF shell acts as a hydrophobic "shield", which not only improves the hydrophobicity and stability of hydrophilic NH 2 -MIL-101(Fe), but also makes the extraction efficiency of flavonoids from MOF@COF composite significantly higher than that of pure NH 2 -MIL-101(Fe) and TAPB-FPBA-COF. In addition, a sensitive analytical method with excellent linearities (0.1–500 ng mL−1, R2 ≥ 0.9967), low limits of detection (0.02–0.04 ng mL−1 for water; 0.04–0.07 ng mL−1 for grape juice; 0.06–0.08 ng mL−1 for honey), good repeatability (intra-day/inter-day precision are 1.86–5.37%/1.82–7.79%, respectively) and only 5 mg of adsorbent per cartridge was established by optimizing the SPE process combined with high performance liquid chromatography with ultraviolet-visible detector (HPLC-UV). Meanwhile, selectivity study and comparative experiments with the commercial C18 adsorbent showed that the MOF@COF adsorbent exhibited satisfactory extraction efficiency for flavonoids due to multiple interactions such as hydrogen bonding, hydrophobic, and π-π interactions. Finally, the good recoveries in grape juice (84.5–102.5%) and honey (87.5–104.6%) samples further validated the applicability of the proposed method in complex samples. [ABSTRACT FROM AUTHOR]

A zirconium(IV)‐based metal organic framework, composed of 4,4′‐biphenyldicarboxylic acid ligands and Zr6O4(OH)4 clusters, was successfully fabricated. Characterizations were performed on fourier transform infrared spectroscopy, scanning electron microscopy, X‐ray diffraction, Brunauer‐Emmett‐Teller, and thermogravimetric analysis, which confirmed that it possessed large specific surface area, high pore volume, and strong acid resistant stability. Furthermore, the prepared material containing biphenyl skeleton and a large number of Zr‐O bonds, can grasp acid herbicides especially phenoxyacetic acid herbicides with aromatic structures through π‐π interaction, hydrophobic interaction and Zr‐O‐H+ bonds. Based on these advantages, a method was developed for the determination of four phenoxyacetic acid herbicides from vegetable samples. Under the optimal conditions, wide linearities from 0.3 to 250 μg/L and low limits of detection from 0.1 to 0.5 μg/L were obtained. The intra‐ and interday relative standard deviations were 1.56‐3.92 and 5.01‐7.65%, respectively. The proposed method was applied to analyze phenoxyacetic acid herbicides residues in the tomato, cucumber, and white gourd samples. The satisfactory recoveries (86.12–103.44%) for the spiked samples in vegetable samples were achieved which demonstrated the method was an efficient pretreatment procedure and has a potential application for the trace determination of phenoxyacetic acids from a complex matrix. [ABSTRACT FROM AUTHOR]

Highlights: [•] Nanoporous array anodic titanium wire was functionalized and used as fiber support. [•] Two imidazolium ILs were synthesized and copolymerized in situ on metal support. [•] Good extraction performance was obtained by combination of NAAT and ILs copolymer. [•] Aliphatic alcohols in liquors were quantified by the GS–SPME–GC method. [Copyright &y& Elsevier]

Magnetic hierarchical nickel/nickel oxide/carbon nanorods (Ni/NiO@C) were prepared via the pyrolysis of a metal-organic framework containing nickel(II) nickel (Ni-MOF; Ni3(BTC)2) under argon atmosphere. In this material, magnetic Ni/NiO@C nanoparticles are embedded in porous carbon nanorods, and the morphology is similar to that of the original Ni-MOF precursor. The synthesized nanorods were applied as magnetic sorbents in the solid-phase extraction of five benzoylurea insecticides (flufenoxuron, chlorbenzuron, teflubenzuron, diflubenzuron and triflumuron), and their performance was evaluated under optimized conditions. The results show that the material exhibits high extraction recoveries from spiked samples (82.9%–107.6%) and linear response in the range of 0.2–450 μg·L−1. It is also characterized by relatively low limits of detection (50–100 ng·mL−1) at a signal-to-noise ratio of 3. The sorbent is chemically stable and can be repeatedly recycled, with little decline in extraction capacity after 20 cycles of reuse. The method was successfully applied to the quantification of benzoylureas in tea, wolfberry, millet, and oat samples, and it showed high extraction efficiency. [ABSTRACT FROM AUTHOR]

Herein, a novel, fusiform-like magnetic metal–organic framework material (Fe3O4-NH2@MOF-235) was fabricated by a facile two-step solvothermal approach. Then, Fe3O4-NH2@MOF-235 was applied as an adsorbent in magnetic solid-phase extraction (MSPE) coupled with high-performance liquid chromatography (HPLC) for the simultaneous extraction and determination of five kinds of benzoylurea insecticides (flufenoxuron, chlorbenzuron, teflubenzuron, diflubenzuron and triflumuron) from honey, fruit juice and tap water samples. Moreover, potential variables influencing the MSPE efficiency were optimized. Under the optimized conditions, an excellent linearity was achieved in the range of 1.0–300.0 μg L−1 for teflubenzuron and flufenoxuron and 2.0–300.0 μg L−1 for diflubenzuron, chlorbenzuron and triflumuron, with the correlation coefficients of 0.9991–0.9995. The limits of detection for the analytes were 0.25–0.5 μg L−1, and the recoveries at three fortified concentration levels ranged from 76.45% to 90.74% for the honey samples, 79.95–95.27% for the fruit juice samples, and 84.02–99.62% for the tap water samples. The π–π stacking and hydrophobic interactions between Fe3O4-NH2@MOF-235 and the analytes played an important role in the adsorption process. Moreover, maximum adsorption could be achieved within 5 minutes with very little adsorbent for all the samples. Therefore, the magnetic Fe3O4-NH2@MOF-235 composite combined with MSPE is a convenient approach to detect benzoylurea insecticides in actual samples. [ABSTRACT FROM AUTHOR]

A zirconium(IV)‐based metal–organic framework material (MOF‐808) has been synthesized in a simple way and used for the extraction of phenoxyacetic acids in complex samples. The material has good thermal and chemical stability, large specific surface area (905.36 m²/g), and high pore size (22.18 Å). Besides, it contains a large amount of Zr‐O groups, easy‐to‐form Zr‐O‐H bond with carboxyl groups of phenoxyacetic acids, and possesses biphenyl skeleton structure, easy to interact with compounds through π‐π and hydrophobic interactions. These characteristics make the material very suitable for the extraction of certain compounds with a high extraction efficiency and excellent selectivity. The extraction conditions were optimized, and then an analytical method was successfully established and applied for analysis of actual samples. The solid‐phase extraction method based on prepared material had a wide linear range of 0.2–250 μg/L and a low detection limit of 0.1–0.5 μg/L for four phenoxyacetic acid compounds including 2,4‐dichlorophenoxyacetic acid, 2‐(2,4‐dichlorophenoxy) propionic acid, 4‐chlorophenoxyacetic acid, and dicamba. The relative standard deviations of intra‐ and interday precision were 1.8–3.8 and 4.3–6.9%, and the recoveries after spiking were between 77.1 and 109.3%. The results showed that the material is a desired substituent for the extraction of compounds with benzene ring structure containing carboxyl groups. [ABSTRACT FROM AUTHOR]

Highlights • A guanidyl functionalized graphene oxide-grafted silica was designed for the extraction of acidic compounds. • Experiment parameters were optimized using the response surface methodology. • The adsorption mechanism was investigated and evaluated. • The proposed method is suitable for the determination of acidic herbicides. Abstract A highly selective and efficient extraction material was synthesized through the functionalization of guanidyl onto the graphene oxide-grafted silica via a simple chemical modification, which was designed and proposed to improve the enrichment capacity for acidic herbicides. The extraction material was confirmed by scanning electron microscopy, Fourier transform infrared spectrometry, X-ray photoelectron spectrometry, thermal gravimetric analyzer and zeta potential analysis. Theoretical adsorption energies, static- and dynamic-state binding experiments, and comparative experiments with various adsorbents were investigated to elucidate the adsorption mechanism. The introduction of guanidyl endowed the sorbent with stronger Lewis base property and electron-donating ability, hence, excellent extraction recoveries for acidic herbicides could be obtained. Besides, electrostatic and π-π interactions were considered as two major driving impetuses in the adsorption process. Single-factor experiment and response surface methodology were utilized for the optimization of extraction and desorption conditions. Under the optimized conditions, the wide linearities were obtained with correlation coefficients ranging from 0.9904 to 0.9980, and the method detection limits were in the range of 0.5–2 μg L−1. The relative standard deviation values of the recoveries of five different extractions were 3.0–7.1%. Coupled with high performance liquid chromatography, the as-proposed method was successfully applied to detect five acidic herbicides in Lycium barbarum (Goji). It turned out that the proposed method provided a promising perspective for the selective extraction and determination of polar acidic compounds in complex samples. [ABSTRACT FROM AUTHOR]

An environmental friendly sorbent of polymeric ionic liquids modified graphene oxide-grafted silica (PILs@GO@Sil) was synthesized for solid-phase extraction (SPE) of phenolic acids. The sorbent was prepared via a chemical layer-to-layer fabrication including amidation reaction, surface radical chain-transfer polymerization and in situ anion exchange. After modification with PILs, the silica surface had higher positive potential so that it would exhibit stronger electrostatic interaction for acidic compounds compared with GO@Sil. The adsorption performance of phenolic acids was investigated through the theoretical calculation and static, kinetic state adsorption experiments. Under the optimized conditions, wide linear ranges were obtained with correlation coefficients ranging from 0.9912 to 0.9998, and limits of detection were in the range of 0.20–0.50 μ g L −1 . Compared with other reported methods, the proposed PILs@GO@Sil-SPE-HPLC showed higher extraction efficiency. Finally, the black wolfberry yogurt and urine were analyzed as real samples and good recoveries spiked with standard solution were obtained. [ABSTRACT FROM AUTHOR]

A solid-phase extraction (SPE) method for the efficient analysis of trace phenolic acids (PAs, caffeic acid, ferulic acid, protocatechuic acid, cinnamic acid) in urine was established. In this work, a graphene oxide (GO) coating was grafted onto pure silica to be investigated as SPE material. The prepared GO surface had a layered and wrinkled structure that was rough and well organized, which could provide more open adsorption sites. Owing to its hydrophilicity and polarity, GO showed higher extraction efficiency toward PAs than reduced GO did, in agreement with the theoretical calculation results performed by Gaussian 09 software. The adsorption mechanism of PAs on GO@Sil was also investigated through static state and kinetic state adsorption experiments, which showed a monolayer surface adsorption. Extraction capacity of the as-prepared material was optimized using the response surface methodology. Under the optimized conditions, the as-established method provided wide linearity range (2-50 μg L for protocatechuic acid and 1-50 μg L for caffeic acid, ferulic acid, and cinnamic acid) and low limits of detection (0.25-1 μg L). Finally, the established method was applied for the analysis of urine from two healthy volunteers. The results indicate that the prepared material is a practical, cost-effective medium for the extraction and determination of phenolic acids in complex matrices. [ABSTRACT FROM AUTHOR]

A solid-phase extraction method for the efficient analysis of the excretion-dynamics of flavonoids in urine was established and described. In this work, in situ surface radical chain-transfer polymerization and in situ anion exchange were utilized to tune the extraction performance of poly(1-vinyl-3-hexylimidazolium bromide)-graphene oxide-grafted silica (poly(VHIm + Br − )@GO@Sil). Graphene oxide (GO) was first coated onto the silica using a layer-by-layer fabrication method, and then the anion of poly(VHIm + Br − )@GO@Sil was changed into hexafluorophosphate (PF 6 − ) by in situ anion exchange. The interaction energies between two PILs and four flavonoids were calculated with the Gaussian09 suite of programs. A Box-Behnken design was used for the optimization of four greatly influential parameters after single-factor experiments to obtain more accurate and precise results. Coupled to high performance liquid chromatography, the poly(VHIm + PF 6 − )@GO@Sil method showed acceptable extraction recoveries for the four flavonoids, with limits of detection in the range of 0.1–0.5 μ g L −1 , and wide linear ranges with correlation coefficients (R) ranging from 0.9935 to 0.9987. Under the optimum conditions, the proposed method was applied to analyze the urines collected from a healthy volunteer. The excretion amount-time profiles revealed that 4–15 h was the main excretion time for the detected flavonoids. The results indicated that the newly developed method offered the advantages of being feasible, green and cost-effective, and could be successfully applied to the extraction and enrichment of flavonoids in human body systems allowing the study of the metabolic kinetics. [ABSTRACT FROM AUTHOR]

A class of novel, environmental friendly ionic liquids (ILs) were synthesized by on-fiber preparation strategy and modified on graphene oxide (GO)-coated stainless steel wire, which was used as a solid-phase microextraction (SPME) fiber for efficient enrichment of polycyclic aromatic hydrocarbons (PAHs) and phthalate esters (PAEs). Surface characteristic of the ILs and polymeric-ILs (PILs) fibers with the wave-structure were inspected by scanning electron microscope. The successfully synthesis of bis(trifluoromethanesulfonyl)imide (NTf 2 − )-based ILs were also characterized by energy dispersive spectrometer analysis. Through the chromatograms of the proposed two ILs (1-aminoethyl-3-methylimidazolium bromide (C 2 NH 2 MIm + Br − ), C 2 NH 2 MIm + NTf 2 − ) and two PILs (polymeric 1-vinyl-3-hexylimidazolium bromide (poly(VHIm + Br − )), poly(VHIm + NTf 2 − ))-GO-coated fibers for the extraction of analytes, NTf 2 − -based PIL demonstrated higher extraction capacity for hydrophobic compounds than other as-prepared ILs. Analytical performances of the proposed fibers were investigated under the optimized extraction and desorption conditions coupled with gas chromatography (GC). Compared with the poly(VHIm + Br − )-GO fiber, the poly(VHIm + NTf 2 − )-GO SPME fiber brought wider linear ranges for analytes with correlation coefficient in the range of 0.9852–0.9989 and lower limits of detection ranging from 0.015–0.025 μg L −1 . The obtained results indicated that the newly prepared PILs-GO coating was a feasible, selective and green microextraction medium, which could be suitable for extraction and determination of PAHs and PAEs in potatoes and food-wrap sample, respectively. [ABSTRACT FROM AUTHOR]

A new polyethylene glycol/graphene oxide composite material bonded on the surface of a stainless-steel wire was used for solid-phase microextraction. The layer-by-layer structure increased the adsorption sites of the novel fiber, which could facilitate the extraction of trace compounds. The polyethylene glycol/graphene oxide was characterized by Fourier transform infrared spectroscopy and elemental analysis, which verified that polyethylene glycol was successfully grafted onto the surface of graphene oxide. The performance of the polyethylene glycol/graphene oxide coated fiber was investigated for phenols and phthalate esters coupled with gas chromatography with flame ionization detection under the optimal extraction and desorption conditions, and the proposed method exhibited an excellent extraction capacity and high thermal stability. Wide linear ranges were obtained for the analytes with good correlation coefficients in the range of 0.9966-0.9994, and the detection limits of model compounds ranged from 0.003 to 0.025 μg/L. Furthermore, the as-prepared fiber was used to determine the model compounds in the water and soil samples and satisfactory results were obtained. [ABSTRACT FROM AUTHOR]

Nanotubular titania film was prepared in situ on titanium wire and was used as the fiber substrate for solid-phase microextraction (SPME) because of its high surface-to-volume ratio, easy preparation, and mechanical stability. Three different functional coatings, β-cyclodextrin (β-CD), β-cyclodextrin-co-poly(ethylenepropylene glycol) (β-CD/PEG), and polyethylene glycol (PEG)-based sorbents were chemically bonded to the nanostructured wire surface via sol-gel technology to further enhance the absorbing capability and extraction selectivity. Coupled to gas chromatography-flame ionic detection (GC-FID), the prepared SPME fibers were investigated using diverse compounds. The results indicated that the fibers showed good mechanical strength, excellent thermal stability, and wonderful capacity and selectivity to polar compounds, including polar aromatic compounds, alcohols, and ketones. Combining the superior hydrophilic property of a bonded functional molecule and the highly porous structure of a fiber coating, the prepared PEG-coated SPME fiber showed much higher adsorption affinity to ephedrine and methylephedrine than β-CD and β-CD/PEG fibers. The as-established PEG-coated SPME-GC analytical method provided excellent sensitivity (LODs, 0.004 and 0.001 ng mL for ephedrine and methylephedrine, respectively) and better linear range (0.01-2 000 μg L). In addition, it has surprising repeatability and reproducibility. Finally, the present approach was used to analyze ephedrine and methylephedrine from real urine samples, and reliable results were obtained. [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

• 2D bimetallic magnetic mesoporous carbon (Ni/ZnO@C) were fabricated. • The Ni/ZnO@C nanosheet was gained by calcining 2D bimetallic Ni-ZIF-8. • The materials were used as magnetic solid phase extraction adsorbents. • The method was used to analyze nitroimidazoles from real water samples. We prepared two-dimensional (2D) bimetallic metal-organic frameworks (Ni-ZIF-8) nanosheets by a simple solvent-free method at room temperature. The morphology and composition of Ni-ZIF-8 can be controlled through adding different amounts of Ni. And then, the 2D magnetic mesoporous nanosheets (Ni/ZnO@C) were synthesized by directly pyrolyzing Ni-ZIF-8 under argon atmosphere and explored as magnetic solid phase extraction (MSPE) adsorbents for the determination of nitroimidazole antibiotics (NIABs). Magnetic Ni nanoparticles embedded in carbon nanosheets uniformly resulted in high magnetization saturation of Ni/ZnO@C for easy separation. The Ni/ZnO@C can form hydrogen bond and π-π interaction with three NIABs resulting from their rich N-H containing imidazole, π-electron. Due to the high specific surface area and high mass transfer rate of 2D Ni/ZnO@C, the materials showed satisfactory adsorption capacity and rapid adsorption kinetics for NIABs. A rapid and effective method of Ni/ZnO@C-MSPE combined with high-performance liquid chromatography was proposed for the determination of NIABs. Several main parameters affecting MSPE were investigated. Under the optimal conditions, wide linear was achieved ranging from 0.1 to 500 µg⋅L−1 with a low detection limit of 0.025-0.05 µg⋅L−1. The established method has been successfully applied to analyze NIABs from environmental water samples with satisfactory recovery from 74.33 to 105.71%. [ABSTRACT FROM AUTHOR]

• A novel Fe 2 O 3 @C was synthesized by carbonizing MOF-235 under Ar atmosphere. • The magnetic Fe 2 O 3 particles were evenly embedded in porous carbon matrix. • The Fe 2 O 3 @C was used to extract benzoylurea insecticides from tea drink samples. • This work studied the removal effect of three washing on residues from tea leaf. • This method showed satisfactory recovery, wide linear range and low LODs. Ferric oxide/carbon (Fe 2 O 3 @C) was fabricated via direct carbonization of metal-organic framework of iron (MOF-235) under argon atmosphere. The magnetic Fe 2 O 3 nanoparticles are evenly embedded in porous carbon matrix, while original morphology of MOF-235 was well-maintained. The synthesized Fe 2 O 3 @C was used as magnetic sorbent for extracting five benzoylurea insecticides (BUs). The materials exhibited excellent extraction performance, which benefited not only from the strong π-π interaction and hydrophobic interaction (π-conjugated system), but also to the abundant adsorption sites and flexible transport channel (the interconnected 3D porous structure). A three-factor-three-level Box-Behnken design (BBD) was selected to optimize three greatly influential parameters: amount of adsorbent (A), desorption time (B) and volume of desorption solvent (C) by response surface methodology. The established method coupled to HPLC-UV detection showed wide linearity with the range of 0.2–450 μg•L−1, relatively low limits of detection (0.05–0.10 μg•L−1) with the relative standard deviation (RSD) (n = 7) lower t than 5.47%. Moreover, the proposed method was successfully applied to analyze BUs in tea samples and investigate the removal effect of different washing on BUs residues from tea leaf. These results indicated that the synthesized Fe 2 O 3 @C is a promising adsorbent material for magnetic solid phase extraction of BUs at trace concentrations from tea samples. [ABSTRACT FROM AUTHOR]

Magnetic N-doped 3D graphene-like framework carbon (Fe 3 O 4 @N-3DFC) was prepared via direct pyrolysis of sodium citrate and further hydrothermal reaction, and employed in the extraction of two cephalosporin antibiotics including cephalexin monohydrate and ceftiofur hydrochloride. The scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectrometry, X-ray photoelectron spectroscopy and X-ray diffraction were employed to confirm the successful synthesis of 3DFC-based adsorbents (3DFCs) including 3DFC, Fe 3 O 4 @3DFC and Fe 3 O 4 @N-3DFC. Fe 3 O 4 @N-3DFC sorbent with 3D graphene-like honeycomb architecture combined magnetic and N doping shows the attractive features including graphene carbon sheets, hierarchical porous structure, good wettability and higher surface affinity for cephalosporin antibiotics. Furthermore, the comparison of extraction efficiency with raw 3DFC and Fe 3 O 4 @3DFC sorbent also confirmed the superiority of Fe 3 O 4 @N-3DFC sorbent. Under optimized conditions, good linearity lines were obtained with the determination coefficients from 0.9953 to 0.9995. The limit of detections were in the range of 0.20–0.45 μg L−1 and 0.03–0.10 μg L−1 for cephalexin and ceftiofur, respectively. The spiked extraction recoveries were between 81.59% and 98.35% with the relative standard deviation values less than 6.98%. Combined with high performance liquid chromatography, Fe 3 O 4 @N-3DFC based magnetic solid-phase extraction was successfully applied in river water and zebrafish samples analysis. 3D graphene-like framework carbon (3DFC), magnetic Fe 3 O 4 @3DFC sorbent and magnetic N-doped Fe 3 O 4 @N-3DFC composite were prepared for the extraction of cephalexin monohydrate and ceftiofur hydrochloride in river water and zebrafish samples. Image 1 • Magnetic N-doped 3D graphene-like carbon were prepared for the extraction research of two cephalosporin antibiotics. • Compared with precursor materials, Fe 3 O 4 @N-3DFC adsorbent exhibited best extraction efficiency for targets. • Selectivity experiment was constructed to evaluate the specific adsorption capacity of as-prepared adsorbent. • Fe 3 O 4 @N-3DFC based MSPE method coupled with HPLC was applied in river water and zebrafish analysis. [ABSTRACT FROM AUTHOR]

• Magnetic carbonized polyaniline nanotube was prepared for colorants extraction. • Fe 3 O 4 nanparticals contributed to the separation and adsorption. • Adsorption kinetics and isotherms studies proved the adsorption mechanisms. • The proposed method was used to detect xanthene colorants in beverage and fish samples. Magnetic carbonized polyaniline nanotube composite (Fe 3 O 4 @c-PANI) was synthesized via a self-assemble approach for the extraction and determination of three xanthene colorants including erythrosine B (EB), phloxine B (PB) and rhodamine B (RB). The scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectrometry, X-ray photoelectron spectroscopy and X-ray diffraction were adopted to confirm the successful synthesis of Fe 3 O 4 @c-PANI. When Fe 3 O 4 @c-PANI was applied for extracting three xanthene colorants, satisfactory extraction recoveries ranging from 89.48% to 94.15% were obtained with the relative standard deviation value of 1.09%–4.01%. Compared with Fe 3 O 4 , c-PANI and commercial adsorbents, Fe 3 O 4 @c-PANI achieved better retraction recovery for three colorants. Furthermore, adsorption kinetics and isotherms studies were analyzed to prove the adsorption mechanism of anionic and cationic colorants on Fe 3 O 4 @c-PANI. The graphite layers and pyrrole groups of the as-prepared composite can provide hydrophobic, π–π and hydrogen bonding interaction with xanthene colorants. Fe 3 O 4 nanoparticles played dual-functional roles contributing to the separation and adsorption. Coupled with high performance liquid chromatography, the established magnetic solid phase extraction method was used for the analysis of beverage and fish samples. [ABSTRACT FROM AUTHOR]