Magnetic covalent triazine framework for rapid extraction of phthalate esters in plastic packaging materials followed by gas chromatography-flame ionization detection

Development of amphiphilic hypercrosslinked porous polymers for magnetic extraction of multiple environmental pollutants in water

Under the principle of similar compatibility, researchers have developed various polarity extractants corresponding to a class of chemicals. Separating different polarities chemicals with one extractant effectively has become a novel research trend in separation science. Given the complexity of environmental sample matrices and the significant differences in polarity and solubility of various compounds, the introduction of hydrophilic groups to hydrophobic material skeletons can lead to sorbents with hydrophilic-lipophilic balance (HLB) property and thus improve their extraction performance for substances with different polarities. In this work, a hypercrosslinked polymer (HCPPz-TPB), designated as HLB, was synthesized by incorporating polar pyrazine and nonpolar triphenylbenzene molecules within each other. Subsequently, a core-shell magnetic composite material was obtained by encapsulating magnetic Fe3O4 nanoparticles in HCPPz-TPB. The material was applied as an adsorbent for magnetic solid phase extraction (MSPE) and combined with a high-performance liquid chromatography-photodiode array detector (HPLC-PDA) to enrich, separate, and detect seven polar contaminants in environmental water samples. The proposed approach, Fe3O4@SiO2@HCPPz-TPB-MSPE-HPLC-PDA, is characterized by its outstanding high sensitivity, low detection limits, wide linear range, and good reproducibility. The method demonstrated satisfactory linearity in the range of 0.05-2 μg mL-1 with R2 values between 0.9969 and 0.9997; the limits of detection (LOD) were observed to be within the range of 0.0019-0.016 μg L-1, and limits of quantification (LOQ) was observed to be within the range of 0.0064-0.054 μg L-1 range with good precision. The recoveries of the different contaminants in the environmental samples ranged from 83.61 to 116.46% (RSD≤10.56, n = 5). The new hydrophilic-lipophilic balance extractant is highly efficient, sensitive, and precise for extracting different polar pollutants. The findings demonstrate that the Fe3O4@SiO2@HCPPz-TPB display a remarkable affinity for multiple targets, driven by complex interactions including multi-stackings and hydrogen bonding as a sorbent. The synthesized Fe3O4@SiO2@HCPPz-TPB may be employed in diverse applications, including extraction, removal, and determination of diverse trace multi-target analytes in complex media.

Hollow multi-shelled MOF derivative adsorbent for efficient magnetic solid-phase extraction of several typical endocrine disrupting compounds from water

Bisphenols and benzophenones are two typical kinds of endocrine-disrupting compounds (EDCs) that have been extensively detected in water environments, posing unanticipated risks to aquatic organisms and humans. It is urgent to develop efficient sample pretreatment methods for precise measurement of such EDCs. In this study, a magnetic and multi-shelled metal-organic framework derivative material has been prepared to extract and enrich trace bisphenols and benzophenones from water. Via a solvothermal reaction induced by sodium citrate followed by a carbonization treatment, a ZIF-67@ZIF-8 derived CoZn-magnetic hierarchical carbon (CoZn-MHC) material has been synthesized as a high-performance magnetic solid-phase extraction (MSPE) adsorbent. This adsorbent exhibited a good specific surface area (213.80 m2⋅g-1) and a saturation magnetization of 63.2 emu·g-1. After the optimization of several parameters (including adsorbent dosage, extraction time, pH, ionic strength, desorption solvent, and solvent volume), an efficient MSPE method for several EDCs (comprising bisphenols and benzophenones) was developed with a good linear range (R2 ≥ 0.990), a high sensitivity range (LODs: 0.793-5.37 ng⋅L-1), and good reusability (RSD ≤4.67 % in five consecutive tests). Furthermore, the material exhibited commendable resistance to matrix interference in natural water samples with the recovery rates of target compounds ranging from 74.8 % to 107 %. We envision that the preparation strategy of this functional metal-organic framework (MOF)-based adsorbent for EDCs may provide insights for relevant research in the future.

Magnetic covalent organic frameworks as sorbents in the chromatographic analysis of environmental organic pollutants

Covalent organic frameworks (COFs) are featured with large specific surface areas, good thermal stability, and abundant pores. These properties are exactly what the sorbents used for extraction or adsorption of interest substances are desired with. While, the low density and hydrophobicity of COFs often makes them difficult to be dispersed evenly and recovered from the aqueous solution. Magnetic covalent organic frameworks (MCOFs) inherit magnetic property of the magnetic particles and porous structure of COFs. They have improved dispersity in aqueous solution and phase separation can be rapidly achieved via external magnetic fields. This review summarized the synthesis strategies for MCOFs, and their application in trace environmental organic pollutants analysis by chromatography techniques. The selection of COFs types and modification with active groups for a certain adsorption purpose is discussed, along with the exploration of adsorption mechanisms, which is beneficial for the design and synthesis of MCOFs.

Dissolution-precipitation method concatenated sodium alginate/MOF-derived magnetic multistage pore carbon magnetic solid phase extraction for determination of antioxidants and ultraviolet stabilizers in polylactic acid food contact plastics

Antioxidants and UV stabilizers have some endocrine disrupting effects and liver toxicity. Both types of additives are still widely used in food contact plastics to improve the durability of plastic products. However, efficient and rapid detection of antioxidants and UV stabilizers has been a challenge due to the complexity of the plastic matrix and the low content of antioxidants and UV stabilizers. In this study, a sodium alginate/MOF-derived magnetic multistage pore carbon material (MIL-101(Fe)/SA-CAs) was developed, having the merits of abundant multistage pore structure, large specific surface area, and good magnetic separation properties. Thus, this material was selected as the sorbent for magnetic solid-phase extraction combined with a dissolution-precipitation method for the extraction and purification of antioxidants and UV stabilizers from polylactic acid food contact plastics. The extraction parameters such as sorbent type, sorbent dosage, sample solution pH, ionic strength, sorption time, elution solution type, volume, and time were investigated. Under the optimized conditions, all the analytes determined by UPLC-MS/MS showed good linear range (r > 0.99), detection limit (0.023-3.105 ng g-1), accuracy (70.6-102.3 %), and reproducibility (RSD<9.8 %). Further, the developed method was applied to determine the antioxidants and UV stabilizers in polylactic acid lunch boxes and straws, showing excellent applicability. The results showed that the antioxidants and UV stabilizers were detected in some of the samples, with a maximum detection of antioxidant 1010 at 7297 ng g-1. This study provided a sensitive, efficient, and environmentally friendly method for antioxidants and UV stabilizers in polylactic acid food contact plastics. The ideas for the design of environmentally friendly metal-organic frameworks and biomass composite multifunctional materials would promise in the sample pretreatment field for the emerging contaminants.

Covalent organic frameworks: spotlight on applications in the pharmaceutical arena

Covalent organic frameworks (COFs) have much potential in the field of analytical separation research due to their distinctive characteristics, including easy modification, low densities, large specific surface areas and permanent porosity. This article provides a historical overview of the synthesis and broad perspectives on the applications of COFs. The use of COF-based membranes in gas separation, water treatment (desalination, heavy metals and dye removal), membrane filtration, photoconduction, sensing and fuel cells is also covered. However, these COFs also demonstrate great promise as solid-phase extraction sorbents and solid-phase microextraction coatings. In addition to various separation applications, this work aims to highlight important advancements in the synthesis of COFs for chiral and isomeric compounds.

Green preparation of magnetic pyrene-based hyper-cross-linked polymer using dual-purpose ferric chloride reagent for extraction of polycyclic aromatic hydrocarbons from natural water bodies

A magnetic hyper-cross-linked polymer Fe3O4/HCPPYR was prepared using pyrene as the monomer and formaldehyde dimethyl acetal (FDA) as the cross-linking agent. The objective of green chemistry was achieved by employing FeCl3 during the synthesis, as it played a dual role of a catalyst for the Friedel-Crafts reaction and an iron source for the synthesis of magnetic Fe3O4, thus maximizing efficiency and minimizing waste. Fe3O4/HCPPYR was applied as a sorbent for magnetic solid-phase extraction (MSPE) to extract fifteen polycyclic aromatic hydrocarbons (PAHs) from water. The effects of different parameters such as the quantity of adsorbent, the extraction time, the desorption conditions, the pH value and the effect of the salt concentration on the extraction efficiency were optimized. A simple and efficient method in combination with gas chromatography-mass spectrometry (GC-MS) (Fe3O4/HCPPYR-MSPE/GC-MS) was developed and successfully applied for the detection of PAHs in environmental water samples The analytical method showed LODs in the range of 0.004-0.06 µg L-1, which proved to be adequate for the detection all 15 PAHs at trace concentration. Spiked recoveries of PAHs in actual water samples ranged from 85.2 % to 118.5 % with relative standard deviations (RSDs) below 10.2%. These results indicate that the method has a good potential for reusability and possesses excellent sensitivity. This study showcased the potential of Fe3O4/HCPPYR composites in effectively removing organic pollutants from the aqueous environments, demonstrating their ability for water treatment applications.

Covalent organic framework-based magnetic solid-phase extraction coupled with gas chromatography-tandem mass spectrometry for the determination of trace phthalate esters in liquid foods

Covalent organic framework-coated magnetite particles (Fe3O4@COF) were synthesized and applied as the adsorbent to the selective capture of phthalate esters (PAEs) in liquid foods. Combined with the magnetic solid-phase extraction (MSPE) technology, a gas chromatography-tandem mass spectrometry (GC-MS/MS) method was employed for the separation and quantification of PAEs. Following optimization of the magnetic extraction and elution parameters, the developed analytical method offered a satisfactory linear range (0.1-5 μg L-1) with determination coefficients ranging from 0.9934 to 0.9975 for the five different PAEs studied. The limits of detection (LOD) were in the range 1.9-12.8 ng L-1. The recoveries ranged from 70.0 to 119.8% with a relative standard deviation (RSD) less than 9.7%. Density functional theory (DFT) calculations established that the dominant adsorption mechanism used by the COF to bind PAEs involved π-π stacking interactions. Results encourage the wider use of COF-based adsorbents and MSPE methods in the analytical determination of PAEs in foods.

Magnetic Covalent Organic Framework Composites for Wastewater Remediation

Covalent organic frameworks (COFs) with high specific surface area, tailored structure, easy functionalization, and excellent chemical stability have been extensively exploited as fantastic materials in various fields. However, in most cases, COFs prepared in powder form suffer from the disadvantages of tedious operation, strong tendency to agglomerate, and poor recyclability, greatly limiting their practical application in environmental remediation. To tackle these issues, the fabrication of magnetic COFs (MCOFs) has attracted tremendous attention. In this review, several reliable strategies for the fabrication of MCOFs are summarized. In addition, the recent application of MCOFs as outstanding adsorbents for the removal of contaminants including toxic metal ions, dyes, pharmaceuticals and personal care products, and other organic pollutants is discussed. Moreover, in-depth discussions regarding the structural parameters affecting the practical potential of MCOFs are highlighted in detail. Finally, the current challenges and future prospects of MCOFs in this field are provided with the expectation to boost their practical application.

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.

Covalent triazine-based frameworks for efficient solid-phase microextraction of phthalic acid esters from food-contacted plastics

Owing to various health threats associated with phthalic acid esters (PAEs), this category of endocrine-disrupting compounds has attracted more and more public scrutiny. However, the efficient preconcentration of PAEs from complex food-contacted plastics still remains challenging. Herein, three covalent triazine-based frameworks (CTFs) were constructed by facile Friedel-Crafts reactions of cyanuric chloride (CC), with triptycene (TPC), fluorene (FL) and 1,3,5-triphenylbenzene (TPB), respectively. Three CTFs were then employed as solid-phase microextraction (SPME) coatings for the extraction of PAEs. Benefiting from the large surface area and high pore volume, the newly-synthesized CC-TPC based SPME method exhibited large enrichment factors (978-2210), low limits of detection (0.027-0.10 ng g ^- 1), satisfactory linear ranges (0.09-20 ng g ^- 1), acceptable repeatabilities (4.3-9.6%) and high relative recoveries (92.0-104.6%).

[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.

Facile synthesis and evaluation of three magnetic 1,3,5-triformylphloroglucinol based covalent organic polymers as adsorbents for high efficient extraction of phthalate esters from plastic packaged foods

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A facile synthetic route for synthesis of three magnetic Tp-based COPs adsorbents was provided.

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Magnetic COP2 showed best extraction performance for PAEs.

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The potential adsorption mechanism was systematically investigated.

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This method was suitable for high efficient extraction of hydrophobic PAEs from foods.

Three covalent organic polymers (COPs) were successfully fabricated by room-temperature solvent-free mechanochemical grinding method between 1,3,5-triformylphloroglucinol (TP) and p-phenyl enediamine (COP1), benzidine (COP2), 4, 4″-diamino-p-terphenyl (COP3), and followed by coprecipitation on the surface of Fe₃O₄ nanoparticles to form three corresponding magnetic Tp-series COPs. The fabricated magnetic COPs were evaluated and then applied for the extraction of phthalate esters from food samples before gas chromatography-tandem spectrometry analysis. Magnetic COP2 exhibited the highest extraction efficiency, which can be attributed to its larger pore size, and its strong hydrophobic and π-π interactions with phthalate esters. The method possessed good linearity (10–1000 μg·kg⁻¹), high sensitivity (0.29–2.59 µg·kg⁻¹ for LODs and 0.97–8.63 µg·kg⁻¹ for LOQs), and satisfactory recoveries (70.2–108.1%) with relative standard deviations lower than 5.2%. This method has potentials for high efficient separation/preconcentration of hydrophobic phthalate esters from foods.

Triazine covalent organic polymer coated stir bar sorptive extraction coupled with high performance liquid chromatography for the analysis of trace phthalate esters in mineral water and liquor samples

Cyanuric chloride and 4,4'-diamino-p-terphenyl were adopted as monomers to synthesize poly (4,4'-diamino-p-terphenyl-triazine) (PDT) covalent organic polymer. PDT coated stir bar was prepared and evaluated for the extraction of five phthalate esters (PAEs) with relatively lower logP values (2.7-4.9), including diethyl phthalate, diallyl phthalate, dipropyl phthalate, benzylbutyl phthalate and dibutyl phthalate. It exhibited higher extraction recovery (> 65%) and faster extraction kinetics (50 min vs 240 min) for target PAEs over commercial polydimethylsiloxane coated stir bar. Based on the superior performance, PDT coated stir bar sorptive extraction was combined with high-performance liquid chromatography-diode array detection for trace analysis of five PAEs plasticizers. The limits of detection for target PAEs were 0.04-0.27 μg/L, with the enrichment factors of 54-80-fold. The potential of the method was demonstrated by detecting five target PAEs in Chinese liquor and mineral water samples. No target analytes were detected in Chinese liquor sample, and recoveries of 85.4-109% were obtained for target analytes in spiked liquor samples; trace diethyl phthalate (1.19-2.98 μg/L) and dibutyl phthalate (0.77-0.91 μg/L) were detected in two mineral water samples, with recoveries of 85.4-117% and 87.4-117% respectively in spiked mineral water samples.

Use of corn straw-derived biochar for magnetic solid-phase microextraction of organophosphorus pesticides from environmental samples

In this study, the potentials of utilizing corn straw-derived biochar in environmental sample pretreatment were examined. An one-step magnetization and carbonization process was developed to prepare magnetic biochar by mixing corn straw powder with Fe²⁺/Fe³⁺ and then pyrolyzed at different temperatures (400-800 °C). The obtained magnetic biochars were characterized by using scanning electron microscopy, Brunauer-Emmett-Teller isotherms, X-ray diffraction and Fourier transform infrared spectroscopy. Various extraction affecting parameters, such as Fe²⁺/Fe³⁺content, pyrolytic temperature, species of desorption solvent, extraction and desorption time, respectively, were studied and optimized. Results showed that the magnetic biochar pyrolyzed at 700 °C exhibited the best extraction performance, with enrichment factors ranging from 52 to 210, presumably due to H-bonding and π-π interactions between biochar and organophosphorus, as well as to the high surface area and pore volume of biochar. The magnetic biochar-based extraction was further combined with gas chromatography-mass spectrometry (GC/MS) to analyze trace organophosphorus pesticides from environmental samples. The method demonstrated good linearity (0.1-50 µg·L^-1), low limits of detection (0.02-0.11 µg·L^-1), and high recoveries (72.4-96.8%) from spiked water and soil samples. The results of this study suggested the promising potentials of utilizing corn straw-derived biochar for efficiently enriching trace organophosphorus pesticides from complex environmental samples.

Magnetic dispersive solid phase extraction based on carbonized cellulose-ferromagnetic nanocomposite for screening phthalate esters in aqueous samples

In this work, a sorbent of the carbonized cellulose-ferromagnetic nanocomposite has been proposed for the magnetic dispersive solid phase extraction of some plasticizers in aqueous samples. Carbonized cellulose nanoparticles were prepared by treatment of cellulose filter paper with concentrated sulfuric acid and then loaded on Fe₃O₄ nanoparticles using coprecipitation. This sorbent is compatible with aqueous samples and can be considered as a viable sorbent for extraction of plasticizers from aqueous samples. In this study, magnetic dispersive solid phase extraction is followed by a dispersive liquid-liquid microextraction method. This combination makes the proposed approach as an efficient clean-up method with high enrichment factors for the selected analytes. The enriched analytes are monitored by gas chromatography equipped with a flame ionization detector. Parameters affecting the method efficiency were investigated in details. Under the optimized extraction conditions, limits of detection could reach up to of 0.15-0.50 µg L^-1. The satisfactory enrichment factors of 286-403 were obtained, and the extraction recoveries were found to be in the range of 57-80%. Relative standard deviations were in the range of 3-7% for intra-day and inter-day precisions for six replicate extractions at 25 µg L^-1 of each plasticizer. Calibration curves were linear in wide ranges with coefficients of determination ≥ 0.995. Eventually, efficiency of the prepared sorbent was confirmed by the extraction of some plasticizers from real samples including fruit juices, mineral water, injection solution, cola, and yoghourt drink packed in plastic containers.

Covalent organic frameworks as multifunctional materials for chemical detection

Sensitive and selective detection of chemical and biological analytes is critical in various scientific and technological fields. As an emerging class of multifunctional materials, covalent organic frameworks (COFs) with their unique properties of chemical modularity, large surface area, high stability, low density, and tunable pore sizes and functionalities, which together define their programmable properties, show promise in advancing chemical detection. This review demonstrates the recent progress in chemical detection where COFs constitute an integral component of the achieved function. This review highlights how the unique properties of COFs can be harnessed to develop different types of chemical detection systems based on the principles of chromism, luminescence, electrical transduction, chromatography, spectrometry, and others to achieve highly sensitive and selective detection of various analytes, ranging from gases, volatiles, ions, to biomolecules. The key parameters of detection performance for target analytes are summarized, compared, and analyzed from the perspective of the detection mechanism and structure-property-performance correlations of COFs. Conclusions summarize the current accomplishments and analyze the challenges and limitations that exist for chemical detection under different mechanisms. Perspectives on how future directions of research can advance the COF-based chemical detection through innovation in novel COF design and synthesis, progress in device fabrication, and exploration of novel modes of detection are also discussed.

Hollow tube covalent organic framework for syringe filter-based extraction of ultraviolet stabilizer in food contact materials

In this work, a novel hollow tube covalent organic framework constructed by cyclotricatechylene and tetrafluoroterephthalonitrile (CTC-TFPN-COF) with polyether bond was synthesized, and it was coated on filter membrane for extraction of ultraviolet stabilizer in migration from food contact materials. Since the monomers of the polymer were linked by polyether bond, the CTC-TFPN-COF exhibited strong chemical stability in severe conditions such as acid, alkali and various organic solvent. The excellent features of high porosity and robust structure endowed the CTC-TFPN-COF good candidate as adsorbent for extraction of ultraviolet stabilizer. Moreover, the CTC-TFPN-COF coated membranes were immobilized on syringe filter and coupled with multiple channel injection pump to realize high throughput sample pretreatment strategy. Subsequently, a sensitive analytical method for ultraviolet stabilizer was established followed by ultra-high performance liquid chromatography-tandem mass spectrometry. The flow rate of extraction and desorption, elution solvent and the volume of desorption solvent were optimized. The method was assessed, which showed wide linear ranges with R2 greater than 0.99, low limits of detection (0.9-91 ng L^-1) and low limits of quantification (3-300 ng L^-1). The developed method was successfully applied to determine trace ultraviolet stabilizer in the migration of food contact materials with different simulated solution, which demonstrated its promising potential in practical analysis.

Release of inhalable particles and viable microbes to the air during packaging peeling: Emission profiles and mechanisms

Packaging is necessary for preserving and delivering products and has significant impacts on human health and the environment. Particle matter (PM) may be released from packages and transferred to the air during a typical peeling process, but little is known about this package-to-air migration route of particles. Here, we investigated the emission profiles of total and biological particles, and the horizontal and vertical dispersion abilities and community structure of viable microbes released from packaging to the air by peeling. The results revealed that a lot of inhalable particles and viable microbes were released from package to the air in different migration directions, and this migration can be regulated by several factors including package material, effective peeling area, peeling speed and angles, as well as the characteristics of the migrant itself. Dispersal of package-borne viable microbes provides direct evidence that viable microbes, including pathogens, can survive the aerosolization caused by peeling and be transferred to air over different distances while remaining alive. Based on the experimental data and visual proof in movies, we speculate that nonbiological particles are package fibers fractured and released to air by the external peeling force exerted on the package and that microbe dispersal is attributed to surface-borne microbe suspension by vibration caused by the peeling force. This investigation provides new information that aerosolized particles can deliver package-borne substances and viable microbes from packaging to the ambient environment, motivating further studies to characterize the health effects of such aerosolized particles and the geographic migration of microbes via packaging.

Determination of Phthalate Esters in Cosmetics and Baby Care Products by a Biosorbent Based on Lawsone Capped Chitosan and Followed by Liquid Chromatography

This research presents a green synthetic pathway for the preparation of a new biosorbent and eco-friendly extraction process of three phthalate esters: dimethyl phthalate, di-butyl phthalate and benzyl butyl phthalate, from cosmetics and baby care products. Dispersive solid-phase extraction was used based on a new core-shell biomass/sorbent; chitosan-loaded lawsone. The proposed method provides fortunate trapping of phthalate esters in a one-step extraction. Under the optimized extraction conditions, the current work was presented low detection limits (0.03-0.15 ng. g-1), limits of quantification (0.1-0.5 ng·g-1) and reasonable linearity (0.1-10 000 ng. g-1). The applicability of the method was estimated by recovery experiments at different spiking levels (n = 5) for phthalate esters in the real samples.

Triazine-triphenylphosphine based porous organic polymer as sorbent for solid phase extraction of nitroimidazoles from honey and water

A triazine-based porous organic polymer was prepared by facile solvothermal polymerization with cyanuric chloride and triphenyl phosphine as functional monomers. The polymer was characterized and then used for the first time as the sorbent for the effective solid-phase extraction of some nitroimidazoles (NDZs) (metronidazole, ronidazole, secnidazole, dimetridazole and ornidazole). The main experimental influencing parameters for the extraction including the eluent solvent, eluent volume, sample loading rate, sample solution pH, salt concentration and sample volume were investigated. The adsorption kinetics and adsorption isotherms were investigated to elucidate the possible adsorption mechanism. With the triazine-based porous organic polymer as the SPE adsorbent, trace NDZs were effectively extracted. The good enrichment capability for the NDZs was mainly attributed to the hydrogen binding interactions by the aromatic 1,3,5-trizine rings. After the SPE, the extracted analytes were analyzed by high-performance liquid chromatograph with ultraviolet detection. Under the selected conditions, the method had a good linear response for the analytes in the range of 0.06-120 ng mL^-1 for water and 1.5-1200 ng g^-1 for honey samples. The limits of detections (S/N=3) fell in the range of 0.02-0.06 ng mL^-1 for water and 0.5-1.5 ng g^-1 for honey samples. The method recoveries for the analytes for spiked samples were in the range of 80.3-118%. The method can be applied for the determination of the NDZs from real samples.

Recent Advances of Triazine-Based Materials for Adsorbent Based Extraction Techniques

This review mainly focused on the synthesis and properties of triazine-based materials as well as the state-of-the-art development of these materials in adsorption-based extraction techniques in the past 5 years, such as solid-phase extraction, magnetic solid-phase extraction, solid-phase microextraction and stir bar sorptive extraction, and the detection of various pollutants, including metal ions, drugs, estrogens, nitroaromatics, pesticides, phenols, polycyclic aromatic hydrocarbons and parabens. In the triazine-functionalized composites, triazine-based polymers and covalent triazine frameworks have been developed as the adsorbents with potential for environmental pollutants, mainly relying on the large surface area and the affinity of triazinyl groups with the targets. Triazine-based adsorbents have satisfactory sensitivity and selectivity towards different types of analytes, attributed from various mechanisms including π-π, electrostatics, hydrogen bonds, and hydrophobic and hydrophilic effects. The prospects of the materials for adsorption-based extraction were also presented, which can offer an outlook for the further development and applications.

Greenness of magnetic nanomaterials in miniaturized extraction techniques: A review

Green analytical chemistry principles should be followed, as much as possible, and particularly during the development of analytical sample preparation methods. In the past few years, outstanding materials such as ionic liquids, metal-organic frameworks, carbonaceous materials, molecularly imprinted materials, and many others, have been introduced in a wide variety of miniaturized techniques in order to reduce the amount of solvents and sorbents required during the analytical sample preparation step while pursuing more efficient extraction methods. Among them, magnetic nanomaterials (MNMs) have gained special attention due to their versatile properties. Mainly, their ability to be separated from the sample matrix using an external magnetic field (thus enormously simplifying the entire process) and their easy combination with other materials, which implies the inclusion of a countless number of different functionalities, highly specific in some cases. Therefore, MNMs can be used as sorbents or as magnetic support for other materials which do not have magnetic properties, the latter permiting their combination with novel materials. The greenness of these magnetic sorbents in miniaturized extractions techniques is generally demonstrated in terms of their ease of separation and amount of sorbent required, while the nature of the material itself is left unnoticed. However, the synthesis of MNMs is not always as green as their applications, and the resulting MNMs are not always as safe as desired. Is the analytical sample preparation field ready for using green magnetic nanomaterials? This review offers an overview, from a green analytical chemistry perspective, of the current state of the use of MNMs as sorbents in microextraction strategies, their preparation, and the analytical performance offered, together with a critical discussion on where efforts should go.

Combination of magnetic solid-phase extraction and HPLC-UV for simultaneous determination of four phthalate esters in plastic bottled juice

A magnetic o-hydroxyazobenzene (M-HAzo) porous organic polymer was facilely prepared by a green azo coupling reaction in aqueous solution. The prepared M-HAzo was applied as a new adsorbent for the first time to pre-concentrate phthalate esters (PAEs) from plastic bottled juice, followed by their determination with high performance liquid chromatography-ultraviolet detection. The effects of various parameters, i.e., the mass ratio of the Fe₃O₄@SiO₂ to HAzo, extraction time, ionic strength, pH of the sample, desorption conditions were optimized. Under the optimized conditions, the M-HAzo based method exhibited good performance in terms of linear range (0.3-50.0 μg L^-1), detection limit (0.08-0.50 μg L^-1), accuracy (recovery of 78.0-115.0%) and repeatability (relative standard deviation of 2.9-7.8%). This work provides a sensitive method for analysis of PAEs at trace levels in drinks, which is featured with high sensitivity, simple operation and environmentally-friendly merit and will have a promising potential in analysis of other organic pollutants.

Covalent Organic Frameworks in Sample Preparation

Covalent organic frameworks (COFs) can be classified as emerging porous crystalline polymers with extremely high porosity and surface area size, and good thermal stability. These properties have awakened the interests of many areas, opening new horizons of research and applications. In the Analytical Chemistry field, COFs have found an important application in sample preparation approaches since their inherent properties clearly match, in a good number of cases, with the ideal characteristics of any extraction or clean-up sorbent. The review article is meant to provide a detailed overview of the different COFs that have been used up to now for sample preparation (i.e., solid-phase extraction in its most relevant operational modes-conventional, dispersive, magnetic/solid-phase microextraction and stir-bar sorptive extraction); the extraction devices/formats in which they have been applied; and their performances and suitability for this task.

Thiol-functionalized magnetic covalent organic frameworks by a cutting strategy for efficient removal of Hg2+ from water

Covalent organic frameworks (COFs) have attracted tremendous attention due to their excellent performance in wastewater remediation, but their practical application still suffers from various challenges. The development of highly-efficient magnetic COFs along with fast adsorption kinetic and high adsorption capacity is very promising. To achieve the purpose, thiol-functionalized magnetic covalent organic frameworks (M-COF-SH) with abundant accessible chelating sites were designed and synthesized by utilizing disulfide derivative as building blocks and subsequently cutting off the disulfide linkage. After the cutting process, the crystallinity, porosity, superparamagnetism of pristine M-COF are well maintained, and the resultant M-COF-SH turned out to be an effective and selective platform for Hg²⁺ capture from water. Impressively, the resulting composite exhibited a maximum adsorption capacity of Hg²⁺ as high as 383 mg g^-1. In addition, it also displays a rapid kinetic, where the adsorption equilibrium can be achieved within 10 min. More importantly, there is no significant loss of its adsorption performance even after recycling 5 times. This work not only offers a reliable platform for wastewater remediation but also provides a conceptual guide to prepare functionalized M-COF composites which cannot be obtained through conventional approaches.

Controlled Fabrication of Silica@Covalent Triazine Polymer Core-Shell Spheres as a Reversed-Phase/Hydrophilic Interaction Mixed-Mode Chromatographic Stationary Phase

The unique properties of covalent triazine-based organic framework/polymers, including large surface area, hydrophilic-lipophilic-balanced adsorption, and economical preparation, make it a promising candidate as a stationary phase for high-performance liquid chromatography. However, irregular shapes and wide size distributions of such particles hinder column packing, resulting in a low column efficiency or a high back pressure. Herein, we describe the fabrication of SiO₂@ covalent triazine-based organic polymer (CTP) core-shell microspheres with a distinct sphere-coating-sphere appearance using aminosilica as the supporting substrate to grow the CTP shell. By adjusting the amount of reactants, the thickness of the CTP shell, which consists of triazine and 1,3,5-triphenylbenzene monomers, was easily controlled. The developed core-shell microspheres were characterized via scanning electron microscopy, energy dispersive X-ray spectroscopy, transmission electron microscopy, solid-state ¹³C nuclear magnetic resonance analysis, and N₂ adsorption experiments. The synergism of the triazine and aromatic moieties on CTP provides the new stationary phase with multiple retention mechanisms, including hydrophobic, π-π, electron donor-acceptor, hydrogen-bonding interactions, and so forth. On the basis of these interactions, successful separation and higher shape selectivity were achieved among several analytes that vary in polarity under both reversed-phase and hydrophilic interaction liquid chromatography conditions. Therefore, SiO₂@CTP microspheres combine the advantages of good column packing properties of the uniform monodisperse silica microspheres and the recognition performance of CTP, generating flexible selectivity and application prospect for both hydrophilic and hydrophobic analytes.

Porous Organic Frameworks: Advanced Materials in Analytical Chemistry

Porous organic frameworks (POFs), a general term for covalent-organic frameworks (COFs), covalent triazine frameworks (CTFs), porous aromatic frameworks (PAFs), etc., are constructed from organic building monomers with strong covalent bonds and have generated great interest among researchers. The remarkable features, such as large surface areas, permanent porosity, high thermal and chemical stability, and convenient functionalization, promote the great potential of POFs in diverse applications. A critical overview of the important development in the design and synthesis of COFs, CTFs, and PAFs is provided and their state-of-the-art applications in analytical chemistry are discussed. POFs and their functional composites have been explored as advanced materials in "turn-off" or "turn-on" fluorescence detection and novel stationary phases for chromatographic separation, as well as a promising adsorbent for sample preparation methods. In addition, the prospects for the synthesis and utilization of POFs in analytical chemistry are also presented. These prospects can offer an outlook and reference for further study of the applications of POFs.