An ultrastable 2D covalent organic framework coating for headspace solid-phase microextraction of organochlorine pesticides in environmental water

Fabrication of MOF-on-MOF composites by surfactant-assisted growth strategy for SPME of polycyclic aromatic hydrocarbons

Polycyclic aromatic hydrocarbons (PAHs) are a class of persistent organic pollutants with strong carcinogenicity and mutagenicity, which cause great harm to the environment and food. Herein, a composite (NH2-MIL-88@PCN-224) was prepared through a guest PCN-224 in situ grown on the host NH2-MIL-88 by a surfactant-assisted growth strategy, and successfully applied for solid-phase microextraction (SPME) of PAHs from milk samples. The prepared SPME coatings exhibited high extraction and adsorption capacity for PAHs due to their porous structure, ultra-large specific surface area, strong π-π stacking, hydrophobic interactions and size-matching effects. The SPME-GC-FID method based on NH2-MIL-88@PCN-224 coated fibers has the significant advantages of wide linear range (1-200 ng mL-1), low detection limit (0.003-0.020 ng mL-1), high recoveries (92.15-106.64 %) and good reproducibility. This work overcomes the lattice-matching limitation by adopting a surfactant-assisted growth strategy, which offers a new direction for the preparation of ultra-high-performance SPME coatings with extremely high extraction efficiency, exceptional thermal stability, and long service life, and greatly expands the variety of MOF SPME coatings.

Miniaturized thermal purge-and-trap device combined with self-calibration colorimetric/SERS dual-model optical sensors for highly rapid and selective detection of sulfur dioxide in wine

Herein, the miniaturized thermal purge-and-trap (MTPT) device combined with self-calibration colorimetric/surface-enhanced Raman spectroscopy (SERS) dual-model optical sensors were designed for effective analysis of sulfur dioxide (SO2) in wine. The SO2 can be rapidly separated from wine and enriched by MTPT device, ensuring colorimetric/SERS dual-model optical sensing based on Karl Fischer reaction. The high separation efficiency of miniaturized MTPT device combined with self-calibration of dual-model optical sensors significantly alleviate matrix interference and improve the detection accuracy. The satisfactory linear range of 0.1-200.0 mg/L and 0.1-500.0 mg/L with limit of detection of 0.03 mg/L can be obtained. Finally, the MTPT-colorimetric/SERS method was applied to determine the content of SO2 in different kinds of wine to verify the practicality. These results provide an ideal strategy in construction of MTPT device combined with self-calibration dual-model optical sensors for quantification of gaseous hazards in complex food samples with high rapidity, anti-interference and accuracy.

Design and fabrication of self-calibration colorimetric/fluorescence/SERS tri-modal optical sensor for highly rapid and accurate detection of mercury ions in foods

The improvement of detection accuracy without loss of rapidity and sensitivity by optical sensors in complex food analysis is still full of challenges owing to the matrix interference. Herein, a novel and simple self-calibration colorimetric/fluorescence/surface-enhanced Raman spectroscopy (SERS) tri-modal optical sensor based on aminated Rhodamine 6G (R6G-NH2) was developed for highly rapid, sensitive, and accurate detection of Hg2+ in food samples. The high recognition specificity of R6G-NH2 for Hg2+ can be achieved through the metal chelation interaction between Hg2+ and -NH2, -COOH groups in R6G-NH2 with formation of R6G-NH2-Hg2+-R6G-NH2 complex. The DFT and FDTD simulations were adopted to confirm the theoretical feasibility in Hg2+ detection by tri-modal optical. Under the optimum conditions, the analytical method based on self-calibration tri-modal optical sensor for Hg2+ detection was established with promising properties (rapidity, linearity, linear range, LOD, and LOQ), providing a strategy in rapid, selective, sensitive, and accurate detection for food safety.

Effective extraction and detection of aflatoxins in cereals using nitrogen-rich benzodiimidazole linkage magnetic covalent organic framework based solid phase extraction and HPLC-MS/MS analysis

Cereals are frequently contaminated by aflatoxins (AFs). The objective of this study was to develop an efficient extraction materials for rapidly extracting and detecting AFs. A novel amino-functionalized benzodiimidazole linkage magnetic covalent organic framework (Fe3O4@BB-COF) was simply fabricated by one-step cyclization and aromatization. The Fe3O4@BB-COF, having multiple N-containing active sites, exhibited excellent extraction capability towards AFs due to synergistic interactions, including the π-π interactions, hydrogen bonding interactions, polar interactions, electrostatic interactions and Lewis acid-base interactions. The Fe3O4@BB-COF based MSPE method for detecting aflatoxins has advantages of simple operation, short extraction time (6 min), and low material consumption (2 mg). This method exhibited satisfactory linearity (0.05-20 μg/kg), and sensitivity (0.01-0.45 μg/L for the detection limits) and accuracy (76.8-97.1 % for recovery) and was successfully applied for extracting and detecting AFs in cereals.

Covalent organic framework-functionalized magnetic MXene nanocomposite for efficient pre-concentration and detection of organophosphorus and organochlorine pesticides in tea samples before gas chromatography-triple quadrupole mass spectrometry analysis

In this study, a hydrophobic covalent organic framework-functionalized magnetic composite (CoFe2O4@Ti3C2@TAPB-TFTA) with a high specific area with 1,3,5-tris(4-aminophenyl)benzene (TAPB) and 2,3,5,6-tetrafluoroterephthalaldehyde (TFTA) was designed and synthesized through Schiff base reaction. An efficient magnetic solid-phase extraction method was established and combined with gas chromatography-triple quadrupole mass spectrometry to sensitively determine 10 organochlorine and organophosphorus pesticides in tea samples. The established method exhibited good linearity in the range of 0.05-120 μg/L and had low limits of detection (0.013-0.018 μg/L). The method was evaluated with tea samples, and the spiked recoveries of pesticides in different tea samples reached satisfactory values of 85.7-96.8%. Moreover, the adsorption of pesticides was spontaneous and followed Redlich-Peterson isotherm and pseudo-second-order kinetic models. These results demonstrate the sensitivity, effectiveness, and reliability of the proposed method for monitoring organochlorine and organophosphorus pesticides in tea samples, providing a preliminary basis for researchers to reasonably design adsorbents for the efficient extraction of pesticides.

In-situ growth of a covalent organic framework-based matrix-compatible microextraction coating for sensitive extraction of multiple pesticides

The potential pesticide hazard to non-target organisms is a global concern. It is critical to develop the sensitive detection methods of multiple pesticides in various complex matrices. Here, benzene-1,3,5-tricarbaldehyde (BTCA) and 1,3,5-Tri (4-aminophenyl) benzene (TAPB) were employed as precursors for the in-situ growth of COFTAPB-BTCA on the surface of amino-functionalized stainless steel wire (SS) via a solvothermal method. The successful COFTAPB-BTCA bonded fiber exhibited significant enrichment capability of pyrethroids insecticides (PYs), organophosphorus (OPPs), and organochlorine (OCPs), with enrichment factors (EFs) ranging from 1133-7762, 1319-7291, and 734.1-2882, respectively. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations indicated that various interactions contributed to its high enrichment capacity. Automated detection of PYs, OPPs, and OCPs in water, foods, and biological samples was realized by coupling this fiber with gas chromatography-mass spectrometry (GC-MS). The detection limits were as low as 0.0370-0.657 ng/L, 0.0128-0.400 ng/L, and 0.0329-0.202 ng/L for PYs, OPPs, and OCPs, respectively. In addition, the environmental risks of these samples were assessed based on the above data. This work not only provided a straightforward technique for sensitive monitoring of pesticides in complex matrices but also presented a novel approach for the in-situ controlled growth of versatile adsorbents with broad-spectrum properties.

Recent advances in solid phase microextraction with various geometries in environmental analysis

Solid phase microextraction (SPME) has emerged as a versatile sample preparation technique for the preconcentration of a broad range of compounds with various polarities, especially in environmental studies. SPME has demonstrated its eco-friendly credentials, significantly reducing the reliance on solvents. The use of biocompatible materials as a coating recipe facilitates the acceptance of SPME devices in analytical chemistry, primarily in the monitoring of environmental pollutants such as persistent organic pollutants (POPs), volatile organic compounds (VOCs), and pesticides from the various environmental matrices. During the last few years, investigators have reported an improvement in the SPME enrichment technique after changing the coating recipe, geometries, and sampling procedure from the complex matrices. Furthermore, the development of various geometries of SPME with large surface areas has enhanced the extraction efficiency of environmental pollutants. As a miniaturized sample preparation technique, SPME significantly reduces the solvent usage, suggesting a potential platform for green chemistry-based research for water, air, and soil analysis. This review article summarizes the evolution of SPME, its various modes, the application of SPME, recent innovations, and prospects for the determination of water, air, and soil pollution. The advantages and disadvantages of SPME in comparison to other extraction techniques have been discussed here. This review serves as a valuable resource for investigators working in sustainable environmental research.

Multiple-component covalent organic frameworks for simultaneous extraction and determination of multitarget pollutants in sea foods

Persistent organic pollutants (POPs), such as perfluoroalkyl and polyfluoroalkyl substances (PFASs), polychlorinated biphenyls (PCBs), and bisphenols (BPs), have been raising global concerns due to their toxic effects on environment and human health. The monitoring of residues of POPs in seafood is crucial for assessing the accumulation of these contaminants in the study area and mitigating potential risks to human health. However, the diversity and complexity of POPs in seafood present significant challenges for their simultaneous detection. Here, a novel multi-component fluoro-functionalized covalent organic framework (OH-F-COF) was designed as SPE adsorbent for simultaneous extraction POPs. On this basis, the recognition and adsorption mechanisms were investigated by molecular simulation. Due to multiple interactions and large specific surface area, OH-F-COF displayed satisfactory coextraction performance for PFASs, PCBs, and BPs. Under optimized conditions, the OH-F-COF sorbent was employed in a strategy of simultaneous extraction and stepwise elution (SESE), in combination with HPLC-MS/MS and GC-MS method, to effectively determined POPs in seafood collected from coastal areas of China. The method obtained low detection limits for BPs (0.0037 -0.0089 ng/g), PFASs (0.0038 -0.0207 ng/g), and PCBs (0.2308 -0.2499 ng/g), respectively. This approach provided new research ideas for analyzing and controlling multitarget POPs in seafood. ENVIRONMENTAL IMPLICATIONS: Persistent organic pollutants (POPs), such as perfluoroalkyl and polyfluoroalkyl substances (PFASs), polychlorinated biphenyls (PCBs), and bisphenols (BPs), have caused serious hazards to human health and ecosystems. Hence, there is a need to develop a quantitative method that can rapidly detect POPs in environmental and food samples. Herein, a novel multi-component fluorine-functionalized covalent organic skeletons (OH-F-COF) were prepared at room temperature, and served as adsorbent for POPs. The SESE-SPE strategy combined with chromatographic techniques was used to achieve a rapid detection of POPs in sea foods from the coastal provinces of China. This method provides a valuable tool for analyzing POPs in environmental and food samples.

Supramolecular Materials as Solid-Phase Microextraction Coatings in Environmental Analysis

Solid-phase microextraction (SPME) has been widely proposed for the extraction, clean-up, and preconcentration of analytes of environmental concern. Enrichment capabilities, preconcentration efficiency, sample throughput, and selectivity in extracting target compounds greatly depend on the materials used as SPME coatings. Supramolecular materials have emerged as promising porous coatings to be used for the extraction of target compounds due to their unique selectivity, three-dimensional framework, flexible design, and possibility to promote the interaction between the analytes and the coating by means of multiple oriented functional groups. The present review will cover the state of the art of the last 5 years related to SPME coatings based on metal organic frameworks (MOFs), covalent organic frameworks (COFs), and supramolecular macrocycles used for environmental applications.

Flexible filament winding strategy to prepare COF@polyionic liquid-coated fibers for non-selective exclusion of macromolecules in electro-enhanced solid-phase microextraction

BACKGROUND

Accurate quantitative analysis of small molecule metabolites in biological samples is of great significance. Hydroxypolycyclic aromatic hydrocarbons (OH-PAHs) are metabolic derivatives of emerging pollutants, reflecting exposure to polycyclic aromatic hydrocarbons (PAHs). Macromolecules such as proteins and enzymes in biological samples will interfere with the accurate quantification of OH-PAHs, making direct analysis impossible, requiring a series of complex treatments such as enzymatic hydrolysis. Therefore, the development of matrix-compatible fiber coatings that can exclude macromolecules is of great significance to improve the ability of solid-phase microextraction (SPME) technology to selectively quantify small molecules in complex matrices and achieve rapid and direct analysis.

RESULTS

We have developed an innovative coating with a stable macromolecular barrier using electrospinning and flexible filament winding (FW) technologies. This coating, referred to as the hollow fibrous covalent organic framework@polyionic liquid (F-COF@polyILs), demonstrates outstanding conductivity and stability. It accelerates the adsorption equilibrium time (25 min) for polar OH-PAHs through electrically enhanced solid-phase microextraction (EE-SPME) technology. Compared to the powder form, F-COF@polyILs coating displays effective non-selective large-size molecular sieving. Combining gas chromatography-tandem triple quadrupole mass spectrometry (GC-MS/MS), we have established a simple, efficient quantitative analysis method for OH-PAHs with a low detection limit (0.008-0.05 ng L-1), wide linear range (0.02-1000 ng L-1), and good repeatability (1.0%-7.3 %). Experimental results show that the coated fiber exhibits good resistance to matrix interference (2.5%-16.7 %) in complex biological matrices, and has been successfully used for OH-PAHs analysis in human urine and plasma.

SIGNIFICANCE

FW technology realizes the transformation of the traditional powder form of COF in SPME coating to a uniform non-powder coating, giving its ability to exclude large molecules in complex biological matrices. A method for quantitatively detecting OH-PAHs in real biological samples was also developed. Therefore, the filament winding preparation method for F-COF@polyILs coated fibers, along with fibrous COFs' morphology control, has substantial implications for efficiently extracting target compounds from complex matrices.

Porous chlorine-functionalized covalent organic framework anchored graphene aerogel composite for synergically enhanced solid phase microextraction of polychlorinated naphthalene in environmental water

The residues of polychlorinated naphthalenes (PCNs) produced in multiple industrial production and life processes are continuously entering environmental waters through atmospheric deposition and land drainage, and the water pollution caused by PCNs is continuing public concern due to their potential threat to aquatic ecosystems and public health. Herein, a new chlorine-functionalized covalent organic framework anchored graphene aerogel (COF-GA) was synthesized by covalent modification technology and used as fiber coating of solid-phase microextraction for synergically enhanced extraction of PCNs in environmental water. The extraction efficiency of COF-GA coated fiber was superior to commercial fiber due to the multiple interactions (π-π, hydrophobic interaction, and halogen bonding interaction). The COF-GA coated fiber has good stability, can avoid water vapor interference at 80 °C for a long time (30 -50 min) to maintain adsorption equilibrium, and can be reused at least 96 times. Combined with gas chromatography-tandem mass spectrometry, a sensitive method for the high-efficient enrichment (enrichment factors were 501 -7453 folds) and ultra-sensitive detection (LODs were 0.001 -0.428 pg/mL) of PCNs in environmental water was established. The enrichment factor for PCNs is significantly higher than in previous studies. This proposed method provides new technical support for the daily monitoring and risk assessment of trace PCNs in environmental water.

Post-synthetic modification of covalent organic framework for efficient adsorption of organochlorine pesticides from cattle's milk

Analysis of organochlorine pesticides (OCPs) residues in milk faces a significant challenge. Herein, a sea urchin structured covalent organic framework bearing boric acid groups named COF-B(OH)2 was synthesized and applied as a coating material for solid-phase microextraction (SPME) of the OCPs in cattle's milk. Its performance was superior to that of three commonly used commercial SPME fibers, which could be due to the coexistence of hydrogen bonding, halogen bonding, π-stacking and electrostatic interactions. Besides, the fiber coating displayed good stability and reusability. After optimization, a COF-B(OH)2 based SPME coupled with gas chromatography-electron capture detection was established for the sensitive detection of the OCPs from milk samples. The limits of detection (S/N = 3) were between 0.04 and 1.00 μg kg-1. Satisfactory accuracy was achieved with the method recoveries in the range of 87.5 % to 112.5 %. These results manifest the feasibility of the COF-B(OH)2 coated fiber for the enrichment of the trace OCPs from milk samples.

Porous covalent organic framework nanofibrous membrane for excellent enrichment and ultra-high sensitivity detection of trace organochlorine pesticides in water

Developing adsorbents with high performance and long service life for effective extracting the trace organochlorine pesticides (OCPs) from real water is attracting numerous attentions. Herein, a self-standing covalent organic framework (COF-TpPa) membrane with fiber morphology was successfully synthesized by using electrospun nanofiber membranes as template and employed as solid-phase microextraction (SPME) coating for ultra-high sensitivity extraction and analysis of trace OCPs in water. The as-synthesized COF-TpPa membrane exhibited a high specific surface area (800.83 m2 g-1), stable nanofibrous structure, and excellent chemical and thermal stability. Based on the COF-TpPa membrane, a new SPME analytical method in conjunction with gas chromatography-mass spectrometry (GC-MS) was established. This proposed method possessed favorable linearity in concentration of 0.05-2000 ng L-1, high sensitivity with enrichment factors ranging from 2175 to 5846, low limits of detection (0.001-0.150 ng L-1), satisfactory precision (RSD < 10 %), and excellent repeatability (>150 cycles), which was better than most of the reported works. Additionally, the density functional theory (DFT) calculations and XPS results demonstrated that the outstanding enrichment performance of the COF-TpPa membrane was owing to synergistic effect of π-π stacking effects, high specific surface area and hydrogen bonding. This work will expect to extend the applications of COF membrane to captures trace organic pollutants in complex environmental water, as well as offer a multiscale interpretation for the design of effective adsorbents.

Pesticides impacts on human health and the environment with their mechanisms of action and possible countermeasures

Pesticides are chemical constituents used to prevent or control pests, including insects, rodents, fungi, weeds, and other unwanted organisms. Despite their advantages in crop production and disease management, the use of pesticides poses significant hazards to the environment and public health. Pesticide elements have now perpetually entered our atmosphere and subsequently contaminated water, food, and soil, leading to health threats ranging from acute to chronic toxicities. Pesticides can cause acute toxicity if a high dose is inhaled, ingested, or comes into contact with the skin or eyes, while prolonged or recurrent exposure to pesticides leads to chronic toxicity. Pesticides produce different types of toxicity, for instance, neurotoxicity, mutagenicity, carcinogenicity, teratogenicity, and endocrine disruption. The toxicity of a pesticide formulation may depend on the specific active ingredient and the presence of synergistic or inert compounds that can enhance or modify its toxicity. Safety concerns are the need of the hour to control contemporary pesticide-induced health hazards. The effectiveness and implementation of the current legislature in providing ample protection for human health and the environment are key concerns. This review explored a comprehensive summary of pesticides regarding their updated impacts on human health and advanced safety concerns with legislation. Implementing regulations, proper training, and education can help mitigate the negative impacts of pesticide use and promote safer and more sustainable agricultural practices.

Deciphering the relationship between the ordered pore structure and solid-phase microextraction behavior of covalent organic frameworks for phenols

The extraction performance of materials is highly related to their physical structure. However, the precise impact of ordered pore structure in covalent organic frameworks (COFs) on extraction performance are still puzzling. To look insight into this, a series of COFs with varying degrees of ordered pore structures were prepared at room temperature by adjusting reaction time and their extraction efficiencies toward phenolic compounds were investigated. The experimental results revealed that the COF with a short range ordered pore structure exhibited a higher affinity for phenolic compounds along with a larger enrichment factor, while the COF with a long range ordered pore structure demonstrated faster extraction kinetics. The investigation into interaction mechanism revealed that the density of available sites is responsible for these differences. Taking COF-OMe-0.5 h as solid-phase microextraction fiber coating, a highly efficient and sensitive quantitative analysis method for phenolic compounds was established by combining it with gas chromatograph-mass spectrometer. The established method boasts high enrichment factors (7192-29440), wide linear ranges (2.0-10000 ng L-1), and low detection limits (0.24-0.54 ng L-1). This study provides a conceptual guide for constructing desirable COFs with controlled pore structures for specific applications.

Pesticide contamination pattern from Morocco, insights into the surveillance situation and health risk assessment: a review

The widespread application of pesticides in Morocco's agriculture renders their monitoring in food and environmental samples very necessary. Recent years have witnessed a growing interest in reporting studies related to the monitoring of pesticide residues in food, water, groundwater, and soil as well as their quantitative health risk assessment. Most published studies have been done by university researchers. However, the lack of research reproducibility remains a problem that considerably limits the possibility of exploiting data from the literature. Our study involves an extensive literature review utilizing search engines with keywords like "pesticide residues," "monitoring," "vegetables and fruits," "water and soil," "risk assessment," and "Morocco" from 2009 to 2023. Analysis of pesticide residues in foodstuffs and environmental samples highlights concerns over compliance with EU regulations, the health risks associated with pesticide exposure, and the necessity for comprehensive monitoring and risk assessment strategies. This paper could help influence policies to develop a strategy and action plan for the sound management of pesticides, including measures to reduce their use, raise awareness, and monitor compliance. Also, this paper could be useful for scientists interested in understanding the current situation and challenges regarding pesticide residues in Morocco, as well as countries with which commercial links exist.

Sea-urchin-like covalent organic framework as solid-phase microextraction fiber coating for sensitive detection of trace pyrethroid insecticides in water

Pyrethroid insecticides residues in water pose a critical threat to the environment from widespread production and overuse. Therefore, it is of major relevance to develop a sensitive and efficient method to detect pyrethroid insecticides in water. In this paper, a covalent organic framework (COF) with NHCO as the structural unit was synthesized using a simple condensation reaction of TTL (NH2) and TDBA (COOH). Various characterization results and density functional theory (DFT) calculations demonstrated that multiple interactions synergistically promoted the adsorption of pyrethroid insecticides on COFTDBA-TTL. Based on the excellent extraction capability of COFTDBA-TTL, efficient detection of 11 pyrethroid insecticides in water was achieved using COFTDBA-TTL-coated SPME fiber and gas chromatography-tandem mass spectrometry (GC-MS). The results showed that the extraction enhancement factors (EFs) of pyrethroid insecticides were as high as 2584-7199, and the extraction efficiencies were 3.28-446 times higher than that of commercial fiber, which reflected its high adsorption property. Meanwhile, the limits of detection (LODs) of the COFTDBA-TTL coated fiber were as low as 0.170-1.68 ng/L under the optimal conditions, and the recoveries of 11 pyrethroid insecticides in the actual water samples were 88.5-108 %. In conclusion, the SPME-GC-MS method based on COFTDBA-TTL coated fiber was simple, rapid, and efficient, and should have a promising application in trace detection of pyrethroid insecticides in the environment.

Recent progress of covalent organic frameworks as attractive materials for solid-phase microextraction: A review

Solid-phase microextraction (SPME) is a green, environmentally friendly, and efficient technique for sample pre-treatment. Covalent organic frameworks (COFs), a class of porous materials formed by covalent bonds, have gained prominence owing to their remarkable attributes, including large specific surface area, tunable pore size, and robust thermal/chemical stability. These characteristics have made COFs highly appealing as potential coatings for SPME fiber over the past decades. In this review, various methods used to prepare SPME coatings based on COFs are presented. These methods encompass physical adhesion, sol-gel processes, in situ growth, and chemical cross-linking strategies. In addition, the applications of COF-based SPME coating fibers for the preconcentration of various targets in environmental, food, and biological samples are summarized. Moreover, not only their advantages but also the challenges they pose in practical applications are highlighted. By shedding light on these aspects, this review aims to contribute to the continued development and utilization of COF materials in the field of sample pretreatment.

Molecularly imprinted polymer sheathed mesoporous silica tube as SPME fiber coating for determination of tobacco-specific nitrosamines in water

Tobacco-specific nitrosamines (TSNAs) are probably carcinogenic disinfection byproducts eliciting health risk concerns. The determination and surveillance of TSNAs in water is still cumbersome due to the lack of advanced sample preparation methods. Herein, we prepared a solid phase microextraction (SPME) fiber coated with the molecularly imprinted polymer (MIP) sheathed mesoporous silica tube (MST) composite material, and developed a highly efficient, selective, and sensitive method for the determination of five TSNAs in water. Benefiting from the TSNAs-specific recognition of MIP and the increased specific surface area derived from MST, the MIP@MST fiber exhibited excellent extraction performance for TSNAs, which was much superior to the commercially available SPME fibers. By coupling to high performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS), the outstanding analytical merits such as low method detection limits (ranging 0.1-6.7 ng L-1) and good reproducibility (intra-fiber and inter-fiber relative standard deviations ranging 4.1 %-11.6 % and 3.5 %-12.2 %, respectively) were achieved with the consumption of 8 mL water sample and 100 μL methanol solvent in 50 min. The feasibility of the SPME-HPLC-MS/MS method was demonstrated in tap water and chloraminated source water, with relative recoveries for the five TSNAs ranging from 85.2 % to 108.5 %. In result, none of the TSNAs were found in the tap water samples, while 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-Butanol (NNAL) were detected in the chloraminated source water samples. The rapid and convenient SPME-HPLC-MS/MS method developed in this study offers a powerful tool for monitoring TSNAs in water.

Synthesis of stable and efficient amide-based covalent organic frameworks fiber coatings for the improved solid-phase microextraction of polar aromatic amines

BACKGROUND

Developing facile and general functionalization strategies to improve the durability of covalent organic framework (COF) coatings and their affinity for polar targets is of great significance for solid-phase microextraction (SPME) technology.

RESULTS

In this work, a facile and general amidation strategy was developed for conversion from reversible (imine) to irreversible (amide) linkages in COF coatings. After the amidation, the durability of the obtained amide-linked covalent organic framework (Am-P-COF) coating was greatly improved, and the adsorption efficiency for polar aromatic amines (AAs) was also significantly increased. Moreover, this strategy is also applicable to the amidation of other two COF coatings, showing good general applicability. The obtained Am-P-COF coated fiber was used for SPME, and then coupled with gas chromatography tandem mass spectrometry (GC-MS/MS) to detect AAs. Under the optimal SPME conditions (extraction temperature: 50 °C, extraction time: 30 min, stirring rate: 600 rpm, pH: 8, NaCl concentration: 5.0 mg mL-1, desorption temperature: 290 °C and desorption time: 10 min), a detection method for trace AAs was established. The established method possess wide linear ranges (0.5-500.0 ng L-1), good correlation coefficients (0.9986-0.9993) and low detection limits (0.1-0.5 ng L-1). Moreover, the established method had also been successfully applied to detection of trace AAs in bottled tea beverage and plastic bags packed tea with satisfactory recoveries (83.5 %-116.8 %).

SIGNIFICANCE AND NOVELTY

This research provides a facile and general pathway for increasing the durability of COF coatings and affinity to the polar AAs. The detection method based on the obtained fibers possesses high sensitivity, satisfactory reproducibility and good precision.

Three-dimensional rose-like zinc oxide fiber coating for simultaneous extraction of polychlorinated biphenyls and polycyclic aromatic hydrocarbons by headspace solid phase microextraction

The three-dimensional (3D) rose-like zinc oxide (ZnO) material was prepared by a simple one-step CTAB-assisted hydrothermal strategy and used as a headspace solid-phase microextraction (HS-SPME) coating. Polychlorinated biphenyls (PCBs) and polycyclic aromatic hydrocarbons (PAHs) were analyzed by gas chromatography with flame ionization detector (GC-FID), and conclusively applied to ultrasensitive detection in lake and river water. Compared with one-dimensional (1D) pencil-like ZnO, the layer-by-layer petal-like structure could fully expose mass adsorption sites on the surface, which could significantly improve the adsorption. The enrichment factors with 7535-8595 for PCBs and 3855-7320 for PAHs were achieved. The established method provided a satisfactory linear range (0.005-30 ng·mL-1), coefficient (R2 > 0.9978), ultra-low limit detection (1-3 pg·mL-1), and long service life (≥ 150 times). The recoveries of 83.42-120.86 % were obtained in the real detection application of lake and river water. This work demonstrated that 3D rose-like ZnO with low cost, simple synthesis, fast extraction ability and high enrichment performance was an ideal coating material, which was hoped to enrich other compounds with similar structures with PCBs and PAHs.

Quinoline Bridging Hyperconjugated Covalent Organic Framework as Solid-Phase Microextraction Coating for Ultrasensitive Determination of Phthalate Esters in Water Samples

Phthalate esters (PAEs) are widely distributed in the environment, and this has caused serious health and safety concerns. Development of rapid and ultrasensitive identification and analysis methods for phthalate esters is urgent and highly desirable. In this work, a novel nitrogen-rich covalent organic framework (N-TTI) derived quinoline bridging covalent organic framework (N-QTTI) was fabricated and used as a solid-phase microextraction (SPME) coating for the ultrasensitive determination of phthalate esters in water samples. The physical and chemical properties of N-QTTI were investigated sufficiently. The N-QTTI-coated fiber demonstrates a superior enrichment performance than either the N-TTI-coated fiber or commercial fibers under the optimized SPME conditions. For the first time, we propose a semi-immersion strategy for the extraction of PAEs from water samples based on N-QTTI-coated SPME fibers. Combined with gas chromatography-mass spectrometry (GC-MS), the developed method N-QTTI-SPME-GC-MS exhibits a wide linear range with a satisfactory linearity (R2 ≥ 0.995). The limits of detection (LOD, S/N = 3) and the limits of quantification (LOQs, S/N = 10) were 0.17-1.70 and 0.57-5.60 ng L-1, respectively. The repeatability of the new method was examined using relative standard deviations (RSDs) between intraday and interday data, which were 0.38-7.98% and 1.22-6.60%, respectively. The spiked recoveries at three levels of 10, 100, and 1000 ng L-1 were in the range of 90.0-106.2% with RSDs of less than 7.48%. The enrichment factors ranged from 291 to 17180. When compared to previously published works, the LODs of the newly established method were improved 5-5400 times, and the enrichment factors were increased by at least 8 times. The absorption mechanism was investigated by X-ray photoelectron spectroscopy and noncovalent interaction force analysis. The technique was successfully employed for detecting PAEs in water samples.

Physisorption Behaviors of Organochlorine Pesticides on the InP3 Monolayer from Theoretical Insight

Dichlorodiphenyltrichloroethane (DDT), hexachlorocyclohexane (BHC), aldrin, and chlordimeform are ubiquitous organochlorine pesticide (OCP) residues in the environment, which pose a great threat to human health and ecosystems due to their high toxicity and easy accumulation. Based on the density functional theory (DFT) calculations, a two-dimensional InP3 monolayer was selected as a sensing material to study the sensitivity detection and adsorption behaviors toward BHC, aldrin, chlordimeform, and DDT. The calculation results show that four pesticide molecules are adsorbed on the InP3 surface by physical interaction. The identified response values (69.1, -43.1%) for DDT and chlordimeform reveal the potential of the InP3 monolayer as a sensing material for the detection of these two pesticides, accompanied by the achievement of cyclic utilization by heating to 498 K. The most satisfactory result is the adsorption of BHC, owing to the admirable sensing response (62.7%) and short recovery time (1.8 s) at room temperature, which makes InP3 a promising pesticide sensor for BHC. However, the InP3 surface is unsuitable for aldrin sensing due to poor response (-1.9%). Our work gives theoretical insight into the good sensitivity and recycling of the InP3 monolayer as a new pesticide sensor to detect DDT, BHC, and chlordimeform, which further broadens the application prospect of the InP3 nanosheet into the sensitive detection of organochlorine pesticides in the ecological environment.

Magnetic tubular nickel@silica-graphene nanocomposites with high preconcentration capacity for organothiophosphate pesticide removal in environmental water: Fabrication, magnetic solid-phase extraction, and trace detection

Organothiophosphate pesticides (OPPs) are the most common water contaminants, significantly endangering human health and bringing serious public safety issues. Thus, developing effective technologies for the removal or trace detection of OPPs from water is urgent. Herein, a novel graphene-based silica-coated core-shell tubular magnetic nanocomposite (Ni@SiO₂-G) was fabricated for the first time and used for the efficient magnetic solid-phase extraction (MSPE) of the OPPs chlorpyrifos, diazinon, and fenitrothion from environmental water. The experimental factors affecting extraction efficiency such as adsorbent dosage, extraction time, desorption solvent, desorption mode, desorption time, and adsorbent type were evaluated. The synthesized Ni@SiO₂-G nanocomposites showed a higher preconcentration capacity than the Ni nanotubes, Ni@SiO₂ nanotubes, and graphene. Under the optimized conditions, 5 mg of tubular nano-adsorbent displayed good linearity within the range of 0.1-1 μg·mL^-1, low limits of detection (0.04-0.25 pg·mL^-1), low limits of quantification (0.132-0.834 pg·mL^-1), good reusability (n = 5; relative standard deviations between 1.46% and 9.65%), low dosage (5 mg), and low real detection concentration (< 3.0 ng·mL^-1). Moreover, the possible interaction mechanism was investigated by density functional theory calculation. Results showed that Ni@SiO₂-G was a potential magnetic material for the preconcentration and extraction of formed OPPs at ultra-trace levels from environmental water.