Selective extraction of bisphenol A from water by one‐monomer molecularly imprinted magnetic nanoparticles

One‐monomer molecularly imprinted magnetic nanoparticles were prepared as adsorbents for selective extraction of bisphenol A from water in this study. A single bi‐functional monomer was adopted for preparation of the molecularly imprinted polymer, avoiding the tedious trial‐and‐error optimizations as traditional strategy. Moreover, bisphenol F was used as the dummy template for bisphenol A to avoid the interference from residual template molecules. These nanoparticles showed not only large adsorption capacity and good selectivity to the bisphenol A but also outstanding magnetic response performance. Furthermore, they were successfully used as magnetic solid‐phase extraction adsorbents of bisphenol A from various water samples, including tap water, river water, and seawater. The developed method was found to be much more efficient, convenient, and economical for selective extraction of bisphenol A compared with the traditional solid‐phase extraction. Separation of these nanoparticles can be easily achieved with an external magnetic field, and the optimized adsorption time was only 15 min. The recoveries of bisphenol A in different water samples ranged from 85.38 to 93.75%, with relative standard deviation lower than 7.47%. These results showed that one‐monomer molecularly imprinted magnetic nanoparticles had the potential to be popular adsorbents for selective extraction of pollutants from water.     

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

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

Magnetic solid‐phase extraction of angiotensin II receptor antagonists in human urine and plasma with a reversed‐phase/cation‐exchange mixed‐mode sorbent

Biocompatible magnetic nanoparticles that featured divinylbenzene and sulfonate functionalities were used for the magnetic solid‐phase extraction of five angiotensin II receptor antagonists from human urine and plasma samples based on a reversed‐phase and cation‐exchange mixed‐mode mechanism. Under the optimized extraction conditions, coupled to high‐performance liquid chromatography with fluorescence detection, this proposed method was found to be accurate and precise with relative standard deviations of less than 11.7%, and a good recovery of 80.1–119.5% for both samples. The linear ranges were 0.2–2000 and 0.2–2500 ng/mL along with correlation coefficients above 0.9923 and 0.9928 for urine and plasma samples, respectively. Limits of detection were 0.01–5.74 and 0.01–1.31 ng/mL, respectively. The proposed magnetic solid‐phase extraction based on the magnetic nanoparticles functionalized with divinylbenzene and sulfonate was a reliable and convenient sample pretreatment method and had the potential for isolating and enriching the angiotensin II receptor antagonists in biological samples.     

Poly(styrene‐co‐N‐methacryloyl‐l‐phenylalanine methyl ester)‐functionalized magnetic nanoparticles as sorbents for the analysis of sodium benzoate in beverages

In this study, poly(styrene‐co‐N‐methacryloyl‐l ‐phenylalanine methyl ester)‐functionalized magnetic nanoparticles were constructed and used as magnetic solid‐phase extraction sorbents for analysis of food preservatives in beverages. To prepare the poly(amino acid)‐based sorbents, N‐methacryloyl‐l ‐phenylalanine methyl ester, and styrene served as the functional monomers and modified onto the magnetic nanoparticles via free radical polymerization. Interestingly, compared with propylparaben and potassium sorbate, the proposed poly(amino acid)‐based sorbents showed a good selectivity to sodium benzoate. The adsorption capacity of the sorbents to sodium benzoate was 6.08 ± 0.31 mg/g. Moreover, the fast adsorption equilibrium could be reached within 5 min. Further, the resultant poly(amino acid)‐based sorbents were applied in the analysis of sodium benzoate in real beverage samples. The results proved that the proposed magnetic solid‐phase extraction sorbents have a great potential for the analysis of preservatives in food samples.     

Magnetic solid‐phase extraction and ultrafast liquid chromatographic detection of Sudan dyes in red wines,juices, and mature vinegars

A nanocomposite of polystyrene‐coated magnetic nanoparticles was successfully synthesized and employed as adsorbent for magnetic solid‐phase extraction of four Sudan dyes (I, II III, and IV) in red wines, juices, and mature vinegars. The prepared magnetic nanoparticles with highly hydrophobic properties have excellent adsorption capacity for these lipophilic Sudan dyes. Extraction conditions were optimized. Experimental results showed that the recoveries of the four Sudan dyes were very satisfactory when 70 mg of polystyrene‐coated magnetic nanoparticles were used and the extraction could be completed within 20 min. It was proved that these magnetic nanoparticles can be reused after an easy washing process. By coupling the magnetic solid‐phase extraction with ultrafast liquid chromatography‐ultraviolet spectrometry, a rapid, green, effective, and sensitive method for the determination of Sudan dyes was developed. The LOD for Sudan I, Sudan II, Sudan III, and Sudan IV were 0.0039, 0.0063, 0.0057, and 0.017 ng/mL, respectively. Recoveries obtained by analyzing spiked water samples at three concentration levels (0.1, 1.0, and 10.0 ng/mL) were between 76.3 and 96.6%. The intra‐ and interday RSDs for the analytes were lower than 9.6%.     

Molecularly imprinted magnetic nanoparticles for the micro solid‐phase extraction of thiabendazole from citrus samples

The preparation of molecularly imprinted core–shell magnetic nanoparticles and their subsequent use in the solid‐phase extraction of thiabendazole from citrus sample extracts is described. Molecularly imprinted core–shell magnetic nanoparticles were prepared by the precipitation copolymerization of the imprinting polymerization mixture on the surface of vinyl‐modified silica magnetic nanoparticles and were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy. The obtained molecularly imprinted core–shell magnetic nanoparticles exhibited a high selectivity for thiabendazole and were easily collected and separated by an external magnetic field without additional centrifugation or filtration steps. Under optimum conditions, a magnetic molecularly imprinted solid‐phase extraction method was developed allowing the extraction of thiabendazole from citrus sample extracts and final determination by high‐performance liquid chromatography with fluorescence detection. The detection limit was 0.2 mg/kg, far lower than the maximum residue limit established within the European Union for thiabendazole in citrus samples.     

Microwave‐assisted preparation of magnetic nanoparticles modified with graphene oxide for the extraction and analysis of phenolic compounds

Here in, magnetic nanoparticles combined with graphene oxide adsorbent were fabricated via a microwave‐assisted synthesis method, and used in the solid‐phase extraction of three phenolic compounds (phenol, 4‐nitrophenol, and m‐methylphenol) in environmental water samples. Various instrumental methods were employed to characterize the magnetic nanoparticles modified with graphene oxide. The influence of experimental parameters, such as desorption conditions, amount of adsorbent, extraction time, and pH, on the extraction efficiency was investigated. Owing to the high surface area and excellent adsorption capacity of the prepared material, satisfactory extraction was achieved. Under optimum conditions, a linear response was observed in the concentration range of 1.000–100.0 μg/L for phenol, 0.996–99.6 μg/L for 4‐nitrophenol, and 0.975–97.5 μg/L for m‐methylphenol, with correlation coefficients in the range of 0.9995–0.9997. The limit of detection (signal‐to‐noise ratio of 3) of the method varied between 0.5 and 0.8 μg/L. The relative standard deviations were <5.2%. The recovery percentages of the method were in the range of 89.1–104.3%. The results indicate that the graphene oxide‐modified magnetic nanoparticles possess high adsorptive abilities toward phenolic compounds in environmental water samples.     

Facile synthesis of poly(ionic liquid)‐bonded magnetic nanospheres as a high‐performance sorbent for the pretreatment and determination of phenolic compounds in water samples

Poly(ionic liquid)‐bonded magnetic nanospheres were easily synthesized and applied to the pretreatment and determination of phenolic compounds in water samples, which have detrimental effects on water quality and the health of living beings. The high affinity of poly(ionic liquid)s toward the target compounds as well as the magnetic behavior of Fe₃O₄ were combined in this material to provide an efficient and simple magnetic solid‐phase extraction approach. The adsorption behavior of the poly(ionic liquid)‐bonded magnetic nanospheres was examined to optimize the synthesis. Different parameters affecting the magnetic solid‐phase extraction of phenolic compounds were assessed in terms of adsorption and recovery. Under the optimal conditions, the proposed method showed excellent detection sensitivity with limits of detection in the range of 0.3–0.8 ng/mL and precision in the range of 1.2–3.3%. This method was also applied successfully to the analysis of real water samples; good spiked recoveries over the range of 82.5–99.2% were obtained.     

Surface modified‐magnetic nanoparticles by molecular imprinting for the dispersive solid‐phase extraction of triazines from environmental waters

Magnetic nanoparticles have been surface modified by molecular imprinting and evaluated as selective sorbents for the extraction of triazines from environmental waters. The use of propazine as template allowed us to synthesize a selective material able to simultaneously recognize and selective extract not only the template but also several other herbicides of the same family. A magnetic molecularly imprinted‐based dispersive solid‐phase extraction procedure was developed and fully optimized. Magnetic molecularly imprinted polymer particles can be easily collected and separated from liquid solvents and samples with the help of an external magnetic field, avoiding in that way any centrifugation or filtration steps, which represents a remarkable advantage over traditional procedures. Under optimum conditions, selective extraction of several triazines (cyanazine, simazine, atrazine, propazine, and terbutylazine) from environmental water samples was performed prior to final determination by high‐performance liquid chromatography with diode‐array detection. Recoveries for the studied triazines were within the range of 75.2–94.1%, with relative standard deviations lower than 11.3% (n = 3). The limits of detection were within 0.16–0.51 µg/L, depending upon the triazine and the type of sample analyzed.     

Application of zein‐modified magnetite nanoparticles in dispersive magnetic micro‐solid‐phase extraction of synthetic food dyes in foodstuffs

A simple method for the simultaneous and trace analysis of four synthetic food azo dyes including carmoisine, ponceau 4R, sunset yellow, and allura red from some foodstuff samples was developed by combining dispersive μ‐solid‐phase extraction and high‐performance liquid chromatography with diode array detection. Zein‐modified magnetic Fe₃O₄ nanoparticles were prepared and used for μ‐solid‐phase extraction of trace amounts of mentioned food dyes. The prepared modified magnetic nanoparticles were characterized by scanning electron microscopy and FTIR spectroscopy. The factors affecting the extraction of the target analytes such as pH, amount of sorbent, extraction time, type and volume of the desorption eluent, and desorption time were investigated. Under the optimized conditions, the method provided good repeatability with relative standard deviations lower than 5.8% (n = 9). Limit of detection values ranged between 0.3 and 0.9 ng/mL with relatively high enrichment factors (224–441). Comparing the obtained results indicated that Fe₃O₄ nanoparticles modified by zein biopolymer show better analytical application than bare magnetic nanoparticles. The proposed method was also applied for the determination of target synthetic food dyes in foodstuff samples such as carbonated beverage, snack, and candy samples.     

Loading controlled magnetic carbon dots for microwave‐assisted solid‐phase extraction: Preparation,extraction evaluation and applications in environmental aqueous samples

An adsorbent of carbon dot@poly(glycidyl methacrylate)@Fe₃O₄ nanoparticles has been developed for the microwave‐assisted magnetic solid‐phase extraction of polycyclic aromatic hydrocarbons in environmental aqueous samples prior to high‐performance liquid chromatography with UV/visible spectroscopy detection. Poly(glycidyl methacrylate) was synthesized by atom transfer radical polymerization. The chain length and amount of carbon dots attached on them can be easily controlled through changing polymerization conditions, which contributes to tunable extraction performance. The successful fabrication of the nano‐adsorbent was confirmed by transmission electronic microscopy, Fourier transform infrared spectroscopy, Raman spectroscopy and vibrating sample magnetometry. The extraction performance of the adsorbent was evaluated by using polycyclic aromatic hydrocarbons as model analytes. The key factors influencing the extraction, such as microwave power, adsorption time, desorption time and desorption solvents were investigated in detail. Under the optimal conditions, the microwave‐assisted method afforded magnetic solid‐phase extraction with short extraction time, wide dynamic linear range (0.02–200 μg/L), good linearity (R² ≥ 98.57%) and low detection limits (20–90 ng/L) for model analytes. The adsorbent was successfully applied for analyzing polycyclic aromatic hydrocarbons in environmental aqueous samples and the recoveries were in the range of 86.0–124.2%. Thus, the proposed method is a promising candidate for fast and reliable preconcentration of trace polycyclic aromatic hydrocarbons in real water samples.     

Magnetic dispersive solid‐phase extraction based on modified magnetic nanoparticles for the detection of cocaine and cocaine metabolites in human urine by high‐performance liquid chromatography–mass spectrometry

An easy‐to‐handle magnetic dispersive solid‐phase extraction procedure was developed for preconcentration and extraction of cocaine and cocaine metabolites in human urine. Divinyl benzene and vinyl pyrrolidone functionalized silanized Fe₃O₄ nanoparticles were synthesized and used as adsorbents in this procedure. Scanning electron microscopy, vibrating sample magnetometry, and infrared spectroscopy were employed to characterize the modified adsorbents. A high‐performance liquid chromatography with mass spectrometry method for determination of cocaine and its metabolites in human urine sample has been developed with pretreatment of the samples by magnetic dispersive solid‐phase extraction. The obtained results demonstrated the higher extraction capacity of the prepared nanoparticles with recoveries between 75.1 to 105.7% and correlation coefficients higher than 0.9971. The limits of detection for the cocaine and cocaine metabolites were 0.09–1.10 ng/mL. The proposed magnetic dispersive solid‐phase extraction method provided a rapid, environmentally friendly and magnetic stuff recyclable approach and it was confirmed that the prepared adsorbents material was a kind of highly effective extraction materials for the trace cocaine and cocaine metabolites analyses in human urine.     

Graphene oxide decorated with silver nanoparticles as a coating on a stainless‐steel fiber for solid‐phase microextraction

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%.     

Preparation of novel ionic‐liquid‐modified magnetic nanoparticles by a microwave‐assisted method for sulfonylurea herbicides extraction

Ionic liquids immobilized on magnetic nanoparticles were prepared by an efficient microwave‐assisted synthesis method, and the properties of the ionic liquids were tuned based on the aromatic functional modification of its anion through a simple metathesis reaction. The novel as‐synthesized magnetic materials were characterized by various instrumental techniques. The magnetic nanoparticles have been utilized as adsorbents for the extraction of four sulfonylurea herbicides in tea samples, in combination with high‐performance liquid chromatography analysis. Significant extraction parameters, including type and volume of desorption solvent, extraction time, amount of adsorbent, and ionic strength were investigated. Under the optimum conditions, good linearity was obtained in the concentration range of 1–150 μg/L for metsulfuron‐methyl and bensulfuron‐methyl, and 3–150 μg/L for sulfometuron‐methyl and chlorimuron‐ethyl, with correlation coefficients R² > 0.9987. Low limits of detection were obtained ranging from 0.13 to 0.81 μg/L. The relative standard deviations were 1.8–3.9%. Comparisons of extraction efficiency with conventional solid‐phase extraction equipped with a commercial C₁₈ cartridge were performed. Results indicated that magnetic solid‐phase extraction is simple, time‐saving, efficient and inexpensive with the reusability of adsorbents. The proposed method has been successfully used to determine sulfonylurea herbicides from tea samples with satisfactory recoveries of 80.5–104.2%.     

Microwave‐assisted extraction and high‐throughput monolithic‐polymer‐based micro‐solid‐phase extraction of organophosphorus,triazole, and organochlorine residues in apple

A high‐throughput micro‐solid‐phase extraction device based on a 96‐well plate was constructed and applied to the determination of pesticide residues in various apple samples. Butyl methacrylate and ethylene glycol dimethacrylate were copolymerized as a monolithic polymer and placed in the cylindrically shaped stainless‐steel meshes of 96‐micro‐solid‐phase extraction device and used as an extracting unit. Before the micro‐solid‐phase extraction, microwave‐assisted extraction was employed to facilitate the transfer of the pesticide residues from the apple matrix to liquid media. Then, 1 mL of the aquatic samples was transferred into the 96‐well plate and the 96‐micro‐solid‐phase extraction device was applied for the extraction of the selected pesticides. Influential parameters, such as sorbent‐to‐sorbent reproducibility, microwave‐assisted extraction time, ionic strength and micro‐solid‐phase extraction time, were optimized. The limits of quantitation were below 120 μg/kg, which are lower than the maximum residue limits. The developed method was successfully implemented for the extraction and determination of the selected pesticides from 20 different apple samples gathered from local markets. Phosalone was identified and quantified at the concentration level of 147 (±16.4) μg/kg in one of the samples.     

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

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

Rapid preparation of molecularly imprinted polymers by custom‐made microwave heating for analysis of atrazine in water

The rapid preparation of an atrazine‐imprinted polymer in a cost‐effective custom‐made microwave reactor was demonstrated. The polymerization reaction was accelerated by microwave heating, and the preparation time was greatly shortened (to 1 h). The resulting polymer was successfully applied as solid‐phase extraction adsorbent for the selective extraction and preconcentration of atrazine in environmental water samples. The binding capacity of the polymer was 1.11 mg/g polymer. The polymer provided selectivity with higher recovery of atrazine than of other interfering related contaminants. The proposed method had good limits of detection and quantitation at 0.20 and 0.60 ng/mL, respectively. The recoveries were from 83 to 89% at two spiking levels, with relative standard deviations less than 5%. This method was successfully applied to determine the atrazine levels in environmental water samples.     

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.     

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

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

Simple magnetization of Fe3O4/MIL‐53(Al)‐NH2 for a rapid vortex‐assisted dispersive magnetic solid‐phase extraction of phenol residues in water samples

The present work describes a simple route to magnetize MIL‐53(Al)‐NH₂ sorbent for rapid extraction of phenol residues from environmental samples. To extend the applications and performances of the metal‐organic frameworks in the field of adsorption materials, we combined the properties of metal‐organic frameworks and magnetite to decrease the extraction time and simplify the extraction process as well. In this study, a simple and quick vortex‐assisted dispersive magnetic solid phase extraction method for the extraction of ten United States Environmental Protection Agency's priority phenols from water samples prior to analysis by high‐performance liquid chromatography with photodiode array detection was proposed. The developed method exhibits a rapid enrichment of the target analytes within 10 s for extraction and 10 s for desorption. Low detection limits of 1.8‐41.7 µg/L and quantitation limits of 6.0‐139.0 µg/L with the relative standard deviations for intra‐ and interday analyses less than 12% were achieved. Satisfactory recoveries in the range of 80‐111% with the relative standard deviations less than 11% demonstrated that Fe₃O₄/MIL‐53(Al)‐NH₂ is promising sorbent in the field of magnetic solid‐phase extraction for environmental samples.