A ratiometric fluorescence sensor for detection of organophosphorus pesticides based on enzyme-regulated multifunctional Fe-based metal-organic framework.

The residues of organophosphorus pesticides (OPs) are increasing environmental pollution and public health concerns. Thus, the development of simple, convenient and sensitive method for detection of OPs is crucial. Herein, a multifunctional Fe-based MOF with fluorescence, catalytic and adsorption, is synthesized by a simple one-pot hydrothermal method.

Covalent organic framework reinforced hollow fiber bar for extraction and detection of bisphenols from beverages.

Bisphenols (BPs) can migrate from packaging materials into foods, resulting in potentially harmful residues. For example, accumulation of BPs is associated with endocrine disorders. Owing to matrix effects, development of an effective and eco-friendly sample pretreatment would be helpful for BPs detection in beverages packed in plastic containers.

Covalent organic framework-sodium alginate-Ca-polyacrylic acid composite beads for convenient dispersive solid-phase extraction of neonicotinoid insecticides in fruit and vegetables.

Neonicotinoids, the fastest-growing class of insecticides, have posed a multi-media residue problem with adverse effects on environment, biodiversity and human health. Herein, covalent organic framework-sodium alginate-Ca-polyacrylic acid composite beads (CACPs), facilely prepared at room temperature, were used in convenient dispersive solid-phase extraction (dSPE) and combined with high-performance liquid chromatography (HPLC) for the detection of five neonicotinoid insecticides (thiamethoxam, acetamiprid, dinotefuran, clothianidin, imidacloprid). CACPs can be completely separated within 1 min without centrifugation.

A colorimetric sensing platform with smartphone for organophosphorus pesticides detection based on PANI-MnO nanozyme.

Organophosphorus pesticides (OPs) are of great concern due to its potential harms on human health and the environment. Herein, a budget-friendly, rapid and convenient colorimetric sensing platform is developed for detection of OPs in the environmental and food samples. The sensing element, PANI-MnO nanozyme with excellent oxidase mimetic activity is synthesized at room temperature, which is able to directly oxidize 3,3,5,5-tetramethylbenzidine (TMB) to generate blue colored oxidized TMB (OxTMB) within 2 min.

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

The presence of estrogens residues in dairy products is a growing concern due to their potential health risk. Herein, in this study, we have developed a membrane-protected magnetic solid-phase extraction (MP-MSPE) method that utilized a magnetic adsorbent (FeO@COF-LZU1) with in-situ growth for the efficient extraction of estrone (E1), 17β-estradiol (E2), and estriol (E3). When combined with HPLC-FLD, this method allows for the efficient detection of estrogens in dairy products.

Electrochemical oxidation diminished toxicity of zearalenone significantly, while reduction increased.

Zearalenone (ZEN), one of the most common mycotoxins in cereals, poses a severe health risk to humans. In this study, electrochemical oxidation and reduction degraded ZEN in solution completely within 8 min and 20 min. The structure of ZEN products was elucidated by mass spectrometry (MS), and their toxicity was evaluated by ECOSAR software and cytotoxicity assay.

Fabrication of β-cyclodextrin-polyacrylamide/covalent organic framework hydrogel at room temperature for the efficient removal of triazole fungicides from environmental water.

Triazole is frequently-used fungicide, which can leach into surface water through farmland and cause serious environmental pollution. Continuous exposure to triazole fungicides may cause harm to human health. Herein, β-cyclodextrin-polyacrylamide/covalent organic framework (β-CD-PAAM/TFPB-BD) hydrogel was fabricated at room temperature and used for the efficient removal of triazole fungicides.

Ratio fluorescence test strip visualized by amino-functionalized metal-organic framework for rapid sensing of glyphosate.

As glyphosate is a broad-spectrum herbicide extensively used in agriculture worldwide, rapid glyphosate detection is essential for food safety and human health. Herein, a ratio fluorescence test strip was prepared and coupled with an amino-functionalized bismuth-based metal-organic framework (NH-Bi-MOF) that bonded with copper ion for rapid visualization and determination of glyphosate. NH-Bi-MOF had excellent fluorescence performance, and the copper ion, a Lewis acid, was selected as the quencher.

Bismuth-based metal-organic framework peroxidase-mimic nanozyme: Preparation and mechanism for colorimetric-converted ultra-trace electrochemical sensing of chromium ion.

A colorimetric-electrochemical dual-mode analytical method based on bismuth metal-organic framework nanozyme was developed for label-free and trace/ultra-trace Cr detection. 3D ball-flower shaped bismuth oxide formate (BiOCOOH) was used as the precursor and template to facilely construct the metal-organic framework nanozyme BiO-BDC-NH, which possesses intrinsic peroxidase-mimic activity to effectively catalyze the colorless 3,3',5,5'-tetramethylbenzidine into blue oxidation products in the presence of hydrogen peroxide. Based on Cr to promote the peroxide-mimic activity of BiO-BDC-NH nanozyme, a colorimetric method for Cr detection was developed with the detection limit of 0.

Paper-based analytical device coupled with Bi-MOF: Electric field amplification and fluorescence sensing of glyphosate.

Glyphosate, a potent herbicide wildly used in the world, involves potential hazards to human health by accumulating in the food chain. Due to its absence of chromophores and fluorophores, the rapid visual detection of glyphosate has always been difficult. Herein, a paper-based geometric field amplification device visualized by the amino-functionalized bismuth-based metal-organic framework (NH-Bi-MOF) was constructed for sensitive fluorescence determination of glyphosate.

Magnetic covalent organic frameworks for rapid solid-phase extraction of phthalate esters and bisphenol A in beverage samples.

Phthalate esters (PAEs) and bisphenol A (BPA) are endocrine-disrupting chemicals (EDCs), which are widely used in the production of food plastic packaging and easily migrate to food. Continuous exposure to EDCs may cause harm to human health. Herein, magnetic covalent organic framework TFP-NDA/FeO was synthesized by magnetizing covalent organic framework TFP-NDA through a facile coprecipitation method, and used as an adsorbent for rapid solid-phase extraction of PAEs (diethyl phthalate (DEP), diisobutyl phthalate (DIBP) and dibutyl phthalate (DBP)) and BPA.

Covalent organic framework in situ grown on FeO hollow microspheres for stir bar sorptive-dispersive microextraction of triazole pesticides.

Based on covalent organic framework (COF) 1,3,5-tris-(4-formylphenyl)benzene-benzidine (TFPB-BD) in situ grown on FeO hollow microspheres and combined with gas chromatography-flame thermionic detector, a rapid and simple stir bar sorptive-dispersive microextraction method was developed for the determination of five triazole pesticides (paclobutrazol, hexaconazole, flusilazole, propiconazole, and tebuconazole). The synthesized TFPB-BD/FeO microspheres were characterized by transmission electron microscope, vibrating sample magnetometer, and thermogravimetric analysis, which showed that the material has strong magnetism and higher load capacity of COF. Under optimal conditions, the extraction equilibrium could be achieved within 9 min with detection limits of 0.

Electro-enhanced solid-phase microextraction with membrane protection for enrichment of bisphenols in canned meat.

Bisphenols (BPs), one of the endocrine disrupting chemicals (EDCs), are harmful to health with the potential carcinogenicity, teratogenicity and neurotoxicity. In this paper, we developed an electro-enhanced solid-phase microextraction with membrane protection method to enrich BPs. The extraction time can be shortened to 10 min with the electric field, and the prepared fiber can be repetitively used 100 times with the membrane protection.

A stack-up electrochemical device based on metal-organic framework modified carbon paper for ultra-trace lead and cadmium ions detection.

A portable device is conducive to the on-site detection of heavy metal ions at trace level in food and the prevention of related food safety issues. In this work, an electrochemical device stacked up with flat electrodes was developed for the detection of Pb and Cd. The top layer of the device is a carbon paper as working electrode, which is modified with amino functionalized cobalt-based metal-organic framework and gold nanoparticles.

A ratio fluorescence sensor based on rhodamine B embedded metal-organic framework for glyphosate detection in agri-food products.

Glyphosate, a broad-spectrum and high-efficiency herbicide, could accumulate in the human body through the consumption of agri-food products. Herein, a ratio fluorescence sensor based on rhodamine B-embedded amino-functionalized iron-based metal-organic framework (MOF, NH-MIL-88(Fe)@RhB) bonded with Cu was developed for rapid detection of glyphosate. The synthesized NH-MIL-88(Fe) was a biconical prism and had a cavity for the embedding of RhB as a reference compound.

Metal-organic framework modified carbon cloth for electric field enhanced thin film microextraction of sulfonamides in animal-derived food.

Sulfonamides (SAs) were widespread in animal-derived food at trace level, which could trigger hazards to human health. Herein, electric field enhanced thin-film microextraction (EE-TFME) was developed based on carbon cloth (CC) modified with metal-organic frameworks (MOFs) for extraction of SAs (sulfadiazine, sulfathiazole, sulfamerazine, sulfadimidine, sulfamethoxazole and sulfisoxazole), which were a series of polar analytes. MIL-101(Cr) was in situ synthesized on CC via hydrothermal reaction and then was used as positive electrode in EE-TFME for adsorption of SAs.

Covalent organic framework modified carbon cloth for ratiometric electrochemical sensing of bisphenol A and S.

A novel ratiometric electrochemical sensor was developed based on a carbon cloth electrodeposited with silver nanoparticles and drop-coated by covalent organic framework (COF-LZU1) for simultaneous determination of bisphenol A (BPA) and bisphenol S (BPS). Carbon cloth exhibited a significantly larger electrochemical active area than common glassy carbon electrodes (27.5 times).

Covalent organic framework DQTP modified pencil graphite electrode for simultaneous determination of bisphenol A and bisphenol S.

The sensitivity and selectivity of electrochemical analysis are challenging due to the materials used for electrode modification as well as electrical conductivity, catalytic activity and recognition ability of the working electrode. In this work, a portable 3D-printed electrochemical electrode clamp was designed and applied in combination with the developed covalent organic framework (COF DQTP)-modified pencil graphite electrode (DQTP/PGE). The β-ketoenamine-linked COF DQTP synthesized by 1,3,5-triformylphloroglucinol (TP) and 2,6-diaminoanthraquinone (DQ) through solvothermal method is a porous crystalline with excellent conductivity and large periodic π-arrays, coupled with commercial available pencil graphite electrode to fabricate a disposable sensor for simultaneous determination of environmental endocrine disruptors bisphenol A and bisphenol S.

Collaborative compounding of metal-organic frameworks for dispersive solid-phase extraction HPLC-MS/MS determination of tetracyclines in honey.

Metal-organic frameworks (MOFs), a sort of dispersive solid-phase extraction (d-SPE) material, has shown considerable prospects in the pretreatment of food, biological and other complex samples. Herein, we developed a method for compounding MOFs for d-SPE and trace determination of tetracyclines (TCs) in honey. When the compounding ratio of MIL-101 (Cr), MIL-100 (Fe) and MIL-53 (Al) was 7:1:2, adsorption-extraction was effective.

Electro-enhanced solid-phase microextraction with covalent organic framework modified stainless steel fiber for efficient adsorption of bisphenol A.

In this work, electro-enhanced solid-phase microextraction (EE-SPME) and covalent organic framework (COF) were adopted to improve the extraction efficiency. A conductive COF synthesized of 2,6-diaminoanthraquinone (DQ) and 1,3,5-triformylphloroglucinol (TP) was in situ bonded to the stainless steel wire via facile solution-phase approach and used as the EE-SPME fiber coating to preconcentrate a typical endocrine disruptor bisphenol A (BPA). Compared with conventional SPME, the DQTP bonded fiber coupled with EE-SPME device exhibited higher extraction efficiency and achieved extraction equilibrium within 10 min.

A competitive fluorescence assay based on free-complementary DNA for ochratoxin A detection.

An ultrasensitive, rapid, and specific method for Ochratoxin A (OTA) detection was designed using complementary sequence to aptamer as a target of molecular beacon (MB). The designed loop structure of the MB has the same sequence as the aptamer with a complementary DNA (cDNA) which translates the level of the target into a measurable response. The presence of the target holds aptamer at the corresponding amount and the additional cDNAs are consumed by unbound aptamers which avails free cDNAs that resulting in fluorescence rising due to unfolding of MBs.

In situ growth of covalent organic framework on titanium fiber for headspace solid-phase microextraction of 11 phthalate esters in vegetables.

Vegetables are easily contaminated by phthalate esters (PAEs) from the environment, agricultural films and fertilizers, affecting human health. In this paper, titanium dioxide (TiO) nanotube arrays were prepared by electrochemical anodic oxidation on the surface of titanium wire. Covalent organic framework of TpBD was in situ bonded to the titanium wire via TiO nanotube arrays using monomers of 1,3,5-trimethylphloroglucinol (Tp) and benzidine (BD).

Colorimetric detection toward halide ions by a silver nanocluster hydrogel.

We reported a novel colorimetric method for highly selective halide ions (Cl, Brand I) recognition by Ag nanoclusters hydrogel (Ag-NCs hydrogel). The Ag-NCs hydrogel could discriminate Cl, Brand I ions from a wide range of environmentally important anions, identified by the distinct UV-vis absorption band changes or the change in the color of Ag-NCs hydrogel. On the basis of this strategy, 20 μM and 200 μM of Cl, 5 μM and 100 μM of Br, 5 μM and 100 μM of I could be recognized within 5 min by UV-vis spectrum and naked eye observation, respectively.

Facile magnetization of covalent organic framework for solid-phase extraction of 15 phthalate esters in beverage samples.

Phthalate esters (PAEs), a category of widely used plasticizers, are tend to migrate from plastic packaging to drinks. In this paper, we develop a simple and rapid coprecipitation method for synthesis of a magnetic covalent organic framework (COF) adsorbent. The fabricated COF-(TpBD)/FeO was applied to magnetic solid phase extraction (MSPE) of 15 phthalate esters (PAEs) for subsequent GC-MS/MS determination in beverage samples.