Evaluation of the performance of a selective magnetite molecularly imprinted polymer for extraction of quercetin from onion samples

DFT simulated Quercetin imprinted polymer: Selective recovery of Quercetin from onion solid waste

Onion peels (OP) are byproduct of food processing industries that poses economic and environmental challenges. However, being rich source of bioactive compounds like Quercetin (Qt), a polyphenolic antioxidant with potential health benefits, harnessing value from such waste can imbibe sustainable practices and protect environment. With this view, the present study targets selective recovery of Qt from OP waste using rationally designed molecularly imprinted polymer (MIP). Density Functional Theory (DFT) was used for the theoretical selection of the best conformer of Qt (template), methacrylic acid (MAA) as functional monomer, ratio of Qt-MAA for getting stable pre-polymerization complex, and to avoid hit and trial experiments. The theoretical results were validated experimentally by synthesizing MIP/ control polymer (NIP) using MAA as functional monomer, EGDMA as a cross-linker and AIBN as initiator. Synthesized MIP/NIP were characterized using various characterization techniques to confirm successful imprinting. Prepared MIP and NIP could effectively rebind the Qt molecule with binding capacity of 46.67 and 20.89 mg g-1 respectively. Furthermore, synthesized MIP could selectively recover 62.81 % of Qt from 1 g of dry onion peel powder. This study can be effectually used for sustainable recovery of Qt in large scale for various foods, cosmetic and pharmaceutical applications.

Photo-Induced Super-Hydrophilicity of Nano-Calcite @ Polyester Fabric: Enhanced Solar Photocatalytic Activity against Imidacloprid

The present study is pertinent to photo-induced, hydrophilic, nano-calcite grown onto the mercerized surface of polyester fabric (PF), treated with UV (10-50 min) and visible light (1-5 h) in addition to its photocatalytic application. The wicking method has been employed to select the most hydrophilic sample of fabric upon irradiation. The micrographs obtained by scanning electron microscopy, transmission electron microscopy, and high-resolution transmission electron microscopy indicated the erosions occurring at the surface of nano-calcite after UV light irradiation, maintaining the crystallinity of the photocatalyst. The surface charge has been measured for as-fabricated and irradiated nano-calcite @ PF for the development of high negative zeta potential after UV light irradiation (-24.6 mV). The irradiated nano-calcite @ PF exhibited a significant change in its contact angle, and the wetting property was enhanced to a considerable extent on UV (55.32°) and visible light irradiation (79.00°) in comparison to as-fabricated nano-calcite @ PF (137.54°). The irradiated samples of nano-calcite @ PF delineated the redshift in harvesting of solar spectrum, as revealed by diffuse reflectance spectroscopy comparative spectra. Additionally, the band gap of untreated nano-calcite was found to be 3.5 eV, while UV- and visible light-irradiated PF showed a reduction in band gap up to 2.95 and 3.15 eV upon UV and visible light irradiation. The photocatalytic efficiency of mesoporous nano-calcite was evaluated by photocatalytic degradation of imidacloprid as the probe pollutant. Higher solar photocatalytic degradation of imidacloprid (94.15%) was attained by UV light-irradiated nano-calcite @ PF. The time-resolved photoluminescence study has verified the high photocatalytic activity of UV light-irradiated nano-calcite @ PF for the generation of high concentration of hydroxyl radicals. The highly efficient reusability of a nano-calcite-based solar photocatalytic reactor has been observed for 10 cycles of treatment of imidacloprid bearing wastewater. The enhanced photocatalytic activity of UV light-exposed (20 min), superhydrophilic, nano-calcite @ PF for mineralization of pollutants suggests it to be an efficient solar photocatalyst for environmental applications.

Advances in Molecular Imprinting Technology for the Extraction and Detection of Quercetin in Plants

Quercetin is a kind of flavonoid compound, which has antioxidative, anti-aging and anti-cancer effects, so it is of great importance to study the efficient extraction and highly sensitive detection of quercetin. Molecular imprinting technology has remarkable selectivity and resistance to complex matrix interference, which is often used for extracting quercetin. The methods of molecular imprinted solid phase extraction, molecularly imprinted microsphere extraction, molecularly imprinted electrochemical sensor recognition and molecularly imprinted composite material extraction of quercetin from plant samples were discussed in detail. This review provides valuable information on efficient and sensitive methods for separating and purifying quercetin in plants. It also provides a technical reference for further investigation of the separation and analysis of active ingredients in natural products.

Selective Adsorption of Quercetin by the Sol-Gel Surface Molecularly Imprinted Polymer

Quercetin, as one of the most biologically active natural flavonoids, is widely found in various vegetables, fruits and Chinese herbs. In this work, molecularly imprinted polymer (MIP) was synthesized through surface molecular imprinting technology with sol-gel polymerization mechanism on SiO₂ at room temperature using quercetin as the template, SiO₂ as the supporter, 3-aminopropyltriethoxysilane (APTES) as the functional monomer, and tetraethoxysilane (TEOS) as the cross-linker. The prepared MIP was characterized via scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR) and nitrogen adsorption measurements to validate its surface morphology, structure and functionality. SEM images revealed that the morphology of MIP was rough and spherical with the particle size of 260 nm larger than that of the support SiO₂. In the FTIR spectra of MIP, the band around 1499 cm^-1 and 2932 cm^-1 were assigned to N-H and C-H groups, respectively. The results indicated that the imprinted polymer layers were grafted on the surface of SiO₂ and the MIP had been successfully prepared. Since the specific surface area and pore volume of MIP were markedly higher than those of NIP and SiO₂ and were 52.10 m² g^-1 and 0.150 cm³ g^-1, respectively, it was evident that the imprinting process created corresponding imprinted cavities and porosity. The MIP for adsorbing quercetin was evaluated by static adsorption experiment. The results indicated that the adsorption equilibrium could be reached within 90 min and the maximum adsorption capacity was as high as 35.70 mg/g. The mechanism for adsorption kinetics and isotherm of MIP for quercetin was proved to conform the pseudo-second-order kinetics model (R² = 0.9930) and the Freundlich isotherm model (R² = 0.9999), respectively, revealing that chemical adsorption and heterogeneous surface with multilayer adsorption dominated. In contrast to non-imprinted polymer (NIP), the MIP demonstrated high selectivity and specific recognition towards quercetin whose selectivity coefficients for quercetin relative to biochanin A were 1.61. Furthermore, the adsorption capacity of MIP can be maintaining above 90% after five regeneration cycles, indicating brilliant reusability and potential application for selective adsorption of quercetin.

Preparation and Application of Molecularly Imprinted Polymers for Flavonoids: Review and Perspective

The separation and detection of flavonoids from various natural products have attracted increasing attention in the field of natural product research and development. Depending on the high specificity of molecularly imprinted polymers (MIPs), MIPs are proposed as efficient adsorbents for the selective extraction and separation of flavonoids from complex samples. At present, a comprehensive review article to summarize the separation and purification of flavonoids using molecular imprinting, and the employment of MIP-based sensors for the detection of flavonoids is still lacking. Here, we reviewed the general preparation methods of MIPs towards flavonoids, including bulk polymerization, precipitation polymerization, surface imprinting and emulsion polymerization. Additionally, a variety of applications of MIPs towards flavonoids are summarized, such as the different forms of MIP-based solid phase extraction (SPE) for the separation of flavonoids, and the MIP-based sensors for the detection of flavonoids. Finally, we discussed the advantages and disadvantages of the current synthetic methods for preparing MIPs of flavonoids and prospected the approaches for detecting flavonoids in the future. The purpose of this review is to provide helpful suggestions for the novel preparation methods of MIPs for the extraction of flavonoids and emerging applications of MIPs for the detection of flavonoids from natural products and biological samples.

Precipitation Polymerization: A Powerful Tool for Preparation of Uniform Polymer Particles

Precipitation polymerization (PP) is a powerful tool to prepare various types of uniform polymer particles owing to its outstanding advantages of easy operation and the absence of any surfactant. Several PP approaches have been developed up to now, including traditional thermo-induced precipitation polymerization (TRPP), distillation precipitation polymerization (DPP), reflux precipitation polymerization (RPP), photoinduced precipitation polymerization (PPP), solvothermal precipitation polymerization (SPP), controlled/‘‘living’’ radical precipitation polymerization (CRPP) and self-stabilized precipitation polymerization (2SPP). In this review, a general introduction to the categories, mechanisms, and applications of precipitation polymerization and the recent developments are presented, proving that PP has great potential to become one of the most attractive polymerization techniques in materials science and bio-medical areas.

Fabrication of nickel-tagged magnetic imprinted polymeric network for the selective extraction of Ni(II) from the real aqueous samples

A new nickel ion, magnetic imprinted polymer was fabricated through the precipitation polymerization process, using amine-functionalized silica-capped iron oxide particles as a core material, and 4-vinyl pyridine as complexing agent methacrylic acid as functional monomer. The resulted magnetic adsorbent was employed to eliminate toxic Ni²⁺ ions from industrial wastewater. The different parameters were optimized, such as pH, shaking speed, and adsorbent dose, to obtain the maximum adsorption capacity. The synthesized material showed high selectivity coefficient for Ni⁺² ions in the presence of other competitive ions and followed pseudo-second-order kinetics and Langmuir isotherm. A good adsorption capacity of 158.73 mg g^-1 was obtained at optimized pH 6 in the concentration of 5 mg L^-1 nickel ions aqueous solution. The limit of detection, quantification, and the percent relative standard deviation was found to be 0.58, 1.93, and 3.4%. This proves the excellent performance of prepared magnetic Ni(II) ion-imprinted polymer for selective detoxification of Ni²⁺ ions from real aqueous samples. Due to tunable magnetic properties, the prepared MMIPs are highly selective and sensitive and highly porous in nature; due to excellent magnetic properties, there is no need for centrifugation. Just use external magnetic field, it has good reusability. Showing preparation of Ni (II) imprinted magnetic polymer.

Monolith/aminated graphene oxide composite-based electric field-assisted solid phase microextraction for efficient capture of phenoxycarboxylic acids herbicides in environmental waters

Efficient capture of strongly polar, ionizable and trace phenoxycarboxylic acids herbicides (PCAHs) from aqueous samples is essential and challenging for environmental monitoring. In the present work, electric field-assisted solid-phase microextraction (EFA-SPME) based on monolith/aminated graphene oxide composite was developed for the first time to efficiently extract trace PCAHs prior to HPLC-tandem mass spectrometry (HPLC-MS/MS) quantification. First, poly (1-allyl-3-methylimidazole difluoromethanesulfonylamide salt-co-divinylbenzene/ethylene dimethacrylate) monolith/aminated graphene oxide composite (MAC) was prepared on the surface of stainless steel wire and employed as the extraction phase of SPME. After that, the MAC-based fiber and a stainless steel wire were connected to a DC power supply that allowed the implement of variable electric fields during adsorption and desorption processes. Various key factors influencing the extraction performance were inspected in detailed. Results well evidenced that the exertion of electric fields improved the enrichment performance, accelerated the trap and release procedures. The proposed MAC/EFA-SPME-HPLC-MS/MS method achieved wide linear ranges (0.005-50.0 μg/L), low limits of detection (0.54-1.3 ng/L) and good precision (2.7-7.0%) for the quantification of PCAHs. The related extraction mechanism was deduced. Additional, the current approach was successfully applied to monitor studied PCAHs at trace contents in environment waters, and the accuracy was confirmed by confirmatory experiments.

Imprinting Technology for Effective Sorbent Fabrication: Current State-of-Art and Future Prospects

In the last 10 years, we have witnessed an extensive development of instrumental techniques in analytical methods for determination of various molecules and ions at very low concentrations. Nevertheless, the presence of interfering components of complex samples hampered the applicability of new analytical strategies. Thus, additional sample pre-treatment steps were proposed to overcome the problem. Solid sorbents were used for clean-up samples but insufficient selectivity of commercial materials limited their utility. Here, the application of molecularly imprinted polymers (MIPs) or ion-imprinted polymers (IIPs) in the separation processes have recently attracted attention due to their many advantages, such as high selectivity, robustness, and low costs of the fabrication process. Bulk or monoliths, microspheres and core-shell materials, magnetically susceptible and stir-bar imprinted materials are applicable to different modes of solid-phase extraction to determine target analytes and ions in a very complex environment such as blood, urine, soil, or food. The capability to perform a specific separation of enantiomers is a substantial advantage in clinical analysis. The ion-imprinted sorbents gained interest in trace analysis of pollutants in environmental samples. In this review, the current synthetic approaches for the preparation of MIPs and IIPs are comprehensively discussed together with a detailed characterization of respective materials. Furthermore, the use of sorbents in environmental, food, and biomedical analyses will be emphasized to point out current limits and highlight the future prospects for further development in the field.