Novel microporous β-cyclodextrin polymer as sorbent for solid-phase extraction of bisphenols in water samples and orange juice

Cyano-functionalized porous hyper-crosslinked cationic polymers for efficient preconcentration and detection of phenolic endocrine disruptors in fresh water and fish

Sensitively analyzing phenolic endocrine-disrupting chemicals (EDCs) in environmental substrates and aquatic organisms provides a significant challenge. Here, we developed a novel porous hyper-crosslinked ionic polymer bearing cyano groups (CN-HIP) as adsorbent for the highly efficient solid phase extraction (SPE) of phenolic EDCs in water and fish. The CN-HIP gave an excellent adsorption capability for targeted EDCs over a wide pH range, and the adsorption capacity was superior to that of several common commercial SPE adsorbents. The coexistence of electrostatic forces, hydrogen bond, and π-π interactions was confirmed as the main adsorption mechanism. A sensitive quantitative method was established by coupling CN-HIP based SPE method with high-performance liquid chromatography for the simultaneously determining trace bisphenol A, bisphenol F, bisphenol B and 4-tert-butylphenol in fresh water and fish. The method afforded lower detection limits (S/N = 3) (at 0.03-0.10 ng mL-1 for water and 0.8-4.0 ng g-1 for fish), high accuracy (the recovery of spiked sample at 88.0%-112 %) and high precision (the relative standard deviation < 8.5 %). This work provides a feasible method for detecting phenolic EDCs, and also opens a new perspective in developing functionalized cationic adsorbent.

Ultrasound-assisted rapid growth of chemically bonded bifunctional mesoporous covalent organic framework submicrospheres on a nickel-chromium alloy support for efficient solid-phase microextraction of bisphenols from water and milk samples

A layer-by-layer chemical bonding strategy was developed for fast in situ growth of bifunctional mesoporous covalent organic framework submicrospheres (COF SMSs) on the nickel-chromium alloy (Ni-Cr) fiber substrate via the ultrasound-assisted Schiff-base reaction for the first time. COF SMSs showed well-defined morphology, extraordinary high surface area (1211 m2·g-1) and narrow mesopore (2.50 nm) as well as excellent stability. Furthermore, the resulting Ni-Cr fiber presented outstanding adsorption capability and improved selectivity for bisphenols (BPs). Consequently, an attractive SPME-HPLC-UV approach with the Ni-Cr@Ni-Cr LDHs NSs@COF SMSs fiber was proposed for rapid preconcentration and sensitive determination of BPs. By optimizing adsorption parameters, the SPME-HPLC-UV method presented good linearity for five BPs in the ranges of 0.02-200 ng·mL-1 with coefficients of determination (R2) higher than 0.999. Limits of detection and limits of quantitation were obtained from 0.003 ng·mL-1 to 0.006 ng·mL-1 and from 0.010 to 0.019 ng·mL-1, respectively. Moreover, the intra-day and inter-day precision expressed as relative standard deviations (RSDs) was 1.57-3.52 % and 2.65-4.38 % for the proposed method with a single fiber, respectively. RSDs of the proposed method with different duplicate fibers were 3.25-6.72 %. The proposed SPME-HPLC-UV method was available for efficient preconcentration and sensitive detection of five BPs from real water and milk samples. The relative recoveries at three spiking levels of BPs were achieved in the range of 80.00-118.8 % with RSDs below 7.81 %. In addition, the prepared fiber still exhibited satisfactory adsorption performance after 120 adsorption-desorption cycles.

Assessing dietary bisphenol A exposure among Koreans: comprehensive database construction and analysis using the Korea National Health and Nutrition Examination Survey

Bisphenol A (BPA) exposure primarily occurs through dietary intake. This study aimed to estimate the extent of dietary BPA exposure among Koreans. A thorough literature search was conducted to establish a BPA content database encompassing common foods consumed in Korea, including various food raw materials and processed food products. Dietary exposure levels were estimated by integrating the constructed BPA database with comprehensive nationwide 24 h-dietary recall datasets. The finding revealed that dietary BPA exposure was low for most Koreans, with a mean of 14.5 ng/kg bw/day, but was higher for preschool-age children (over 23 ng). Canned foods accounted for 9-36% of the total dietary exposure of the highest dietary exposure groups; while across all age groups, a considerable amount was derived from canned tuna, contribution of canned fruits and canned coffee (milk-containing) was high for preschool-age children and adults, respectively. Notably, for adults, a substantial proportion also stemmed from beer packaged in cans. While diet contributed over 80% of aggregate exposure for most age groups, preschool-age children experienced 60% exposure through diet due to additional exposure from indoor dust. Even at the high exposure scenario, aggregate BPA exposure levels remained lower than the current tolerable daily intake (TDI) set by the Korean agency (20 μg/kg bw/day). Nevertheless, most Koreans were exposed to BPA levels surpassing the strictest TDI (0.2 ng/kg bw/day) set by the European Food Safety Authority.

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

Bisphenols (BPs) can migrate from packaging materials into foods, resulting in potentially harmful residues. For example, accumulation of BPs is associated with endocrine disorders. Owing to matrix effects, development of an effective and eco-friendly sample pretreatment would be helpful for BPs detection in beverages packed in plastic containers. In this work, an extraction bar, composed of hollow fiber (HF) functionalized with covalent organic frameworks (COF@Tp-NDA) and 1-ocanol, was prepared for extraction of five BPs simultaneously. The synergistic effect of COF@Tp-NDA and 1-octanol improved the extraction efficiency of BPs from milk-based beverage, juice, and tea beverage. Under optimal conditions, limits of detection ranged from 0.10 to 2.00 ng mL-1 (R2 ≥ 0.9974) and recoveries ranged from 70.1 % to 106.8 %. This method has the potential to enrich BPs, supporting their accurate determination in complex beverages.

High-Performance enrichment and sensitive analysis of bisphenol and its analogues in water and milk using a novel Ni-Based cationic Metal-Organic framework

A novel cationic metal-organic framework (iMOF-Ni) was designed and synthesized by a solvothermal method. It was fabricated as a solid-phase extraction (SPE) cartridge and exhibited high adsorption performance for Bisphenols (BPs). The theoretical simulation demonstrated that the adsorption mechanism between iMOF-Ni and BPs was attributed to cation-π bonding, π-π interaction, and electrostatic interactions. Under optimized SPE, a method for analyzing BPs was established by combining high-performance liquid chromatography-diode array detection (HPLC-DAD). The developed method has good linearity (R2 ≥ 0.994), low detection limits (0.07-0.16 ng/mL), and good reproducibility (1.72-6.35 %, n = 6). The applicability of the method was further evaluated by analyzing water and milk samples. Recoveries of four BPs in spiked samples were from 72.2 % to 96.6 %.

Large-size porous spherical 3D covalent organic framework for preconcentration of bisphenol F in water samples and orange juice

Large-size spherical sorbents with particle size of 10-50 μm are widely applied in separation fields, however it is still a great challenge to synthesize such large-size spherical covalent organic framework (COF). In this work, a type of large-size porous 3D COF was size-controablly synthesized via a two-step strategy, in which a large-size porous 3D spherical polymer was prepared first through a Pickering emulsion polymerization using nano silica as the stabilizer, and subsequently it was converted into porous spherical 3D COF by a solvothermal method. The as-prepared porous spherical COF (COF-320 as a model) showed size-controllable uniform spherical morphology within 15-45 μm, large specific surface area, fine crystalline structure, and good chemical stability. When used as the sorbent for dispersive solid-phase extraction (d-SPE) of bisphenol F (BPF), the porous spherical COF-320 (15 μm) displayed high adsorption capacity (Qmax = 335.6 mg/g), high enrichment factor (80 folds), and good reusability (at least five cycles). By coupling the d-SPE method to HPLC, a new analytical approach was developed and successfully applied to the determination of trace BPF in two water samples, an orange juice and a standard sample with recoveries of 96.0-102.2 % (RSD = 1.1-1.5 %), 95.7-97.4 % (RSD = 1.4-4.4 %) and 98.7 % (RSD = 2.3 %), respectively. The limit of detection (S/N = 3) and limit of quantification (S/N = 10) were 0.1 and 0.3 ng/mL, respectively. The new synthesis strategy opens a viable way to prepare large-size porous spherical COFs, and the developed analytical method can be potentially applied to sensitively detect the trace BPF in water samples and beverages.

Thermal and bisphenol-A adsorption properties of a zinc ferrite/β-cyclodextrin polymer nanocomposite

The present study investigated the use of a nanocomposite, produced by reinforcing nanosize zinc ferrite (ZnFe₂O₄) in a porous β-CD based polymeric matrix (β-CD-E-T/ZnFe₂O₄), for the removal of Bisphenol A (BPA) from aqueous solutions via adsorption. The thermal stability of the β-CD-based polymer and β-CD-E-T/ZnFe₂O₄ nanocomposite were investigated using simultaneous thermal analysis at four heating rates. Non-isothermal isoconversion methods were employed to study the thermal degradation kinetics of the β-CD based polymer before and after ZnFe₂O₄ nano-filling. The results showed that ZnFe₂O₄ nano-reinforcement increased the activation energy barrier for the thermal degradation of the β-CD-based polymeric matrix. Adsorption experiments showed that the β-CD-E-T/ZnFe₂O₄ nanocomposite exhibited very high BPA adsorption within 5 minutes. Isotherm, kinetics, and thermodynamic investigations revealed that the adsorption of BPA was via multilayer adsorption on a heterogeneous β-CD-E-T/ZnFe₂O₄ surface. The thermodynamic studies indicated that BPA adsorption on β-CD-E-T/ZnFe₂O₄ was spontaneous and exothermic. Overall, the β-CD-E-T/ZnFe₂O₄ nanocomposite showed less thermal degradation and high efficiency for removing BPA from contaminated water, indicating its potential as a promising material for wastewater treatment applications.

Solvent-assisted dispersive micro-solid phase extraction of bisphenols using iron(III) thenoyltrifluoroacetonate complex (Fe(TTA)3) as a new nanostructured sorbent: a proof of concept

In this work, we describe for the first time the use of iron(III) thenoyltrifluoroacetonate complex (Fe(TTA)₃) as a novel sorbent for solvent-assisted dispersive micro-solid phase extraction (SA-dμSPE) of bisphenols from water samples. The extraction procedure is based on the formation of nanoparticles in situ following the rapid injection of a methanolic solution of Fe(TTA)₃ into the stirred aqueous sample. Herein, the synthesis of Fe(TTA)₃ and study of the essential parameters of the preparative procedure are described. The optimized procedure allowed for efficient enrichment of bisphenols from various water samples, chosen as model contaminants and matrix, within 2.5 min. The sorbent was collected by centrifugation, dissolved in methanol, and injected to perform HPLC with spectrophotometric detection. The limits of detection and quantification obtained ranged from 1.0-3.1 and 3.1-7.5 μg L^-1, respectively. Intraday and interday precisions of <7% relative standard deviation (RSD) and <8% RSD with analyte recoveries ranging between 70-117% (103.8% on average) were obtained for the analysis of river water, wastewater treatment plant effluent, and bottled water.

Hydroxy-Containing Covalent Organic Framework Combined with Nickel Ferrite as a Platform for the Recognition and Capture of Bisphenols

A hydroxy-containing covalent organic framework (COF) was successfully obtained via a simple nitrogen-purge synthetic procedure for the first time. The COF favored a serrated AA-stacking arrangement, which enhanced the stability compared with common AA or AB arrangements. To validate the potential of the COF in environmental applications, we decorated the COF onto NiFe₂O₄ and used the NiFe₂O₄@COF nanocomposite for magnetic solid-phase extraction of trace bisphenols (BPs). The parameters affecting extraction efficiencies were systematically optimized. Under the optimum extraction conditions, calibration plots showed good linearity (5.0-1.0 × 10³ ng mL^-1) for six BPs, and limits of detection varied from 0.14 to 0.73 ng mL^-1. Molecular polarity indexes and molecular dynamics simulations revealed why the COF could efficiently recognize and capture BPs. An adsorption mechanism related to the interaction between BP clusters and the COF was discovered. Ecotoxicological assessment of BPs further unraveled the significance of the developed method for the timely tracking of the concentration, distribution, and migration of BPs in environmental media.

A novel polyhedral oligomeric silsesquioxane-based hybrid monolith as a sorbent for on-line in-tube solid phase microextraction of bisphenols in milk prior to high performance liquid chromatography-ultraviolet detection analysis

An on-line in-tube solid-phase microextraction (in-tube SPME) coupled with high-performance liquid chromatography (HPLC) method was proposed based on a novel polyhedral oligomeric silsesquioxane (POSS)-hybrid monolith for the determination of four bisphenols (BPs) in milk. The monolith was synthesized using acrylamide (AM) and monomethacrylate-functionalized POSS (mono-MA-POSS) as functional monomers to copolymerize with ethylene dimethacrylate (EDMA). Due to the abundant hydrogen bonding, π-π and hydrophobic interaction sites, the synthetic monolith displayed satisfying extraction performance for target BPs. Under the optimized conditions, the developed on-line in-tube SPME-HPLC method exhibited low limits of detection (LODs) (0.030-0.055 ng mL^-1). The spiked recoveries were between 85.4 % and 111.8 %, and the relative standard deviations (RSDs) were less than 3.5 % for all the analytes. The results showed that the proposed method provided alternative for the analysis of BPs in complex samples.

New low viscous hydrophobic deep eutectic solvents for the ultrasound-assisted dispersive liquid-liquid microextraction of endocrine-disrupting phenols in water, milk and beverage

In the present work, several new hydrophobic deep eutectic solvents (HDESs) were prepared with quaternary ammonium salts as hydrogen bond acceptors (HBAs) and salicylate esters as hydrogen bond donors (HBDs). Then, the obtained HDESs were used as extraction solvents to establish an ultrasound-assisted dispersive liquid-liquid microextraction method combined with high-performance liquid chromatography-ultraviolet detection technique for the determination of four endocrine-disrupting phenols (EDPs) compounds. One of the obtained HDESs composed of tetrabutylammonium chloride (N₄₄₄₄Cl) and methyl salicylate possessed a viscosity of 89.28 mPa•s lower than most reported ionic HDESs (>200 mPa•s), and the low viscous HDES was selected as the optimal extraction solvent. Several key parameters affecting the extraction efficiency were investigated, including the type and volume of HDES, ultrasound time, sample solution pH and salt addition. Under the optimized experimental conditions, the proposed method had good coefficients of determination (R² > 0.9976) in the linear range of 0.5-400 µg•L^-1, the limits of quantification and limits of detection respectively were 0.5-2.5 µg•L^-1 and 0.25-1 µg•L^-1, and the recoveries were in the range of 81.79-109.82%. Finally, the method was used for the preconcentration and determination of EDPs in different samples, including bottled water, tea beverage and milk.

Fabrication of stable multivariate metal-organic frameworks with excellent adsorption performance toward bisphenols from environmental samples

As a type of environmental endocrine disrupting chemicals, bisphenols (BPs) have a certain embryonic toxicity and teratogenicity, which can significantly increase the risks of breast cancer, prostate cancer, leukemia and other cancers. In this work, stable multivariate metal-organic frameworks (UiO-66-NH₂/TCPP_x) were synthesized via in situ one-pot method and used as miniaturized dispersive solid-phase extraction (dμSPE) sorbents for extraction of trace BPs from environmental samples. The phase purity, crystal morphology and physical properties of UiO-66-NH₂/TCPP_x samples were varied by adjusting the mass ratio of TCPP. The extraction performance of UiO-66-NH₂/TCPP_x samples were investigated and UiO-66-NH₂/TCPP_1.0 exhibited the highest adsorption efficiency. Besides, UiO-66-NH₂/TCPP_1.0 possessed excellent recycling stability for the adsorption and desorption of BPs more than 20 cycles. The experimental parameters including amount of adsorbent, adsorption time, sample solution pH, temperature, desorption time and desorption solvents which affecting the efficiency of dμSPE were studied, respectively. Good linearity (R² > 0.9992) in range of 0.1-200 ng mL^-1 was obtained. The detection limits (S/N = 3) and quantification limits (S/N = 10) were achieved at 0.03-0.08 ng mL^-1 and 0.1-0.5 ng mL^-1, respectively. The relative standard deviations (RSDs) of intra-day and inter-day ranged from 2.5 to 5.5% and 1.1-6.8%. Enrichment factors were calculated in the range of 303-338. The obtained recoveries of bisphenol F (BPF), bisphenol A (BPA), bisphenol B (BPB) and bisphenol AF (BPAF) were 81.26-91.03% (RSDs = 0.96-6.47%), 82.2-97.27% (RSDs = 0.45-6.15%), 87.56-97.26% (RSDs = 1.1-6.22%) and 82.2-100.8% (RSDs = 0.46-4.07%). The UiO-66-NH₂/TCPP_1.0 can be employed as potential dμSPE sorbents for the enrichment of trace BPs in the environmental samples.

[Advances in solid-phase extraction for bisphenols in environmental samples]

Owing to the strict restrictions on the production and use of bisphenol A (BPA), bisphenol analogs (e. g., bisphenol S and bisphenol F) are gradually coming to use in many fields. BPA and these bisphenol analogs are so-called bisphenols (BPs). BPs as a class of endocrine disrupters are widely distributed in the environment (water, sediments, sludge, and aquatic products). BPs enter the human body through various routes, leading to endocrine disruption, cytotoxicity, genotoxicity, reproductive toxicity, dioxin-like effects, and neurotoxicity. The Canadian government has identified BPs as substances for further scoping/problem formulation. Because of the widespread attention paid to BPs in the environmental field, research is being expanded to cover water, sediment, dust, and biological samples, and other media. Given the significant differences in the complexity and pollution concentration of environmental samples, the development of pretreatment methods that afford high extraction efficiency, good purification selectivity, strong universality, operational simplicity, and high-throughput extraction and purification, are necessary to realize the highly sensitive detection of BPs in environmental media. In recent years, solid-phase extraction (SPE), accelerated solvent extraction (ASE), microwave-assisted extraction (MAE), and dispersion liquid-liquid-microextraction (DLLME) as new pretreatment technologies have gradually replaced the traditional liquid-liquid extraction and Soxhlet extraction. SPE has seen rapid development for the extraction and purification of BPs in various environmental samples, overcoming the bottlenecks related to time, energy, and solvent consumption in traditional methods while extending technical support for the analysis of emerging pollutants. The physicochemical properties, usage, and environmental hazards of typical BPs were briefly reviewed, with emphasis on the application of SPE products, development of new adsorbents, and transformation of the SPE mode. Commercialized SPE products are universally applicable in the field of environmental monitoring, while products suitable for the pretreatment of BPs are limited. The development of new adsorbents mainly focused on their adsorption capacity and selectivity. For example, ordered mesoporous silicon, carbon nanomaterials, metal-organic frameworks, and cyclodextrins have large surface areas, good adsorption performance, and regular pore structures, which improve the adsorption capacity of BPs. Molecularly imprinted polymers (MIPs) and mixed-mode ion-exchange polymers are mainly used to improve the selectivity of BPs in the purification process. In addition, MIPs have high chemical, mechanical, and thermal stabilities, which ensures their widespread application in the extraction, preconcentration, and separation of BPs. A variety of new SPE adsorbents can partially meet the diverse needs for detection. There is a consensus that the current challenges in analytical chemistry include the determination of contaminants at low concentration levels, but at the same time, more efficient and environment-friendly methodologies are required. With the introduction of high-sensitivity instruments in the market, the SPE model is seeing gradual development in terms of miniaturization, automation, and simplification. This in turn has minimized solvent consumption, analysis time, and labor cost, resulting in more efficient and affordable analytical methods such as QuEChERS, solid-phase microextraction (SPME), and magnetic solid-phase extraction (MSPE) to adapt to the new development scenario.

1-Octyl-3-methylimidazolium hexafluorophosphate-functionalised magnetic poly β-cyclodextrin for magnetic solid-phase extraction ofpyrethroids from tea infusions

In this study, a novel sorbent, 1-octyl-3-methylimidazolium hexafluorophosphate functionalised magnetic poly β-cyclodextrin, was successfully synthesised and applied to magnetic solid-phase extraction for the determination of pyrethroids in tea infusions. The sorbent was characterised by transmission electron microscopy, energy-dispersive spectroscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, vibrating sample magnetometer and Brunauer-Emmett-Teller measurement. All factors affecting extraction efficiency, such as sorbent amount, extraction time, ionic strength and desorption conditions, were optimised individually. Under the chosen conditions, wide linearity (2.5-500 μg L^-1) with determination coefficients ranging from 0.9995 to 0.9999, low limits of detection of 0.32-0.54 μg L^-1 and good precision (intra-day: 2.6-7.0%; inter-day: 3.5-7.6%) were achieved for four pyrethroids in tea infusions. The relative recoveries of target analytes in real tea infusion samples were from 70% to 101% with relative standard deviations lower than 9.1%. We conclude that the proposed method is promising in the detection of pyrethroids in tea infusions.

Efficient removal of bisphenol pollutants on imine-based covalent organic frameworks: adsorption behavior and mechanism

The extensive use of bisphenol analogues in industry has aggravated the contamination of the water environment, and how to effectively remove them has become a research hotspot. This study presents two imine-based covalent organic frameworks with different pore sizes (COFs) [TAPB (1,3,5-tris(4-aminophenyl)benzene)-Dva (2,5-divinylterephthaldehyde)-PDA (terephthalaldehyde) (COF-1), and TAPB (1,3,5-tris(4-aminophenyl)benzene)-Dva (2,5-divinylterephthaldehyde)-BPDA (biphenyl dialdehyde) (COF-2)], which have achieved the efficient adsorption of bisphenol S (BPS) and bisphenol A (BPA). The maximum adsorption capacity of COF-2 for BPS and BPA obtained from Langmuir isotherms were calculated as 200.00 mg g⁻¹ and 149.25 mg g⁻¹. Both hydrogen bonding and π–π interactions might have been responsible for the adsorption of BPS and BPA on the COFs, where the high adsorption capacity of COFs was due to their unique pore dimensions and structures. Different types of pharmaceutical adsorption studies indicated that COF-2 exhibited a higher adsorption performance for different types of pharmaceuticals than COF-1, and the adsorption capacity was ranked as follows: bisphenol pharmaceuticals > anti-inflammatory pharmaceuticals > sulfa pharmaceuticals. These results confirmed that COFs with larger pore sizes were more conducive to the adsorption of pollutants with smaller molecular dimensions. Moreover, COF-1 and COF-2 possessed excellent pH stability and recyclability, which suggested strong potential applications for these novel adsorbents in the remediation of organic pollutants in natural waterways and aqueous ecosystems.

Two imine-based covalent organic frameworks with different pore sizes were synthesized, and can be used as adsorbents for the removal of bisphenol pollutants, showing high affinity toward bisphenol S and bisphenol A.

Rapid elimination of trace bisphenol pollutants with porous β-cyclodextrin modified cellulose nanofibrous membrane in water: adsorption behavior and mechanism

A porous β-cyclodextrin modified cellulose nano-fiber membrane (CA-P-CDP) was fabricated and employed to treat the trace bisphenol pollutants (bisphenol A (BPA), bisphenol S (BPS), and bisphenol F (BPF)) in water. The characterization highlighted the porous structure, stable crystal structure, good thermal stability of the obtained CA-P-CDP, as well as abundant functional groups, which could greatly improve the adsorption of bisphenol pollutants and recovery. During the static adsorption process, the adsorbents dosage, temperature and pH showed significant influence on the adsorption performance. At the selected conditions (25 °C, 7.0 of pH and 0.1 g L^-1 of CA-P-CDP dosage), the BPA/BPS/BPF adsorption on CA-P-CDP could rapidly reached the equilibrium in 15 min by following the pseudo-second-order kinetic model, and the maximum adsorption capacities were 50.37, 48.52 and 47.25 mg g^-1, respectively, according to Liu isotherm model. The mechanisms between the bisphenol pollutants and CA-P-CDP mainly involved the synergism of hydrophobic effects, hydrogen-bonding interactions and π-π stacking interactions. Besides, the dynamic adsorption data showed that the volume of treated water for CA-P-CDP (0.58 L) was 14.5 times larger than that of pristine cellulose membrane (0.04 L), revealing satisfactory adsorption performance of trace BPA in water. Furthermore, during the treatment of real water samples (lake water and river water) with trace bisphenol pollutants, the complete removal of the pollutants were evidently observed, which strongly verified the possibility of CA-P-CDP for the practical application.

One-pot fabrication of lignin-based aromatic porous polymers for efficient removal of bisphenol AF from water

To remove the bisphenol AF (BPAF) from aqueous solution, two different types of lignin-based aromatic porous polymers (LAPP-1 and LAPP-2) were fabricated via one-pot crosslinking of lignin with 1,4-dichloroxylene and 4,4'-bis(chloromethyl)-1,1'-biphenyl, respectively. The successful synthesis of LAPPs was confirmed by FTIR and XPS, SEM, TEM and N₂ adsorption-desorption analysis. Then, batch adsorption experiments were conducted to investigate adsorption properties toward BPAF. Based on the results, the adsorption processes were in accordance with the pseudo-second-order kinetic model and the Freundlich isotherm model, and the thermodynamic studies showed that the adsorption was a spontaneous and exothermic process. It is remarkable that LAPPs exhibited good adsorption performance in wide ranges of pH and ionic strength as well as in recycling process. Notably, compared to LAPP-1, LAPP-2 exhibited higher adsorption capacity for BPAF, which can be ascribed to its higher porosity and content of aromatic ring. Moreover, the comprehensive analysis of experimental and theoretical results indicated that the π-π interactions and pore adsorption may jointly drive the uptake process of BPAF. Considering the simple fabrication method employed and excellent BPAF adsorption performance, LAPPs provided new insights into the development of advanced lignin-based adsorbents for removal of BPAF from water.

A green molecular imprinted solid-phase extraction protocol for bisphenol A monitoring with HPLC-UV to guarantee the quality and safety of walnuts under different storage conditions

Monitoring the residual toxicant concentrations in foods is the key step for minimizing potential hazards. The huge interest about food contamination and exposure to endocrine disruptors such as bisphenol A has emerged the development of sensitive analytical methodologies to guarantee the safety and quality of foods. In this work, a green molecularly imprinted solid-phase extraction protocol coupled with high-performance liquid chromatography with UV detection was optimized following the principles of green analytical chemistry. An imprinted sol-gel silica-based hybrid inorganic-organic polymeric sorbent was used to monitor the leaching of bisphenol A from different packaging materials (glass vessels, cans, and polypropylene containers) in walnuts stored within a period of 6 months at 25 and 4°C. Extraction parameters including loading time (5-20 min), solvent type (acetonitrile, ethanol, methanol, acetone, acetonitrile:methanol, 50:50, v/v), and elution flow rate (0.2-1 mL/min) were optimized with one-factor-at-a-time method. The selected extraction optimum parameters incorporated elution with acetonitrile at 0.2 mL/min flow rate, for 10 min sample holding time. The imprinting factor was equal to 4.55 ± 0.26 (n = 3). The optimized method presented high recovery (94.3 ± 4.2%, n = 3), good linearity (>0.999), intra-assay repeatability (90.2-95.6%, n = 3), and interassay precision (86.7-93.1%, n = 3).

Cyclodextrins as a Key Piece in Nanostructured Materials: Quantitation and Remediation of Pollutants

Separation and pre-concentration of trace pollutants from their matrix by reversible formation of inclusion complexes has turned into a widely studied field, especially for the benefits provided to different areas. Cyclodextrins are non-toxic oligosaccharides that are well known for their host–guest chemistry, low prices, and negligible environmental impact. Therefore, they have been widely used as chiral selectors and delivery systems in the pharmaceutical and food industry over time. However, their use for extraction purposes is hampered by their high solubility in water. This difficulty is being overcome with a variety of investigations in materials science. The setting-up of novel solid sorbents with improved properties thanks to the presence of cyclodextrins at their structure is still an open research area. Some properties they can offer, such as an increased selectivity or a good distribution along the surface of a solid support, which provides better accessibility for guest molecules, are characteristics of great interest. This systematic review reports the most significant uses of cyclodextrins for the adsorption of pollutants in different-origin samples based on the works reported in the literature in the last years. The study has been carried out indistinctly for quantitation and remediation purposes.

Water Dynamics at the Solid-Liquid Interface to Unveil the Textural Features of Synthetic Nanosponges

A fast-field-cycling NMR investigation was carried out on a set of polyurethane cyclodextrin nanosponges, in order to gain information on their textural properties, which have been proven to be quite difficult to assess by means of ordinary porosimetric techniques. Experiments were performed on both dry and wet samples, in order to evaluate the behavior of the “nonexchangeable” C-bound ¹H nuclei, as well as the one of the mobile protons belonging to the skeletal hydroxyl groups and the water molecules. The results acquired for the wet samples accounted for the molecular mobility of water molecules within the channels of the nanosponge network, leading back to the possible pore size distribution. Owing to the intrinsic difficulties involved in a quantitative assessment of the textural properties, in the present study we alternatively propose an extension to nanosponges of the concept of “connectivity”, which has been already employed to discuss the properties of soils.

The classification and application of cyclodextrin polymers: a review

After introducing the concept of cyclodextrin polymers, their classification and applications have been summarized.

β-Cyclodextrin-based hollow nanoparticles with excellent adsorption performance towards organic and inorganic pollutants

In this work, β-cyclodextrin (β-CD) based hollow nanoparticles (denoted as β-CDHN) with abundant active sites and high specific surface area were first fabricated via a facile one-step method. The β-CDHN presented a maximum adsorption capacity of 2080.35, 427.35 and 120.48 mg g^-1 towards the cationic dye methylene blue (MB), heavy metal ions (Pb²⁺) and bisphenol A (BPA), respectively, much higher than those of many other adsorbents. Furthermore, β-CDHN also exhibited fast adsorption kinetics towards these pollutants with adsorption rate constants 6 to 200 times higher than those of activated carbon and other β-CD-based adsorbents, meaning the former can remove these pollutants at a much faster adsorption rate than the latter adsorbents. More importantly, the removal efficiency of these pollutants on β-CDHN almost remained stable after 10 regeneration cycles with favorable recyclability. The prepared β-CDHN show great potential in practical applications due to their low costs and high efficiency in the treatment of organic and inorganic pollutants from wastewater.

Cyclodextrin-based sorbents for solid phase extraction

Cyclodestrins (CDs) are cyclic oligosaccharides well-known for their ability to form host-guest inclusion complexes with properly sized compounds. They have been used for decades as chiral selectors as well as drug delivery systems within the frameworks of separation science and pharmaceutical science. More recently, their use has been extended to the field of extractive science under the stimulus of additional advantageous characteristics, such as low-price, negligible environmental impact, non-toxicity, as arising from the fact that natural CDs are starch degradation products. To abate their solubility in water and generate novel sorbents for solid phase extraction, the following approaches have been employed: (i) immobilization onto inert materials (silica, attapulgite, etc.); (ii) immobilization onto nanomaterials (magnetic nanoparticles, titanium oxide, carbon nanotubes, graphene oxide, etc.); (iii) polymerisation with specific cross-linkers to form the so-called CD-based nanosponges. Particularly promising are these last ones for their selectivity, mesoporous structure, insolubility in aqueous media and good dispersibility. This review offers a concise overview on the state of art and future prospects of CDs in this important sector of the analytical chemistry, offering a critical perspective of the most significant applications.

A poly(glycidyl-co-ethylene dimethacrylate) nanohybrid modified with β-cyclodextrin as a sorbent for solid-phase extraction of phenolic compounds

A hybrid material made of β-cyclodextrin anchored to a polymeric network is described and evaluated as a sorbent for solid-phase extraction of phenolic compounds (phenol, cresol isomers, 2-methoxy-4-vinylphenol, 4-ethylphenol, 4-vinylphenol, 4-ethylguaiacol, guaiacol, and eugenol). The polymeric backbone of the sorbent consists of a poly(glycidyl-co-ethylene dimethacrylate) network, whose surface has been modified with β-cyclodextrin by a click-chemistry based procedure. The resulting material has been characterized by different techniques, and it has shown to be viable as a sorbent for its use in extraction cartridges. In this way, a method for the determination of the above analytes in tea has been validated. Under optimum conditions, the method has good repeatability, with coefficients of variation between 0.6 and 7.2%. In addition, recoveries from spiked samples at the level of 50 μg L^-1 are between 57 and 101%. The method has been then applied to the determination of phenolic compounds in the drinkable portion of infusions made from tea bags. The quantification has been carried out by using gas chromatography coupled to a mass spectrometry detector. Following their elution from the sorbent with a mixture of acetonitrile and methanol, the limits of quantification reached are between 4.6 and 400 μg L^-1. Results have been compared with those obtained with a reference method by using the paired t-test for comparing individual differences. The solid phase is reusable, and no cyclodextrin is lost during extraction due to its covalent anchoring to the polymeric support. Graphical abstract Schematic representation of the structure and characterization of the hybrid material made of β-cyclodextrin anchored to a polymeric network. The material is described and evaluated as a sorbent for the solid-phase extraction of phenolic compounds.

Determination of Enantiomeric Excess by Solid-Phase Extraction Using a Chiral Metal-Organic Framework as Sorbent

Metal-organic frameworks (MOFs) have recently attracted considerable attention because of their fascinating structures and intriguing potential applications in diverse areas. In this study, we developed a novel method for determination of enantiomeric excess (ee) of (±)-1,1′-bi-2-naphthol by solid-phase extraction (SPE) using a chiral MOF, [Co(l-tyr)]_n(l-tyrCo), as sorbent. After optimization of the experimental conditions, a good linear relationship between the ee and the absorbance of the eluate (R² = 0.9984) was obtained and the standard curve was established at the concentration of 3 mmol L⁻¹. The ee values of (±)-1,1′-bi-2-naphthol samples can be rapidly calculated using the standard curve after determination of the absorbance of the eluate. The method showed good accuracy, with an average error of 2.26%, and is promising for ee analysis.