One‐step hydrothermal synthesis of magnetic nitrogen‐doped graphene for magnetic solid‐phase extraction of nonsteroidal anti‐inflammatory drugs in environmental water samples

Graphene oxide has received extensive attention because of its unique properties and potential applications. In this study, magnetic nitrogen‐doped graphene was prepared by one‐step hydrothermal reaction using urea as the dopant and reductant, and ferroferric oxide nanoparticles were in situ deposited on the surface of the nanohybrids. The magnetic nitrogen‐doped graphene was characterized using various physical and chemical methods. It was used as a new adsorbent for the magnetic solid‐phase extraction of four nonsteroidal anti‐inflammatory drugs from the river water. The parameters influencing the extraction efficiency were optimized in detail. Under optimal conditions, this method provided a wide linear range (5–200 ng/mL). The limits of detection were in the range of 1.07–5.10 ng/mL. The recoveries varied from 81.2 to 121.5% with relative standard deviations of less than 10.8%. Overall, we can conclude that the proposed method offers an efficient pretreatment and enrichment and can be successfully applied for the extraction and determination of nonsteroidal anti‐inflammatory drugs in complex matrices.     

One‐pot synthesis of magnetic zeolitic imidazolate framework/grapheme oxide composites for the extraction of neonicotinoid insecticides from environmental water samples

Magnetic zeolitic imidazolate framework 67/graphene oxide composites were synthesized by one‐pot method at room temperature for the first time. Electrostatic interactions between positively charged metal ions and both negatively charged graphene oxide and Fe₃O₄ nanoparticles were expected to chemically stabilize magnetic composites to generate homogeneous magnetic products. The additional amount of graphene oxide and stirring time of graphene oxide, Co²⁺, and Fe₃O₄ solution were investigated. The zeolitic imidazolate framework 67 and Fe₃O₄ nanoparticles were uniformly attached on the surface of graphene oxide. The composites were applied to magnetic solid‐phase extraction of five neonicotinoid insecticides in environmental water samples. The main experimental parameters such as amount of added magnetic composites, extraction pH, ionic strength, and desorption solvent were optimized to increase the capacity of adsorbing neonicotinoid insecticides. The results show limits of detection at signal‐to‐noise ratio of 3 were 0.06–1.0 ng/mL under optimal conditions. All analytes exhibited good linearity with correlation coefficients of higher than 0.9915. The relative standard deviations for five neonicotinoid insecticides in environmental samples ranged from 1.8 to 16.5%, and good recoveries from 83.5 to 117.0% were obtained, indicating that magnetic zeolitic imidazolate framework 67/graphene oxide composites were feasible for analysis of trace analytes in environmental water samples.     

Facile preparation of magnetic graphene oxide/nanoscale zerovalent iron adsorbent for magnetic solid‐phase extraction of ultra‐trace quinolones in milk samples

A simple pH‐responsive magnetic solid‐phase extraction method was developed using graphene oxide–coated nanoscale zerovalent iron nanoparticles as an efficient adsorbent prior to high‐performance liquid chromatography‐tandem mass spectrometry for determination of ultra‐trace quinolones in milk samples. Various parameters affecting maghemite synthesis and separation such as pH of sample solution, amount of magnetic adsorbent, eluent type, and volume were optimized. The limits of detection are from 3.1 to 13.3 ng/L. The intra‐ and interprecision values are in the range of 2.9–6.9% and 7.6–15.1%, respectively. Recoveries are from 82.4 to 103.9%. Therefore, this simple and sensitive method is suitable for detecting ultra‐trace quinolone residues in milk.     

Fabrication of magnetic zinc adeninate metal–organic frameworks for the extraction of benzodiazepines from urine and wastewater

In this study, an alternative method for synthesizing magnetic cobalt adeninate metal–organic frameworks was developed, and the synthesized materials were examined for their potential application for separating and enriching benzodiazepines from complex samples. Benzodiazepines, widely used as hypnotics, muscle relaxants, sedatives, and anxiolytics, are a class of drugs that require accurate detection and monitoring. Results showed that Fe₃O₄ nanoparticles could be well anchored onto the external surface of cobalt adeninate metal–organic frameworks by using amino‐silane as a linkage. Their adsorption of benzodiazepines was mainly promoted by intermolecular hydrogen binding, π–π interactions and electrostatic attraction. Their potential application was evaluated by extraction of benzodiazepines in urine and wastewater samples prior to liquid chromatography with mass spectrometry. Under optimum conditions, the calibration curves were linear with a correlation coefficient of ≥0.9928 in the concentration range of 10–5000 ng/L for lorazepam and 5–5000 ng/L for estazolam, chlordiazepoxide, alprazolam, midazolam and triazolam. The limits of detection were in the range of 0.71–2.49 ng/L. The percent of extraction recoveries were 80.2–94.5% for urine and 84.1–94.4% for wastewater, respectively. Results suggested that magnetic cobalt adeninate metal–organic frameworks could potentially be a promising material for enriching benzodiazepines from urine and wastewater with high accuracy and precision.     

Dispersive magnetic solid‐phase extraction of phthalate esters from water samples and human plasma based on a nanosorbent composed of MIL‐101(Cr) metal–organic framework and magnetite nanoparticles before their determination by GC–MS

In this study, a magnetic metal–organic framework was synthesized simply and utilized in the dispersive magnetic solid‐phase extraction of five phthalate esters followed by their determination by gas chromatography with mass spectrometry. First, MIL‐101(Cr) was prepared hydrothermally in water medium without using highly corrosive hydrofluoric acid, utilizing an autoclave oven heat supply. Afterward, Fe₃O₄ nanoparticles were decorated into the matrix of MIL‐101(Cr) to fabricate magnetic MIL‐101 nanocomposite. The nanocomposite was characterized by various techniques. The parameters affecting dispersive magnetic solid‐phase extraction efficiency were optimized and obtained as: a sorbent amount of 15 mg; a sorption time of 20 min; an elution time of 5 min; NaCl concentration, 10% w/v; type and volume of the eluent 1 mL n‐hexane/acetone (1:1 v/v). Under the optimum conditions detection limits and linear dynamic ranges were achieved in the range of 0.08–0.15 and 0.5–200 μg/L, respectively. The intra‐ and interday RSD% values were obtained in the range of 2.5–9.5 and 4.6–10.4, respectively. Ultimately, the applicability of the method was successfully confirmed by the extraction and determination of the model analytes in water samples, and human plasma in the range of microgram per liter and satisfactory results were obtained.     

Magnetic iron(III)‐based framework composites for the magnetic solid‐phase extraction of fungicides from environmental water samples

We adopted a facile hydrofluoric acid‐free hydro‐/solvothermal method for the preparation of four magnetic iron(III)‐based framework composites (MIL‐101@Fe₃O₄‐COOH, MIL‐101‐NH₂@Fe₃O₄‐COOH, MIL‐53@Fe₃O₄‐COOH, and MIL‐53‐NH₂@Fe₃O₄‐COOH). The obtained four magnetic iron(III)‐based framework composites were applied to magnetic separation and enrichment of the fungicides (prochloraz, myclobutanil, tebuconazole, and iprodione) from environmental samples before high‐performance liquid chromatographic analysis. MIL‐101‐NH₂@Fe₃O₄‐COOH showed more remarkable pre‐concentration ability for the fungicides as compared to the other three magnetic iron(III)‐based framework composites. The extraction parameters affecting enrichment efficiency including extraction time, sample pH, elution time, and the desorption solvent were investigated and optimized. Under the optimized conditions, the standard curve of correlation coefficients were all above 0.991, the limits of detection were 0.04–0.4 μg/L, and the relative standard deviations were below 10.2%. The recoveries of two real water samples ranged from 71.1–99.1% at the low spiking level (30 μg/L). Therefore, the MIL‐101‐NH₂@Fe₃O₄‐COOH composites are attractive for the rapid and efficient extraction of fungicides from environmental water samples.     

Preparation of metal‐organic framework UiO‐66‐incorporated polymer monolith for the extraction of trace levels of fungicides in environmental water and soil samples

A zirconium terephthalate metal‐organic framework‐incorporated poly(N‐vinylcarbazole‐co‐divinylbenzene) monolith was fabricated in a capillary by a thermal polymerization method. The optimized monolith had a homogeneous structure, good permeability, and stability. The monolith could be used for the effective enrichment of fungicides through π‐π interactions, electrostatic forces, and hydrogen bonds. The potential factors that affect the extraction efficiency, including ionic strength, solution pH, sample volume, and eluent volume, were investigated in detail. The monolith‐based in‐tube solid‐phase microextraction coupled with ultra‐high‐performance liquid chromatography and high‐resolution Orbitrap mass spectrometry was performed for the analysis of five fungicides (pyrimethanil, tebuconazole, hexaconazole, diniconazole, and flutriafol) in environmental samples. Under the optimized conditions, the linear ranges were 0.005–5 ng/mL for pyrimethanil, 0.01–5 ng/mL for flutriafol, and 0.05–5 ng/mL for other fungicides, respectively, with coefficients of determination ≥0.9911. The limits of detection were 1.34–14.8 ng/L. The columns showed good repeatability (relative standard deviations ≤9.3%, n = 5) and desirable column‐to‐column reproducibility (relative standard deviations 5.3–9.4%, n = 5). The proposed method was successfully applied for the simultaneous detection of five fungicides in water and soil samples, with recoveries of 90.4–97.5 and 84.0–95.3%, respectively.     

Preparation of magnetic attapulgite/polypyrrole nanocomposites for magnetic effervescence‐assisted dispersive solid‐phase extraction of pyrethroids from honey samples

In this work, a novel extraction technique based on the effervescence‐assisted dispersion and magnetic recovery of attapulgite/polypyrrole sorbents was developed for determining the concentrations of five pyrethroids in honey samples. The magnetic nanoparticles were synthesized by a one‐pot method. Several experimental parameters that affected the extraction efficiency, including the dispersion conditions, pH, ionic strength, and desorption conditions, were investigated. Under optimal conditions, the calibration curves for the five pyrethroids in honey samples exhibited good linearity, with r² values ranging from 0.9979 to 0.9990. The limits of detection varied between 0.21 and 0.34 µg/L. Satisfactory recoveries of 81.42–106.73% with intra‐ and interday relative standard deviations of less than 6.94 and 10.89%, respectively, were obtained. Moreover, the sorbents exhibited acceptable batch‐to‐batch repeatability in the range of 5.06–15.01%, and each sorbent could be reused for up to four extraction cycles without a significant loss in the extraction recovery.     

Dispersive micro‐solid‐phase extraction using carbon‐based adsorbents for the sensitive determination of verapamil in plasma samples coupled with capillary electrophoresis

A dispersive micro‐solid‐phase extraction procedure coupled with capillary electrophoresis ultraviolet detection was developed for determination of verapamil in plasma samples. Graphene oxide/polydopamin was synthesized by a one‐step polymerization method, and graphene oxide/Fe₃O₄ (magnetic graphene oxide) nanocomposite was prepared by coprecipitation method. Moreover, they were fully characterized. The use of hazardous and water‐immiscible solvents was scaled down, and only 500 μL of acetone was required as the desorption solvent. The detector response concentration plots were linear in the range of 5–500 ng/mL, and the proposed method was validated according to guidelines. The precision and accuracy were less than 15%. Dispersive micro‐solid‐phase extraction method provides a rapid, environmentally friendly, and sensitive analysis for the verapamil in patient plasma samples, which is adequate for therapeutic drug monitoring and pharmacokinetic studies.     

Quantitative determination of trace phenazopyridine in human urine samples by hyphenation of dispersive solid‐phase extraction and liquid‐phase microextraction followed by gas chromatography/mass spectrometry analysis

Magnetic dispersive solid‐phase extraction followed by dispersive liquid?liquid microextraction coupled with gas chromatography/mass spectrometry was applied for the quantitative analysis of phenazopyridine in urinary samples. Magnetic dispersive solid‐phase extraction was carried out using magnetic graphene oxide nanoparticles modified by poly(thiophene‐pyrrole) copolymer. The eluting solvent of this step was used as the disperser solvent for the dispersive liquid?liquid microextraction procedure. To reach the maximum efficiency of the method, effective parameters including sorbent amount, adsorption time, type and volume of disperser and extraction solvents, pH of the sample solution, and ionic strength as well as desorption time, and approach were optimized, separately. Characterization of the synthesized sorbent was studied by utilizing infrared spectroscopy, scanning electron microscopy, and energy‐dispersive X‐ray analysis. Calibration curve was linear in the range of 0.5?250 ng/mL (R² = 0.9988) with limits of detection and quantification of 0.1 and 0.5 ng/mL, respectively. Intra‐ and interday precisions (RSD%, n = 3) of the method were in the range of 4.6?5.4% and 4.0?5.5%, respectively, at three different concentration levels. Under the optimal condition, this method was successfully applied for the determination of phenazopyridine in human urine samples. The relative recoveries were obtained in the range of 85.0?89.0%.     

Magnetic metal–organic framework MIL‐100(Fe) microspheres for the magnetic solid‐phase extraction of trace polycyclic aromatic hydrocarbons from water samples

In this work, a magnetic metal–organic framework designated as MIL‐100(Fe) was prepared and applied as a magnetic solid‐phase extraction sorbent for the determination of trace polycyclic aromatic hydrocarbons in environmental water samples by coupling with high‐performance liquid chromatography and fluorescence detection. The magnetic microspheres exhibited large surface areas and high extraction ability, making them excellent candidates as sorbents for enrichment of trace polycyclic aromatic hydrocarbons. Under the optimized experimental conditions, good sensitivity levels were achieved with low detection limits ranging from 32 to 2110 pg/mL and good linearities with correlation coefficients higher than 0.9990 for the investigated 13 polycyclic aromatic hydrocarbons. The proposed method has been validated in the analysis of real water samples with mean recoveries in the range of 81.4–126.9% at four spiked levels and the relative standard deviations in the range of 1.3–17.0%. The magnetic MIL‐100(Fe) microspheres were stable enough for 150 extractions without a significant loss of extraction performance.     

Determination of trace amounts of aromatic amines after magnetic solid‐phase extraction using silver‐modified Fe3O4/graphene nanocomposite

In this work, a fast and simple magnetic dispersive solid phase extraction methodology was developed utilizing Ag@magnetite nanoparticles@graphene nanocomposite as an efficient magnetic nanosorbent for preconcentration and determine of five aromatic amines in water samples. The sorbent was characterized by diverse characterization techniques. After the extraction, high‐performance liquid chromatography with UV detection was utilized to analysis the aromatic amines. The effects of different factors on the extraction process were studied thoroughly via design of experiment and desirability function. Detection limits and linear dynamic ranges were obtained in the range of 0.10–0.20 and 0.3–300 μg/L, respectively. The relative standard deviations (n = 5) were in the range of 4.3–6.5%. Eventually, the method was employed for determination of target aromatic amines in various water samples.     

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.     

Magnetic graphene oxide modified by imidazole‐based ionic liquids for the magnetic‐based solid‐phase extraction of polysaccharides from brown alga

Magnetic graphene oxide was modified by four imidazole‐based ionic liquids to synthesize materials for the extraction of polysaccharides by magnetic solid‐phase extraction. Fucoidan and laminarin were chosen as the representative polysaccharides owing to their excellent pharmaceutical value and availability. Fourier transform infrared spectroscopy, field‐emission scanning electron microscopy, and thermogravimetric analysis were applied to characterize the synthesized materials. Single‐factor experiments showed that the extraction efficiency of polysaccharides was affected by the amount of ionic liquids for modification, solid–liquid ratio of brown alga and ethanol, the stirring time of brown alga and ionic liquid‐modified magnetic graphene oxide materials, and amount of 1‐(3‐aminopropyl)imidazole chloride modified magnetic graphene oxide materials added to the brown alga sample solution. The results indicated that 1‐(3‐aminopropyl)imidazole chloride modified magnetic graphene oxide possessed better extraction ability than graphene oxide, magnetic graphene oxide, and other three ionic‐liquid‐modified magnetic graphene oxide materials. The highest extraction recoveries of fucoidan and laminarin extracted by 1‐(3‐aminopropyl)imidazole chloride modified magnetic graphene oxide were 93.3 and 87.2%, respectively. In addition, solid materials could be separated and reused easily owing to their magnetic properties.     

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.     

Dispersive solid‐phase extraction adsorbent of methamphetamine using in‐situ synthesized carbon‐based conductive polypyrrole nanocomposite: focus on clinical applications in human urine

Determination of methamphetamine is of great importance in clinical and forensic laboratories because there are low dosages of drugs in the biological media and social problems created due to the methamphetamine consumption. Polymeric carbon based‐nano composites are reasonable candidates for dispersive solid phase extraction method due to facial and affordable synthesis process and high selectivity and sensitivity. Nano graphene oxide polypyrolle composite was synthesized and employed as dispersive solid‐phase extraction adsorbent for methamphetamine extraction from complex urine matrix. Full characterization of the prepared nano graphene oxide polypyrolle composite was completed and the influential extraction parameters were investigated through one‐parameter‐at‐a‐time method. High‐performance liquid chromatography detectors were applied as detection and quantification instrument. The optimized extraction parameters included 300 µL of methanol, 10 min of extraction and desorption time, 6000 stirring rate, urine pH value of 10, 60 mg of adsorbent, and 6 mL of urine volume. After outlining the calibration curve, the linear range of the method was considered as 30–800 ng/mL. The detection limit for the suggested method was 9 ng/mL. The analysis of addicted subjects with the proposed method confirmed the utility of the method in different analytical and clinical laboratories.     

Simultaneous determination of seven nitrogen‐containing phenyl ethers in cosmetics by gas chromatography with mass spectrometry and dispersive solid‐phase extraction

An analytical method was established for the simultaneous determination of seven nitrogen‐containing phenyl ethers (2‐anisidine, 3‐anisidine, 4‐anisidine, 2‐nitroanisole, 3‐nitroanisole, 4‐nitroanisole, and 3,3'‐dimethoxybenzidine) in cosmetics by gas chromatography with mass spectrometry in this work. The samples were extracted with ethyl acetate and purified with primary secondary amine during the dispersed solid‐phase extraction. The analytes were separated by a DB‐17MS column and detected in the electron ionization mode of mass spectrometry in the selected ions monitoring mode. The extraction solvent, purification adsorbents, and chromatographic column behavior were optimized. The results indicated that the seven analytes show good linear relationship (R ² > 0.9965) in the concentrations of 5.0–5000 μg/L. The quantitation limits of the method ranged from 19.0 to 84.8 μg/kg. The recovery rates of seven analytes were in the range of 72.6–114% with the relative standard deviations of 1.1–7.5%. Real sample analyses showed that this accurate and precise method could be appropriate for simultaneous determination of seven nitrogen‐containing phenyl ethers in cosmetics.     

Solid‐phase extraction of phenoxyacetic acid herbicides in complex samples with a zirconium(IV)‐based metal–organic framework

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.     

Dispersive solid‐phase extraction of buprenorphine from biological fluids using metal‐organic frameworks and its determination by ultra‐performance liquid chromatography

In this work, various types of metal‐organic frameworks were synthesized, and their affinities toward buprenorphine were evaluated using dispersive solid‐phase extraction. The extracted buprenorphine was determined by ultra high performance liquid chromatography‐ultraviolet detection system. The highest extraction recovery was observed by employing zeolitic imidazole framework‐67. Then, a facile and fast extraction method was designed for the extraction and purification of the target drug. Optimization of the extraction method was carried out by the design of experiment approach. A linearity range of 1–1000 μg/L with the limit of detection of 0.15 μg/L and relative standard deviations (50 μg/L, n = 5) of 3.4% was obtained for standard sample analysis. Under optimized experimental and instrumental conditions, the relative recoveries were in the range of 95 to 111%. Eventually, zeolitic imidazole framework‐67 was successfully employed for the extraction and determination of buprenorphine in the biological fluids with satisfactory results.     

Graphene oxide composites for magnetic solid‐phase extraction of trace cytokinins in plant samples followed by liquid chromatography–tandem mass spectrometry

In this work, an easy, effective, and sensitive method based on graphene oxide@silica@magnetite composites as adsorbent of magnetic solid‐phase extraction combined with liquid chromatography and tandem mass spectrometry, was established and validated for the trace analysis of cytokinins in different plants. The prepared magnetic composite was characterized by infrared spectroscopy, transmission electron microscopy, Brunauer–Emmett–Teller analysis, and magnetic hysteresis. Under the optimized conditions, good linearities in the range of 0.5–100 ng/mL were obtained with the corresponding linear correlation coefficient >0.9989 for the investigated four cytokinins, and good sensitivity levels were achieved with low detection limits ranging from 93 to 120 pg/mL. The established magnetic solid‐phase extraction with liquid chromatography and tandem mass spectrometry method has been validated in the separation and analysis of four cytokinins in plant samples with good recoveries between 78.9 and 97.3% for four cytokinins with the relative standard deviations lower than 13.5%.