β-Cyclodextrin-/AuNPs-functionalized covalent organic framework-based magnetic sorbent for solid phase extraction and determination of sulfonamides

Determination of sulfonamide antibiotics by magnetic porous carbon solid-phase extraction coupled with capillary electrophoresis

Sulfonamide antibiotics (SAs) have been widely used as antibacterial drugs for the prevention and treatment of livestock and poultry diseases, but they seriously threaten human health because they can accumulate in humans. Therefore, it is highly important to develop methods for monitoring sulfonamide residues in aquaculture and food. In this research, based on the generation of porous carbon (PC) by the pyrolysis of sodium citrate, magnetic porous carbon (PC@Fe3O4) was synthesized by a solvothermal method and used as an adsorbent for the magnetic solid-phase extraction of SAs. The effects of the proportion of PC in PC@Fe3O4, adsorbent dosage, adsorption time, eluent type, extraction pH, salt concentration and eluent dosage on the extraction efficiency were systematically studied. The adsorption performance and behavior of PC@Fe3O4 on SAs were evaluated using adsorption kinetics and adsorption isotherms, and the adsorption mechanism was preliminarily discussed. Under optimal conditions, combined with capillary electrophoresis diode array detection, a sensitive detection method for SAs was developed. The proposed method can be used for the determination of six SAs in fishpond water and milk samples, with a linear range of 0.5-200 ng mL-1, detection limits of 0.24-0.34 ng mL-1, and spiked recoveries of 85.9-109.0 %.

Fabrication and characterization of magnetic mesoporous nanoparticles for efficient determination and magnetic separation of sulfonamides in food samples

A magnetic, mesoporous core/shell structured Fe3O4@SiO2@mSiO2 nanocomposite was synthesized and employed as a magnetic solid phase extraction (MSPE) sorbent for the determination of trace sulfonamides (SAs) in food samples. The synthesized nanocomposite was characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, X-ray diffraction, N2 sorption analysis and vibrating sample magnetometry. The results showed that Fe3O4@SiO2@mSiO2 possessed a mesoporous structure with a large surface area. Batch experiments were carried out to investigate the adsorption ability for SAs. Fe3O4@SiO2@mSiO2 showed fast kinetics and high adsorption capacity, and the pseudo-second-order model and Langmuir adsorption isotherm are well fitted with the experimental data, indicating that chemical adsorption might be the rate-limiting step. Moreover, the high adsorption capacity can be maintained for at least 8 runs, indicating excellent stability and reusability. The proposed method exhibited good linearity in the range of 0.2-500 μg L-1, the R2 values of all the analytes were greater than 0.99 and the LODs were all lower than 0.2 μg L-1. Furthermore, real food samples were successfully analyzed with Fe3O4@SiO2@mSiO2 and high recoveries varying from 89.7% and 110.6% were obtained with low relative standard deviations ranging from 1.78% to 6.91%. The Fe3O4@SiO2@mSiO2 magnetic nanocomposite is a promising sorbent for the efficient extraction of SAs from complex food samples.

Determination of trace fluoroquinolones in honey and milk based on cyclodextrin modified magnetic metal-organic frameworks solid phase extraction coupled with ultra-high performance liquid chromatography

Long-term intake of animal-derived foods with excessive fluoroquinolones (FQs) will cause damage to human health, so it is critical to establish a feasible approach for sensitive and rapid monitoring of FQs residues. In this study, a new cyclodextrin modified magnetic metal-organic frameworks (Fe3O4@UiO-66-CD) was successfully synthesized by amidation reaction and applied to magnetic solid phase extraction (MSPE) for FQs analysis. The adsorption behavior of Fe3O4@UiO-66-CD was consistent with the pseudo-second-order kinetics and Freundlich isothermal adsorption model, which indicated that the designed material had various interactions on FQs, such as host-guest interaction and π-π interaction. The parameters of MSPE were optimized and the determination method of norfloxacin, enrofloxacin, lomefloxacin and gatifloxacin was established by using MSPE combined with ultra-high performance liquid chromatography (UHPLC) and fluorescence detector (FLD). The method validation results displayed that the detection limits were 0.02-0.09 ng/mL, and the RSDs of intra-day and inter-day precision were less than 4.1 and 6.4 %, respectively. In the target FQs analysis of real honey and milk samples, the recoveries at different fortified concentrations were in the ranges of 88.4 % to 108.6 % with RSD ≤ 5.7 %. The results showed that the proposed method was sensitive, accurate and reliable for the determination of trace FQs in animal-derived foods.

Advanced porous organic materials for sample preparation in pharmaceutical analysis

The development of novel sample preparation media plays a crucial role in pharmaceutical analysis. To facilitate the extraction and enrichment of pharmaceutical molecules in complex samples, various functionalized materials have been developed and prepared as adsorbents. Recently, some functionalized porous organic materials have become adsorbents for pharmaceutical analysis due to their unique properties of adsorption and recognition. These advanced porous organic materials, combined with consequent analytical techniques, have been successfully used for pharmaceutical analysis in complex samples such as environmental and biological samples. This review encapsulates the progress of advanced porous materials for pharmaceutical analysis including pesticides, antibiotics, chiral drugs, and other compounds in the past decade. In addition, we also address the limitations and future trends of these porous organic materials in pharmaceutical analysis.

Synthesis of a magnetic covalent organic framework for extraction and separation of ultraviolet filters in beverage samples

In this study, a novel magnetic covalent organic framework (Fe₃O₄@TAPB-BTT) was successfully synthesized under mild conditions. The prepared magnetic COF exhibited large surface area (876.3 m² g^-1), porous feature as well as sizeable π-conjugated network structure. Due to the above advantages, Fe₃O₄@TAPB-BTT showed good adsorptive performance for ultraviolet (UV) filters with adsorption capacities ranging from 80.8 to 120.1 mg g^-1. Then the adsorbent was applied to magnetic solid phase extraction (MSPE) of UV filters in beverage samples, followed by UHPLC-MS/MS analysis. The established method showed good accuracy, precision, and reproducibility with satisfactory recoveries (76.9-95.6 %), low limits of detection (0.001-0.15 µg/L), and low relative standard deviations (<9.8 %). Besides, the adsorbent can be reutilized at least ten times, demonstrating satisfactory reusability. This work provided an effective method for the analysis and determination of UV filters in drinks.

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.

[Application progress of covalent organic framework materials in extraction of toxic and harmful substances]

Toxic and hazardous substances constitute a category of compounds that are potentially hazardous to humans, other organisms, and the environment. These substances include pesticides (benzoylureas, pyrethroids, neonicotinoids), persistent organic pollutants (polycyclic aromatic hydrocarbons, polychlorinated biphenyls, perfluorinated compounds), plasticizers (phthalate esters, phenolic endocrine disruptors), medicines (sulfonamides, non-steroid anti-inflammatory drugs, tetracyclines, fluoroquinone antibiotics), heterocyclic aromatic amines, algal toxins, and radioactive substances. Discharge of these toxic and harmful substances, as well as their possible persistence and bioaccumulation, pose a major risk to human health, often to the extent of being life-threatening. Therefore, it is important to analyze and detect toxic and hazardous substances in the environment, drinking water, food, and daily commodities. Sample pretreatment is an imperative step in most of the currently used analytical methods, especially in the analysis of trace toxic and harmful substances in complex samples. An efficient and fast sample pretreatment technology not only helps improve the sensitivity, selectivity, reproducibility, and accuracy of analytical methods, but also avoids contamination of the analytical instruments and even damages the performance and working life of instruments. Sample pretreatment techniques widely used in the extraction of toxic and hazardous substances include solid-phase extraction (SPE), solid-phase microextraction (SPME), and dispersed solid-phase extraction (DSPE). The adsorbent material plays a key role in these pretreatment techniques, thereby determining their selectivity and efficiency. In recent years, covalent organic frameworks (COFs) have attracted increasing attention in sample pretreatment. COFs represent an exciting new class of porous crystalline materials constructed via the strong covalent bonding of organic building units through a reversible condensation reaction. COFs present four advantages: (1) precise control over structure type and pore size by consideration of the target molecular structure based on the connectivity and shape of the building units; (2) post-synthetic modification for chemical optimization of the pore interior toward optimized interaction with the target; (3) straightforward scalable synthesis; (4) feasible formation of composites with magnetic nanoparticles, carbon nanotubes, graphene, silica, etc., which is beneficial to enhance the performance of COFs and meet the requirement of diverse pretreatment technologies. Because of the well-defined crystalline porous structures and tailored functionalities, COFs have excellent potential for use in target extraction. However, some issues need to be addressed for the application of COFs in the extraction of toxic and hazardous substances. (1) For the sample matrix, most of the reported COFs are highly hydrophobic, which limits their dispersibility in water-based samples, leading to poor extraction performance. COFs with good dispersibility in water-based samples are urgently required. (2) Besides, COFs rely on hydrophobic interaction, size repulsion, π-π stacking, and Van der Waals forces to extract target substances, but they are not effective for some polar targets. Thus, it is necessary to develop COFs with high affinity for polar toxic and hazardous substances. (3) Methods for the synthesis of COFs have evolved from solvothermal methods to room-temperature methods, mechanical grinding, microwave-assisted synthesis, ion thermal methods, etc. Most of the existing methods are time-consuming, laborious, and environmentally unfriendly. The starting materials are too expensive to prepare COFs in large quantities. More effort is required to improve the synthesis efficiency and overcome the obstacles in the application of COFs for extraction. This article summarizes and reviews the research progress in COFs toward the extraction of toxic and hazardous substances in recent years. Finally, the application prospects of COFs in this field are summarized, which serves as a reference for further research into pretreatment technologies based on COFs.

Recent Advances in the Application of Covalent Organic Frameworks in Extraction: A Review

Covalent organic frameworks (COFs) are a class of emerging materials that are synthesized based on the covalent bonds between different building blocks. COFs possess unique attributes in terms of high porosity, tunable structure, ordered channels, easy modification, large surface area, and great physical and chemical stability. Due to these features, COFs have been extensively applied as adsorbents in various extraction modes. Enhanced extraction performance could be reached with modified COFs, where COFs are presented as composites with other materials including nanomaterials, carbon and its derivatives, silica, metal-organic frameworks, molecularly imprinted polymers, etc. This review article describes the recent advances, developments, and applications of COF-based materials being utilized as adsorbents in the extraction methods. The COFs, their properties, their synthesis approaches as well as their composite structures are reviewed. Most importantly, suggested mechanisms for the extraction of analyte(s) by COF-based materials are also discussed. Finally, the current challenges and future prospects of COF-based materials in extraction methods are summarized and considered in order to provide more insights into this field.

Development of a rapid efficient solid-phase microextraction: An overhead rotating flat surface sorbent based 3-D graphene oxide/ lanthanum nanoparticles @ Ni foam for separation and determination of sulfonamides in animal-based food products

In this study, an overhead rotating flat surface sorbent based solid-phase microextraction was developed as a rapid and efficient method for simultaneous separation and determination of sulfonamides in animal based-food products. 3D graphene oxide/ lanthanum nanoparticles @ Ni foam was introduced as a novel selective sorbent. SEM-EDX and FT-IR techniques were applied for characterization of the sorbent. At optimum conditions, the linear ranges of 0.4-700.0 (µg L^-1), 0.3-900.0 (µg L^-1), and 0.25-500 (µg L^-1) and the enrichment factors of 606.8, 604.3, 608.9 were obtained for SDZ, SMX, and SMZ, respectively. The LOD (S/N = 3) of 0.14, 0.11, 0.08 (µg L^-1) were achieved for SDZ, SMX, and SMZ, respectively. The intra-day and inter-day precision (%) (five days, n = 7) for the concentration of 100 µg L^-1 were less than 4.3 and 3.8, respectively. The recoveries over 90.0 % revealed high capability of the method for utilization in complex matrixes.

Simultaneous Determination of Sulfonamides Antibiotics in Environmental Water and Seafood Samples Using Ultrasonic-Assisted Dispersive Liquid-Liquid Microextraction Coupled with High Performance Liquid Chromatography

The residues and abuse of antibiotics have seriously endangered ecological balance and human health; meanwhile, antibiotics determination is very difficult because of their low levels and multiple categories in complicated matrices. Appropriate sample pretreatment is usually imperative to enrich (ultra)trace antibiotics and eliminate matrix interference prior to chromatographic analysis. Dispersive liquid-liquid microextraction (DLLME) has become an ideal pretreatment technique owing to its simplicity, effectiveness, low-consumption, etc. In this work, an ultrasonic-assisted DLLME (UA-DLLME) was developed for the simultaneous extraction of seven sulfonamides (SAs) antibiotics in environmental water and seafood samples coupled with HPLC-DAD determination. Several parameters affecting UA-DLLME efficiency were systematically optimized, and consequently the SAs were separated and detected within 14.5 min. The obtained limits of detection (LODs) and limits of quantification (LOQs) ranged from 0.7-7.8 μg/L and 2.4-26.0 μg/L for three water samples (seawater, aquaculture wastewater and lake water) and two seafood samples (pomfrets and shrimps). High recoveries (80.0-116.0%) with low relative standard deviations (0.1-8.1%) were achieved for all the tested samples at three spiked levels. Notably, sulfadimethoxine was found at 24.49 μg/L in one seawater sample. The facile, robust and benign DLLME-HPLC method demonstrated promising perspectives for multiresidue analysis of antibiotics.

Highly sensitive multiplex detection of foodborne pathogens using a SERS immunosensor combined with novel covalent organic frameworks based biologic interference-free Raman tags

Rapid and reliable multiplex detection of foodborne pathogens is in great demand for ensuring food safety and preventing foodborne diseases. In this study, we developed a highly sensitive SERS immunosensor for the simultaneous detection of multiple foodborne pathogens. Novel biologic interference-free Raman tags synthesized by using the covalent organic frameworks (COF) TBDP as nanocontainer to load biologic interference-free Raman reporters and specific antibodies for interested targets were used to convert and amplify signals of foodborne pathogens. In addition, lectin functionalized magnetic nanoparticles (MNPs@Con A) which could efficiently bind to the carbohydrate constituents on the surface of pathogens were prepared to capture and isolate multiple pathogens simultaneously. The recognition of the target foodborne pathogen impels the generation of sandwich-like composites of MNPs@Con A/pathogen/TBDP@Raman tags, and these composites could be quickly separated from the sample matrix with the assistance of an external magnet. Besides, a mass of Raman reporters was released by eluting the collected MNPs@Con A/pathogen/TBDP@Raman tags composites. Combined with a portable Raman system, characteristic Raman signals (2271 and 2113 cm^-1) of the occupied reporters located at the biologic interference-free region were observed and used for the simultaneous detection of two different foodborne pathogenic strains. And an equal limit of detection of 10¹ CFU/mL was achieved for each strain. This strategy provides new insight into the application of SERS in the detection of pathogenic bacteria.

Self-assembly of core-shell structured multiwalled nanotubes@covalent organic frameworks composite for solid-phase extraction of four phytohormones from fruit juices

Covalent organic frameworks (COFs) have attracted considerable attention in sample pretreatment because of their unique characteristics. However, the submicron or micron size of COFs has restricted their wider applications in solid-phase extraction (SPE). Herein, multiwalled nanotubes (MWNTs) were used as substrate materials to synthesize core-shell structured MWNTs@COFs composites (MWNTs@SNW-1) using a simple self-assembly method. The as-prepared MWNTs@SNW-1 composite exhibited a high BET surface area, good thermal stability, and good adsorption capacity. The MWNTs@SNW-1 composite was used as an adsorbent in cartridge-based SPE to extract four phytohormones before determining their levels by high-performance liquid chromatography. The experimental parameters affecting extraction efficiency, including the amount of adsorbents, solution pH, ionic strength, eluent type, and eluent volume, were investigated. The developed method showed a wide linear range (0.37-100 ng mL^-1), low detection limits (0.11-0.32 ng mL^-1), low limits of quantification (0.37-1.07 ng mL^-1), high enrichment factors (45.9-49.3), and good reproducibility (<4.8%) for phytohormones. The developed analytical method was used to analyze trace phytohormones in fruit juices with good recoveries, highlighting the potential of the MWNTs@SNW-1 composite as an adsorbent in sample preparation.

Miniaturized green sample preparation approaches for pharmaceutical analysis

The development of green sample preparation procedures is an extremely important research field in which more and more applications are constantly being proposed in different areas, including pharmaceutical analysis. This review article is aimed at providing a general overview of the development of miniaturized green analytical sample preparation procedures in the pharmaceutical analysis field, with special focus on the works published between January 2017 and July 2021. Particular attention has been paid to the application of environmentally friendly solvents and sorbents as well as nanomaterials or high extraction capacity sorbents in which the solvent volumes and reagents amounts are drastically reduced, with their subsequent advantages from the sustainability point of view.

Hotpots and trends of covalent organic frameworks (COFs) in the environmental and energy field: Bibliometric analysis

Covalent organic frameworks (COFs) have attracted extensive attention due to their low density, adjustable structure, functionalization, and good stability. This paper systematically and comprehensively describes to qualitatively and quantitatively the progress, trends, and hotspots of COFs in the environmental and energy fields from the perspective of bibliometrics. Herein, based on the Web of Science database, a total of 2589 articles from 2005 to October 6, 2020, were collected. Thereafter, co-occurrence, co-citation analysis, and cluster analysis were conducted using CiteSpace and VOSviewer software. The results indicated that COFs research shows the characteristics of rapid growth. The active countries were mainly USA, Germany, Japan, China, and India. More than half of the top 20 active institutions were from China. The research hotspots in this field were systematically elaborated, including synthesis, adsorption, catalysis, membrane, sensor, and energy storage. Research has shown that various COFs are reasonably designed, synthesized, and used in different applications. For example, when COFs are used for photocatalysis, groups containing photocatalytic active sites are integrated into COFs to improve photocatalytic activity. Finally, some challenges were proposed, that are beneficial to the rapid and balanced development of the COFs field. For instance, the preparation methods still need to be further improved for mass production and there is an imbalance in environmental applications such as fewer sensor and membrane applications. We believe that this study provides a comprehensive and systematic overview of the environmental and energy applications of COFs for future investigations.

[Synthesis and application progress of covalent organic polymers in sample preparation for food safety analysis]

食品安全关系身体健康和生命安全,是全球关注的热点之一。食品基质复杂,痕量有毒有害物质分析之前必须经过有效的前处理。目前发展的前处理技术如固相萃取、磁固相萃取、固相微萃取等,其关键是吸附介质。共价有机聚合物是一类通过共价键连接而成的有机多孔材料,具有质轻、稳定性好、比表面积大、结构可控、易于修饰等特性,是一类优异的新型吸附材料。该文综述了近年来共价有机聚合物(COPs)在食品安全分析前处理中的应用进展。共价有机聚合物及其功能化复合材料通过简单的装填、聚合反应或化学键合固定到小柱或毛细管柱中用作固相萃取的吸附介质;通过一锅法、原位还原法、原位生长法或共沉淀法生成具有磁性的固相萃取吸附介质;或者通过物理涂覆、化学键合、溶胶凝胶法及原位生长法制备固相微萃取纤维。基于以上高吸附容量共价有机聚合物的样品前处理技术,食品中农残兽残、添加剂、环境污染物及生物毒素等得到了有效富集。最后,展望了COPs在食品分析样品前处理应用中的发展方向:简单高效绿色制备方法的开发,功能化COPs的设计合成;萃取机理的研究;高通量、高灵敏度分析方法研究。这些研究将促进COPs在样品前处理领域获得更广泛的应用。

Recent advances and applications of cyclodextrins in magnetic solid phase extraction

Cyclodextrins (CDs) as a family of cyclic oligosaccharides are toroidal with a hydrophobic interior and a hydrophilic exterior. They are well-known for their ability to form host-guest inclusion complexes with different compounds. They are used as chiral stationary phases in high performance liquid chromatography (HPLC) and gas chromatography (GC) or as chiral reagents in the background electrolyte of capillary electrophoresis (CE). In recent years, they have been used for modification of sorbents or as sorbents in solid phase extraction (SPE) procedures. Magnetic solid-phase extraction (MSPE), as a new type of SPE procedure, has received considerable attention due to its rapid phase separation process as compared to traditional extraction mode. This review covers the synthesis of CD-based magnetic sorbents (such as immobilization of CDs onto the different supports, production of nanosponges, and making hybrid substances with nanomaterials) and the use of these compounds in MSPE of different analytes from biological, environmental, and food samples. Also, prospects of CD-based sorbents for sample pre-treatment are also proposed.

Heteropore covalent organic framework-based composite membrane prepared by in situ growth on non-woven fabric for sample pretreatment of food non-targeted analysis

A heteropore covalent organic framework (COF)-based composite membrane material was prepared and proved to have a satisfactory effect on the pretreatment of vegetable samples. The composite membrane was fabricated by in situ growth of a dual-pore COF on the surface of polydopamine (PDA)-aminated non-woven (NW) fabric. Due to the difference in the strength of the interaction between the phytochromes/COF and the pesticides/COF, the removal of phytochromes and the recovery of pesticides can be achieved by adjusting the composition of the solution. Through a simple immersion or filtration operation, NW@PDA@COF composite membrane can quickly and almost completely remove interfering phytochromes in the samples. The recovery of pesticides was determined by HPLC-MS/MS, and the recovery efficiencies were 72.3~101.7% and 67.3~106.7% for immersion and filtration modes of five different vegetable samples, respectively; the RSD is between 1.1 and 19% (n = 3). The limits of detection and quantification for the 13 pesticides investigated were 0.08 μg·L^-1 and 0.23 μg·L^-1, respectively. A wide linear range of 1~1000 μg·L^-1 was observed with R² values from 0.9774 to 0.9998. The membrane can be repeatedly used for at least 10 times by using a facile elution treatment. Compared to other commonly used sample pretreatment materials, heteropore COF-based composite membrane is superior in terms of sorbent amount, treatment time, operation simplicity, and material reusability.

Bipyridine-linked three-dimensional covalent organic frameworks for fluorescence sensing of cobalt(II) at nanomole level

A novel fluorometric method based on bipyridine-linked three-dimensional covalent organic frameworks (COFs) was developed for the determination of Co²⁺. The COFs were synthesized by the polyreaction of tetrakis(4-aminophenyl)methane (TAPM), 2,2'-bipyridine-5,5'-diamine (Bpy), and 4,4'-biphenyldicarboxaldehyde (BPDA) under solvothermal conditions. The fluorescence of the COFs, with excitation/emission peaks at 324/406 nm, is quenched by Co²⁺. Under the optimal conditions, the fluorescence quenching degrees (F₀-F) of the resulted COFs linearly enhance as the concentrations of Co²⁺ increase in the range 0.01 to 0.25 μM, and a limit of detection of 2.63 nM is achieved. The fluorescence response mechanism was discussed in detail. This proposed approach has also been successfully employed to determine Co²⁺ in complex samples (shrimp and tap water), and satisfactory recoveries (88.1 ~ 109.7%) was obtained. The relative standard deviations are below 4.9%.

Cyclodextrins as a Key Piece in Nanostructured Materials: Quantitation and Remediation of Pollutants

Separation and pre-concentration of trace pollutants from their matrix by reversible formation of inclusion complexes has turned into a widely studied field, especially for the benefits provided to different areas. Cyclodextrins are non-toxic oligosaccharides that are well known for their host–guest chemistry, low prices, and negligible environmental impact. Therefore, they have been widely used as chiral selectors and delivery systems in the pharmaceutical and food industry over time. However, their use for extraction purposes is hampered by their high solubility in water. This difficulty is being overcome with a variety of investigations in materials science. The setting-up of novel solid sorbents with improved properties thanks to the presence of cyclodextrins at their structure is still an open research area. Some properties they can offer, such as an increased selectivity or a good distribution along the surface of a solid support, which provides better accessibility for guest molecules, are characteristics of great interest. This systematic review reports the most significant uses of cyclodextrins for the adsorption of pollutants in different-origin samples based on the works reported in the literature in the last years. The study has been carried out indistinctly for quantitation and remediation purposes.

Fabrication of a functionalized magnetic covalent organic framework composite as an efficient adsorbent for sulfonamide extraction from food samples

A carboxyl group functionalized magnetic covalent organic framework as an adsorbent to extract sulfonamides from meat samples was proposed.