Nanoporous carbon derived from a metal organic framework as a new kind of adsorbent for dispersive solid phase extraction of benzoylurea insecticides

Zeolitic imidazolate framework-8 as a high-affinity adsorbent for dispersive solid-phase extraction in the analysis of plant growth regulators in fruits

Facile and sensitive determination of plant growth regulators (PGRs) in food samples is crucial but still poses a significant challenge. In this study, to enhance the sensitivity of the HPLC-DAD method for PGR detection, a dispersive solid phase extraction (d-SPE) method using zeolitic imidazolate framework-8 (ZIF-8) as the highly effective adsorbent is developed. ZIF-8 nanoparticles are formed through the coordination of Zn2+ with 2-methylimidazole. Due to its high porosity, large surface area, abundant π electronics and nitrogen electronics, ZIF-8 exhibits a strong affinity to PGRs due to the synergistic effects of π-π interaction, van der Waals force, H-bond, and surface effect. Under the optimal d-SPE conditions, the sensitivity of the method is significantly enhanced with outstanding performances, including a wide range of linearity (2.0-200 ng g-1) with high correlation coefficients (R ≥ 0.9989), low limits of detection (LODs, 0.9-8.0 ng g-1 for all PGRs), satisfactory precision (intra-day RSDs ≤ 3.3%, inter-day RSDs ≤ 4.2%), and high accuracy (recovery: 86.6-101.5%). The developed method was successfully applied to quantitatively detect 9 PGRs in fruit samples, yielding satisfactory results. This d-SPE-HPLC-DAD method, characterized by high sensitivity, simplicity, efficiency, ease of practice and cost-effectiveness for PGR detection, shows potential for detecting PGRs in other complex samples and provides a strategy for designing target-affinity adsorbents.

Alien species water hyacinth realizes waste into treasure: The preparation of biomass sorbent to determine benzoylurea insecticides in tea products

A fast and effective analytical method with biomass solid-phase microextraction sorbent combined with a high-performance liquid chromatography-ultraviolet detector was proposed for the determination of benzoylurea (BU) insecticides in tea products. The novel sorbent was prepared by activating and then carbonizing water hyacinth with a fast growth rate and low application value as raw material and showed a high specific surface area and multiple interactions with analytes, such as electrostatic action, hydrogen bonding, and π-π conjugation. After optimizing the three most important extraction parameters (pH [X1], sample loading rate [X2], and solution volume [X3]) by Box-Behnken design, the as-established analytical method showed good extraction performance: excellent recovery (80.13%-106.66%) and wide linear range (1-400 µg/L) with a determination coefficient of 0.9992-0.9999, a low limit of detection of 0.02-0.1 µg/L and the satisfactory practical application results in tea products. All these indicate that the water hyacinth-derived material has the potential as a solid-phase extraction sorbent for the detection and removal of BU insecticides from tea products, and at the same time, it can also achieve the effect of rational use of biological resources, maintaining ecological balance, turning waste into treasure, and achieving industrial production.

Bacteria-templated ZIF-8 embedded in polyacrylonitrile nanofibers as a novel sorbent for thin film microextraction of benzoylurea insecticides

In the present work, the rod-like ZIF-8 (ZIF8@E coli) was prepared by fast, easy and environmentally friendly method of biomimetic mineralization with Escherichia coli bacteria as a bio-template and was exploited for the first time in the microextraction. In this regard, electrospun nanofiber mats of polyacrylonitrile (PAN) and ZIF8@E coli were prepared by electrospinning method and used as a new sorbent for thin film microextraction (TFME) of benzoylurea insecticides such as Hexaflumuron and Teflubenzuron as model analytes. The PAN/ZIF8@E coli nanocomposite was characterized using electron scanning microscopy and various spectroscopy techniques. Factors affecting the proposed extraction method were screened and optimized using the experiment design strategy. Then, the model analytes were measured by high-performance liquid chromatography (HPLC) with ultraviolet (UV) detector after microextraction. Satisfactory figures of merit were obtained for suggested TFME-HPLC-UV under optimum conditions. The suitable linearity varied in the range of 0.5-200 μg L-1 with R2 greater than 0.9968. The limit of detections for Hexaflumuron and Teflubenzuron were 0.12 and 0.15 μg L-1, respectively. The application of the method in the real sample was investigated by analyzing the selected analytes in environmental water and food samples. The spiking recovery of the selected analytes varied in the range of 93.0-109.8 % (RSD≤7.68). The results confirm the efficient application of this new sorbent in TFME approach. Considering the high availability, ease of production, and environmental friendliness of bacteria along with the significant improvement of metal-organic framework (MOF) growth efficiency, biomimetic mineralization is expected to be efficient method for the synthesis of ordered MOFs for use in extraction fields.

An electrochemical sensor derived from Cu-BTB MOF for the efficient detection of diflubenzuron in food and environmental samples

Diflubenzuron is widely used as a benzoylurea insecticide, and its impact on human health should not be underestimated. Therefore, the detection of its residues in food and the environment is crucial. In this paper, octahedral Cu-BTB was fabricated using a simple hydrothermal method. It served as a precursor for synthesizing Cu/Cu₂O/CuO@C with a core-shell structure through annealing, creating an electrochemical sensor for the detection of diflubenzuron. The response of Cu/Cu₂O/CuO@C/GCE, expressed as ΔI/I₀ exhibited a linear correlation with the logarithm of the diflubenzuron concentration ranging from 1.0 × 10^-4 to 1.0 × 10^-12 mol·L^-1. The limit of detection (LOD) was determined to be 130 fM using differential pulse voltammetry (DPV). The electrochemical sensor demonstrated excellent stability, reproducibility, and anti-interference properties. Moreover, Cu/Cu₂O/CuO@C/GCE was successfully employed to quantitatively determine diflubenzuron in actual food samples (tomato and cucumber) and environmental samples (Songhua River water, tap water, and local soil) with good recoveries. Finally, the possible mechanism of Cu/Cu₂O/CuO@C/GCE for monitoring diflubenzuron was thoroughly investigated.

TiO2@MOF-919(Fe-Cu) as a sorbent for the extraction of benzoylurea pesticides from irrigation water and fruit juices

The TiO₂@MOF-919(Fe-Cu) solid-phase extraction material was prepared by growing MOF-919(Fe-Cu) in situ on three-dimensional radial TiO₂ microspheres by a simple solvothermal method. This combination drew on both the resources of good single dispersion and extraction rate, which made it a better extraction material. It was accompanied with high-performance liquid chromatography (SPE-HPLC) for the separation and determination of four benzoylurea pesticides (triflumuron, chlorbenzuron, teflubenzuron and diflubenzuron) in afforestation irrigation water and juice samples (grape, peach and apple juices). Under the optimal conditions, the linearity of the method ranged from 1 to 400 μg L^-1 with a correlation coefficient (R²) ≥ 0.9994, while the detection limit was in the range of 0.40-0.56 μg L^-1 for the four pesticides. The adopted material showed good reusability and can be used no less than 10 times. The intra-day and inter-day precision were in the range of 1.78-3.24% and 4.06-5.08%, respectively. The proposed method was then successfully applied for the detection of benzoylurea pesticides in the spiked samples with good recoveries (72.3-108.4%) and good precision (5.15%) due to π-π and hydrophobic interactions between the analytes and adsorbent. The results show that the composite had the potential to be used as a SPE adsorbent for the enrichment and extraction of benzene ring structures containing imide groups in actual samples.

Zeolitic imidazolate framework-8 as a dispersive solid phase extraction sorbent for simultaneous determination of 145 pesticide residues in polyphenol-rich plants

Many plants showed higher polyphenol content, which caused the matrix effect and made the analysis of trace pesticide residues highly challenging. A common approach to improving matrix effects is to purify pesticides through the use of sorbents, but this requires a combination of multiple sorbents and extensive use. Zeolitic imidazolate framework-8 is widely used for pesticide analysis due to its high porosity, large specific surface area and versatility. Here, We established and validated a modified quick, easy, cheap, effective, rugged, and safe method based on a zeolitic imidazolate framework-8 that was used to test the removal ability for polyphenols. And 145 pesticide residues in peppermint, perilla, fennel, and mulberry leaves were analyzed by the modified method coupled with LC-MS/MS. The mean recoveries of all pesticide residues were in the range of 74.3%-103.7%, with mean relative standard deviations≤ 9.1% at spiked concentrations of 1, 10, 50, and 100 μg kg^-1 for mulberry leaves. The limits of quantitation of the method ranged from 1 to 50 μg kg^-1 . This study offers a reliable approach for the accurate quantitative analysis of various trace substances in the polyphenol-rich plants. This article is protected by copyright. All rights reserved.

Fabrication of a Magnetic Fluorinated Covalent Organic Framework for the Selective Capture of Benzoylurea Insecticide Residue in Beverages

Efficient capture of benzoylurea insecticide (BU) residue in food is a vital procedure for food safe monitoring. Herein, a core-shell structured magnetic fluorinated covalent organic framework with good magnetic responsiveness and abundant fluorine affinity sites was successfully synthesized, suitable for magnetic solid-phase extraction (MSPE) of BUs. Using a room-temperature synthesis strategy, the magnetic fluorinated covalent organic framework was fabricated by in situ polymerization of 1,3,5-tris(4-aminophenyl) triazine (TAPT) and 2,3,5,6-tetrafluoroterephthaldehyde (TFTA) on the surface of carboxylated Fe₃O₄ nanoparticles. The competitive adsorption experiment and molecular simulation verified that this magnetic fluorinated covalent organic framework possesses favorable adsorption affinity for BUs. This magnetic fluorinated covalent organic framework could be easily regenerated and reused at least eight times with no reduction of enrichment performance. Combining this magnetic fluorinated covalent organic framework-based MSPE with high-performance liquid chromatography-tandem mass spectrometry, a novel sensitive method for the analysis of BUs was developed. In yellow wine and fruit juice samples, good linear correlations were obtained for BUs in the range of 10-2000 and 20-4000 ng·L^-1, respectively. The limit of quantitation of the BUs ranged from 1.4 to 13.3 ng·L^-1 in the two beverage matrices. Desirable precision was achieved, with intraday and interday relative standard deviations lower than 11%.

[Research progress in application of metal-organic framework-derived materials to sample pretreatment]

Sample pretreatment technology plays a vital role throughout the analysis of complex samples. Sample pretreatment can not only increase the concentration of trace targets in the sample, but also effectively eliminate interference from the sample matrix in instrumental analysis. Adsorbent materials are a key component of sample pretreatment technology. Therefore, the development of efficient and stable new adsorbent materials has acquired significance in research on pretreatment technology. Porous materials are advantageous for use in diverse applications, such as in adsorbents, when they possess controllable nanostructures, a tailored pore surface chemistry, and abundant porosity, and are inexpensive. Particularly in recent years, porous materials derived from metal-organic frameworks (MOFs) feature excellent properties, such as diverse morphology and structure, adjustable pore size, high specific surface area, good thermal stability, and chemical resistance. MOF-derived materials, when used as adsorbents for sample pretreatment, offer the following advantages: (1) The porous materials derived from MOFs typically possess a larger specific surface area than other porous materials. This characteristic is beneficial to improve the extraction capacity and extraction efficiency via an increase in the contact area between the materials and targets; (2) The microscopic porous structure of MOF-derived materials can be easily tuned (by controlling the temperature and time during pyrolysis, gas atmosphere, and heating rate), which is conducive to improve the selectivity of sample pretreatment methods; (3) The metal active sites can be evenly distributed. Owing to the ordered distribution of metal ions in the precursor MOFs and a good periodic framework structure, the metal active sites of the derivatives formed can still maintain a corresponding distance. These metal active sites will not form agglomerates and affect the extraction performance; conversely, other porous materials often require extremely complicated processes to achieve a uniform distribution; (4) Heteroatoms such as nitrogen and sulfur can be easily doped on the framework of MOF-derived porous materials. This doping enables the materials to induce additional interactions such as hydrogen bonding and π-π stacking for adsorbing target analytes. The excellent properties of MOF-derived materials make them promising for use in sample pretreatment. Novel sample pretreatment methods that use MOF-derived materials are constantly being developed. However, the use of MOF-derived materials is limited by the complex preparation process and high production cost of MOF precursors, along with difficulties in mass production. Further, the precise design or functionalization of MOF-derived materials according to the characteristics of targets is a new direction with immense challenges as well as application potential. This review summarizes the application of MOF-derived materials in sample pretreatment methods, including dispersive solid phase extraction (dSPE), magnetic solid phase extraction (MSPE), solid phase microextraction (SPME), stir bar sorptive extraction (SBSE), and dispersive micro solid phase extraction (DMSPE). The preparation methods, functional control, and enrichment efficiencies of various MOF-derived materials are also reviewed. Finally, the application prospects of MOF-derived materials in sample pretreatment are discussed to provide a clear outlook and reference for further related research.

One step extraction followed by HPLC-ESI-MS/MS for multi-residue analysis of diacylhydrazine insecticides in water, sediment, and aquatic products

A multi-residue analysis of six diacylhydrazine insecticides in water, sediment, and aquatic products was established by liquid chromatography triple quadrupole tandem mass spectrometry (LC-MS/MS). The water sample was extracted with acetonitrile by low-temperature enrichment liquid-liquid extraction technology. The sediment and aquatic products were prepared using QuEChERS technique. Method validation showed perfect linearity with correlation coefficients (R) more than 0.9992 for all insecticides, and the matrix effects were nearly negligible (-1.42% to -0.27%) for water, sediment and aquatic products. The recoveries were 80.0-99.7% at three spiked levels (0.02 ng·mL^-1, 0.1 ng·mL^-1, 0.5 ng·mL^-1; 2.0, 10, and 50 ng·g^-1) and the precisions (intra-day and inter-day precision) were lower than 5.28%, with the low LODs (3.8 ~ 9.6 pg·mL^-1; 0.38-0.96 ng·g^-1) and LOQs (12.7 ~ 32.0 pg·mL^-1; 1.27-3.20 ng·g^-1) for water, sediment, and aquatic products, indicating the good accuracy and precision of the proposed method. The applicability, efficiency, and sensitivity of this method have been proved in the analysis of six diacylhydrazine insecticides in water, sediment, and crucian carp in Rice- crucian carp - integrated planting system.

New frontiers and prospects of metal-organic frameworks for removal, determination, and sensing of pesticides

Pesticides have been widely used in agriculture to control, reduce, and kill insects. Humans are also being using pesticides to control insidious animals in daily life. By these practices, a huge volume of pesticides is introduced to the environment. Despite broad-spectrum applicability, pesticides also have hazardous effects on both humans and animals at high and low concentrations. Long-term exposure to pesticides can cause different diseases, like leukemia, lymphoma, and cancers of the brain, breasts, prostate, testis, and ovaries. Reproductive disorders from pesticides include birth defects, stillbirth, spontaneous abortion, sterility, and infertility. Therefore, the application of determination and treatment methods for pre-concentration and removal of these toxic materials from the environment appears a vital concern. To date, different materials and approaches have been employed for these purposes. Among these approaches, multifunctional metal-organic frameworks (MOFs)-assisted adsorption and determination processes have always been in the spotlight. These facts are due to exclusive properties of MOFs in terms of the crystallinity, large surface area, high chemical, and physical stability, and controllable structure as well as unique features of adsorption and determination process in terms of simple, easy, cheap, available method and ability to use in large and industrial scales. In the present work, we illustrate the exceptional features of MOFs as well as the possible mechanism for the adsorption of pesticides by MOFs. The use of these fantastic materials for pre-concentration and removal of pesticides are extensively explored. In addition, the performance of MOFs was compared with other adsorbents. Finally, the new frontiers and prospects of MOFs for the determination, sensing, and removal of pesticides are presented.

Hyperbranched aromatic polyamide modified magnetic nanoparticles for the extraction of benzoylurea insecticides

Herein, a novel hyperbranched aromatic polyamide-coated magnetic sorbent was prepared by in situ polymerization on the surface of amino-functionalized Fe₃ O₄ nanoparticles. The magnetic sorbent was characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, elemental analysis, Brunauer-Emmett-Teller measurement, and X-ray photoelectron spectroscopy, etc. The new magnetic sorbent was used in the magnetic solid-phase extraction for the detection of seven benzoylurea insecticides. Under optimum conditions, low method detection limits (0.56-1.20 ng/mL), acceptable coefficient of determination (0.9967-0.9996), wide linear ranges (2.5-500.0 ng/mL), and good repeatability (intraday: 2.0-7.3%; interday: 1.9-9.2%) were achieved. The magnetic solid-phase extraction method based on the new magnetic sorbent showed good reliability in the analysis of seven benzoylurea insecticides in real water samples, as the relative recoveries were in the range from 80.1 to 116.3% with satisfactory RSDs (0.1-9.8%). By means of density functional theory and semiempirical quantum mechanical, the binding configuration and interaction energy of hyperbranched aromatic polyamide and benzoylurea insecticides were calculated. The result of theoretical calculation revealed that the adsorption of benzoylurea insecticides by hyperbranched aromatic polyamide was derived from hydrogen bonding and π-π stacking. The contribution of π-π stacking was greater than that of hydrogen bond, which was confirmed by energy decomposition analysis.

Phosphonium-based deep eutectic solvent coupled with vortex-assisted liquid-liquid microextraction for the determination of benzoylurea insecticides in olive oil

In this study, a novel method using a phosphonium-based deep eutectic solvent coupled with vortex-assisted liquid-liquid microextraction was investigated for the enrichment and separation of five benzoylurea insecticides in olive oil. The experimental factors affecting the extraction efficiency, including the extractant type, deep eutectic solvent volume, extraction time, and extraction mode, were optimized. Under optimal conditions, good linearity was observed for all target analytes, with correlation coefficients (r) ranging from 0.9971 to 0.9998; the limits of detection were in the range of 1.5 to 7.5 μg/L, and the recoveries of analytes using the proposed method ranged between 66.9 and 111.0%. The simple, rapid, and effective method was successfully applied for detecting target analytes in olive oil sample.

Zeolitic imidazolate frameworks in analytical sample preparation

Zeolitic imidazolate frameworks are a class of metal-organic frameworks that are topologically isomorphic with zeolites. Zeolitic imidazolate frameworks are composed of tetrahedrally coordinated metal ions connected by imidazolate linkers and have a high porosity and chemical stability. Here, we summarize the progress made in the application of zeolitic imidazolate frameworks in sample preparation for analytical purposes. This review is focused on analytical methods based on liquid chromatography, gas chromatography, or capillary electrophoresis, where the use of zeolitic imidazolate frameworks has contributed to increasing the sensitivity and selectivity of the method. While bulk zeolitic imidazolate frameworks have been directly used in analytical sample preparation protocols, a variety of strategies for their magnetization or their incorporation into sorbent particles, monoliths, fibers, stir bars, or thin films, have been developed. These modifications have facilitated the handling and application of zeolitic imidazolate frameworks for a number of analytical sample treatments including magnetic solid-phase extraction, solid-phase microextraction, stir bar sorptive extraction, or thin film microextraction, among other techniques.

Dissolvable Mg/Al layered double hydroxides and surfactant as an extractant for trace analysis of benzoylurea insecticides by high performance liquid chromatography

A rapid and simple preconcentration method using dissolvable Mg/Al layered-double hydroxides (LDHs) and high performance liquid chromatography-photodiode array detection (HPLC-PDA) was developed for the analysis of benzoylurea insecticides (BUs) in water and honey samples. The proposed dissolvable LDHs for the extraction can be prepared in one step by the sequential addition of sodium hydroxide, magnesium chloride, aluminium chloride, and sodium dodecyl sulfate into the sample solution containing the target BUs. The co-precipitate phase was simply obtained after centrifugation, and the phase was then dissolved with formic acid before analysis by HPLC. The developed method provided an enrichment factor of 12.5-23.7. LODs were obtained in the range of 0.1-0.3 μg L^-1 for deionized water, 0.2-2.0 μg L^-1 for environmental waters, and 0.5-2.0 μg L^-1 for the analyzed honey samples. Good recoveries ranging from 78.4 to 117.8% and 72.7 to 117.9% for water and honey samples, respectively, were obtained.

Cost-efficient magnetic nanoporous carbon derived from citrus peel for the selective adsorption of seven insecticides

A magnetic solid-phase extraction adsorbent that consisted of citrus peel-derived nanoporous carbon and silica-coated Fe₃ O₄ microspheres (C/SiO₂ @Fe₃ O₄ ) was successfully fabricated by co-precipitation. As a modifier for magnetic microspheres, citrus peel-derived nanoporous carbon was not only economical and renewable for its raw material, but exerted enormous nanosized pore structure, which could directly influence the type of adsorbed analytes. The C/SiO₂ @Fe₃ O₄ also possessed the advantages of Fe₃ O₄ microspheres like superparamagnetism, which could be easily separated magnetically after adsorption. Integrating the superior of biomass-derived nanoporous carbon and Fe₃ O₄ microspheres, the as-prepared C/SiO₂ @Fe₃ O₄ showed high extraction efficiency for target analytes. The obtained material was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and the Brunauer-Emmett-Teller method, which demonstrated that C/SiO₂ @Fe₃ O₄ was successfully synthesized. Under the optimal conditions, the adsorbent was selected for the selective adsorption of seven insecticides before gas chromatography with mass spectrometry detection, and good linearity was obtained in the concentration range of 2-200 μg/kg with the correlation coefficient ranging from 0.9952 to 0.9997. The limits of detection were in the range of 0.03-0.39 μg/kg. The proposed method has been successfully applied to the enrichment and detection of seven insecticides in real vegetable samples.

Recent advances in metal-organic frameworks for adsorption of common aromatic pollutants

This review (with 85 refs.) summarizes the recent literature on the adsorption of common aromatic pollutants by using modified metal-organic frameworks (MOFs). Four kinds of aromatic pollutants are discussed, namely benzene homologues, polycyclic aromatic hydrocarbons (PAHs), organic dyes and their intermediates, and pharmaceuticals and personal care products (PPCPs). MOFs are shown to be excellent adsorbents that can be employed to both the elimination of pollutants and to their extraction and quantitation. Adsorption mechanisms and interactions between aromatic pollutants and MOFs are discussed. Finally, the actual challenges of existence and the perspective routes towards future improvements in the field are addressed. Graphical abstract Recent advance on adsorption of common aromatic pollutants including benzene series, polycyclic aromatic hydrocarbons, organic dyes and their intermediates, pharmaceuticals and personal care products by metal-organic frameworks.

Magnetic dispersive micro solid-phase extraction and gas chromatography determination of organophosphorus pesticides in strawberries

Magnetic nanoparticles (MNPs) with different sizes and characteristics were synthesized to be used as a QuEChERS sorbents for the determination of seven organophosphorus pesticides (OPPs) in strawberries by gas chromatography analysis with flame photometric and mass spectrometry detection. To achieve the optimum conditions of modified QuEChERS procedure several parameters affecting the cleanup efficiency including the amount of the sorbents and cleanup time were investigated. The results were compared with classical QuEChERS methodologies and the modified QuEChERS procedure using MNPs showed the better performance. Under the optimum conditions of the new methodology, three spiking levels (25, 50 and 100 μg kg^-1) were evaluated in a strawberry sample. The results showed that the average recovery was 93% and the relative standard deviation was less than 12%. The enrichment factor ranged from 111 to 145%. The good linearity with coefficients of determination of 0.9904-0.9991 was obtained over the range of 25-250 μg kg^-1 for 7 OPPs. It was determined that the MNPs have an excellent function as sorbent when purified even using less amount of sorbents and the magnetic properties allowed non-use of the centrifugation in cleanup step. The new methodology was applied in strawberry samples from conventional and organic farming. The new sorbents were successfully applied for extraction and determination of OPPs in strawberries.

Graphene-based metal and nitrogen-doped carbon composites as adsorbents for highly sensitive solid phase microextraction of polycyclic aromatic hydrocarbons

Herein, a graphene-based metal and nitrogen-doped carbon (GNC-Co) composite, derived from zeolite imidazolate framework-67 (ZIF-67)-graphene oxide composites, was successfully developed and applied as an excellent fiber coating for solid phase microextraction (SPME) with enhanced performance. The fabricated carbon has a hierarchically micro/mesoporous structure with a high specific surface area of 123 m2 g-1. The study found that pyrolytic graphene (G) has good adsorption properties for anthracene, phenanthrene, fluoranthene and pyrene, while pyrolytic ZIF-67 (NC-Co) has good adsorption properties for naphthalene, acenaphthylene, acenaphthylene and fluorene. Combined with the advantage of G and NC-Co, the synthesized composite GNC-Co enabled the integration of the unique properties of these two fascinating materials and proved to show better performance in the extraction of all polycyclic aromatic hydrocarbons (PAHs). Compared to the commercial PDMS fiber, the self-made fiber achieved GC responses about 2-9 times as high as those obtained by the commercial 30 μm PDMS fiber. Furthermore, the self-made fiber obtained low detection limits in the range of 0.01-0.74 ng L-1 and wide linearity under the optimized extraction conditions. Finally, the GNC-Co coated fiber was successfully used for the detection of PAHs in real river water samples, which proved the applicability of the method.

A boronate-decorated porous carbon material derived from a zinc-based metal–organic framework for enrichment of cis-diol-containing nucleosides

A new boronate-decorated carbon material derived from Zn-MOF was synthesized and used to selectively enrich cis-diol nucleosides.

Using cobalt/chromium layered double hydroxide nano-sheets as a novel packed in-tube solid phase microextraction sorbent for facile extraction of acidic pesticides from water samples

Cobalt/chromium-layered double hydroxide (Co/Cr (NO₃⁻)-LDH) nano-sheets were employed as a packed in-tube solid phase microextraction sorbent for efficient extraction of acidic pesticides from water samples.

Porphyrin based porous organic polymer modified with Fe3O4 nanoparticles as an efficient adsorbent for the enrichment of benzoylurea insecticides

Porphyrin-based porous organic polymers (P-POPs) are amorphous polymers linked by strong covalent bonds between the porphyrin subunits that act as building blocks. The authors describe a magnetic P-POP that possesses high surface area, a highly porous structure, and strong magnetism. The MP-POP was employed as a magnetic sorbent for the extraction of benzoylurea insecticides from cucumber and tomato samples prior to their determination by HPLC. The sorbent has a typical sorption capacity of 1.90-2.00 mg∙g^-1. The method exhibits a good linear range (0.8-160 ng·g^-1), low limits of detection (0.08-0.2 ng·g^-1), and high method recoveries (81.8-103.5%) for cucumber and tomato samples. The MP-POP has different adsorption capabilities for the benzoylurea insecticides, phenylurea herbicides and phenols compounds, and the adsorption mechanism is found to be based on π-stacking, hydrogen-bonding, and hydrophobic interactions. Graphical abstract A novel magnetic porphyrin-based porous organic polymer was fabricated and used as the adsorbent for the efficient extraction of benzoylurea insecticides.

Recent advances in metal-organic frameworks and covalent organic frameworks for sample preparation and chromatographic analysis

In the field of analytical chemistry, sample preparation and chromatographic separation are two core procedures. The means by which to improve the sensitivity, selectivity and detection limit of a method have become a topic of great interest. Recently, porous organic frameworks, such as metal-organic frameworks (MOFs) and covalent organic frameworks (COFs), have been widely used in this research area because of their special features, and different methods have been developed. This review summarizes the applications of MOFs and COFs in sample preparation and chromatographic stationary phases. The MOF- or COF-based solid-phase extraction (SPE), solid-phase microextraction (SPME), gas chromatography (GC), high-performance liquid chromatography (HPLC) and capillary electrochromatography (CEC) methods are described. The excellent properties of MOFs and COFs have resulted in intense interest in exploring their performance and mechanisms for sample preparation and chromatographic separation.

Recent applications of metal-organic frameworks in sample pretreatment

Metal-organic frameworks are promising materials in diverse analytical applications especially in sample pretreatment by virtue of their diverse structure topology, tunable pore size, permanent nanoscale porosity, high surface area, and good thermostability. According to hydrostability, metal-organic frameworks are divided into moisture-sensitive and water-stable types. In the actual applications, both kinds of metal-organic frameworks are usually engineered into hybrid composites containing magnetite, silicon dioxide, graphene, or directly carbonized to metal-organic frameworks derived carbon. These metal-organic frameworks based materials show good extraction performance to environmental pollutants. This review provides a critical overview of the applications of metal-organic frameworks and their composites in sample pretreatment modes, that is, solid-phase extraction, magnetic solid-phase extraction, micro-solid-phase extraction, solid-phase microextraction, and stir bar solid extraction.

Nanoarchitectured Design of Porous Materials and Nanocomposites from Metal-Organic Frameworks

The emergence of metal-organic frameworks (MOFs) as a new class of crystalline porous materials is attracting considerable attention in many fields such as catalysis, energy storage and conversion, sensors, and environmental remediation due to their controllable composition, structure and pore size. MOFs are versatile precursors for the preparation of various forms of nanomaterials as well as new multifunctional nanocomposites/hybrids, which exhibit superior functional properties compared to the individual components assembling the composites. This review provides an overview of recent developments achieved in the fabrication of porous MOF-derived nanostructures including carbons, metal oxides, metal chalcogenides (metal sulfides and selenides), metal carbides, metal phosphides and their composites. Finally, the challenges and future trends and prospects associated with the development of MOF-derived nanomaterials are also examined.

Zeolitic imidazolate framework-8 derived nanoporous carbon as an effective and recyclable adsorbent for removal of ciprofloxacin antibiotics from water

The nanoporous carbons (NPC) derived from a one-step carbonization of zeolitic imidazolate framework-8 (ZIF-8) were synthesized and used for ciprofloxacin (CIP) removal from water. The resultant products were characterized by SEM, TEM, FT-IR, Raman, N₂ adsorption-desorption analysis, XRD, TGA and Zeta potential. The optimized NPC-700 (carbonized at 700°C for 2h) exhibited an optimal performance in CIP adsorption removal. CIP adsorption on NPC-700 as a function of contact time, initial CIP concentration, adsorbent dosage, pH, ionic strength and humic acid concentration were investigated. Kinetics of CIP removal was found to follow pseudo-second-order rate equation. Both Langmuir and Freundlich models fitted the adsorption data well and gave similar correlation coefficients (>0.96). However, Freundlich isotherm gave a better fit (r²=0.9969), suggesting a multilayer adsorption of CIP onto surface of NPC-700 adsorbent. The maximum adsorption capacity for CIP based on Langmuir model was 416.7mg/g, which was higher than those of other adsorbents. The NPC-700 material showed no apparent loss in CIP adsorption after seven cycles. These features reveal that the metal-organic framework (MOF) derived NPC may be a promising adsorbent for CIP removal from water.