Advances in organic-inorganic hybrid sorbents for the extraction of organic and inorganic pollutants in different types of food and environmental samples

Hierarchical covalent organic framework hollow nanofibers-bonded stainless steel fiber for efficient solid phase microextraction

The solid phase microextraction (SPME) technique has been widely applied in the detection of trace compounds in food, environment, and medicine due to its advantages of easy quantification, simple operation, and greenness. Herein, a templating strategy with SiO2 nanofibers (SiO2 NFs) is reported to synthesize hierarchical covalent organic framework hollow nanofibers (COF HNFs)-coated stainless steel fiber for SPME application with dramatically enhanced enrichment performance for trace analytes. The construction of hierarchical porosity inside the microextraction coatings can not only increase the specific surface area of COF extraction materials for obtaining more abundant adsorption sites but also greatly improve the accessibility of internal COF micropores. Moreover, the thicknesses of the microextraction COF coatings can be facilely tailored by adjusting the amount of SiO2 NFs pre-assembled on the SPME fibers. On the headspace solid phase microextraction (HS-SPME) of antimicrobial residues, the developed COF TpBD-Me2 HNFs-12 fibers achieve enrichment factors of 2026 and 1823 for thymol and carvacrol respectively, which are significantly higher than those obtained from the counterpart COF TpBD-Me2-bonded fiber (8.5-8.2 times) and commercial CAR/PDMS fiber (3.3-4.4 times). Furthermore, the developed method was demonstrated to have wide linearity (0.1-50 μg L-1), low limits of detection (0.010 μg L-1), good thermal stability and excellent reusability (>60 recycles), demonstrating great application potential in the extraction of trace organic pollutants. The strategy developed in this work is applicable to preparing a variety of topological COF (e.g., TpBD, TpPa-1) HNFs-bonded fibers.

Application of conventional and emerging low-cost adsorbents as sustainable materials for removal of contaminants from water

The impact of water pollution has led to the search for cost-effective and environmentally friendly treatment processes to alleviate the associated environmental hazards. Adsorption is identified as an advanced treatment technology that offers simplicity and cheap alternatives to water treatment technologies when low-cost adsorbents such as industrial by-products, waste, and agricultural waste are utilized. The utilization of these materials as low-cost adsorbents for the treatment of drinking water will bring them some value. Several practices have been done to improve the removal efficiencies of the low-cost adsorbents in order to achieve WHO standards of drinking water quality. The paper highlights some of the synthesis routes employed for the modification of low-cost adsorbents. This updated review provides information on the different applications of low-cost adsorbents in removing pollutants and their adsorption capacities in an attempt to deploy the recent sustainable low-cost adsorbents with high removal efficiencies for water treatment. Future research should focus on the fabrication of hybrid low-cost adsorbents with multifunctional and antimicrobial properties. In addition, life cycle assessment (LCA) should be conducted to reveal the environmental burdens associated with the modification of the low-cost adsorbent to improve their removal efficiencies.

Evaluation of Organofunctionalized Polydimethylsiloxane Films for the Extraction of Furanic Compounds

Hybrid membranes with three different thicknesses, PMDS_C1, PMDS_C2, and PMDS_C3 (0.21 ± 0.03 mm, 0.31 ± 0.05 mm, and 0.48 ± 0.07 mm), were synthesized by the sol-gel method using polydimethylsiloxane, hydroxy-terminated, and cyanopropyltriethoxysilane. The presence of cyano, methyl, and silicon-methyl groups was confirmed by FTIR analysis. Contact angle analysis revealed the membranes' hydrophilic nature. Solvent resistance tests conducted under vortex and ultrasonic treatments (45 and 60 min) demonstrated a preference order of acetonitrile > methanol > water. Furthermore, the membranes exhibited stability over 48 h when exposed to different pH conditions (1, 3, 6, and 9), with negligible mass losses below 1%. The thermogravimetric analysis showed that the material was stable until 400 °C. Finally, the sorption analysis showed its capacity to detect furfural, 2-furylmethylketone, 5-methylfurfural, and 2-methyl 2-furoate. The thicker membrane was able to adsorb and slightly desorb a higher concentration of furanic compounds due to its high polarity provided by the addition of the cyano groups. The results indicated that the membranes may be suitable for sorbent materials in extracting and enriching organic compounds.

Creatine@SiO2 @Fe3 O4 nanocomposite as an efficient sorbent for magnetic solid-phase extraction of escitalopram and chlordiazepoxide from urine samples through quantitation via HPLC-UV

An efficient, cost-effective, and fast-synthesis method is presented in the current study to prepare magnetic nanoparticles covered by cheap and nitrogen-rich creatine. The hydrothermal method was used for the synthesis of the magnetic core. The prepared magnetic core was then covered by SiO₂ and subsequently functionalized using creatine. The prepared creatine@SiO₂ @Fe₃ O₄ was utilized as a sorbent in the magnetic solid-phase extraction of the selected antidepressants including escitalopram and chlordiazepoxide as the model drugs. The extracted drugs were desorbed by a suitable organic solvent and analyzed by high-performance liquid chromatography equipped with an ultraviolet detection system. The influence of different variables on the magnetic solid-phase extraction method was examined by the Plackett-Burman and Box-Behnken designs for screening and optimization, respectively. Under the obtained optimum conditions, the linear ranges of the method were found to be in the range of 1-500 µg L^-1 . The limits of detection and limits of quantification were in the range of 0.27-0.63 µg L^-1 and 0.89-1.93 µg L^-1 for the selected analytes, respectively. Furthermore, the enrichment factors were found to be 79.8 and 92.7 for chlordiazepoxide and escitalopram, respectively. The method was successfully employed for the analysis of selected drugs in urine samples.

Single enrichment systems possibly underestimate both exposures and biological effects of organic pollutants from drinking water

Comprehensive enrichment of contaminants in drinking water is an essential step for accurately determining exposure levels of contaminants and testing their biological effects. Traditional methods using a single absorbent for enriching contaminants in water might not be adequate for complicated matrices with different physical-chemical profiles. To examine this hypothesis, we used an integrated enrichment system that had three sequential stages-XAD-2 resin, poly (styrene-divinylbenzene) and activated charcoal to capture organic pollutants and disinfection by-products (DBPs) from drinking water in Shanghai. Un-adsorbed Organic Compounds in Eluates (UOCEs) named UOCEs-A, -B, and-C following each adsorption stage were determined by gas chromatography-mass spectrometry to evaluate adsorption efficiency of the enrichment system. Meanwhile, biological effects such as cytotoxicity, effects on reactive oxygen species (ROS) generation and glutathione (GSH) depletion were determined in human LO2 cells to identify potential adverse effects on exposure to low dose contaminants. We found that poly-styrene-divinylbenzene (PS-DVB) and activated charcoal (AC) could still partly collect UOCEs-A and-B that the upper adsorption column incompletely captured, and that potential carcinogens like 2-naphthamine were present in all eluates. UOCEs-A at (1-4000), UOCEs-B at (1000-4000), and UOCEs-C at (2400-4000) folds of the actual concentrations had significant cytotoxicity to LO2 cells. Additionally, ROS and GSH change in cells treated with UOCEs indicated the potential for long-term effects of exposure to some mixtures of contaminants such as DBPs at low doses. These results suggested that an enriching system with a single adsorbent would underestimate the exposure level of pollutants and the biological effects of organic pollutants from drinking water. Effective methods for pollutants' enrichment and capture of drinking water should be given priority in future studies on accurate evaluation of biological effects exposed to mixed pollutants via drinking water.

Analytical Extraction Methods and Sorbents' Development for Simultaneous Determination of Organophosphorus Pesticides' Residues in Food and Water Samples: A Review

Extensive use of organophosphorus pesticides in agriculture leads to adverse effects to the environment and human health. Sample preparation is compulsory to enrich target analytes prior to detection as they often exist at trace levels and this step is critical as it determines the concentration of pollutants present in samples. The selection of a suitable extraction method is of great importance. The analytical performance of the extraction methods is influenced by the selection of sorbents as sorbents play a vital role in the sensitivity and selectivity of an analytical method. To date, numerous sorbent materials have been developed to cater to the needs of selective and sensitive pesticides' detection. Comprehensive details pertaining to extraction methods, developed sorbents, and analytical performance are provided. This review intended to provide a general overview on different extraction techniques and sorbents that have been developed in the last 10 years for organophosphorus pesticides' determinations in food and water samples.

Ethanol-activated granular aerogel as efficient adsorbent for persistent organic pollutants from real leachate and hospital wastewater

Hydrophobic aerogels were used to remove three types of persistent organic pollutants: pharmaceutical drugs (i.e. doxorubicin [DOX], paclitaxel [TAX]), phthalates (diethyl phthalate [DEP]), and hydrophilic rhodamine dye (RhB) from synthetic and real wastewaters, using Lumira granular aerogel from Cabot activated with EtOH (ET-GAG). The hydrophobic silica aerogel was characterized by X-ray diffraction (XRD), High-Resolution Transmission Electron Microscopy (HRTEM), Brunauer-Emmet-Teller (BET) and attenuated total reflection-Fourier transform infrared spectroscopy. The pollutants were analysed by high-performance liquid chromatography (HPLC)-UV and HPLC-mass spectrometry. The adsorption process was governed by hydrophobic- hydrophobic interactions between the ET-GAG and micropollutants. The adsorption capacity of ET-GAG, examined by batch experiments, for DOX, TAX and DEP were 13.80, 14.28 and 17.54 mg/g respectively. The rate of adsorption to ET-GAG is high in the initial 40 min followed by no change in the rate due to saturation of adsorption sites. ET-GAG was able to completely remove micropollutants from real leachate and hospital wastewater, implying practical applications. Regeneration of the aerogel was studied by solvent extraction. Et-GAG adsorbent demonstrated better removal of toxic chemotherapeutic drugs and phthalates than GAC.

Materials for Solid-Phase Extraction of Organic Compounds

This review provides an overview of the most recent developments involving materials for solid-phase extraction applied to determine organic contaminants. It mainly concerns polymer-based sorbents that include high-capacity, as well as selective sorbents, inorganic-based sorbents that include those prepared using sol-gel technology along with structured porous materials based on inorganic species, and carbon nanomaterials, such as graphene and carbon nanotubes. Different types of magnetic nanoparticles coated with these materials are also reviewed. Such materials, together with their main morphological and chemical features, are described, as are some representative examples of their application as solid-phase extraction materials to extract organic compounds from different types of samples, including environmental water, biological fluids, and food.

A beta-cyclodextrin-functionalized magnetic metal organic framework for efficient extraction and determination of prochloraz and triazole fungicides in vegetables samples

A β-cyclodextrin-functionalized magnetic zinc-metal organic framework (M-MOF/β-CD) was synthesized via a facile one-pot reaction. M-MOF/β-CD was used as a magnetic porous absorbent for the extraction and determination of prochloraz and three triazole fungicides in vegetable samples. M-MOF/β-CD was prepared by creating MOF layers on the surface of a Fe₃O₄-graphene oxide (GO) nanocomposite and bonding them with β-CD molecules. Characterization suggested that a 3D porous structure was formed, with M-MOF/β-CD exhibiting high superparamagnetism and a large surface area. As a new strategy, integrating MOFs with Fe₃O₄-GO could improve their water-resistance and mechanical strength by providing a rigid nanosupport interface. Combining M-MOF and β-CD resulted in excellent selective adsorption capacities for prochloraz and three triazole fungicides. The static adsorption process was evaluated and the results were in good agreement with the Freundlich model. Subsequently, M-MOF/β-CD was applied to extracting prochloraz and triazole fungicides from tomato and lettuce vegetables, followed by HPLC-MS/MS determination. The limits of detection for the above fungicides were found to be 0.25-1.0 μg/L at a signal-to-noise ratio of 3, with spiked recoveries of 74.13%-119.83%, indicating that M-MOF/β-CD was promising for application to the extraction and determination of fungicides in complex matrices.

Efficacy of spent black tea for the removal of nitrobenzene from aqueous media

Nitrobenzene (NB) is a kind of persistent organic pollutant. A ubiquitous and cost-effective substance spent black tea (SBT) was investigated for the removal of nitrobenzene from aqueous media. The maximum uptake potential of dried biomass (SBT) for NB was found to be 14.86 mg per gram (q_max) in a batch experimental set-up. Equilibration time for NB sorption was about 50 min, and optimal removal efficiency was achieved at a dosage of 2 g/L with an initial concentration of 100 mg/L of NB. Findings revealed that NB uptake increased with an increase in the temperature from 273 K to 353 K. Sorption was also found to be pH sensitive, sorption improved as the pH value changes from alkaline to acidic (from 10 to 2). Different isotherm (Langmuir, Freundlich, Temkin and Dubinin Radushkevich) and kinetic models (pseudo-1st order, pseudo-2nd order and Elovich models) were applied to experimental results; the sorption mechanism was well described by the Freundlich and pseudo-2nd order models. Moreover, Scanning electron micrographs, ATR-FTIR spectra and the results of elemental analysis also supported the efficacy of SBT as an efficient bio-sorbent for the elimination of NB from water.

Solid-phase extraction using octadecyl-bonded silica modified with photosynthetic pigments from Spinacia oleracea L. for the preconcentration of lead(II) ions from aqueous samples

Spinacia oleracea L. extract was immobilized on an octadecyl-bonded silica surface to produce a new sorbent for the solid-phase extraction of trace amounts of metal ions from aqueous neutral samples. A measurement of the metal content has been performed by using graphite furnace atomic absorption spectroscopy. The affinity of the investigated bivalent metal cations for the modified sorbent are in the order: Pb(II) > Cu(II) > Ni(II) > Zn(II) ≈ Cd(II) ≈ Co(II). The quantum-chemically calculated chlorophyll-a-metal ion binding energies were consistent with the measured affinities of the corresponding metal ions to the investigated sorbent. The maximum sorption capacity obtained for Pb(II) was equal to 1.44 μmol/g. The value of lead uptake was significantly higher in comparison to the one reported for other sorbents and biosorbents. Immobilized chlorophyll a is responsible for a chelation process with stoichiometry 1:1 owing to the porphyrin rings, which was confirmed by the quantitative analysis performed by reversed-phase high-performance liquid chromatography with diode array detection. The Toth adsorption isotherm model was applicable to the description of the adsorption process of either chlorophyll a or Pb(II). The structural analysis of sorbent was done using Fourier-transform Raman spectroscopy and scanning electron microscopy with an energy dispersive X-ray detector.

Solid-phase microextraction based on an agarose-chitosan-multiwalled carbon nanotube composite film combined with HPLC-UV for the determination of nonsteroidal anti-inflammatory drugs in aqueous samples

We describe the preparation, characterization, and application of a composite film adsorbent based on blended agarose-chitosan-multiwalled carbon nanotubes for the preconcentration of selected nonsteroidal anti-inflammatory drugs in aqueous samples before determination by high performance liquid chromatography with ultraviolet detection. The composite film showed a high surface area (4.0258 m² /g) and strong hydrogen bonding between the multiwalled carbon nanotubes and agarose/chitosan matrix, which prevent adsorbent deactivation and ensure long-term stability. Several parameters, such as sample pH, addition of salt, extraction time, desorption solvent, and concentration of multiwalled carbon nanotubes in the composite film were optimized using a one-factor-at-time approach. The optimum extraction conditions obtained were as follows: isopropanol as conditioning solvent, 10 mL of sample solution at pH 2, extraction time of 30 min, stirring speed of 600 rpm, 100 μL of isopropanol as desorption solvent, desorption time of 5 min under ultrasonication, and 0.4% w/v of composite film. Under the optimized conditions, the calibration curve showed good linearity in the range of 1-500 ng/mL (r²  = 0.997-0.999), and good limits of detection (0.89-8.05 ng/mL) were obtained with good relative standard deviations of < 4.59% (n = 3) for the determination of naproxen, diclofenac sodium salt, and mefenamic acid drugs.