A Zn-based metal coordination cluster Zn5 used for solid phase microextraction of ten phenolic compounds from water and soil

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.

Nitrogen-doped hollow quadruple-shelled carbon-silicon nanosphere as a solid-phase microextraction adsorbent for the extraction of 19 polycyclic aromatic hydrocarbons in milk samples

In this study, nitrogen-doped hollow multi-shelled carbon-silicon nanospheres (NSiC-Homs-NS) were prepared using a template method and employed as a coating material for solid-phase microextraction (SPME) fibers. The extraction efficiency of single-, double-, triple-, and quadruple-shelled NSiC-Homs-NS coated fibers for polycyclic aromatic hydrocarbons (PAHs) were investigated, respectively. The NSiC-Homs-NS based SPME fiber coupled with gas chromatography-mass spectrometry was applied to detect 19 PAHs in milk samples. The extraction parameters of SPME were optimized using a central composite design methodology. Under the optimized conditions, the established method exhibited good linearity for the PAHs, ranging from 0.03 to 500 ng g-1, with coefficients of determination (r2) between 0.9952 and 0.9983. The limits of detection (S/N of 3) of the PAHs in milk samples ranged from 0.01 to 4.0 ng g-1. The relative standard deviations of the single-fiber repeatability (n = 5) and fiber-to-fiber reproducibility (n = 5) were all less than 12 %. The method recoveries of the PAHs in seven milk samples, evaluated at three different spiking concentrations, ranged from 80.4 % to 119 % with RSDs less than 12 %. The developed method exhibited good repeatability and accuracy.

A comprehensive review of covalent organic frameworks (COFs) and their derivatives in environmental pollution control

Covalent organic frameworks (COFs) have gained considerable attention due to their design possibilities as the molecular organic building blocks that can stack in an atomically precise spatial arrangement. Since the inception of COFs in 2005, there has been a continuous expansion in the product range of COFs and their derivatives. This expansion has led to the evolution of three-dimensional structures and various synthetic routes, propelling the field towards large-scale preparation of COFs and their derivatives. This review will offer a holistic analysis and comparison of the spatial structure and synthesis techniques of COFs and their derivatives. The conventional methods of COF synthesis (i.e., ultrasonic chemical, microwave, and solvothermal) are discussed alongside the synthesis strategies of new COFs and their derivatives. Furthermore, the applications of COFs and their derived materials are demonstrated in air, water, and soil pollution management such as gas capture, catalytic conversion, adsorption, and pollutant removal. Finally, this review highlights the current challenges and prospects for large-scale preparation and application of new COFs and the derived materials. In line with the United Nations Sustainable Development Goals (SDGs) and the needs of digital-enabled technologies (AI and machine learning), this review will encompass the future technical trends for COFs in environmental pollution control.

Hierarchically spherical assembly of carbon nanorods derived from metal-organic framework as solid-phase microextraction coating for nitrated polycyclic aromatic hydrocarbon analysis

Nitrated polycyclic aromatic hydrocarbons (nitro-PAHs) are pervasive contaminants in aquatic environments. They are characterized by persistence, toxicity, bioaccumulation, and long-range transport, significantly threatening human health. The development of sensitive methods for nitro-PAH analysis in environmental samples is in great need. This study developed a novel carbonaceous SPME coating derived from metal-organic framework (MOF), namely a spherical assembly consisting of carbon nanorods with hierarchical porosity (HP-MOF-C), for the extraction and determination of nitro-PAHs in waters. The HP-MOF-C coated fiber demonstrated superior nitro-PAH extraction efficiencies, with enrichment factors 2∼70 times higher than commercial fibers. This enhancement was due to the strong hydrophobic, π-π electron coupling/stacking, and π-π electron donor-acceptor interactions between the carbonaceous framework of HP-MOF-C and the nitro-PAHs. Moreover, the unique hierarchical porous structure of HP-MOF-C accelerated the diffusion of nitro-PAHs, further facilitating their enrichment. The fiber also exhibited good thermal stability, remarkable chemical stabilities against common acid, base, and polar/non-polar solvents, and long service life (> 150 SPME cycles). The nitro-PAH determination method based on HP-MOF-C coating yielded wide linear ranges, low detection limits (0.4∼5.0 ng L-1), satisfactory repeatability and reproducibility, and good recoveries in real water samples. The proposed method was considered to be green according to the Analytical GREEnness assessment. The present study not only offers an efficient SPME coating for the enrichment of nitro-PAHs, but also provides insights into the design of porous coating materials.

Sustainable approaches to analyzing phenolic compounds: a green chemistry perspective

Innovative and eco-friendly methodologies for the determination of phenolic compounds, showing a paradigm shift in analytical chemistry toward sustainability. Phenolic compounds, valued for their diverse health benefits, have historically been analyzed using methods that often involve hazardous solvents and energy-intensive processes. This review focuses on green analytical chemistry principles, emphasizing sustainability, reduced environmental impact, and analytical efficiency. The use of DES, specifically Ch: Chl-based DES, emerges as a prominent green alternative for extracting phenolic compounds from various sources. The integration of UAE with DES enhances extraction efficiency, contributing to a more sustainable analytical approach. Furthermore, the review highlights the significance of DLLME and SPME in reducing solvent consumption and simplifying extraction procedures. These techniques exemplify the commitment to making phenolic compound analysis environmentally friendly. The incorporation of portable measurement tools, such as smartphones, into analytical methodologies is a notable aspect discussed in the review. Techniques like UA-DLLME leverage portable devices, making phenolic compound determination more accessible and versatile. Anticipating the future, the review foresees ongoing advancements in sustainable analytical approaches, driven by collaborative efforts across diverse disciplines. Novel solvents, extraction techniques, and portable measurement methods are expected to play pivotal roles in the continuous evolution of green analytical methodologies for the analysis of phenolic compounds. The review encapsulates a transformative journey toward environmentally responsible and efficient analytical practices, paving the way for further research and application in diverse analytical settings.

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.

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.

A novel top-down strategy for in situ construction of vertically oriented hexagonal NiCr LDHs nanosheet arrays with intercalated sulfate ions on Nichrome fiber for selective solid-phase microextraction of phenolic compounds in water samples

BACKGROUND

Phenolic compounds (PCs) are a class of polar aromatic pollutants with high toxicity in environmental water. Generally the efficient sample preparation is essential for the quantification of ultra-trace target PCs in real water sample before appropriative instrumental analysis. SPME is a convenient, solvent-free and time-saving miniaturized technique and has been recognized as a green alternative to conventional extraction techniques. In SPME, however, commercial fused-silica fibers are limited to the fragility, operation temperature, extraction capacity and selectivity as well as lifetime. Therefore, the development of new SPME fibers is always needed to overcome such limitations.

RESULTS

We presented a novel top-down strategy for in situ construction of vertically oriented hexagonal sulfate intercalated NiCr layered double hydroxide nanosheet arrays (NiCr LDHs-SO4 NSAs) on the Nichrome (NiCr) substrate by hydrothermal treatment in NaOH solution containing (NH4)2S2O8. The results showed that much shorter hydrothermal time was needed for the construction of NiCr@NiCr LDHs-SO4 NSAs fiber in the presence of (NH4)2S2O8. Moreover, the unique NiCr LDHs-SO4 NSAs coating offered open access structure, and thereby more available surface area for adsorption. The resulting fiber exhibited better extraction efficiency for phenolic compounds (PCs), faster mass transfer rate, higher mechanical stability, and longer service life than original NiCr@NiCr LDHs NSs fiber and typical commercially fused-silica fibers. After optimizing conditions, the SPME-HPLC-UV method demonstrated a linear range from 0.05 μg L-1 to 200 μg L-1 with LODs of 0.015-0.156 μg L-1 (S/N = 3) and LOQs of 0.048-0.498 μg L-1 (S/N = 10), as well as good repeatability (3.06%-5.22%) and fiber-to-fiber reproducibility (4.32%-6.49%).

SIGNIFICANCE

The developed SPME-HPLC-UV method with the constructed fiber was applied to the preconcentration and detection of different types of PCs in real water samples, showing satisfactory recoveries ranging from 86.20% to 107.8% with RSDs of 3.18%-6.69%. This study provides a new strategy for in situ construction of bimetallic hydroxides and their derived nanocomposite coatings on the NiCr fiber substrate in practical SPME application.

In-situ formation of CO2-incorportaed solid sorbent for dispersive solid phase extraction of phenolic compounds from water and wastewater samples prior to gas chromatography-flame ionization detector

BACKGROUND

Herein, a new extraction procedure based on in-situ formation of carbon dioxide-incorporated solid sorbent was introduced for dispersive solid phase extraction of phenolic compounds from aqueous samples. In this study, incorporation of carbon dioxide into the structure of a diamine led to the formation of a solid compound in the sample solution that adsorbed the analytes.

RESULTS

The sample solution was mixed with isophorone diamine and placed under carbon dioxide stream. By doing so, isophorone diamine reacted with carbon dioxide and produced a carbamic acid analogue. It was dispersed into the sample solution as tiny particles that adsorbed the analytes. The adsorbed analytes were eluted by a volatile organic solvent and concentrated more by the vaporization of the eluate. The extraction procedure was done at low temperature to limit the releasing carbon dioxide from the produced compound. To obtain the reliable results, the method was validated and the obtained limits of detection and quantification were in the ranges of 0.29-41 and 0.96-1.3 ng/mL, respectively. Acceptable relative standard deviation (≤7.3%) and coefficient of determination (≥0.994) values confirmed the method repeatability and linearity. High enrichment factors (410-435) and extraction recoveries (82-87%) were attained with the introduced method.

SIGNIFICANCE AND NOVELTY

In this work, a chemical reaction was done between isophorone diamine and carbon dioxide in solution. The produced product (sorbent) was insoluble in solution and dispersed in whole parts of the solution as tiny particles. A high contact area between the sorbent and analytes provided high extraction efficiency for the analytes. The method was successful utilized in determining target analytes in real samples and the matrix effect of the samples had no important effect on the obtained results.

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.