β‐Cyclodextrin polymer@Fe3O4 based magnetic solid‐phase extraction coupled with HPLC for the determination of benzoylurea insecticides from honey,tomato, and environmental water samples

In this work, a magnetic β‐cyclodextrin polymer was successfully prepared and used as an adsorbent for the magnetic solid‐phase extraction of six benzoylurea insecticides (diflubenzuron, triflumuron, hexaflumuron, teflubenzuron, flufenoxuron, and chlorfluazuron) from honey, tomato, and environmental water samples. The influence of the main experimental conditions on the extraction was studied. Under the optimized conditions, the β‐cyclodextrin polymer@Fe₃O₄ showed an excellent extraction performance for the benzoylurea insecticides. A good linearity was obtained for the analytes in the range of 3.0–800 ng/g for honey samples, 0.3–160 ng/g for tomato samples, and 0.1–80.0 ng/mL for water samples, with the correlation coefficients above 0.9998. Satisfactory repeatabilities were achieved, with the relative standard deviations less than 5.7%. The limits of detection (S/N = 3) of the method for the benzoylurea insecticides were 0.2–0.8 ng/g for honey samples, 0.04–0.10 ng/g for tomato samples, and 0.02–0.05 ng /mL for water samples. The method was successfully used for the determination of the six benzoylurea insecticides residues in honey, tomato, and environmental water samples with a satisfactory result.     

Magnetic porous carbon derived from a metal–organic framework as a magnetic solid‐phase extraction adsorbent for the extraction of sex hormones from water and human urine

An iron‐embedded porous carbon material (MIL‐53‐C) was fabricated by the direct carbonization of MIL‐53. The MIL‐53‐C possesses a high surface area and good magnetic behavior. The structure, morphology, magnetic property, and porosity of the MIL‐53‐C were studied by scanning electron microscopy, transmission electron microscopy, vibrating sample magnetometry, and N₂ adsorption. With the use of MIL‐53‐C as the magnetic solid‐phase extraction adsorbent, a simple and efficient method was developed for the magnetic solid‐phase extraction of three hormones from water and human urine samples before high‐performance liquid chromatography with UV detection. The developed method exhibits a good linear response in the range of 0.02–100 ng/mL for water and 0.5–100 ng/mL for human urine samples , respectively. The limit of detection (S/N = 3) for the analytes was 0.005–0.01 ng/mL for water sample and 0.1–0.3 ng/mL for human urine sample. The limit of quantification (S/N = 10) of the analytes were in the range of 0.015–0.030 and 0.3–0.9 ng/mL, respectively.     

Magnetic N‐doped mesoporous carbon as an adsorbent for the magnetic solid‐phase extraction of phthalate esters from soft drinks

A new kind of magnetic N‐doped mesoporous carbon was prepared by the one‐step carbonization of a hybrid precursor (glucose, melamine, and iron chloride) in a N₂ atmosphere with a eutectic salt (KCl/ZnCl₂) as the porogen. The obtained magnetic N‐doped mesoporous carbon showed excellent characteristics, such as strong magnetic response, high surface area, large pore volume, and abundant π‐electron system, which endow it with a great potential as a magnetic solid‐phase extraction adsorbent. To evaluate its adsorption performance, the magnetic N‐doped mesoporous carbon was used for the extraction of three phthalate esters from soft drink samples followed by high‐performance liquid chromatographic analysis. Under the optimum conditions, the developed method showed a good linearity (1.0–120.0 ng/mL), low limit of detection (0.1–0.3 ng/mL, S/N = 3), and good recoveries (83.2–119.0%) in soft drink samples. The results indicated that the magnetic N‐doped mesoporous carbon has an excellent adsorption capacity for phthalate esters and the present method is simple, accurate, and highly efficient for the extraction and determination of phthalate esters in complex matrix samples.     

Novel molecularly imprinted magnetic nanoparticles for the selective extraction of protoberberine alkaloids in herbs and rat plasma

In this work, a novel magnetic nanomaterial functionalized with a molecularly imprinted polymer was prepared for the extraction of protoberberine alkaloids. Molecularly imprinted polymers were made on the surface of Fe₃O₄ nanoparticles by using berberine as template, acetonitrile/water as porogen, acrylamide as functional monomer and ethylene glycol dimethacrylate as cross‐linker. The optimized molar ratio of template/functional monomer was 1:7. The polymeric magnetic nanoparticles were characterized by transmission electron microscopy and Fourier transform infrared spectroscopy. The stability and adsorption capacity of the molecularly imprinted polymers were investigated. The molecularly imprinted polymers were used as a selective sorbent for the magnetic molecularly imprinted solid‐phase extraction and determination of jatrorrhizine, palmatine, and berberine. Extraction parameters were studied including loading pH, sample volume, stirring speed, and extraction time. Finally, a magnetic molecularly imprinted solid‐phase extraction coupled to high‐performance liquid chromatography method was developed. Under the optimized conditions, the method showed good linear range of 0.1–150 ng/mL for berberine and 0.1–100 ng/mL for jatrorrhizine and palmatine. The limit of detection was 0.01 ng/mL for berberine and 0.02 ng/mL for jatrorrhizine and palmatine. The proposed method has been applied to determine protoberberine alkaloids in Cortex phellodendri and rat plasma samples. The recoveries ranged from 87.33–102.43%, with relative standard deviation less than 4.54% in Cortex phellodendri and from 102.22–111.15% with relative standard deviation less than 4.59% in plasma.     

New application of chitosan‐grafted polyaniline in dispersive solid‐phase extraction for the separation and determination of phthalate esters in milk using high‐performance liquid chromatography

Chitosan‐grafted polyaniline was synthesized and applied as a sorbent for the preconcentration of phthalate esters in dispersive solid‐phase extraction. By coupling dispersive solid‐phase extraction with high‐performance liquid chromatography and response surface methodology (central composite design), a reliable, sensitive, and cost‐effective method for simultaneous determination of phthalate esters including dimethyl phthalate, di‐n‐butyl phthalate, and di(2‐ethylhexyl)phthalate was developed. The morphology of sorbent had been studied by scanning electron microscopy and its chemical structure confirmed by Fourier transform infrared spectroscopy. Under optimum condition, good linearity was observed in the range of 5.0–5000.0 ng/mL. The limits of detection (S/N = 3) and limits of quantification (S/N = 10) were 0.1–0.3 and 0.3–1 ng/mL, respectively. The relative standard deviations were less than 8.8%. Finally, this procedure was employed for extraction of trace amounts of phthalic acid esters in milk samples, the relative recoveries ranged from 82 to 103%.     

Phytic acid induced three‐dimensional graphene for the enrichment of phthalate esters from bottled water and sports beverage samples

A three‐dimensional graphene was synthesized through a hydrothermal reaction of graphene oxide with phytic acid. The microstructure and morphology of the phytic acid induced three‐dimensional graphene were investigated by nitrogen adsorption–desorption isotherms, scanning electron microscopy, and transmission electron microscopy. With a large surface area and three‐dimensional structure, the graphene was used as the solid‐phase extraction adsorbent for the extraction of phthalate esters from bottled water and sports beverage samples before high‐performance liquid chromatographic analysis. The results indicated that the graphene was efficient for the solid‐phase extraction of phthalate esters. The limits of detection (S/N = 3) of the method for the analytes were 0.02–0.03 ng/mL for the water samples and 0.03–0.15 ng/mL for the sports beverage sample. The limits of quantitation (S/N = 9) for the analytes were 0.06–0.09 ng/mL for water samples and 0.09–0.45 ng/mL for sports beverage sample. The calibration curves for the phthalate esters by the method had a good linearity from 0.1 to 80.0 ng/mL with correlation coefficients larger than 0.9997. The recoveries of the analytes for the method fell in the range of 86.7–116.2% with the relative standard deviations between 1.5 and 6.8%.     

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%.     

Electrospun magnetic polybutylene terephthalate nanofibers for thin film microextraction

A thin film microextraction method using elecrospun magnetic polybutylene terephthalate nanofibers is developed and implemented to isolate some selected triazines. Due to the high mechanical stability of these nanofibers, they are repeatedly used under harsh magnetic stirring and ultrasonic conditions without any damage and structure degradation. The presence of magnetic nanoparticles within the nanofiber structure increases the extraction efficiency while the fibers could be collected by an external magnet. The synthesized nanocomposite showed strong affinity toward the selected analytes. Apart from the concentration of magnetic nanoparticles within the nanocomposite network, the effect of different parameters on the extraction and desorption processes including the sample pH, extraction time, sample volume, type of desorption solvent, solvent volume, and desorption time were optimized. Eventually, the detection limits were in the range of 0.02–0.05 ng/mL, while the limits of quantification were between 0.1 and 0.2 ng/mL. The linear dynamic range was 0.1–100 ng/mL, and the relative standard deviations were 4–9% (n =  3). The developed method was extended to the real water samples, and the relative recoveries were in the range of 86–103%, indicating that the prepared sorbent is suitable for extraction of triazines from environmental samples.     

Ionic‐liquid‐mediated poly(dimethylsiloxane)‐ grafted carbon nanotube fiber prepared by the sol–gel technique for the head space solid‐phase microextraction of methyl tert‐butyl ether using GC

A headspace solid‐phase microextraction method was developed for the preconcentration and extraction of methyl tert‐butyl ether. An ionic‐liquid‐mediated multiwalled carbon nanotube–poly(dimethylsiloxane) hybrid coating, which was prepared by covalent functionalization of multiwalled carbon nanotubes with hydroxyl‐terminated poly(dimethylsiloxane) using the sol–gel technique, was used as solid‐phase microextraction adsorbent. This innovative fiber exhibited a highly porous surface structure, high thermal stability (at least 320°C) and long lifespan (over 210 uses). Potential factors affecting the extraction efficiency were optimized. Under the optimum conditions, the method LOD (S/N = 3) was 0.007 ng/mL and the LOQ (S/N = 10) was 0.03 ng/mL. The calibration curve was linear in the range of 0.03–200 ng/mL. The RSDs for one fiber (repeatability, n = 5) at three different concentrations (0.05, 1, and 150 ng/mL) were 5.1, 4.2, and 4.6% and for the fibers obtained from different batches (reproducibility, n = 3) were 6.5, 5.9, and 6.3%, respectively. The developed method was successfully applied to the determination of methyl tert‐butyl ether in different real water samples on three consecutive days. The relative recoveries for the spiked samples with 0.05, 1, and 150 ng/mL were between 94–104%.     

Electroless deposition of silver nanofractals on copper wire by galvanic displacement as a simple technique for preparation of porous solid‐phase microextraction fibers

A novel and porous solid‐phase microextraction fiber was prepared by quick and simple galvanic displacement reaction and applied to the determination of some polycyclic aromatic hydrocarbons in sunflower oil. The parameters affecting the porosity and thickness of the fiber, and parameters affecting the extraction efficiency, including the extraction time, temperature, and ionic strength, were investigated and optimized. The morphology of prepared fiber was characterized by optical and scanning electron microscopy and thermal and chemical stabilities of the fiber were studied. Under the optimum conditions, the limits of detection ranged between 0.1 ng/mL for pyrene to 1.2 ng/mL for anthracene, and LOQ ranged between 0.3 ng/mL for pyrene to 3.6 ng/mL for anthracene. The relative standard deviations, including repeatability (within fibers) and reproducibility (between fibers), varied between 3.2–8.9 and 5.6–9.8%, respectively.     

Preparation of a magnetic porous carbon with hierarchical structures from waste biomass for the extraction of some carbamates

In this study, corn stalk was used to synthesize a magnetic adsorbent by pyrolysis together with KHCO₃ as the chemical activator and iron(III) salt as the magnetic reagent. The characterization by scanning electron microscopy, transmission electron microscopy and N₂ adsorption–desorption analysis showed that the magnetic carbon adsorbent had a structure of hierarchical pores with a high specific surface area. To evaluate its adsorption performance, the adsorbent was used for the extraction of carbamates pesticides (propoxur, isoprocarb and fenobucarb) from water and zucchini samples before high‐performance liquid chromatography analysis. The result showed that the adsorbent had a good adsorption capability for the analytes. Under the optimized conditions, a good linearity for the analytes existed in the range of 0.1–100.0 ng/mL for water samples and 0.5–100.0 ng/g for zucchini samples with the correlation coefficients of 0.9992–0.9998. The limits of detection for the analytes at a signal to noise ratio of 3 were 0.03 ng/mL for water samples and 0.20–0.50 ng/g for zucchini samples.     

Magnetic graphene oxide as adsorbent for the determination of polycyclic aromatic hydrocarbon metabolites in human urine

Detection of monohydroxy polycyclic aromatic hydrocarbons metabolites in urine is an advisable and valid method to assess human environmental exposure to polycyclic aromatic hydrocarbons. In this work, novel Fe₃O₄/graphene oxide composites were prepared and their application in the magnetic solid‐phase extraction of monohydroxy polycyclic aromatic hydrocarbons in urine was investigated by coupling with liquid chromatography and mass spectrometry. In the hybrid material, superparamagnetic Fe₃O₄ nanoparticles provide fast separation to simplify the analytical process and graphene oxide provides a large functional surface for the adsorption. The prepared magnetic nanocomposites were characterized by X‐ray diffraction, scanning electron microscopy, transmission electron microscopy, and vibrating sample magnetometry. The experimental conditions were optimized systematically. Under the optimal conditions, the recoveries of these compounds were in the range of 98.3–125.2%, the relative standard deviations ranged between 6.8 and 15.5%, and the limits of detection were in the range of 0.01–0.15 ng/mL. The simple, quick, and affordable method was successfully used in the analysis of human urinary monohydroxy polycyclic aromatic hydrocarbons in two different cities. The results indicated that the monohydroxy polycyclic aromatic hydrocarbons level in human urine can provide useful information for environmental exposure to polycyclic aromatic hydrocarbons.     

Polyvinylimidazole/sol–gel composite as a novel solid‐phase microextraction coating for the determination of halogenated benzenes from aqueous solutions

A polyvinylimidazole/sol–gel composite is proposed as a novel solid‐phase microextraction fiber to extract five halobenzenes from the headspace of aqueous solutions in combination with gas chromatography with mass spectrometry. The prepared fiber was characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The obtained results showed that porous polyvinylimidazole/sol–gel composite was chemically deposited on fused silica fiber. The effect of important extraction parameters including extraction temperature, extraction time, and salt content were investigated. The optimum conditions were as follows: extraction temperature 25°C, extraction time 20 min, and salt concentration 30 w/v%. Detection limits and relative standard deviations of the developed method for halogenated benzenes were below 0.1 pg/mL and 15%, respectively. Repeatability of the proposed method, explained by relative standard deviation, varied between 5.48 and 9.15% (n = 5). The limits of detection (S/N = 3) ranged between 0.01 and 0.10 ng/L using gas chromatography with mass spectrometry with selected ion monitoring mode. For real sample analysis, three types of water samples with different matrices (ground, surface, and tap water) were studied. The optimized procedure was applied to extraction and method validation of halogenated benzenes in spiked water samples.     

Magnetic spherical carbon as an efficient adsorbent for the magnetic extraction of phthalate esters from lake water and milk samples

Magnetic spherical carbon was synthesized by a facile hydrothermal carbonization procedure with biomass glucose as the carbon precursor and nanoclusters iron colloid as magnetic precursor. The textures of the as‐prepared magnetic spherical carbon were characterized by nitrogen adsorption–desorption isotherms, X‐ray diffraction, transmission electron microscopy, scanning electron microscopy and vibration sample magnetometry. Results indicated that the magnetic spherical carbon possessed high surface area as well as strong magnetism, which endows the material with good adsorption capability and easy separation properties. To assess its absorption performance, the magnetic spherical carbon was employed as adsorbent for the extraction and preconcentration of phthalate esters from lake water and milk samples before high‐performance liquid chromatographic analysis. Some key parameters that could influence the enrichment efficiency were investigated. Under the optimum conditions, a good linearity was achieved with the linear correlation coefficients higher than 0.9973. The limits of detection (S/N = 3) were 0.05–0.08 ng/mL for lake water and 0.1–0.2 ng/mL for milk samples. The recoveries of the analytes for the method were in the range 80.1–112.6%.     

Magnetic porous carbon derived from Co‐doped metal–organic frameworks for the magnetic solid‐phase extraction of endocrine disrupting chemicals

Metal–organic frameworks‐5 (MOF‐5) was explored as a template to prepare porous carbon due to its high surface area, large pore volume, and permanent nanoscale porosity. Magnetic porous carbon, Co@MOF‐5‐C, was fabricated by the one‐step direct carbonization of Co‐doped MOF‐5. After carbonization, the magnetic cobalt nanoparticles are well dispersed in the porous carbon matrix, and Co@MOF‐5‐C displays strong magnetism (with the saturation magnetization intensity of 70.17emu/g), high‐specific surface area, and large pore volume. To evaluate its extraction performance, the Co@MOF‐5‐C was applied as an adsorbent for the magnetic solid‐phase extraction of endocrine disrupting chemicals, followed by their analysis with high‐performance liquid chromatography. The developed method exhibits a good linear response in the range of 0.5–100 ng/mL for pond water and 1.0–100 ng/mL for juice samples. The limits of detection (S/N  = 3) for the analytes were in the range of 0.1–0.2 ng/mL.     

Determination and removal of sulfonamides and quinolones from environmental water samples using magnetic adsorbents

In this study, the magnetic materials known as polymerized ionic liquid@3‐(trimethoxysilyl)propyl methacrylate@Fe₃O₄ nanoparticles were synthesized and utilized as potential adsorbents. First, these nanoparticles were applied to the analysis of sulfonamides and quinolones present in different water samples using magnetic solid phase extraction and high‐performance liquid chromatography. Under optimized conditions, the developed method showed excellent detection sensitivity, with limits of detection (S/N = 3) and quantification limits (S/N = 10) within 0.2–1.0 and 0.8–3.4 μg/L, respectively. The spiked recoveries of the SAs and QNs in environmental water samples ranged from 83.5 to 103.0%, with RSDs of less than 4.5%. In addition, the adsorbents effectively removed sulfamethoxazole and ofloxacin present in existing aquatic environments. The adsorption kinetics and isotherms of sulfamethoxazole and ofloxacin on the magnetic adsorbents were studied to assess removal performance. The results indicate that the adsorption process follows a pseudo‐second‐order mechanism, which reveals that the sorption mechanism is the rate‐limiting step and produces high q_max values (sulfamethoxazole = 70.35 mg/g and ofloxacin = 48.95 mg/g), thus demonstrating the enormous adsorption capacity of these magnetic adsorbents.     

Magnetic nanoporous carbon as an adsorbent for the extraction of phthalate esters in environmental water and aloe juice samples

In this work, magnetic nanoporous carbon with high surface area and ordered structure was synthesized using cheap commercial silica gel as template and sucrose as the carbon source. The prepared magnetic nanoporous carbon was firstly used as an adsorbent for the extraction of phthalate esters, including diethyl phthalate, diallyl phthalate, and di‐n‐propyl‐phthalate, from lake water and aloe juice samples. Several parameters that could affect the extraction efficiency were optimized. Under the optimum conditions, the limit of detection of the method (S/N = 3) was 0.10 ng/mL for water sample and 0.20 ng/mL for aloe juice sample. The linearity was observed over the concentration range of 0.50–150.0 and 1.0–200.0 ng/mL for water and aloe juice samples, respectively. The results showed that the magnetic nanoporous carbon has a high adsorptive capability toward the target phthalate esters in water and aloe juice samples.     

Determination of trace hydroxyl polycyclic aromatic hydrocarbons in urine using graphene oxide incorporated monolith solid‐phase extraction coupled with LC‐MS/MS

The biomonitoring of hydroxy polycyclic aromatic hydrocarbons in urine, as a direct way to access multiple exposures to polycyclic aromatic hydrocarbons, has raised great concerns due to their increasing hazardous health effects on humans. Solid‐phase extraction is an effective and useful technique to preconcentrate trace analytes from biological samples. Here, we report a novel solid‐phase extraction method using a graphene oxide incorporated monolithic syringe for the determination of six hydroxy polycyclic aromatic hydrocarbons in urine coupled with liquid chromatography‐tandem mass spectrometry. The effect of graphene oxide amount, washing solvent, eluting solvent, and its volume on the extraction performance were investigated. The fabricated monoliths gave higher adsorption efficiency and capacity than the neat polymer monolith and commercial C₁₈ sorbent. Under the optimum conditions, the developed method provided the detection limits (S/N = 3) of 0.02–0.1 ng/mL and the linear ranges of 0.1–1500 ng/mL for six analytes in urine sample. The recoveries at three spiked levels ranged from 77.5 to 97.1%. Besides, the intra column‐to‐column (n = 3) and inter batch‐to‐batch (n = 3) precisions were ≤ 9.8%. The developed method was successfully applied for the determination of hydroxy polycyclic aromatic hydrocarbons in urine samples of coke oven workers.     

Graphene oxide as a micro‐solid‐phase extraction sorbent for the enrichment of parabens from water and vinegar samples

A simple hydrophilic polyamide organic membrane protected micro‐solid‐phase extraction method with graphene oxide as the sorbent was developed for the enrichment of some parabens from water and vinegar samples prior to gas chromatography with mass spectrometry detection. The main experimental parameters affecting the extraction efficiencies, such as the type and amount of the sorbent, extraction time, stirring rate, salt addition, sample solution pH and desorption conditions, were investigated. Under the optimized experimental conditions, the method showed a good linearity in the range of 0.1–100.0 ng/mL for water samples and 0.5–100.0 ng/mL for vinegar samples, with the correlation coefficients varying from 0.9978 to 0.9997. The limits of detection (S/N = 3) of the method were in the range of 0.005–0.010 ng/mL for water samples and 0.01–0.05 ng/mL for vinegar samples, respectively. The recoveries of the method for the analytes at spiking levels of 5.0 and 70.0 ng/mL were between 84.6 and 106.4% with the relative standard deviations varying from 4.2 to 9.5%. The results indicated that the developed method could be a practical approach for the determination of paraben residues in water and vinegar samples.     

Magnetic solid-phase extraction of organophosphorus pesticides from apple juice and environmental water samples using magnetic graphene oxide coated with poly(2-aminoterephthalic acid-co-aniline) nanocomposite as a sorbent

An effective magnetic solid-phase extraction method was proposed using magnetic graphene oxide coated with poly(2-aminoterephthalic acid-co-aniline) as a sorbent for preconcentration and extraction of organophosphorus pesticides from environmental water and apple juice samples, and determined using the gas chromatography-mass spectrometry analysis. To approve the successful synthesis of the magnetic nanocomposite, the prepared sorbent was characterized by field emission scanning electron microscopy, X-ray diffraction, vibrating sample magnetometer, and Fourier transforms infrared techniques. The main parameters affecting the extraction efficiency were considered and studied to afford an optimized procedure. Systematic method validation verified its suitable recoveries (89.4–107.3%), and precision (relative standard deviations < 6.8%). The method showed a wide linear dynamic range (0.04–700 ng/mL) with low limits of detection (0.01–0.06 ng/mL) and quantification (0.04–0.21 ng/mL). This method presented good potential and great sensitivity for the pesticides determination.