Functionalization of amino terminated carbon nanotubes with isocyanates for magnetic solid phase extraction of sulfonamides from milk and their subsequent determination by liquid chromatography-high resolution mass spectrometry

Recent Advances in Nontargeted Screening of Chemical Hazards in Foodstuffs

The emergence of several chemical substances continues to enrich and facilitate the development of food science, but their irrational use also poses a threat to food safety and human health. Nontargeted screening (NTS) has become an important tool for rapid traceability and efficient identification of chemical hazards in food matrices. NTS in food analysis is highly integrated with sample pretreatment, instrumental analysis platforms, data acquisition and analysis, and toxicology. This article is a systemic review of current sample preparation, analytical platforms, and toxicity-guided NTS techniques and provides the latest advancements in workflows and innovative applications of the NTS process based on mass spectrometric techniques. High-throughput toxicity screening platforms play an important role in NTS of unknown chemical hazards of complex food matrices. Advanced machine learning and artificial intelligence are increasingly accessible fields that may effectively process large-scale screening data and advance food NTS research.

Preparation and evaluation of Fe3O4@C@NiCo-LDH@CDs composites for magnetic solid-phase extraction of trace endocrine disruptors

The widespread use of endocrine disruptors (EDPs) has certain potential hazards to organisms and environments, and it is particularly important to develop effective pretreatment methods before detection of EDPs in complex samples. In this work, a novel magnetic nanocomposite decorated with layered double hydroxides (LDHs) and carbon dots (CDs) was designed and prepared for magnetic solid-phase extraction (MSPE) of EDPs (bisphenol S, bisphenol F, bisphenol A, bisphenol AF, diethylstilbestrol and 4-cumylphenol) combined with high-performance liquid chromatography-ultraviolet (HPLC-UV) detection. The prepared composites were characterized by field emission scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS), and the adsorption mechanism towards these EDPs might be mainly based on hydrogen bonds and π-π conjugation. Under the optimized conditions, the proposed method showed limits of detection within 0.05-0.50 μg L-1 and limits of quantitation within 0.2-2.0 μg L-1, and good linearity (R2 ≥ 0.9975) was presented in the range of 0.2-200 μg L-1. Finally, the Fe3O4@C@NiCo-LDH@CDs composite-based MSPE-HPLC-UV method was applied for enrichment and determination of EDPs in water, milk, and tea beverage samples with recoveries in the range of 81.2-119.8% and relative standard deviations below 9.7%.

Covalent functionalization of 1D and 2D sp2-carbon nanoallotropes - twelve years of progress (2011-2023)

Carbon nanoallotropes have attracted significant attention in the field of materials science due to their unique combination of physicochemical and biological properties, with numerous applications. One-dimensional (1D) and two-dimensional (2D) sp2-carbon nanoallotropes, such as carbon nanohorns (CNHs), carbon nanotubes (CNTs), and graphene, have emerged as prominent candidates for a variety of technological advancements. To fully exploit their exceptional characteristics, the covalent functionalization of these nanostructures may alleviate the problems with the processing and final performance. This route of the carbon nanoallotrope functionalization is based on a covalent attachment of functional groups or molecules (via linkers of various strengths) to their surfaces, enabling precise control over physical, chemical, biological, and electronic properties. Such an approach opens up new avenues for tailoring the nanoallotrope characteristics, such as solubility/dispersibility, reactivity, and interactions with other materials. Over more than the last decade, significant progress has been made in the covalent functionalization of both 1D and 2D sp2-carbon nanoallotropes, paving the way for diverse applications in the nanoelectronics, energy storage, sensing, and biomedical fields. In this comprehensive review, we provide state-of-the-art advancements and achievements in the covalent functionalization of 1D and 2D sp2-carbon nanoallotropes during the past dozen years. We aim to highlight the key strategies, methodologies, and breakthroughs that have significantly contributed to this field. Eventually, we discuss the implications of those advancements and explore the opportunities for future research and applications.

Effective extraction and determination of 24 quinolones in water and egg samples using a novel magnetic covalent organic framework combined with UPLC-MS/MS

The excessive use of quinolones (QNs) has seriously threatened human health. In this study, a novel functionalized magnetic covalent organic framework Fe3O4@SiO2@Ah-COF was fabricated with biphenyl-3,3',5,5'-tetracarbaldehyde and hydrazine hydrate (85%) as monomers and was used as a magnetic solid-phase extraction (MSPE) absorbent for the determination of 24 QNs in water and egg samples through ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS). The extraction parameters of MSPE were optimized, including pH, adsorbent dosage, adsorption time, and eluent type. An effective and rapid detection method was then established, which showed good linearity (R2 ≥ 0.9990), low limits of detection (0.003-0.036 μg L-1) and low limits of quantitation (0.008-0.110 μg L-1) for QNs. The good recoveries of 24 QNs in water and egg samples were in the range of 70.3-106.1% and 70.4-119.7%, respectively, with relative standard deviations lower than 10% (n = 5). As a result, Fe3O4@SiO2@Ah-COF is a promising magnetic adsorbent, and the established method was successfully applied for the determination of 24 QNs in water and egg samples.

Recent advances and applications of magnetic covalent organic frameworks in food analysis

Recently, covalent organic frameworks (COFs) have been widely used to prepare magnetic adsorbents for food analysis due to their highly tunable porosity, large specific surface area, excellent chemical and thermal stability and large delocalised π-electron system. This review summarises the main types and preparation methods of magnetic COFs and their applications in food analysis for the detection of pesticide residues, veterinary drugs, endocrine-disrupting phenols and estrogens, plasticisers and other food contaminants. Furthermore, challenges and future outlook in the development of magnetic COFs for food analysis are discussed.

Three-dimensional flower-like SnS2 materials for dispersive solid-phase extraction of endocrine-disrupting phenols

In this study, three-dimensional flower-like tin disulfide materials were prepared, and a highly efficient dispersive solid-phase extraction method was developed using the obtained three-dimensional tin disulfide adsorbents for the preconcentration and determination of six endocrine-disrupting phenols in combination with high-performance liquid chromatography-ultraviolet detection. Several important experimental parameters influencing extraction efficiency were investigated, including the amount of adsorbent, ultrasound time, sample solution pH, sample volume, type of elution solvent, desorption time, and the number of desorption times. Under the optimized experimental conditions, the developed method showed good linearity with the determination coefficients of 0.993-0.998 in the linear range of 0.5-400 ng/ml and low limits of detection in the range of 0.15-1.0 ng/ml, as well as satisfactory intra-day and inter-day precisions with relative standard deviations of 0.1-9.8%. Finally, the proposed method was successfully applied for the enrichment and determination of trace endocrine-disrupting phenols in milk, tea beverage, and plastic bottled water samples, and acceptable recoveries were obtained from 70.1% to 119.1% under four different spiked concentration levels. The results showed that the three-dimensional tin disulfide materials had great potential for the extraction of endocrine-disrupting phenols contaminants in environmental and food samples.

Synthesis of the Magnetically Nanoporous Organic Polymer Fe3O4@SiO2-NH2-COP and Its Application in the Determination of Sulfonamide Residues in Surface Water Surrounding a Cattle Farm

Efficient extractions of trace antibiotic residues in the environment are a key factor for accurate quantification of the residues. A new nanoporous material, namely, magnetically covalent organic polymer (MCOP, Fe₃O₄@SiO₂-NH₂-COP) was synthesized in this work and was used for magnetic solid-phase extraction (MSPE). The combination of MSPE with high-performance liquid chromatography separation together with ultraviolet detection (HPLC-UV) was established as an effective method for the determination of four sulfonamide (SA) residues in surface water surrounding a cattle farm. The synthesized magnetic material was characterized by SEM, TEM, FT-IR, magnetic properties measurement system (MPMS), and nitrogen gas porosimetry. The material possessed many attractive features, such as a unique microporous structure, a larger specific surface area (137.93 m²·g⁻¹) than bare Fe₃O₄ (24.84 m²·g⁻¹), high saturation magnetization (50.5 emu·g⁻¹), open adsorption sites, and high stability. The influencing parameters, including pH, the used amount of MCOPs, the type of eluent, adsorption solution, and desorption time, were optimized. Under the optimized conditions, the method conferred good linearity ranges (R² ≥ 0.9990), low detection limits (S/N = 3, LOD, 0.10–0.25 μg·L⁻¹), and satisfactory recoveries (79.7% to 92.2%). The enrichment factor (EF) for the four SAs was 34.13–38.86. The relative standard deviations of intraday (n = 5) and of interday (n = 3) were less than 4.8% and 8.9%, respectively. The equilibria between extraction and desorption for SAs could be reached within 150 s. The proposed method was sensitive and convenient for detecting SA residues in complex environmental matrices, and the successful application of the new MCOPs as an adsorbent was demonstrated.

Room temperature fabrication of magnetic covalent organic frameworks for analyzing sulfonamide residues in animal-derived foods

A magnetic solid phase extraction method based on magnetic covalent organic frameworks (TpBD@Fe₃ O₄ ) combined with high performance liquid chromatography has been developed to detect the sulfonamides including sulfadiazine, sulfamerazine, sulfamethazine and sulfamethoxazole in milk and meat. TpBD@Fe₃ O₄ were synthesized at room temperature under mild reaction conditions with a simple and rapid operation. The TpBD@Fe₃ O₄ exhibited higher extraction efficiency because of the π-π and electrostatic interactions between the benzene ring structure of the TpBD and the SA molecules. The extraction conditions including the dosage of adsorbents, the type and dosage of eluent, the elution time and the pH of the sample solution were fully optimized. The detection results showed good linearity over a wide range (50-5×10⁴ ng/mL) and low detection limits (3.39-5.77 ng/mL) for the SA targets. The practicability of this MSPE-HPLC method was further evaluated by analyzing milk and meat samples, with recoveries of the targets of 71.6%-110.8% in milk and 71.9%-109.7% in pork. The successful detection of SAs residues has demonstrated the TpBD@Fe₃ O₄ excellent practical potential for analyzing pharmaceutical residues in animal-derived foods. This article is protected by copyright. All rights reserved.

Simultaneous preconcentration and determination of sulfonamide antibiotics in milk and yoghurt by dynamic pH junction focusing coupled with capillary electrophoresis

A dynamic pH junction was used in capillary electrophoresis (CE-DAD) to on-line preconcentrate, separate, and determine trace amounts of sulfonamide antibiotics (SAs) in milk and yoghurt samples in this study. A sample matrix with 0.15% acetic acid and 10% methanol (MeOH) at a pH of 4.0, and a background electrolyte (BGE) that contained 35 mM sodium citrate with 10% MeOH at a pH of 8.5, and an acidic barrage of 0.4% acetic acid with 10% MeOH at a pH of 2.5 were utilised to achieve a stacking effect for SAs through a dynamic pH junction. Under optimised conditions, the proposed preconcentration method showed good linearity (30-500 ng/mL, r² ≥ 0.9940), low limits of detection (LODs) of 4.1-6.3 ng/mL, and acceptable analytes recovery (81.2-106.9%) with relative standard deviations (RSDs) within 5.3-13.7 (n = 9). The limits of quantification (LOQs) were below the maximum residue limit approved by the European Union (EU) in this type of matrices. Sensitivity enhancement factors of up to 129 were reached with the optimised dynamic pH junction using CE with a diode array detector (DAD). The method was used to determine SAs in fresh milk, low-fat milk, full-cream milk, and yoghurt samples.

Sulfonamide-Selective Ambient Mass Spectrometry Ion Source Obtained by Modification of an Iron Sheet with a Hydrophilic Molecularly Imprinted Polymer

We have described a sulfonamide-selective ambient ion source coupled with electrospray ionization mass spectrometry (ESI-MS) for selective extraction and determination of trace sulfonamide antibiotics. It is obtained by modifying an iron sheet with a sulfadiazine-templated hydrophilic molecularly imprinted polymer (SF-HMIP). It behaves as both an online extractor and a MS ion source. Five sulfonamide antibiotics, including sulfamethoxazole (SMZ), sulfamerazine (SMR), sulfisoxazole (SIZ), sulfathiazole (ST), and sulfameter (SMD), were chosen to evaluate SF-HMIP coupled with ESI-MS, which showed good linearity in the range of 0.2-1000 ng/mL with correlation coefficient values (R²) over 0.9946. The limits of detection (LODs) for analysis of pure water and honey were in the range of 0.1-0.2 and 0.2-1.5 ng/mL, respectively. Limits of quantitation (LOQs) for analysis of pure water and honey were in the range of 0.3-0.5 and 1.0-5.0 ng/mL, respectively. The results demonstrated that SF-HMIP combined with ESI-MS could be applied for the direct analysis of five trace sulfonamide compounds in honey and pure water with recoveries ranging from 76 to 129%.

Determination of sulfonamides in milk and egg samples by HPLC with mesoporous polymelamine-formaldehyde as magnetic solid-phase extraction adsorbent

In this work, magnetic mesoporous polymelamine-formaldehyde composites were synthesized via a facile Schiff base reaction. The magnetic mesoporous polymelamine-formaldehyde composites combined both the properties of mesoporous polymelamine-formaldehyde and the magnetism of NH₂ -SiO₂ @Fe₃ O₄ nanoparticles, possessing high specific surface area (150.66 m² g^-1 ) and good magnetism (24.50 emu g^-1 ). The magnetic mesoporous polymelamine-formaldehyde composites were employed as magnetic adsorbent for the extraction of sulfonamides. Under optimal conditions, good linearities with correlation coefficients higher than 0.9984 were obtained between peak area and sulfonamides concentration (2-200 μg L^-1 ) with limits of detection in the range of 0.33-0.58 μg L^-1 . The established method was successfully applied for the determination of sulfonamides in egg and milk samples. The adsorption mechanisms demonstrated that the adsorption of magnetic mesoporous polymelamine-formaldehyde composites toward sulfonamides was a multilayer process, and adsorption kinetics followed the pseudo-second-order model.

Current Applications of Magnetic Nanomaterials for Extraction of Mycotoxins, Pesticides, and Pharmaceuticals in Food Commodities

Environmental pollutants, such as mycotoxins, pesticides, and pharmaceuticals, are a group of contaminates that occur naturally, while others are produced from anthropogenic sources. With increased research on the adverse ecological and human health effects of these pollutants, there is an increasing need to regularly monitor their levels in food and the environment in order to ensure food safety and public health. The application of magnetic nanomaterials in the analyses of these pollutants could be promising and offers numerous advantages relative to conventional techniques. Due to their ability for the selective adsorption, and ease of separation as a result of magnetic susceptibility, surface modification, stability, cost-effectiveness, availability, and biodegradability, these unique magnetic nanomaterials exhibit great achievement in the improvement of the extraction of different analytes in food. On the other hand, conventional methods involve longer extraction procedures and utilize large quantities of environmentally unfriendly organic solvents. This review centers its attention on current applications of magnetic nanomaterials and their modifications in the extraction of pollutants in food commodities.

A novel analytical strategy for the determination of perfluoroalkyl acids in various food matrices using a home-made functionalized fluorine interaction SPME in combination with LC-MS/MS

In this study, a fluorine-fluorine interaction approach through fluoridating boron nitride nanosheets (BNNs) for sensing perfluoroalkyl acids (PFAAs) in multiple food matrices was developed. Through a facile hydrothermal fluorination modification, the BNNs were transferred into homogeneous fluorinated boron nitride nanoparticles (F-BNNs) with robust networks and specific surface area. After morphological modification, the particles displayed strong adsorption and sensing capabilities on PFAAs in both solid and liquid food matrix. Under the evaluation of mass spectrometry, F-BNNs based microextraction approach exhibited low method detection limits (MDLs) in the ranges of 0.9-3.9 pg mL^-1 and 3.6-15.8 pg g^-1 for milk and meat matrices, respectively, with satisfactory repeatability (RSD% <13.5%) and recoveries (77.7-110.5%). This work not only depicted a facile approach for preparing F-BNNs based SPME fiber, but also provided a routine analysis protocol for monitoring PFAAs in food systems.

Three-dimensional magnetic stannic disulfide composites for the solid-phase extraction of sulfonamide antibiotics

In the present work, three-dimensional (3D) and flower-like SnS₂ materials were coated on the surface of Fe₃O₄@nSiO₂ through an in-situ growth method. The 3D architecture could avoid the accumulation and reaggregation with better stability and was beneficial for the exposure of more active sites. The prepared magnetic SnS₂ composites were used for the enrichment of sulfonamide antibiotics (SAs), and various experimental parameters affecting the extraction efficiency were investigated. The results showed the equilibrium of extraction and desorption towards target SAs could be reached within 3 min by using the Fe₃O₄@nSiO₂-SnS₂ composites. Under optimized conditions, the proposed approach possessed good linearity in the range of 0.1-200 ng·mL^-1 with correlation coefficients r² above 0.9964 and low limits of detection (LODs) from 0.025 to 0.250 ng·mL^-1 for the five target SAs. Moreover, good repeatability was obtained with the intra-day and inter-day precision in terms of relative standard deviations (RSDs) within 1.1%-10.8% and 7.4%-13.1%, and the recoveries under three spiked concentrations were between 81.8% and 119.7% with adequate accuracy. Different samples including tap water, milk and honey were collected for magnetic solid-phase extraction and determination of target SAs by using the obtained Fe₃O₄@nSiO₂-SnS₂ composites to demonstrate the utility. All the results indicated that the proposed method had great potential for effective preconcentration and determination of SAs in complex samples.

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.

[Research progress in the application of magnetic solid phase extraction based on carbon based magnetic materials in food analysis]

Trace toxic substances in food pose a serious threat to human health, and need to be detected and analyzed to ensure food safety. However, there are many kinds of toxic substances in food, with small amounts and complex matrices, making it necessary to select an appropriate sample pretreatment technology for extraction and purification. There are some disadvantages to sample pretreatment methods such as solid phase extraction and liquid-liquid extraction, in terms of poor selectivity, significant influence of matrix interference, large sample requirement, long extraction time, use of a large amount of harmful organic solvents, and cumbersome and time-consuming operation. Magnetic solid phase extraction (MSPE) combines the advantages of magnetic separation and traditional SPE technology, avoids time-consuming column loading, and can extract the target analyte efficiently. Because of its advantages, in that it has simple operation, is time-saving and fast, requires no centrifugal filtration, and is environmentally friendly, it is considered an efficient sample pretreatment technology and applied in food analysis. The adsorption capacity and selectivity of the magnetic adsorbent used in MSPE are the key factors affecting the extraction efficiency and selectivity of MSPE, and play a key role in the accuracy of the established method. Carbon-based magnetic materials are a type of new functional magnetic materials prepared by the co-precipitation of carbon-based materials (carbon nanotubes, graphene, metal-organic framework-derived carbon, or activated carbon) and magnetic materials. In order to endow carbon-based magnetic materials with the advantages of both, carbon materials and magnetic materials, while also reflecting the advantages of high specific surface area, good stability, low cost, environmental friendliness, excellent physical and chemical properties, high porosity, and high adsorption capacity, proper functional modification is needed. Carbon-based magnetic materials modified by functionalization can efficiently enrich organic and inorganic analytes with different properties, and have seen significant progress in environmental analysis, biological detection, pollution control, and other fields. In recent years, MSPE technology based on carbon-based magnetic materials has been gradually applied in food analysis and pretreatment, but its use is still in infancy and holds immense application potential. Reference to more than 50 papers published in SCI and Chinese core journals over the past four years reveals that carbon-based materials include carbon nanotubes modified by functional groups, reagents, or materials; graphene, graphene oxide, and reduced graphene oxide; carbon derived from a gold organic framework; activated carbon biochar; and nanodiamond. The harmful substances in food samples include esters, mycotoxins, polycyclic aromatic hydrocarbons, antibiotics, alkaloids, phenols, vitamins, and antibiotics. Based on the classification of carbon-based materials, this review reveals that carbon-based magnetic materials have good preconcentration ability for harmful substances in food samples. MSPE can be combined with GC-MS, liquid chromatography-high resolution mass spectrometry (LC-HRMS), ultra-fast liquid chromatography-tandem mass spectrometry (UFLC-MS/MS), ultra high performance liquid chromatography-Q-Exactive high resolution mass spectrometry (UHPLC-Q-Exactive HRMS), high performance liquid chromatography-diode array detection (HPLC-DAD), gas chromatography micro-electron capture detection (GC-μECD), high performance liquid chromatography fluorescence with post-column photochemical derivatization (HPLC-PCD-FLD), and HPLC-UV to analyze food samples. These combined technologies have high accuracy and recovery. However, the synthesis methods of carbon-based magnetic materials such as carbon nanotubes and graphene, incur high energy consumption and high cost, and involve complex processes, which limit their application. Therefore, a carbon-based magnetic adsorbent with low cost, high selectivity, and high extraction efficiency was developed by further exploring functional modification with biochar as a carbon base. This is a very promising direction to develop MSPE technology utilizing biochar-based magnetic materials for food sample pretreatment. This review provides a theoretical basis and technical support for the wide application of carbon-based magnetic materials in MSPE technology for food analysis.

A colorimetric microfluidic paper-based analytical device for sulfonamides in cow milk using enzymatic inhibition

To increase milk production, antibiotics are administered to animals to provide weight gain and to prevent or treat diseases. The inappropriate use of these substances can lead to antibiotic resistance and allergic reactions and toxic effects to milk consumers. We describe the development of a simple, fast, portable, and low-cost microfluidic paper-based analytical device (μPAD) to quantify sulfonamides in milk using the inhibition of the colorimetric reaction between carbonic anhydrase (CA) and 4-nitrophenyl acetate. The main advantages presented by the μPAD include reproducible batch production, simple application, and precise analysis without previous treatment. The µPAD displayed good linearity (R² ≥ 0.986) in a wide range of sulfonamides in milk (2.5 to 40.0 µmol L^-1), being selective for the drugs even in a highly complex matrix. We expect that this device allows in situ monitoring of milk quality, reducing the prejudicial conditions associated with high concentrations of sulfonamides in milk.

Iron Oxide Nanoparticles: Multiwall Carbon Nanotube Composite Materials for Batch or Chromatographic Biomolecule Separation

Carbon-based materials are the spearhead of research in multiple fields of nanotechnology. Moreover, their role as stationary phase in chromatography is gaining relevance. We investigate a material consisting of multiwall carbon nanotubes (CNTs) and superparamagnetic iron oxide nanoparticles towards its use as a mixed-mode chromatography material. The idea is to immobilize the ion exchange material iron oxide on CNTs as a stable matrix for chromatography processes without a significant pressure drop. Iron oxide nanoparticles are synthesized and used to decorate the CNTs via a co-precipitation route. They bind to the walls of oxidized CNTs, thereby enabling to magnetically separate the composite material. This hybrid material is investigated with transmission electron microscopy, magnetometry, X-ray diffraction, X-ray photoelectron and Raman spectroscopy. Moreover, we determine its specific surface area and its wetting behavior. We also demonstrate its applicability as chromatography material for amino acid retention, describing the adsorption and desorption of different amino acids in a complex porous system surrounded by aqueous media. Thus, this material can be used as chromatographic matrix and as a magnetic batch adsorbent material due to the iron oxide nanoparticles. Our work contributes to current research on composite materials. Such materials are necessary for developing novel industrial applications or improving the performance of established processes.

Determination of sulfonamide residues in animal foodstuffs by magnetic dispersive solid-phase extraction using magnetic carbon nanocomposites coupled with ion pair-dispersive liquid–liquid micro-extraction combined with HPLC-DAD

In this study, magnetic-dispersive solid-phase extraction coupled with ion pair-dispersive liquid–liquid micro-extraction (MSPE-i-DLLME) was used to the pre-concentration and extraction of five sulfonamides residues (sulfadiazine, sulfathiazole, sulfacetamide, sulfamethazine and sulfamethoxazole) in animal foodstuffs. The sulfonamides are extracted using magnetic carbon nanocomposite and then eluted with acetonitrile. In the DLLME step, the target analytes are collected in 1-octanol containing 10% Aliquat-336 (as extraction solvent). Finally, the compounds are quantified by HPLC with DAD detection. The extraction parameters optimized using the one at the time and central composite design methods. Under the optimized conditions: sample solution volume was 100 mL; initial pH: 12, amounts of MCNs: 30 mg; desorption solvent (ACN) volume, 1 mL; desorption condition, 10 min sonication at two step; extraction solvent (1-octanol + 10% aliquat) volume, 115 µL; pH of DLLME step, 3; salt effect, 24.6%, (w/v) NaCl; centrifuge, 5 min, 4000 rpm. In these extraction conditions, the proposed procedure represented good pre-concentration factors between 130 and 490; detection limits in the range from 0.01 to 5 μg kg−1 (at S/N = 3), and linear response in the 0.1–400 μg kg−1 concentration range. The method is successfully applied to the determination of sulfonamides residues in animal foodstuffs.

Polyethyleneimine-modified magnetic carbon nanotubes as solid-phase extraction adsorbent for the analysis of multi-class mycotoxins in milk via liquid chromatography-tandem mass spectrometry

Polyethyleneimine-modified magnetic multi-walled carbon nanotubes were developed to extract 10 mycotoxins. Simple modification of polyethyleneimine was achieved on the magnetic substrate by using an epoxy-containing silane agent as a linker. The resultant magnetic adsorbent was integrated with reverse phase and anion exchange interaction sites. Under optimal extraction conditions, only 20.0 mg adsorbent was used to extract the mycotoxins from 50.0 mL loading solution. The maximum adsorption capacities of the adsorbent toward the mycotoxins ranged from 4.9 to 10.2 mg/g. Adsorption and desorption were completed within 3.0 and 2.0 min, respectively. The adsorbent could be used for six repeated runs without evident change in extraction performance. The adsorbent combined with liquid chromatography-tandem mass spectrometry was applied further to analyze the mycotoxins in milk. The absolute recoveries of the 10 mycotoxins ranged from 88.3 to 103.5% with relative standard deviations that ranged from 2.4 to 6.5%, and their limits of detection were 0.003 to 0.442 μg/kg. The proposed adsorbent has great potential in the routine analysis of mycotoxins in ordinary analytical chemistry laboratory.

Determination of estrogens by solid-phase quadruplex stable isotope dansylation coupled with liquid chromatography-high resolution mass spectrometry in environmental samples

Estrogens distribute widely in the environment as endocrine-disrupting chemicals (EDCs), which have to be monitored to evaluate their environmental impact. Aim to improve the analytical throughput of liquid chromatography-high resolution mass spectrometry (LC-HRMS), a quadruplex stable isotope dansylation method was developed, with which three real samples could be quantitatively analyzed in one injection. As the estrogens were at trace level in complex matrices, magnetic solid-phase extraction (MSPE) was applied to enrich these analytes and remove the interfaces. By integrating MSPE and quadruplex stable isotope dansylation, a solid-phase quadruplex labeling method was developed for the LC-HRMS analysis of estrogen analogues. For the tested seven estrogens, the developed method showed low detection limits (0.1-0.5 ng/L for pond water and 0.01-0.05 μg/kg for poultry manure), good precision (RSD < 5.5%) and accuracy (96.8-108.3%). The method was applied in the determination of estrogens in environmental samples, and the results revealed that all the tested estrogens were present in the estuary water (unquantifiable to 71.2 ng/L) and chicken manure (undetectable to 25.43 μg/kg).

Recent Applications of Magnetic Nanoparticles in Food Analysis

Nanotechnology has become a topic of interest due to the outstanding advantages that the use of nanomaterials offers in many fields. Among them, magnetic nanoparticles (m-NPs) have been one of the most widely applied in recent years. In addition to the unique features of nanomaterials in general, which exclusively appear at nanoscale, these present magnetic or paramagnetic properties that result of great interest in many applications. In particular, in the area of food analysis, the use of these nanomaterials has undergone a considerable increase since they can be easily separated from the matrix in sorbent-based extractions, providing a considerable simplification of the procedures. This allows reducing cost and giving fast responses, which is essential in the food trade to guarantee consumer safety. These materials can also be easily tunable, providing higher selectivity. Moreover, their particular electrical, thermal and optical characteristics allow enhancing sensor signals, increasing the sensitivity of the approaches based on this type of device. The aim of this review article is to summarise the most remarkable applications of m-NPs in food analysis in the last five years (2016–2020) showing a general view of the use of such materials in the field.

The fabrication of a thiol-modified chitosan magnetic graphene oxide nanocomposite and its adsorption performance towards the illegal drug clenbuterol in pork samples

A novel thiol (provided by (3-mercaptopropyl) trimethoxysilane, MPTS)-modified chitosan magnetic graphene oxide nanocomposite (Fe₃O₄@SiO₂/GO/CS/MPTS) was synthesized and characterized for the first time as an efficient magnetic sorbent for the enrichment and extraction of trace levels of clenbuterol in pork samples (muscle, fat, heart and liver). Various greatly influential parameters were optimized using a Box-Behnken design (BBD) through the response surface methodology (RSM) to obtain more satisfactory recovery. Under optimum conditions, the method detection limits (MDLs) were in the range of 0.054-0.136 ng g^-1. The recoveries of three spiked levels ranged from 84.7% to 101.1%, and the relative standard deviations (RSDs) were lower than 9.3%. The results of the adsorption experiments showed that the maximum adsorption capacity of Fe₃O₄@SiO₂/GO/CS/MPTS for clenbuterol was 214.13 mg g^-1. The adsorption process was most consistent with pseudo second-order kinetics and Langmuir adsorption isotherm, indicating a homogeneous process with a chemisorptive nature. Also, the nanocomposite exhibited high adsorption capability for clenbuterol compared with Fe₃O₄@SiO₂/GO and Fe₃O₄@SiO₂/GO/CS. In addition, regeneration of the nanocomposite was effectively achieved, and it retained about 82% of its initial capacity after four cycles. All these results indicate that the synthetic nanocomposite is a promising efficient adsorbent for the adsorption of clenbuterol with high adsorption capacity and low cost.

Trends in sensitive detection and rapid removal of sulfonamides: A review

Sulfonamides in environmental water, food, and feed are a major concern for both aquatic ecosystems and public health, because they may lead to the health risk of drug resistance. Thus, numerous sensitive detection and rapid removal methodologies have been established. This review summarizes the sample preparation techniques and instrumental methods used for sensitive detection of sulfonamides. Additionally, adsorption and photocatalysis for the rapid removal of sulfonamides are also discussed. This review provides a comprehensive perspective on future sulfonamide analyses that have good performance, and on the basic methods for the rapid removal of sulfonamides.