Exploration of a novel triazine-based covalent organic framework for solid-phase extraction of antibiotics

Characterization of a conjugate between poly(N-vinyl caprolactam) and a triazine-based covalent organic framework as a potential biomaterial

Thermoresponsive polymers (TRPs) have been explored over decades for biomedical applications, and poly(N-vinylcaprolactam) (PVCL) TRP is extensively investigated due to its low toxicity and lower critical solution temperature (LCST), close to physiological temperatures. Besides this, the utilization of covalent organic frameworks (COFs), which belong to a class of porous polymers, in bio-based applications is of great interest due to their remarkable properties. Thus, the integration of PVCL and covalent organic frameworks (COFs) as conjugate materials can lead to advanced bio-based applications; however, the need is to understand the influence of the COF on the PVCL conformation. Herein, a triazine-based COF, CC-TAPT-COF, has been synthesized and completely characterized. Later, the effect of CC-TAPT-COF on the PVCL polymer conformation was studied using various techniques. In fluorescence spectroscopy, a fluorescence quenching for PVCL in the presence of CC-TAPT-COF was observed, which indicated conformational changes. Later, results from thermal fluorescence studies and dynamic light scattering as a function of temperature showed a slight decrease in LCST value for PVCL after the addition of CC-TAPT-COF concentrations. These results showed a slight effect of CC-TAPT-COF on the PVCL conformation. Likewise, a slight decrease in the transmittance value for specific bands in infrared spectra showed a slight effect of CC-TAPT-COF on the PVCL conformation. Further, results from electron microscopy and atomic force microscopy revealed a conjugate formation between PVCL and CC-TAPT-COF due to the presence of binding interactions between them. Overall, the results from several studies showed a slight effect of CC-TAPT-COF on the PVCL during conjugate formation between PVCL and CC-TAPT-COF. This study will be beneficial for the development of COF-thermoresponsive polymer conjugates with a mixture of their unique features as advanced biomaterials.

Carboxyl-functionalized covalent organic frameworks for the extraction of malachite green and crystal violet in environmental water samples prior to quantification by high-performance liquid chromatography

In this study, monodisperse, uniform, and spherical covalent organic frameworks (COFs) were synthesized using 1,3,5-tris (4-aminophenyl) benzene and 1,3,5-tricarboxaldehyde benzene at room temperature. Post-modification of 6-aminocaproic acid on the COFs yielded carboxyl-modified COFs (COFs-COOH). The modification enhanced the hydrophilicity and adsorption efficiencies of COFs-COOH for malachite green (MG) and crystal violet (CV). A COFs-COOH-based dispersive solid-phase extraction coupled with high-performance liquid chromatography was developed for the analysis of MG and CV. The method showed a linear range from 10 to 1000 ng/mL with detection limits of 1.82 and 0.70 ng/mL for MG and CV detection, respectively. The recoveries of MG and CV from water samples collected from fish farms and markets ranged from 91.63% to 107.10% with relative standard deviations below 5%. Reproducibility tests demonstrated that the adsorption efficiencies of COFs-COOH were maintained at above 85.86% over 15 cycles. The study verified the potential of COFs-COOH as sorbents for the enrichment and separation of triphenylmethane dyes from complex samples.

Covalent organic frameworks: Pioneering remediation solutions for organic pollutants

Covalent Organic Frameworks (COFs) have emerged as a promising class of crystalline porous materials with customizable structures, high surface areas, and tunable functionalities. Their unique properties make them attractive candidates for addressing environmental contamination caused by pharmaceuticals, pesticides, industrial chemicals, persistent organic pollutants (POPs), and endocrine disruptors (EDCs). This review article provides a comprehensive overview of recent advancements and applications of COFs in removing and remedying various environmental contaminants. We delve into the synthesis, properties, and performance of COFs and their potential limitations and future prospects.

Exploration of porous imine-based covalent organic framework for solid-phase extraction of five trace sulfonamides in food samples

In this article, a highly crystalline porous imine-based covalent organic framework was synthesized at room temperature and used as solid-phase extraction (SPE) adsorbent for the purification and enrichment of trace sulfonamides (SAs) from food samples. The structure of the obtained material was characterized and studied in detail. The extraction process was optimized and the final elution was determined by the ultra-high-performance liquid chromatography-quadrupole time of flight mass spectrometry method. Low limits of detection (0.02-0.19 μg/kg) were obtained under optimal conditions, with the recoveries ranging from 70.5% to 105.3% when spiked at different levels. The adsorption process of the material for SAs was fitted by the Langmuir and Freundlich adsorption isotherm model, and the extraction capacity for Nitrofuran metabolites from food samples was also investigated for comparison. The results demonstrated that the framework was a good candidate SPE adsorbent that can be used for the enrichment of drug residues in complex matrix, and the work may provide a systematic study method for the development of porous adsorbents.

Advances in solid-phase extraction techniques: Role of nanosorbents for the enrichment of antibiotics for analytical quantification

Antibiotics are life-saving medications for treating bacterial infections; however it has been discovered that resistance developed by bacteria against these incredible agents is the primary contributing factor to rising global mortality rates. The fundamental cause of the emergence of antibiotic resistance in bacteria is the presence of antibiotic residues in various environmental matrices. Although antibiotics are present in diluted form in environmental matrices like water, consistent exposure of bacteria to these minute levels is enough for the resistance to develop. So, identifying these tiny concentrations of numerous antibiotics in various and complicated matrices will be a crucial step in controlling their disposal in those matrices. Solid phase extraction, a popular and customizable extraction technology, was developed according to the aspirations of the researchers. It is a unique alternative technique that could be implemented either alone or in combination with other approaches at different stages because of the multitude of sorbent varieties and techniques. Initially, sorbents are utilized for extraction in their natural state. The basic sorbent has been modified over time with nanoparticles and multilayer sorbents, which have indeed helped to accomplish the desired extraction efficiencies. Among the current traditional extraction techniques such as liquid-liquid extraction, protein precipitation, and salting out techniques, solid-phase extractions (SPE) with nanosorbents are most productive because, they can be automated, selective, and can be integrated with other extraction techniques. This review aims to provide a broad overview of advancements and developments in sorbents with a specific emphasis on the applications of SPE techniques used for antibiotic detection and quantification in various matrices in the last two decades.

Facile room temperature synthesis of a NiFe2O4-based magnetic covalent organic framework for the extraction of tetracycline residues in environmental water samples prior to HPLC

In this study, a functionalized magnetic covalent organic framework (NiFe₂O₄@TAPB-TPA) was fabricated with NiFe₂O₄ nanoparticles as the magnetic core, and 1,3,5-tris(4-aminophenyl)benzene (TAPB) and terephthalaldehyde (TPA) as building blocks by a facile room temperature strategy. Benefitting from the π-π stacking and hydrogen bond interaction, NiFe₂O₄@TAPB-TPA showed great potential as a magnetic adsorbent for the extraction of tetracyclines (TCs). Under optimal conditions, good linearities (R² > 0.9990) were obtained between the peak area and TC concentration in the range of 1-500 μg L^-1 with limits of detection ranging from 0.09 to 0.26 μg L^-1. The intra-day and inter-day relative standard deviations were less than 2.2% and 4.7%, respectively. The established method was successfully applied for the determination of TCs in diverse environmental water samples with satisfactory recoveries in the range of 91.6-102.7%. In addition, NiFe₂O₄@TAPB-TPA showed good reusability with the recoveries for TCs higher than 73.1% after nine recycles, indicating potential application of NiFe₂O₄@TAPB-TPA as an ideal adsorbent for the enrichment of TCs.

Exploration of an imine-based covalent organic framework for the solid phase extraction of nitroimidazoles in milk and meat samples

TAPT-AN-COF, an imine-based covalent organic framework, was synthesized by a solvothermal method of 2,4,6-trihydroxy-benzene-1,3,5-tricarbaldehyde (TP) and 4,4',4″-(1,3,5-Triazine-2,4,6-triyl)trianiline (TAPT). The structure was characterized and tested by several techniques, revealing that the material had good stability and high specific surface area. The adsorption experiment demonstrates that the adsorption isotherm of TAPT-AN-COF followed the Freundlich isothermal equation, while its adsorption kinetics conformed to the pseudo second-order kinetic model. After characterization, the prepared TAPT-AN-COF was used to separate and enrich nitroimidazoles (NDZs) in milk and meat as the solid-phase extraction (SPE) adsorbent. The effects of adsorbent dosage, pH value, washing solvent, elution solvent type and volume on recoveries were studied. Under the optimal conditions, a method for the determination of NDZs in milk and meat samples was established based on high performance liquid chromatography-ultraviolet detection(HPLC-UVD).The result showed that NDZs had good linearity in the concentration range of 25-500 µg·kg^-1, and the determination coefficients (r²) were all above 0.99. When spiked at 25, 50 and 125 µg·kg^-1, the recoveries of three kinds of food samples ranged from 64.5% to 85.3%, the limits of detection (LODs) were between 2 and 10 µg·kg^-1, and the relative standard deviations were all below 15.9%. In addition, the recoveries of NDZs didn't decrease significantly after being reused for 6 times, showing that TAPT-AN-COF has excellent reusability. Compared with HLB and MCX sorbents, TAPT-AN-COF had better extraction efficiency and qualified purification efficiency. The established method had a satisfying performance on the determination of NDZs in food samples.

Triazine 2D Nanosheets as a New Class of Nanomaterials: Crystallinity, Properties and Applications

Based on the recent (2015–2021) literature data, the authors analyze the mutual dependence of crystallinity/amorphism and specific surface area and porosity in covalent triazine frameworks (CTFs), taking into account thermodynamic and kinetic control in the synthesis of these 2D nanosheets. CTFs have now become a promising new class of high-performance porous organic materials. They can be recycled and reused easily, and thus have great potential as sustainable materials. For 2D CTFs, numerous examples are given to support the known rule that the structure and properties of any material with a given composition depend on the conditions of its synthesis. The review may be useful for elder students, postgraduate students, engineers and research fellows dealing with chemical synthesis and modern nanotechnologies based on 2D covalent triazine frameworks.

Evaluation of a porous imine-based covalent organic framework for solid-phase extraction of nitroimidazoles

Covalent organic framework materials (COFs), a kind of porous organic material, have excellent potential application in the field of sample pretreatment due to their high surface areas and thermal stability. In this work, a porous imine-based COF, named BP-COF, was fabricated by a solvothermal method using 2,2'-bipyridine-5,5'-dicarboxaldehyde and 1,3,5-tris(4-aminophenyl) benzene as monomers. After a series of structural characterization studies, the BP-COF was used as a solid-phase extraction (SPE) adsorbent for the extraction and enrichment of nitroimidazoles and their metabolites. Several parameters were investigated during the extraction process, including the sorbent dosage, loading pH value, the washing and elution solvent, and the breakthrough volume. By coupling with UPLC-QTOF-MS/MS, a sensitive and facile method was established for the quantitation analysis of NDZs. Under the optimum conditions, a low detection limit (0.015-0.12 ng mL^-1) and wide linearity (0.2-500 ng mL^-1) with higher R² were obtained. In addition, the developed method was applied for the determination of NDZs in four water samples with recoveries in the range of 71.7-115.9% and RSDs less than 8.3%. The results indicated that the BP-COF shows great potential for the enrichment of NDZs in water samples.

Recent advances in porous organic frameworks for sample pretreatment of pesticide and veterinary drug residues: a review

Rapid and accurate detection of pesticide and veterinary drug residues is a continuing challenge because of the complex matrix effects. Thus, appropriate sample pretreatment is a crucial step for the effective extraction of the analytes and removal of the interferences. Recently, the development of nanomaterial adsorbents has greatly promoted the innovation of food sample pretreatment approaches. Porous organic frameworks (POFs), including polymers of intrinsic microporosity, covalent organic frameworks, hyper crosslinked polymers, conjugated microporous polymers, and porous aromatic frameworks, have been widely utilized due to their tailorable skeletons and pores as well as fascinating features. This review summarizes the recent advances for POFs to be utilized in adsorption and sample preparation of pesticide and veterinary drug residues. In addition, future prospects and challenges are discussed, hoping to offer a reference for further study on POFs in sample pretreatment.

Chemical and computational strategy for design of "switchable" sorbent based on hydroxyapatite nanoparticles for dispersive micro-solid phase extraction of tetracyclines

A challenging task in analytical chemistry is an application of renewable and natural materials for isolation of hazardous substances such as antimicrobial drugs from environmental samples. The energy-efficient scalable hydrothermal procedure to fabricate the eco-friendly "switchable" sorbent based on hydroxyapatite nanoparticles with in situ modified surface using a small amount of capping agents was developed. Sorbents characterization including the surface composition investigation via quantum-chemical calculation based on the original approach was provided. The sorbents demonstrated well expressed controllable surface switching and high values of the sorption and elution efficiency for tetracycline, oxytetracycline, and chlortetracycline achieved by simple change of the medium pH. These processes were thoroughly discussed based on the results of chemical and computational experiments. A simple and universal strategy for choosing a suitable sorbent for solid phase extraction of target analytes was proposed for the first time. It was shown that the developed eco-friendly sample preparation procedure with use of biocompatible sorbents could be applied both for removal of target analytes from sample matrix (water samples) as well as for the quantitative analytes determination after elution step. It is believed that the presented research is significant for the determination of different amphoteric analytes in wide variety of samples.

[Recent advance of new sample preparation materials in the analysis and detection of environmental pollutants]

针对复杂样品的分析和痕量目标物的检测,样品前处理是必不可少的,高效的样品前处理技术不仅可以去除或减小样品基质干扰而且能够实现分析物的富集,提高分析检测的准确性和灵敏度。近年来,固相萃取、磁分散固相萃取、枪头固相萃取、搅拌棒萃取、固相微萃取等高效的样品前处理技术已在环境污染物分析检测中获得广泛关注,萃取效率主要取决于萃取材料,所以新型的高效萃取材料一直是样品前处理研究领域的重要发展方向。该文总结和讨论了近年来新型样品前处理材料在环境污染物分析检测中的研究进展,主要聚焦在石墨烯、氧化石墨烯、碳纳米管、无机气凝胶、有机气凝胶、三嗪基功能材料、三嗪基聚合物、分子印迹聚合物、共价有机框架材料、金属有机框架材料以及它们的功能化萃取材料等。这些材料已经被应用于环境样品中不同类别污染物的萃取富集,如重金属离子、多环芳烃、塑化剂、烷烃、苯酚、氯酚、氯苯、多溴联苯醚、全氟磺酸、全氟羧酸、雌激素、药物残留、农药残留等。这些样品前处理材料具有高的表面积、大量的吸附位点,并涉及多种萃取机理如π-π、静电、疏水、亲水、氢键、卤键等相互作用。基于这些萃取材料的多种样品前处理技术与各类检测方法如色谱、质谱、原子吸收光谱、荧光光谱、离子迁移谱等相结合,已广泛应用于环境污染物的高灵敏分析检测。最后,该文总结了样品前处理发展中存在的问题,并展望了其未来在环境分析中的发展趋势。

Facile fabrication of magnetic covalent organic frameworks for magnetic solid-phase extraction of diclofenac sodium in milk

A robust magnetic solid-phase extraction (MSPE) method based on magnetic covalent organic framework (MCOF) coupled with high-performance liquid chromatography (HPLC)-ultraviolet (UV)/mass spectrometry (MS) was proposed for the determination of trace diclofenac sodium (DS) in milk. The prepared MCOF exhibited high extraction efficiency, which can be attributed to its high specific surface area as well as strong π-π and hydrophobic interactions between MCOF and DS. In addition, the potential influencing factors, including sample volume, adsorbent dosage, extraction time, and elution parameters, were fully estimated. The experimental results demonstrated that the established method was sensitive for the quantification of DS with high accuracy. Remarkably, the detection limit of DS was found to be 10 ng/kg under the optimal conditions. More impressively, the developed method was successfully applied to monitor trace DS in milk, demonstrating its outstanding durability and practical potential as an appealing method to regular monitor trace pharmaceutical contaminants in real food samples.

Covalent organic frameworks: an ideal platform for designing ordered materials and advanced applications

Covalent organic frameworks offer a molecular platform for integrating organic units into periodically ordered yet extended 2D and 3D polymers to create topologically well-defined polygonal lattices and built-in discrete micropores and/or mesopores.

Porous framework-based hybrid materials for solar-to-chemical energy conversion: from powder photocatalysts to photoelectrodes

Porous framework materials such as metal organic frameworks (MOFs) and covalent organic frameworks (COFs) can be considered promising materials for solar-to-chemical energy conversion.

The fabrication of a covalent triazine-based organic framework for the solid-phase extraction of fourteen kinds of sulfonamides from meat samples

A novel covalent triazine-based organic framework (CTF), SCAU-2, was fabricated and used as an adsorbent for the solid-phase extraction of fourteen kinds of sulfonamides (SAs) from meat. Another CTF, SCAU-1, was adopted as a comparison material, as it has a similar motif. A series of structural characterization steps was carried out on the synthesized materials and several parameters were investigated during the extraction process, including the amount of adsorbent, the dilution ratio, the pH of the sample, and the washing and elution solvents. After detection with UHPLC-Q/TOF-MS/MS, the results revealed that SCAU-2 showed high extraction efficiencies towards the selected SAs. The LOD values are from 0.05 to 0.54 ng g-1, and the recoveries are from 84.1% to 91.9%, with RSDs ranging from 3.2% to 4.8% for SCAU-2 when spiked at 50 ng g-1. The results demonstrated that the proposed method has good applicability for the determination of SAs in complicated samples.