Magnetic solid-phase extraction based on magnetic carbon nanotube for the determination of estrogens in milk

Membrane-protected magnetic covalent organic framework for efficient extraction of estrogens in dairy products

The presence of estrogens residues in dairy products is a growing concern due to their potential health risk. Herein, in this study, we have developed a membrane-protected magnetic solid-phase extraction (MP-MSPE) method that utilized a magnetic adsorbent (Fe3O4@COF-LZU1) with in-situ growth for the efficient extraction of estrone (E1), 17β-estradiol (E2), and estriol (E3). When combined with HPLC-FLD, this method allows for the efficient detection of estrogens in dairy products. The stability of the MP-MSPE was improved by the presence of a dialysis membrane, which remained a high extraction efficiency (90 %) even after ten reuse cycles. The hydrogen bonding, π-π interactions and pore size effect contribute to the excellent adsorption of three estrogens onto Fe3O4@COF-LZU1. Under optimal conditions, the method exhibits a low detection limit (0.01-0.15 μg L-1), wide linear range (0.1-800 μg L-1), and favorable recoveries (77.3 %-109.4 %) at three concentration levels (10, 50 and 100 μg L-1). This proposed method is characterized by its simplicity, high efficiency and eco-friendliness, making it a promising approach for extracting estrogens from dairy products.

Magnetic phytic acid-modified kapok fiber biochar as a novel sorbent for magnetic solid-phase extraction of antidepressants in biofluids

BACKGROUND

Therapeutic drug monitoring (TDM) of antidepressants is essential for monitoring patient medication to avoid drug toxicity, complications, or nonadherence. Chromatographic techniques with high sensitivity and reproducibility are the main detection method for antidepressants. Effective pretreatment of biological sample processes is necessary prior to instrumental analysis. Magnetic solid-phase extraction (MSPE) has received much attention for its advantages of simple operation, rapidity, cost-effectiveness and low organic solvent consumption. Therefore, the development of a suitable and green magnetic sorbent for the detection of antidepressants in plasma and urine is apparently necessary. (88) RESULTS: A magnetic phytic acid-modified kapok fiber biochar sorbent (Fe3O4/PAKFBC) was successfully synthesized by pyrolytic impregnation and physical milling methods. Fe3O4/PAKFBC exhibited a large specific surface area (214 m2 g-1) and a rich pore structure (5-10 nm). The extraction equilibrium, using 10 mg Fe3O4/PAKFBC, can be completed in about 1 min. The density functional theory (DFT) results showed that the adsorption mechanism of Fe3O4/PAKFBC on the six antidepressants mainly included electrostatic interactions, van der Waals interactions, π-π interactions and weak hydrogen bonding. Examination using the greenness assessment tools showed that the developed method exhibited excellent greenness. By combining with liquid chromatography-ultraviolet (LC-UV), a quantitative method with good linearity (R2 > 0.993) and relative recoveries (92.4-107.7%) and negligible matrix effect (-11.5-6.0%) was developed. The Fe3O4/PAKFBC successfully detected six antidepressants in plasma and urine samples, requiring no pH adjustment with buffer salts. (142) SIGNIFICANCE: The environmental sustainability of the proposed methods was affirmed by six greenness evaluation tools, all indicating exceptional eco-friendliness. The Fe3O4/PAKFBC demonstrated outstanding greenness in both its creation and analytical application, proving highly effective in real sample applications and showcasing potential for broader use. This study contributes to a deeper and broader understanding of the microscopic adsorption mechanism, which can help in the optimization and development of more green sorbents. (69).

Preparation of COPs Mixed Matrix Membrane for Sensitive Determination of Six Sulfonamides in Human Urine

In this study, TpDMB-COPs, a specific class of covalent organic polymers (COPs), was synthesized using Schiff-base chemistry and incorporated into a polyvinylidene fluoride (PVDF) polymer for the first time to prepare COPs mixed matrix membranes (TpDMB-COPs-MMM). A membrane solid-phase extraction (ME) method based on the TpDMB-COPs-MMM was developed to extract trace levels of six sulfonamides from human urine identified by high-performance liquid chromatography (HPLC). The key factors affecting the extraction efficiency were investigated. Under the optimum conditions, the proposed method demonstrated an excellent linear relationship in the range of 3.5-25 ng/mL (r2 ≥ 0.9991), with the low limits of detection (LOD) between 1.25 ng/mL and 2.50 ng/mL and the limit of quantification (LOQ) between 3.50 ng/mL and 7.00 ng/mL. Intra-day and inter-day accuracies were below 5.0%. The method's accuracy was assessed by recovery experiments using human urine spiked at three levels (7-14 ng/mL, 10-15 ng/mL, and 16-20 ng/mL). The recoveries ranged from 87.4 to 112.2% with relative standard deviations (RSD) ≤ 8.7%, confirming the applicability of the proposed method. The developed ME method based on TpDMB-COPs-MMM offered advantages, including simple operation, superior extraction affinity, excellent recycling performance, and easy removal and separation from the solution. The prepared TpDMB-COPs-MMM was demonstrated to be a promising adsorbent for ME in the pre-concentration of trace organic compounds from complex matrices, expanding the application of COPs and providing references for other porous materials in sample pre-treatment.

Application of magnetic carbon nanotube composite nanospheres in magnetic solid-phase extraction of trace perfluoroalkyl substances from environmental water samples

The layer-by-layer assembly technique was used to synthesize novel multiwalled carbon nanotubes (MWCNTs) on magnetic carbon (Fe₃O₄@C) nanospheres, which were then used to extract six perfluoroalkyl substances (PFAS) in environmental real water samples using ultra high-performance liquid chromatography coupled to tandem mass spectrometry. The as-synthesized sorbent MWCNTs@Fe₃O₄@C was employed for magnetic solid-phase extraction (MSPE). The as-prepared MWCNTs@Fe₃O₄@C was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and vibrating sample magnetometer (VSM). The main extraction parameters were systematically optimized by Box-Behnken design. Under optimal conditions, excellent results were achieved. The synthesized sorbent showed wide linear ranges (0.1-1000 ng L^-1), low detection limits (0.03-0.09 ng L^-1) and good repeatability (3.80%-9.52%) for extracting and detecting six PFAS. The developed method was also applied to analyze six PFAS from environmental water samples. This study indicated that MWCNTs@Fe₃O₄@C composites are promising materials for the extraction and determination of PFAS from water samples.

[Analysis of parabens in environmental water samples by covalent organic framework-based magnetic solid-phase extraction-high performance liquid chromatography]

Parabens are a class of antimicrobial preservatives that are widely used in cosmetics, pharmaceuticals, and food products because of their ease of production, antimicrobial effect, and low price. The widespread use of these parabens, poses potential risks to human health. Therefore, it is necessary to establish a simple and rapid method for the detection of parabens. The large number of substrate interferences in complex samples is an important factor affecting the sensitivity of analytical methods. Magnetic solid-phase extraction (MSPE) has received much attention because of its advantages of easy operation, short extraction time, small sample amount, low cost, and environmental friendliness. Covalent organic frameworks (COFs) with high crystallinity, high specific surface area, adjustable pore size, regular porosity, as well as high chemical and thermal stability are now widely used in separation and analysis. Therefore, a sample pretreatment method combining MSPE and COF for the analysis of parabens in complex matrices is very promising. A magnetic covalent organic framework, Fe₃O₄@TbBd, was successfully synthesized by the Schiff base reaction of 1,3,5-triformylbenzene (Tb) and benzidine (Bd) at room temperature using Fe₃O₄ nanoparticles as magnetic cores. Characterization by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), X-ray diffraction (XRD), vibrating sample magnetometer (VSM) measurements, etc. revealed that the magnetic COF has high magnetic responsiveness, as well as good thermal and chemical stability, which make it an ideal adsorbent for the MSPE of parabens. Some factors related to the extraction efficiency, including the amount of adsorbent, extraction time, pH, desorption solvent, desorption time, and number of desorption were systematically investigated. A method involving MSPE and high performance liquid chromatography-ultraviolet detection (HPLC-UV) based on the Fe₃O₄@TbBd was developed for the determination of four parabens (ethylparaben, propylparaben, butylparaben, and benzylparaben) in environmental water samples. Under the optimal extraction conditions, the method showed good linearities. The limits of detection and limits of quantification were 0.2-0.4 μg/L and 0.7-1.4 μg/L for the four analytes, respectively. The recoveries at three spiked levels were in the range of 86.1%-110.8% with intra-day and inter-day RSDs of less than 5.5% and 4.9%, respectively. The method was successfully applied to the determination of parabens in East Lake water, Yangtze water, and domestic wastewater. Ethyl paraben and propyl paraben were detected in domestic wastewater at the levels of 1.8 μg/L and 0.4 μg/L, respectively. The recoveries of the parabens at different spiked levels ranged from 80.7% to 117.5%, with RSDs of 0.2%-8.8%. The method has good potential for the determination of parabens in environmental water samples because of its operational simplicity, short extraction time, high sensitivity, and environmental friendliness.

Sulfide-Doped Magnetic Carbon Nanotubes Developed as Adsorbent for Uptake of Tetracycline and Cefixime from Wastewater

In this study, a magnetic solid-phase extraction method was developed based on multi-wall carbon nanotubes decorated by magnetic nanoparticles (Fe₃O₄) and cadmium sulfide nanoparticles (Fe₃O₄@MWCNT-CdS) for trace extraction of cefixime and tetracycline antibiotics from urine and drug company wastewater. The adsorbent features were characterized by Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscope (FESEM), and energy dispersive X-ray analysis (EDX). Various effective parameters on the sorption and desorption cycle, such as sorption time, the mass of adsorbent, pH, salt addition, and material ratio, were investigated and optimized. The data were evaluated using isotherm models, and experimental data were well-fitted to both Langmuir (R² = 0.975) and Freundlich (R² = 0.985) models. Moreover, kinetic of reaction was agreement with pseudo-second-order (R² = 0.999) as compared pseudo-first-order (R² = 0.760). The maximum adsorption capacity for tetracycline and cefixime was achieved at 116.27 and 105.26 mg·g^-1, respectively. Hence, the prepared adsorbent can be used as an alternative material for enhanced determination of pharmaceutical substances in biological fluids.

A new core–shell magnetic mesoporous surface molecularly imprinted composite and its application as an MSPE sorbent for determination of phthalate esters

In this study, a new core–shell magnetic mesoporous surface molecularly imprinted polymer (Fe₃O₄@SiO₂@mSiO₂-MIPs) which has specific adsorption and rapid adsorption rate for phthalate esters (PAEs) was prepared by a convenient method. Based on this composite as a magnetic solid phase extraction (MSPE) material, a rapid, efficient and sensitive matrix dispersion magnetic solid-phase extraction gas chromatography-mass spectrometry method (DMSPE-GC/MS) was developed for the determination of PAEs in multiple liquid samples. It is the first time that Fe₃O₄@SiO₂@mSiO₂-MIPs have been prepared by bonding amino groups on the surface of a double layer silicon substrate with diisononyl phthalate (DINP) as virtual template and 3-(2-aminoethyl)-aminopropyl trimethoxymethylsilane (TSD) as functional monomer. FT-IR, TEM, EDS, SEM, XRD, BET and VSM were used to characterize the composite. The adsorption isotherm and kinetics of Fe₃O₄@SiO₂@mSiO₂-MIPs showed that it possessed fast adsorption rates (approximately 5 min to reach equilibrium), high adsorption capacities (523.9 mg g⁻¹) and good recognition of PAEs. The real samples were preconcentrated by Fe₃O₄@SiO₂@mSiO₂-MIPs, under the optimum DMSPE-GC/MS conditions. Validation experiments showed that the method presented good linearity (R² > 0.9971), satisfactory precision (RSD < 5.7%) and high recovery (92.1–105.8%), and the limits of detection ranged from 1.17 ng L⁻¹ to 3.03 ng L⁻¹. The results indicated that the novel method had good sensitivity, high efficiency and wide sample application and was suitable for the determination of PAEs in liquid drink samples such as water, alcohol, beverages and so on.

A new core–shell magnetic mesoporous surface molecularly imprinted polymer (Fe3O4@SiO2@mSiO2-MIPs) which has specific adsorption for phthalate esters was synthesized by a facile and convenient method.

The Power of Carbon Nanotubes on Sensitive Drug Determination Methods

Nowadays, carbon nanotubes (CNTs) due to their inorganic conducting, semiconducting, and organic π-π stacking properties are becoming innovative materials. CNTs have an adjustable size, large surface area, and other significant chemical properties. Due to their excellent electrical, optical, and mechanical properties, CNTs play an important role in various application fields. In the past decade, many unique intrinsic physical and chemical properties have been intensively explored for pharmaceutical, biological, and biomedical applications. The functionalization of CNTs results in a remarkably reduced cytotoxicity and at the same time increased biocompatibility. The toxicity studies reveal that highly water-soluble and serum stable nanotubes are biocompatible, nontoxic, and potentially useful for biomedical applications. Ultrasensitive drug determination from its dosage form and/or biological samples with carbon nanotubes can be realized after surface modification. The main purpose of this review is to present recent achievements on CNTs which are investigated in electrochemical and chromatographically sensing technologies.

Magnetic nanomaterials as sorbents for trace elements analysis in environmental and biological samples

This review focuses on magnetic nanomaterials as sorbents for trace elements analysis in environmental and biological samples. The design and preparation of magnetic nanomaterials with specific functional groups for trace elemental analysis are summarized, along with relevant adsorption mechanism. The application of these magnetic sorbents in different operation modes for the quantification of trace elements and their species in environmental and biological samples are discussed. The trend of development in this field is also prospected.

Nanoplatform-Integrated Miniaturized Solid-Phase Extraction Techniques: A Critical Review

Preparation of the biological samples is one of the most critical steps in sample analysis. In past decades, the liquid-liquid extraction technique has been used to extract the desired analytes from complex biological matrices. However, solid-phase extraction (SPE) gained popularity due to versatility, simplicity, selectivity, reproducibility, high sample recovery %, solvent economy, and time-saving nature. The superior extraction efficiency of SPE can be attributed to the development of advanced techniques, including the nanosorbents technology. The nanosorbent technology significantly simplified the sample preparation, improved the selectivity, diversified the application, and accelerated the sample analysis. This review critically expands on the to-date advancements reported in SPE with particular regards to the nanosorbent technology.

High-Coverage Screening of Sulfonamide Metabolites in Goat Milk by Magnetic Doped S Graphene Combined with Ultrahigh-Performance Liquid Chromatography-High-Resolution Mass Spectrometry

Currently, there are more than 1000 varieties of synthetic sulfonamides universally used as antibiotics causing severe results of potential carcinogenicity and drug resistance for human health due to excessive residue of animal-derived food. A facile and novel approach for untargeted screening of sulfonamides (SAs) and metabolites was proposed based on magnetic solid-phase extraction-ultrahigh-performance liquid chromatography-tandem high-resolution mass spectrometry (MSPE-UHPLC-HRMS). Compared with QuEChERS without the clean-up procedure and SPE in terms of matrix effect and absolute recovery, magnetic doped S graphene (S-doping level: 2.82%) synthesized via a solid-state microwave approach and the aggregation wrap mechanism was used as a novel adsorbent for nonspecific extraction of desired analytes by the noncovalent interaction between electron-deficient thiophene sulfur and electron donors such as amino or amide as well as π-π stacking interactions. Combined with variable data-independent acquisition, characteristic fragment-ion filtering (m/z 156.01138 or m/z 108.04439) and assignment of extracted-ion chromatograms of marked fragment ions were successfully utilized to screen the desired analytes and subsequently confirmed with the availability of reference standards. The optimized and validated approach for spiked 26 SAs and 9 metabolites in control goat milk demonstrated satisfactory accuracy (80.1-112.6%) and precision (RSDs < 6.4%) for matrix-matched standard addition. After applying suspect goat milk samples, untargeted SA analytes including sulfanilamide or an N⁴-acetylsulfamethazine metabolite with concentration ranging from 66.3 to 398.5 ng L^-1 were determined in 5 of 45 goat milk samples.

Application of magnetic nanomaterials in bioanalysis

The importance of magnetic nanomaterials and magnetic hybrid materials, which are classified as new generation materials, in analytical applications is increasingly understood, and research on the adaptation of these materials to analytical methods has gained momentum. Development of sample preparation techniques and sensor systems using magnetic nanomaterials for the analysis of inorganic, organic and biomolecules in biological samples, which are among the samples that analytical chemists work on most, are among the priority issues. Therefore in this review, we focused on the use of magnetic nanomaterials for the bioanalytical applications including inorganic and organic species and biomolecules in different biological samples such as primarily blood, serum, plasma, tissue extracts, urine and milk. We summarized recent progresses, prevailing techniques, applied formats, and future trends in sample preparation-analysis methods and sensors based on magnetic nanomaterials (Mag-NMs). First, we provided a brief introduction of magnetic nanomaterials, especially their magnetic properties that can be utilized for bioanalytical applications. Second, we discussed the synthesis of these Mag-NMs. Third, we reviewed recent advances in bioanalytical applications of the Mag-NMs in different formats. Finally, recently literature studies on the relevance of Mag-NMs for bioanalysis applications were presented.

Magnetic hydrophobic solids prepared from Pickering emulsions for the extraction of polycyclic aromatic hydrocarbons from chamomile tea

Two types of magnetic hydrophobic solids were prepared by Pickering emulsion photopolymerization using polystyrene-modified magnetic nanoparticles (PS-MNPs) as emulsion stabilizers. Additionally, PS-MNPs provided magnetic character to the final solids. W/O Pickering emulsions were produced with high amounts of oily phase (above 50 wt%), while O/W Pickering emulsions were formed with higher amounts of aqueous phase (above 60 wt%). These two types of emulsions led to two kind of solids with very different structures despite being formed by the same components. In this way, W/O Pickering emulsions produced monolithic solids, while O/W Pickering emulsions formed magnetic microparticles. Multi-walled carbon nanotubes (MWCNTs) were also added to the emulsions to provide higher hydrophobic character to the final solids. The structure and morphology of both magnetic solids containing the MWCNTs was characterized by scanning electron microscopy (SEM). Finally, their extraction efficiency was evaluated using polycyclic aromatic hydrocarbons (PAHs) as target analytes, both qualitatively (visually by the fluorescence emitted before and after the extraction) and quantitatively (using gas chromatography coupled to mass spectrometry). Therefore, the LODs ranged from 1 to 4 μg L^-1 and the LOQs were between 3 and 12 μg L^-1. The reproducibility of the extraction procedure with different batches of emulsions was acceptable with RSD values <13%. Finally, a recovery study was carried out in complex matrices such as chamomile tea, obtaining excellent recovery values which ranged from 99 to 108%.

Fabric Phase Sorptive Extraction of Selected Steroid Hormone Residues in Commercial Raw Milk Followed by Ultra-High-Performance Liquid Chromatography-Tandem Mass Spectrometry

Hormones in edible matrices, such as milk, are a subject of concern because of their adverse effects on the endocrine system and cell signaling and the consequent disruption of homeostasis in human consumers. Therefore, the assessment of the presence of hormones in milk as potential endocrine-disrupting compounds is warranted. However, the complexity of milk as a sample matrix and the ultra-low concentration of hormones pose significant analytical challenges. Fabric phase sorptive extraction (FPSE) has emerged as a powerful analytical technique for the extraction of emerging pollutants from complex aqueous matrices. FPSE allows for substantially simplified sample handling and short extraction and desorption times, as well as the decreased use of organic solvents. It is considered a green alternative to traditional extraction methodologies. In this work, the FPSE technique was evaluated to perform the simultaneous extraction of 15 steroid hormones from raw milk without employing any sample pretreatment steps. Clean and preconcentrated hormone solutions obtained from FPSE of raw milk were analyzed using ultra-high-performance liquid chromatography–tandem mass spectrometry to achieve low detection limits, which ranged from 0.047 to 1.242 ng·mL⁻¹. Because of the presence of many interferents in milk, such as proteins, lipids, and sugar, the effect of fat content on the extraction procedure was also thoroughly studied. Additionally, for the first time, the effect of lactose on the extraction of steroid hormones was evaluated, and the results showed that the extraction efficiencies were enhanced in lactose-free samples. Finally, the optimized methodology was applied to commercial samples of cow and goat milk, and no measurable concentrations of the studied hormones were detected in these samples.

Magnetic Solid-Phase Extraction of Drugs and Pesticides from Human Plasma Using COOH-mMWCNTs

Carbon nanotubes (CNTs) are useful for extracting chemical compounds due to their properties, such as surface area and the potential for chemical modification. Especially the formation of CNTs with carboxylic acid functional group makes them disperse in water-based samples and have strong interaction forces with cationizable analytes. Based on these features, carboxylic acid functionalized multi-walled CNTs (COOH-MWCNTs) have been used as extraction sorbents. CNT can also be gathered using an external magnet by forming complex with iron oxide (Fe3O4) magnetic nanoparticles (MNPs). In this study, COOH-MWCNTs with MNPs were subjected to magnetic solid-phase extraction (mSPE) in order to extract the targeted substances such as diphenhydramine, doxylamine, tramadol, escitalopram, zolpidem, diphenamid, paclobutrazol, hexaconazole, cyproconazole and mepronil from human plasma samples. The following five factors were optimized: (i) the ratio of COOH-MWCNTs to MNPs as a sorbent from 1:1 to 1:4; (ii) sorbent amount starting from 12.5 to 75%; (iii) sample pH tested pH 2 to pH 10 with 1 N hydrochloride and 1 N sodium hydroxide; (iv) agitating time from 0 to 4 min and (v) elution solvent. Limit of detection of 10 targeted substances in human plasma were in the range of 0.1-0.4 mg/L. The recovery of targeted substances (except diphenamid) in human plasma was 73.06-110.28% for intra-day and 83.00-107.70% for inter-day and the precision (relative standard deviation, %) in human plasma was 0.3-13.3% for intra-day and 2.9-15.6% for inter-day. The method was applied to nine authentic biological samples from overdose patients in the emergency room of Chungnam National University Hospital. The performance of mSPE was compared with the liquid-liquid extraction method using ethyl acetate. The results showed that the newly developed method in this study can be used for screening analysis in forensic and clinical toxicology.

Multi-Walled Carbon Nanotubes for Magnetic Solid-Phase Extraction of Six Heterocyclic Pesticides in Environmental Water Samples Followed by HPLC-DAD Determination

Magnetic multi-walled carbon nanotubes were prepared as magnetic solid-phase extraction (MSPE) adsorbent for the enrichment of six heterocyclic pesticides in environmental water samples, including imidacloprid, triadimefon, fipronil, flusilazole, chlorfenapyr and fenpyroximate. Then six heterocyclic pesticides were separated and determined by high-performance liquid chromatography-diode-array detector (HPLC-DAD). Major factors influencing MSPE efficiency, including the dose of mag-multi-walled carbon nanotubes (mag-MWCNTs), extraction time, solution pH, salt concentration, type and volume of eluent and desorption time were investigated. Under the optimized conditions, the enrichment factor of the method reached to 250. The linearity was achieved within 0.05–10.0 μg/L for imidacloprid and chlorfenapyr, 0.10–10.0 μg/L for fipronil, flusilazole, triadimefon and fenpyroximate. Limits of detection were in the range of 0.01–0.03 μg/L. Good precision at three spiked levels were 1.1–11.2% (intra-day) and 1.7–11.0% (inter-day) with relative standard deviation of peak area, respectively. The developed method was utilized to analyze tap water, river water and reservoir water samples and recoveries at three spiked concentration levels ranged from 72.2% to 107.5%. The method was proved to be a convenient, rapid and practical method for sensitive determination of heterocyclic pesticides.

Application of aqueous two-phase system for selective extraction and clean-up of emerging contaminants from aqueous matrices

This review approaches how aqueous two-phase systems (ATPS), in their various compositions (e.g., polymer + salt, copolymer + salt, ionic liquid + salt, acetonitrile + salt), can be efficiently used for extraction, preconcentration, and clean-up of analytes in aqueous samples to determine the compounds classified as emerging contaminants (ECs). In the literature, there are some studies using ATPS applied to ECs, like pesticides, pharmaceuticals, illicit drugs, personal care products, alkaloids, and hormones, even when in trace concentrations. The ATPS is an alternative to the conventional liquid-liquid extraction technique. However, it is predominantly composed of water and do not generally use organic solvents and, therefore, is based on the principles of green chemistry. An ATPS approach has a unique advantage because it can extract neutral, anionic, cationic, polar, and nonpolar compounds, even when present simultaneously in the same sample. This review covers how this simple and low environmental impact technique has been employed for the analysis of different classes of emerging contaminants.

A functionalized carbon nanotube nanohybrids-based QuEChERS method for detection of pesticide residues in vegetables and fruits

A self-separating, analyte-compatible, and efficient clean-up method for QuEChERS extracts was designed and developed based on dispersive solid-phase extraction using a branched polyethylenimine and nanoscale CaSO₄ functionalized carboxylated multi-walled carbon nanotubes (MWCNTs) nanohybrids as sorbent. The feasibility of using a self-separating strategy based on the functionalization of sorbent in a purification procedure was analyzed for the first time in this study. Compared to the traditional QuEChERS method, the proposed method is rapid and convenient without centrifugation of numerous samples in the clean-up process. The use of nanohybrids overcame the issue of low recoveries for planar pesticides, which are easily adsorbed using MWCNTs. A better clean-up capability of the nanohybrids to remove matrix interferences and reduce matrix effect was demonstrated compared with that of traditional clean-up sorbent primary secondary amine. The method was validated by determining twenty-eight pesticides in cucumber, cabbage, apple, and orange. Limits of detections were in the range of 0.0001-0.0026 mg/kg. Spike recoveries of pesticides were within 75.3 - 113.6%, with relative standard deviations less than 14.3% at levels 0.01 mg/kg and 0.1 mg/kg. The developed method was successfully applied to monitor the multi-residues.

Effect of Heavy Metal Ions on Steroid Estrogen Removal and Transport in SAT Using DLLME as a Detection Method of Steroid Estrogen

Environmental endocrine-disrupting chemicals have become a global environmental problem, and the distribution, transport, and fate of estrogens in soil and water environments closely relate to human and ecological health as well as to the remediation scheme design. A new micro-extraction technique termed dispersive liquid–liquid micro-extraction (DLLME) combined with high-performance liquid chromatography with fluorescence detector (HPLC-FLD) was developed for the determination of the concentration of steroid estrogens in water samples. The detection limits of HPLC-FLD and DLLME-HPLC/FLD were 0.68–1.73 μg L−1 and 7.16–69.22 ng L−1, respectively. Based on this method, the isothermal adsorption of 17β-E2 on sand and a breakthrough experiment of 17β-E2 and Cu2+ in a soil aquifer treatment (SAT) system were studied. The 17β-E2 adsorption capacity of sand in 17β-E2 solution was detected to be larger than that in a mixed solution of 17β-E2 and Cu(NO3)2 solution, and the breakthrough curves of 17β-E2 and Cu2+ in the mixed solution shifted forward in sand column experiments. Both suggested that the competitive adsorption of 17β-E2 and Cu2+ in the mixed solution might occur on the surface of the sand. In the process of the removal of 17β-E2 in wastewater by SAT, the existence of Cu2+ slightly inhibited the adsorption of 17β-E2 and accelerated the breakthrough of 17β-E2. These results ought to be a warning for SAT application for 17β-E2 removal in water where heavy metals coexist.

Magnetic solid-phase extraction method for extraction of some pesticides in vegetable and fruit juices

A new version of magnetic solid-phase extraction performed in a narrow-bore tube has been proposed for the extraction and preconcentration of different pesticides from various vegetable and fruit juices followed by gas chromatography. A few milligrams of C₈ @SiO₂ @Fe₃ O₄ nanoparticles are added into an aqueous sample solution placed in a narrow-bore tube. The sorbent particles move down through the tube under gravity and are collected at the end of the tube by applying an external magnetic field. The end of the tube is narrower and it is connected to a stopcock. After a predetermined time, the stopcock is opened and the solution is passed through the bed of the sorbent maintained by the magnet. Then the adsorbed analytes are desorbed using an elution solvent. To achieve high enrichment factors, a dispersive liquid-liquid microextraction method is carried out. The nanoparticles were characterized by scanning electron microscopy, X-ray diffraction, and FTIR spectroscopy. Under the optimum extraction conditions, limits of detection and quantification were in the ranges of 0.1-0.3 and 0.3-0.9 μg/L, respectively. High enrichment factors (1166-1605) and good extraction recoveries (58-80%) were obtained.

Novel functionalized magnetic ionic liquid green separation technology coupled with high performance liquid chromatography: A rapid approach for determination of estrogens in milk and cosmetics

Several magnetic ionic liquids (MILs), [P_6,6,6,14⁺][FeCl₄^-], [P_6,6,6,14⁺]₂[MnCl₄^2-], [P_6,6,6,14⁺]₂[CoCl₄^2-] and [P_6,6,6,14⁺]₂[NiCl₄^2-] were synthesized and applied for the extraction of six estrogens (estrone, estradiol, 17-α-hydroxyprogesterone, chloromadinone 17-acetate, megestrol 17-acetate and medroxyprogesterone 17-acetate) in dispersive liquid-liquid microextraction (DLLME). The [CoCl₄^2-]-based MIL was selected as extraction solvent for the separation and concentration of estrogens from milk and cosmetics due to its visual recognition, no sign of hydrolysis, solution acquisition easier and the highest extraction capacity. In addition, the [CoCl₄^2-]-based MIL with low UV absorbance allows direct analysis of the extraction solvent by HPLC-UV. The influence of the mass of MIL, extraction time, salt concentration, and the pH of the sample solution was investigated to obtain optimized extraction efficiency. Besides, extraction conditions including salt concentration, mass of MIL and extraction time were further optimized by the Box-Behnken design through the response surface method. Under optimized conditions, the limits of detection (LODs) of all estrogens were ranged from 5 ng mL^-1 to 15 ng mL^-1. The recoveries ranging from 98.5% to 109.3% in milk and from 96.3% to 111.4% in cosmetics were also studied, respectively. Furthermore, the proposed method were statistically compared with the reported conventional IL-DLLME method and the National standard methods of food safety and cosmetics. The experimental results showed that the functionalized MIL could successfully applied for extraction, separation and pretreatment of estrogens in milk and cosmetics.

Magnetic Solid-Phase Extraction of Dichlorodiphenyltrichloroethane and Its Metabolites from Environmental Water Samples Using Ionic Liquid Modified Magnetic Multiwalled Carbon Nanotube/Zeolitic Imidazolate Framework-8 as Sorbent

As persistent organic pollutants, dichlorodiphenyltrichloroethanes (DDTs) and their metabolites pose considerable risks to human health and the environment. Therefore, monitoring DDTs in the environment is essential. Here, we developed a green, simple, and effective magnetic solid-phase extraction (MSPE) method coupled with gas chromatography tandem triple-quadrupole mass spectrometry to determine the DDT content of environmental water samples. A magnetic ionic liquid (IL) adsorbent was developed based on a modified magnetic multiwalled carbon nanotube/zeolitic imidazolate framework-8 (MM/ZIF-8/IL), synthesized by immobilizing the IL on the surface of MM/ZIF-8. We confirmed successful synthesis of MM/ZIF-8/IL by material characterization, and our results suggested that the MM/ZIF-8/IL had a high Brunauer-Emmett-Teller surface area (159.9 m2 g-1), good thermostability (<800 °C), and a high degree of superparamagnetism (52.9 emu g-1). Several experimental conditions affecting the MSPE efficiency were optimized. Under the best conditions, good detection linearity was achieved (0.5-500 µg L-1) with determination coefficients ranging from 0.9927 to 0.9971. The lower limits of detection (0.0016-0.0072 µg L-1) also had good precision, having an intraday relative standard deviation (RSD) ≤ 6.5% and an interday RSD ≤ 8.9%. Finally, we used the as-developed method to determine DDT levels in environmental water samples.

Advancements of molecularly imprinted polymers in the food safety field

Molecularly imprinted technology (MIT) has been widely employed to produce stable, robust and cheap molecularly imprinted polymer (MIP) materials that possess selective binding sites for recognition of target analytes in food, such as pesticides, veterinary drugs, mycotoxins, illegal drugs and so on. Because of high selectivity and specificity, MIPs have drawn great attention in the food safety field. In this review, the recent developments of MIPs in various applications for food safety, including sample preparation, chromatographic separation, sensing, immunoassay etc., have been summarized. We particularly discuss the advancements and limitations in these applications, as well as attempts carried out for their improvement.

Synthesis and characterization of MIL-101(Cr) intercalated by polyaniline composite, doped with silica nanoparticles and its evaluation as an efficient solid-phase extraction sorbent

A metal-organic framework/polyaniline composite was synthesized and doped with silica nanoparticles. The structure and morphology of the composite were characterized using Fourier transform infrared spectroscopy and scanning electron microscopy. It was packed inside a cartridge and evaluated for the solid-phase extraction of thymol and carvacrol, followed by gas chromatography with flame ionization detection measurement. The influence of the important experimental variables on the efficiency of the proposed method, including pH, ionic strength, volume of sample solution and type, and volume of eluent were studied and optimized. Under the optimal conditions, the relative standard deviations were found to be 3.8 and 9.8% for thymol and carvacrol, respectively, and the corresponding limits of detection were 0.1 and 1.0 ng/mL. The linear dynamic ranges for the calibration curves of the analytes were 10-10000 ng/mL, with determination coefficients (R² ) > 0.993. The limits of quantifications were found to be 0.01 and 0.5 μg/mL, for thymol and carvacrol, respectively. The prepared nanocomposite sorbent was applied successfully to the extraction and determination of thymol and carvacrol in Lamiaceae plant extracts and a honey sample, with relative recoveries in the range of 90.28-122.0%.

Magnetic molecularly imprinted polymers for the determination of β-agonist residues in milk by ultra high performance liquid chromatography with tandem mass spectrometry

A simple, accurate, and highly sensitive analytical method was developed in this study for the determination of nine β-agonists in milk. In this method, a new magnetic adsorbent of molecularly imprinted polymers/magnetic nanoparticles prepared by simple physical blending was adopted, which enabled magnetic solid-phase extraction. Thus, the resultant material can be separated from the solvent rapidly and conveniently by a magnet. Two kinds of molecularly imprinted polymer/magnetic nanoparticles materials were fabricated, and the characteristics of materials such as the ratio, pH, amount, desorption, and regeneration were investigated. The analytes were quantified by ultra high performance liquid chromatography coupled to an electrospray ionization tandem mass spectrometer operating in multiple reaction monitoring modes. The detection limit of the method was 0.003-0.3 μg/L, and the detection capability was 0.01-0.3 μg/L. The recoveries of these compounds were 65.7-114% at three spiked levels. Reproducibility represented by relative standard deviation was 11.2% or less. The method was successfully applied to the screening of real samples obtained from local markets and confirmation of the suspected target analytes.

Preparation of a magnetic multiwalled carbon nanotube@polydopamine/zeolitic imidazolate framework-8 composite for magnetic solid-phase extraction of triazole fungicides from environmental water samples

A novel magnetic zinc-based zeolitic imidazolate framework (MMP/ZIF-8) has been prepared using a magnetic multiwalled carbon nanotube@polydopamine nanocomposite as the magnetic core and support. It was then used as an adsorbent for magnetic solid-phase extraction of triazole fungicides from environmental water samples. Successful synthesis of MMP/ZIF-8 was confirmed by material characterization, and the results showed that the synthetic composite has a high Brunauer–Emmett–Teller surface area (141.56 m² g⁻¹), large total pore volume (0.636 mL g⁻¹), and high superparamagnetism with a saturation magnetization of 44.1 emu g⁻¹. To evaluate the extraction performance of MMP/ZIF-8, the main parameters that affect the extraction efficiency were optimized. Under the optimal conditions, the developed method shows good linearity (R² ≥ 0.9915) in the concentration range 1–400 μg L⁻¹. Low limits of detection (0.08–0.27 μg L⁻¹, signal/noise = 3 : 1) and good precision (intraday relative standard deviation ≤ 7.73%, interday relative standard deviation ≤ 9.65%) are also achieved. The developed method was applied for analysis of triazole fungicides in environmental water samples.

A magnetic ZIF-8 composite was prepared based on Fe₃O₄/MWCNT@PDA and used as an adsorbent for MSPE of triazoles from environmental water samples.

Efficient extraction method using magnetic carbon nanotubes to analyze cocaine and benzoylecgonine in breast milk by GC/MS

Aim: The increasing use of cocaine (COC) during breastfeeding has led to growing concern about exposure of infants. Therefore, to study this exposure, a new method to analyze COC and benzoylecgonine in breast milk was developed. Methodology: A new extraction method was used for the first time to analyze COC and its major metabolite, benzoylecgonine, in breast milk using magnetic carbon nanotubes partially doped with nitrogen. Results: The calibration curves were linear in the range 5.0–180.0 ng ml-1. The limit of quantification was 5.0 ng ml-1. Coefficients of variation were between 3.2 and 13.9%. Recovery was between 89.6 and 99.2%. Conclusion: The proposed method is simple, efficient and suitable to determine analytes in breast milk.

Reduced Graphene Oxide-Based Solid-Phase Extraction for the Enrichment and Detection of microRNA

MicroRNAs (miRNAs) are endogenous molecules with regulatory functions. The purification and enrichment of miRNA are essential for its precise and sensitive detection. miRNA isolated using commercial kits contains abundant interfering RNAs, and the concentration of miRNA may not be adequate for detection. Herein, we prepared a reduced graphene oxide (rGO)-based magnetic solid-phase extraction material for the enrichment and ultrasensitive detection of miRNA from intricate nucleic acid solutions. In situ reverse transcription (RT) was developed as the most efficient approach to desorb miRNA from rGO among the methods that are compatible for the subsequent amplification reported thus far. Additionally, rolling circle amplification and qPCR were used to detect let-7a with a decrease of the limit of detection by 24.7- and 31.3-fold, respectively. This material was also successfully used to extract and detect miRNA from total RNA isolated from human plasma. Our results show that the material prepared in this study has the potential for cancer biopsy in clinics and the discovery of new miRNAs in scientific research.