Porous covalent organic frameworks-improved solid phase microextraction ambient mass spectrometry for ultrasensitive analysis of tetrabromobisphenol-A analogs

In situ growth of hierarchical porous covalent organic framework coating for enhanced solid-phase microextraction of phenolic compounds

Covalent organic frameworks (COFs), when utilized as solid-phase microextraction (SPME) coating materials, exhibit remarkable abilities to concentrate phenols by thousands-fold owing to their vast surface area and exceptional stability. However, the prevalent micropores inherent in COFs can impede rapid mass transfer of target molecules, prolonging SPME extraction times. To addresses this limitation, this work introduces a novel approach by integrating hierarchical porous structures into COFs, leveraging polystyrene microspheres as hard templates during the in situ growth process of the SPME coating. Due to the presence of a hierarchical porous structure derived from the template, the resulting hierarchical porous TpBD coating, termed HP-TpBD, demonstrated enhanced extraction efficiency, accelerated extraction kinetics, and notably shortened extraction times for phenolic compounds. Coupled with gas chromatography-mass spectrometry, a highly sensitive method featuring a low limit of detection (0.20-0.28 ng L-1), a broad linear range (1.0∼1.0 × 104 ng L-1), and excellent precision (RSD < 8.5 %) was established. This methodology enables accurate quantitative analysis of phenols in water and soil samples. This work provides valuable insights into developing COF-based SPME coatings for the efficient extraction of volatile contaminants, paving the way for more efficient and sensitive analytical procedures.

Advances in covalent organic frameworks for sample preparation

Sample preparation is crucial in analytical chemistry, impacting result accuracy, sensitivity, and reliability. Solid-phase separation media, especially adsorbents, are vital for preparing of liquid and gas samples, commonly analyzed by most analytical instruments. With the advancements in materials science, covalent organic frameworks (COFs) constructed through strong covalent bonds, have been increasingly employed in sample preparation in recent years. COFs have outstanding selectivity and/or excellent adsorption capacity for a single target or can selectively adsorb multiple targets from complex matrix, due to their large specific surface area, adjustable pore size, easy modification, and stable chemical properties. In this review, we summarize the classification of COFs, such as pristine COFs, COF composite particles, and COFs-based substrates. We aim to provide a comprehensive understanding of the different classifications of COFs in sample preparation within the last three years. The challenges and development trends of COFs in sample preparation are also presented.

Fluorine-functionalized covalent organic framework coated solid-phase microextraction probe coupled with electrospray ionization mass spectrometry for monitoring triclosan, triclocarban, and chlorophenols in mice

Triclosan (TCS), triclocarban (TCC), and chlorophenols (CPs) are broad-spectrum antibacterials widely used in dermatological and oral hygiene products, which could induce severe liver and intestine injuries. Hence, it is essential to establish a rapid and sensitive method to monitor TCS, TCC, and CPs in various organisms. In this work, fluorine-functionalized covalent organic framework (COF-F) was prepared by using 4,4',4''-(1,3,5-triazine-2,4,6-triyl)tri-aniline and 2,3,5,6-tetrafluoroterephthalaldehyde as two building units and employed as a solid phase microextraction (SPME) probe for the extraction of TCS, TCC and CPs. The COF-F possessed excellent hydrophobicity, a large specific surface area (1354.3 m2 g-1) and high uniform porosity (3.2 nm), which facilitated high selectivity and adsorption properties towards TCS, TCC, and CPs. Therefore, the as-prepared COF-F-SPME in combination with electrospray ionization mass spectrometry has been developed to provide fast and ultrasensitive detection of TCS, TCC, and CPs in biological samples. The established method demonstrated satisfactory linear ranges (0.01-100.00 μg L-1) and low limits of detection (0.003-0.040 μg L-1) for TCS, TCC and CPs. The developed method could be successfully applied to detect TCS, TCC and CPs in the liver and kidney tissues of mice, demonstrating the potential for the detection of chlorinated aromatic pollutants in the biological samples.

Layer-by-layer fabrication of covalent organic frameworks on stainless steel needles as solid-phase microextraction probe coupled with electrospray ionization mass spectrometry for enrichment and determination of tyrosine kinase inhibitors in biosamples

Sunitinib, N-desmethyl imatinib, dasatinib, imatinib, and bosutinib are tyrosine kinase inhibitors (TKIs) that are commonly employed in the treatment of a multitude of cancers. However, the inappropriate concentrations of TKIs can result in ineffective treatment or the emergence of multiple adverse effects. Consequently, the development of a rapid and sensitive analytical method for TKIs is of paramount importance for the safe administration of drugs. In this work, solid-phase microextraction (SPME) probe combined with an electrospray ionization mass spectrometry (ESI-MS) coupling platform was constructed for rapid and sensitive determination of TKIs. The covalent organic frameworks (COFs) coated SPME probe was made of 2,4,6-tris(4-aminophenyl)-1,3,5-triazine (TAPT) and 2,5-dibutoxyterephthalaldehyde (DBTA) by in-situ layer-by-layer chemical bonding synthesis strategy. The TAPT-DBTA-SPME probe exhibited several advantageous properties which rendered it suitable for the enrichment of TKIs. Under the optimal conditions, the developed analytical method demonstrated a broad linear range (0.05-500.00 µg/L), a low limit of detection (0.02 µg/L) and a high enrichment factor (51-203) for TKIs. The developed analytical method was successfully applied to a pharmacokinetic study of TKIs in mouse plasma and tissue matrix, demonstrating that the proposed analytical method has promise for clinical applications and metabolic monitoring.

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.

In situ fabrication of covalent organic frameworks on solid-phase microextraction probes coupled with electrospray ionization mass spectrometry for enrichment and determination of androgens in biosamples

Solid-phase microextraction (SPME) coupled with electrospray ionization mass spectrometry (ESI-MS) was developed for rapid and sensitive determination of endogenous androgens. The SPME probe is coated with covalent organic frameworks (COFs) synthesized by reacting 1,3,5-tri(4-aminophenyl)benzene (TPB) with 2,5-dioctyloxybenzaldehyde (C8PDA). This COFs-SPME probe offers several advantages, including enhanced extraction efficiency and stability. The analytical method exhibited wide linearity (0.1-100.0 µg L-1), low limits of detection (0.03-0.07 µg L-1), high enrichment factors (37-154), and satisfactory relative standard deviations (RSDs) for both within one probe (4.0-14.8%) and between different probes (3.4-12.7%). These remarkable performance characteristics highlight the reliability and precision of the COFs-SPME-ESI-MS method. The developed method was successfully applied to detect five kinds of endogenous androgens in female serum samples, indicating that the developed analytical method has great potential for application in preliminary clinical diagnosis.

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.

Magnetic covalent organic frameworks for extraction and determination of endocrine-disrupting chemicals in beverage and water samples

BACKGROUND

Phenolic endocrine-disrupting chemicals (EDCs) are widespread and easily ingested through the food chain. They pose a serious threat to human health. Magnetic solid-phase extraction (MSPE) is an effective sample pre-treatment technology to determine traces of phenolic EDCs.

RESULTS

Magnetic covalent organic framework (COF) (Fe3 O4 @COF) nanospheres were prepared and characterized. The efficient and selective extraction of phenolic EDCs relies on a large specific surface and the inherent porosity of COFs and hydrogen bonding, π-π, and hydrophobic interactions between COF shells and phenolic EDCs. Under optimal conditions, the proposed magnetic solid-phase extraction-high-performance liquid chromatography-ultra violet (MSPE-HPLC-UV) based on the metallic covalent organic framework method for phenolic EDCs shows good linearities (0.002-6 μg mL-1 ), with R2 of 0.995 or higher, and low limits of detection (6-1.200 ng mL-1 ).

CONCLUSION

Magnetic covalent organic frameworks (Fe3 O4 @COFs) with good MSPE performance for phenolic EDCs were synthesized by the solvothermal method. The magnetic covalent organic framework-based MSPE-HPLC-UV method was applied successfully to determine phenolic EDCs in beverage and water samples with satisfactory recoveries (90.200%-123%) and relative standard deviations (2.100%-12.100%). © 2023 Society of Chemical Industry.

Construction of hierarchically porous metal-organic framework HP-UiO-66-30% for sensitive determination of benzoylurea insecticides

Due to widespread application of benzoylurea insecticides (BUs) and its persistence in environment, the effective capture of benzoylurea insecticides residues in environment is an important issue of environmental safety monitoring. To obtain excellent adsorption performance, creating defective structure in metal-organic frameworks (MOFs) can be employed as the method for adjusting its properties. Zirconium(Ⅳ)-based MOF termed as UiO-66-30% was constructed with 2-aminoterephthalic acid (NH₂-BDC) and terephthalic acid (H₂BDC) as building blocks. After calcination and removal of thermal-sensitive ligand (NH₂-BDC), hierarchically porous UiO-66-30% (HP-UiO-66-30%) with multistage pore structure and good stability was obtained. The unique structure of HP-UiO-66-30% endowed it to achieve instantaneous equilibrium (within 2 min) when it was used as a dispersed solid phase extraction (d-SPE) adsorbent to extract BUs from environmental samples, greatly reducing the operation time. A wide linear range (0.05-200 ng mL^-1), good linearity (R² ≥ 0.9980), low detection limits (0.01-0.03 ng mL^-1) and quantification limits (0.05-0.1 ng mL^-1) were obtained for BUs. In addition, the HP-UiO-66-30% material possessed the good reusability and the adsorption capacity did not change significantly over 16 adsorption-desorption cycles. Finally, the established dispersed solid phase extraction-high performance liquid chromatography-diode array detector (d-SPE-HPLC-DAD) method was successfully applied to determination of BUs residues in environmental soil samples. The results demonstrated that HP-UiO-66-30% was an excellent sorbent for extraction BUs from environmental samples.

A Review on Tetrabromobisphenol A: Human Biomonitoring, Toxicity, Detection and Treatment in the Environment

Tetrabromobisphenol A (TBBPA) is a known endocrine disruptor employed in a range of consumer products and has been predominantly found in different environments through industrial processes and in human samples. In this review, we aimed to summarize published scientific evidence on human biomonitoring, toxic effects and mode of action of TBBPA in humans. Interestingly, an overview of various pretreatment methods, emerging detection methods, and treatment methods was elucidated. Studies on exposure routes in humans, a combination of detection methods, adsorbent-based treatments and degradation of TBBPA are in the preliminary phase and have several limitations. Therefore, in-depth studies on these subjects should be considered to enhance the accurate body load of non-invasive matrix, external exposure levels, optimal design of combined detection techniques, and degrading technology of TBBPA. Overall, this review will improve the scientific comprehension of TBBPA in humans as well as the environment, and the breakthrough for treating waste products containing TBBPA.

Simultaneous and dynamic measurement of Schisandrol A changes in rat blood and brain and its comparative pharmacokinetic study in control and Parkinson's disease rats by dual-probe in vivo microdialysis

Schisandrol A (SchA) is the main active ingredient of Schisandra chinensis (Turcz.) Baill., which is a famous traditional Chinese herbal medicine. SchA can penetrate the blood-brain barrier and has a significant neuroprotective effect. A group of multiplexed stable isotope mass tags (MSIMTs, m/z 332, 338, 346, 349, 351, 354, 360, 363, 374 and 377) were synthesized to perform multiplexed stable isotope labeling derivatization (MSILD) of SchA in rat microdialysates and standards. A new magnetic molecularly imprinted polymer was prepared using MSIMT-375-SchA as dummy template. All the 10-plexed derivatives of MSIMTs-SchA can be efficiently and selectively enriched and purified using this adsorbent by magnetic dispersive solid phase extraction (MDSPE) before ultra high performance liquid chromatography tandem mass spectrometry (UHPLC-MS/MS) analysis. It should be pointed out that the MSIMT-346-SchA standard derivative was used as internal standard in the process of MDSPE and UHPLC-MS/MS. On these bases, 9 different rat microdialysate samples can be determined by UHPLC-MS/MS in a single run. The utilization of MSIMTs significantly increased the sensitivity, accuracy, selectivity and analysis throughput. Under the optimized conditions, satisfactory linearity (R²> 0.987), limit of detection (LODs, 0.15-0.26 pg/mL) and lower limit of quantitative (LLOQ, 0.8-2.0 pg/mL) were obtained. Intra- and inter-day precisions were in the range of 2.2% -12.5%, and recoveries 94.2% -106.2%. The matrix effects were very low, and the average derivatization efficiency of 10-plex MSIMTs to SchA was as high as 97.8%. Using the developed dual-probe in vivo microdialysis sampling technique, the proposed analytical method has been applied for comparative pharmacokinetics of SchA in the brain and blood of control and Parkinson's disease (PD) rats.

Extraction and determination of terpenoids from Zexie Decoction based on a porous organic cage-doped monolithic cartridge

A monolithic solid-phase extraction (SPE) cartridge packed with a composite adsorbent was fabricated via polymerization using dodecene as the monomer with the porous organic cage (POC) material doped, combing with an analytical column through a high-performance liquid chromatography (HPLC) instrument, which was used for the online extraction and separation of 23-acetyl alismol C, atractylodes lactone II and atractylodes lactone III from Zexie Decoction. The POC-doped adsorbent shows porous structure with a relatively high specific surface area of 85.50 m²/g, which was obtained from the characterizations of a scanning electron microscope and an automatic surface area and porosity analyser. Efficient extraction and separation of three target terpenoids was achieved by an online SPE-HPLC method based on the POC-doped cartridge, which exhibits strong matrix-removal ability and good terpenoids-retention ability with a high adsorption capacity, due to the interactions of hydrogen bond and hydrophobicity between the terpenoids and the POC-doped adsorbent. Method validation shows good linearity (r ≥ 0.9998) of the regression equation, and high accuracy with the spiked recovery in the range of 99.2 %-100.8 % of the proposed method. Compared to the generally disposable adsorbent, this work fabricated a reusable monolithic cartridge, which can be used for at least 100 times, with the RSD based on the peak area of the three terpenoids less than 6.6 %.

An Azo-Group-Functionalized Porous Aromatic Framework for Achieving Highly Efficient Capture of Iodine

The strong radioactivity of iodine compounds derived from nuclear power plant wastes has motivated the development of highly efficient adsorbents. Porous aromatic frameworks (PAFs) have attracted much attention due to their low density and diverse structure. In this work, an azo group containing PAF solid, denoted as LNU-58, was prepared through Suzuki polymerization of tris-(4-(4,4,5,5-tetramethyl-1,3,2-dioxaborolan-2-yl)-phenyl)-amine and 3,5-dibromoazobenzene building monomers. Based on the specific polarity properities of the azo groups, the electron-rich aromatic fragments in the hierarchical architecture efficiently capture iodine molecules with an adsorption capacity of 3533.11 mg g−1 (353 wt%) for gaseous iodine and 903.6 mg g−1 (90 wt%) for dissolved iodine. The iodine uptake per specific surface area up to 8.55 wt% m−2 g−1 achieves the highest level among all porous adsorbents. This work illustrates the successful preparation of a new type of porous adsorbent that is expected to be applied in the field of practical iodine adsorption.

Integrating a Luminescent Porous Aromatic Framework into Indicator Papers for Facile, Rapid, and Selective Detection of Nitro Compounds

Porous aromatic framework materials with high stability, sensitivity, and selectivity have great potential to provide new sensors for optoelectronic/fluorescent probe devices. In this work, a luminescent porous aromatic framework material (LNU-23) was synthesized via the palladium-catalyzed Suzuki cross-coupling reaction of tetrabromopyrene and 1,2-bisphenyldiborate pinacol ester. The resulting PAF solid exhibited strong fluorescence emission with a quantum yield of 18.31%, showing excellent light and heat stability. Because the lowest unoccupied molecular orbital (LUMO) of LNU-23 was higher than that of the nitro compounds, there was an energy transfer from the excited LNU-23 to the analyte, leading to the selective fluorescence quenching with a limit of detection (LOD) ≈ 1.47 × 10⁻⁵ M. After integrating the luminescent PAF powder on the paper by a simple dipping method, the indicator papers revealed a fast fluorescence response to gaseous nitrobenzene within 10 s, which shows great potential in outdoor fluorescence detection of nitro compounds.

Introducing Polar Groups in Porous Aromatic Framework for Achieving High Capacity of Organic Molecules and Enhanced Self-Cleaning Applications

Due to the frequent oil/organic solvent leakage, efficient oil/water separation has attracted extensive concern. However, conventional porous materials possess nonpolar building units, which reveal relatively weak affinity for polar organic molecules. Here, two different polarities of superhydrophobic porous aromatic frameworks (PAFs) were synthesized with respective orthoposition and paraposition C=O groups in the PAF linkers. The conjugated structure formed by a large number of alkynyl and benzene ring structures enabled porous and superhydrophobic quality of PAFs. After the successful preparation of the PAF solids, PAF powders were coated on polyester fabrics by a simple dip-coating method, which endowed the resulting polyester fabrics with superhydrophobicity, porosity, and excellent stability. Based on the unique structure, the oil/water separation efficiency of two superhydrophobic flexible fabrics was more than 90% for various organic solvents. Polar LNU-26 PAF showed better separation performance for the polar oils. This work takes the lead in adopting the polar groups as building units for the preparation of porous networks, which has great guiding significance for the construction of advanced oil/water separation materials.

Covalent organic framework-based solid phase microextraction coupled with electrospray ionization mass spectrometry for sensitive screening and quantitative evaluation of carbamazepine and its metabolite in mice

Carbamazepine (CBZ) and its metabolite carbamazepine-10,11-epoxide (CBZEP) play vital role in the treatment of epilepsy. It is of great importance to develop a method for rapid and sensitive monitoring of CBZ and CBZEP due to their narrow therapeutic index. Herein, an imine-linked-based covalent organic framework was synthesized by using 1,3,5-tris (4-aminophenyl) benzene (TPB) and 1,3,5-triformylbenzene (TFB) (denoted as TPB-TFB-COF)，and applied as a solid-phase microextraction (SPME) probe for extracting CBZ and CBZEP. The TPB-TFB-COF showed large surface areas (371 m² g^-1), high regular porosity (1.23 nm) and extraordinary stability, which rendered it an ideal adsorbent for highly efficient enrichment of CBZ and CBZEP. Accordingly, an attractive strategy of the combination of the TPB-TFB-COF-based SPME probe and electrospray ionization mass spectrometry system (ESI/MS) was proposed for rapid screening and sensitive monitoring of CBZ and CBZEP. Under the optimized parameters, the developed method exhibited good linearity for CBZ and CBZEP in the range of 4-1000 μg L^-1 with correlation coefficient (r) no less than 0.9953, and the corresponding limits of detection (LODs) were 0.4 and 2.5 μg L^-1, respectively. Moreover, high enrichment factors (EFs, 202-351 folds) and satisfactory relative standard deviations (RSDs) of one probe (3.3-5.1%) and probe-to-probe (4.8-5.6%) were obtained. By using the proposed method, sensitive screening and quantitative evaluation of CBZ and CBZEP in mice whole blood and tissue homogenates were successfully achieved, indicating the promising applicability of the TPB-TFB-COF-SPME-AMIS as a powerful tool for drug monitoring.