Hybrid molecularly imprinted polymers modified by deep eutectic solvents and ionic liquids with three templates for the rapid simultaneous purification of rutin,scoparone, and quercetin from Herba Artemisiae Scopariae

Different kinds of deep eutectic solvents based on choline chloride and ionic liquids based on 1‐methylimidazole were used to modify hybrid molecularly imprinted polymers with the monomer γ‐aminopropyltriethoxysilane‐methacrylic and three templates (rutin, scoparone, and quercetin). The materials were adopted as solid‐phase extraction packing agents, and were characterized by FTIR spectroscopy and field emission scanning electron microscopy. The hybrid molecularly imprinted polymers modified by deep eutectic solvents had high recoveries and a strong recognition of rutin, scoparone, and quercetin in Herba Artemisiae Scopariae than those modified by ionic liquids. In the procedure of solid‐phase extraction, deep eutectic solvents‐2‐hybrid molecularly imprinted polymers were obtained with the best recoveries with rutin (92.27%), scoparone (87.51%), and quercetin (80.02%), and the actual extraction yields of rutin (5.6 mg/g), scoparone (2.3 mg/g), and quercetin (3.4 mg/g). Overall, the proposed approach with the high affinity of hybrid molecularly imprinted polymers might offer a novel method for the purification of complex samples.     

Ternary choline chloride/caffeic acid/ethylene glycol deep eutectic solvent as both a monomer and template in a molecularly imprinted polymer

A molecularly imprinted polymer based on a ternary deep eutectic solvent comprised of choline chloride/caffeic acid/ethylene glycol was prepared. The caffeic acid in the ternary deep eutectic solvent was used as both a monomer and template. The molecularly imprinted polymer based on the ternary deep eutectic solvent was characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, field‐emission scanning electron microscopy, Brunauer–Emmett–Teller surface area analysis, atomic force microscopy, and elemental analysis. A series of molecularly imprinted polymers based on choline chloride/caffeic acid/ethylene glycol with different molar ratios was prepared and applied to the molecular recognition of polyphenols. A comparison of the recognition ability of molecularly imprinted polymers to polyphenols revealed that the choline chloride/caffeic acid/ethylene glycol (1:0.4:1, molar ratio) molecularly imprinted polymer had the best molecular recognition effect with 132 μg/g of protocatechuic acid, 104 μg/g of catechins, 80 μg/g of epicatechin, and 123 μg/g of caffeic acid in 6 h, as well as good molecular recognition ability for polyphenols from a Radix Asteris sample. These results show that the ternary deep eutectic solvent based molecularly imprinted polymer is a potential medium that can be applied to drug purification, drug delivery, and drug analysis.     

Determination of Chlorogenic Acid and Rutinum in Herba Artemisiae Scopariae with Multitemplate Molecularly Imprinted Polymers for Solid-phase Extraction with High-performance Liquid Chromatography

Novel multitemplate molecularly imprinted polymers were prepared using mixtures of chlorogenic acid and rutinum as molecular templates, acrylamide as a functional monomer, divinylbenzene as the cross-linker, and 20:80 methanol:acetone as the porogen. The polymers were assessed for solid-phase extraction (SPE) for the purification of two compounds from Herba Artemisiae Scopariae. The synthesized molecularly imprinted polymers were identified by infrared spectroscopy and scanning electron microscopy. Systematic characterization of the functional monomer and porogens on the recognition properties of the molecularly imprinted polymers were carried out. Comparison with single-template molecularly imprinted polymers showed that the multitemplate molecular polymers exhibited higher selectivity and adsorption capacity for multiple analytes. The optimization of washing solvent as 1:9 acetone:water and the elution solvent as 9:1 acetonitrile:acetic acid provided a reliable analytical method with strong recognition toward multiple analytes in Herba Artemisiae Scopariae extracts with satisfactory recoveries of 89.6% for chlorogenic acid and 93.8% for rutinum. These results demonstrate that the multitemplate molecularly imprinted polymers coupled with SPE are effective for the selective purification of bioactive compounds in complex samples.     

Magnetic molecularly imprinted polymers for recognition and enrichment of polysaccharides from seaweed

New magnetic molecularly imprinted polymers with two templates were fabricated for the recognition of polysaccharides (fucoidan and alginic acid) from seaweed by magnetic solid‐phase extraction, and the materials were modified by seven types of deep eutectic solvents. It was found that the deep eutectic solvents magnetic molecularly imprinted polymers showed stronger recognition and higher recoveries for fucoidan and alginic acid than magnetic molecularly imprinted polymers, and the deep eutectic solvents‐4‐magnetic molecularly imprinted polymers had the best effects. The practical recovery of the two polysaccharides (fucoidan and alginic acid) purified with deep eutectic solvents‐4‐magnetic molecular imprinted polymers in seaweed under the optimal conditions were 89.87, and 92.0%, respectively, and the actual amounts extracted were 20.6 and 18.7 μg/g, respectively. To sum up, the developed method proved to be a novel and promising method for the recognition of complex polysaccharide samples from seaweed.     

Deep eutectic solvents for the purification of chloromycetin and thiamphenicol from milk

Deep eutectic solvents were used in both dispersive liquid–liquid microextraction and solid‐phase extraction for the purification of chloromycetin and thiamphenicol from milk. In the dispersive liquid–liquid microextraction procedure, deep eutectic solvents mixed with chloroform at different ratios (0:1–5:1, v/v) were used as the extraction agent to optimize the procedure, and the ratio of 2:1 v/v was found to be the best extraction agent with 87.23 and 83.17% recoveries of chloromycetin and thiamphenicol, respectively. Furthermore, deep eutectic solvents were also used to modify molecular imprinted polymers in solid‐phase extraction procedure, and the polymers were used to purify chloromycetin and thiamphenicol from milk. Fourier transform infrared spectroscopy, and nuclear magnetic resonance spectroscopy were used to characterize the polymers. The solid‐phase extraction recoveries with deep eutectic solvents with molecularly imprinted polymers (chloromycetin and thiamphenicol, two templates), molecularly imprinted polymers (without deep eutectic solvents), and nonimprinted polymers (without a template) for chloromycetin were 91.23, 82.64, and 57.3%, respectively, and recoveries for thiamphenicol were 87.02, 79.03, and 52.27%, respectively. The recoveries of chloromycetin and thiamphenicol from milk in the solid‐phase extraction procedure were higher than using deep eutectic solvents mixed with chloroform as the extraction agent in the dispersive liquid–liquid microextraction procedure.     

Ternary deep eutectic solvent magnetic molecularly imprinted polymers for the dispersive magnetic solid‐phase microextraction of green tea

Ternary deep eutectic solvent magnetic molecularly imprinted polymers grafted on silica were developed for the selective recognition and separation of theophylline, theobromine, (+)‐catechin hydrate, and caffeic acid from green tea through dispersive magnetic solid‐phase microextraction. A new ternary deep eutectic solvent was adopted as a functional monomer. The materials obtained were characterized by FTIR spectroscopy, field emission scanning electron microscopy, transmission electron microscopy, NMR spectroscopy, and powder X‐ray diffraction. The practical recovery of the theophylline, theobromine, (+)‐catechin hydrate, and caffeic acid isolated with ternary deep eutectic solvent magnetic molecularly imprinted polymers in green tea were 91.82, 92.13, 89.96, and 90.73%, respectively, and the actual amounts extracted were 5.82, 4.32, 18.36, and 3.69 mg/g, respectively. The new method involving the novel material coupled with dispersive magnetic solid‐phase microextraction showed outstanding recognition, selectivity and excellent magnetism, providing a new perspective for the separation of bioactive compounds.     

Optimized extraction of bioactive compounds from Herba Artemisiae Scopariae with ionic liquids and deep eutectic solvents

Ionic liquids with length of alkyl chain and different anions, deep eutectic solvents with choline chloride and 7 different hydrogen bond donors were applied as extraction additives after optimizing the extraction conditions to increase the extraction amounts of rutin, quercetin, and scoparone from Herba Artemisiae Scopariae. The extraction conditions were optimized as follows: refluxing with methanol with a solid/liquid ratio of 1:120 under 60°C for 60 min after changing the different extraction conditions of: extraction methods (dipping, ultrasonic, reflux and soxlet), extraction solvents (methanol, water and ethanol), extraction temperature (30, 40, 50, 60, 70 and 80°C), extraction time (30, 60, 80, 100 and 120 min), extraction ratio of solid to liquid (1:5, 1:10, 1:20, 1:50, 1:100, 1:120 and 1:150). Under these optimal conditions, the best preformed extraction additive among the 7 kinds of ionic liquids and 7 kinds of deep eutectic solvents extraction additives were selected and optimized with its contraction of 0.5mg/mL. Using the most effective extraction additive, [BMIM][Br], 10275.92 µg/g rutin, 899.73 µg/g quercetin, and 554.32 µg/g scoparone were obtained. Overall, ionic liquids and deep eutectic solvents have potential applications as extraction additives for the extraction of bioactive compounds from nature plants.     

Molecularly Imprinted Polymers Modified by Deep Eutectic Solvents and Ionic Liquids with Two Templates for the Simultaneous Solid-Phase Extraction of Fucoidan and Laminarin from Marine Kelp

Molecularly imprinted polymers modified by deep eutectic solvents and ionic liquids (ILs) were prepared as packing materials for the solid-phase extraction (SPE) of fucoidan and laminarin. The prepared materials were characterized by field emission scanning electron microscopy and Fourier transform infrared spectroscopy. The polymers modified by the deep eutectic solvent prepared by choline chloride and urea had the best extraction efficiencies for fucoidan and laminarin (95.5% and 87.6%, respectively) from marine kelp. The relative standard deviations for intraday and interday determination were less than 4.23%. The molecularly imprinted polymers modified by deep eutectic solvents and ILs showed outstanding applications for SPE and may offer novel sample pretreatment for other analytes.     

Application of Deep Eutectic Solvents as Additives in Ultrasonic Extraction of Two Phenolic Acids from Herba Artemisiae Scopariae

This paper reports the extraction of two phenolic acids from Herba Artemisiae Scopariae using deep eutectic solvents that were synthesized with various salt and hydrogen bond donors. The optimal conditions were found to be 50% of a synthesized deep eutectic solvent from tetramethyl ammonium chloride and urea (1:4) mixed with methanol/water (60:40, v/v). Phenolic acid extraction was optimized using an ultrasonic power of 89 W for 30 min with a solid/liquid ratio of 1:10. Under the optimized conditions, good calibration curves were observed at phenolic acid concentrations ranging from 10.0 to 500.0 µg/mL. The method recovery ranged from 97.3% to 100.4%, and the inter-day and intra-day relative standard deviations were less than 5%. Under the optimal extraction conditions, the amounts of chlorogenic acid and caffeic acid extracted from Herba Artemisiae Scopariae were 9.35 mg/g and 0.31 mg/g, respectively.     

槲皮素-铜(Ⅱ)配位分子印迹聚合物的制备及其结合特性研究

以槲皮素-铜(Ⅱ)配合物(Qu-Cu)为模板分子、α-甲基丙烯酸为功能单体在强极性溶剂甲醇中合成了一种新型的配位分子印迹聚合物.紫外-可见光谱研究表明槲皮素与铜(Ⅱ)形成1:2配合物,槲皮素、铜(Ⅱ)和功能单体α-甲基丙烯酸三者发生了络合作用.利用透射电镜及平衡结合实验研究了溶剂用量对配位分子印迹聚合物形貌及其吸附性能...     

Ordered macroporous quercetin molecularly imprinted polymers: Preparation,characterization, and separation performance

Ordered macroporous molecularly imprinted polymers were prepared by a combination of the colloidal crystal templating method and the molecular imprinting technique by using SiO₂ colloidal crystal as the macroporogen, quercetin as the imprinting template, acrylamide as the functional monomer, ethylene glycol dimethacrylate as the cross‐linker and tetrahydrofuran as the solvent. Scanning electron microscopy and Brunauer–Emmett–Teller measurements show that the ordered macroporous molecularly imprinted polymers have a more regular macroporous structure, a narrower pore distribution and a greater porosity compared with the traditional bulk molecularly imprinted polymers. The kinetic and isothermal adsorption behaviors of the polymers were investigated. The results indicate that the ordered macroporous molecularly imprinted polymers have a faster intraparticle mass transfer process and a higher adsorption capacity than the traditional bulk molecularly imprinted polymers. The ordered macroporous molecularly imprinted polymers were further employed as a sorbent for a solid‐phase extraction. The results show that the ordered macroporous molecularly imprinted polymers can effectively separate quercetin from the Gingko hydrolysate.     

A new ionic liquid surface‐imprinted polymer for selective solid‐phase‐extraction and determination of sulfonamides in environmental samples

Toward improving the selective adsorption performance of molecularly imprinted polymers in strong polar solvents, in this work, a new ionic liquid functional monomer, 1‐butyl‐3‐vinylimidazolium bromide, was used to synthesize sulfamethoxazole imprinted polymer in methanol. The resulting molecularly imprinted polymer was characterized by Fourier transform infrared spectra and scanning electron microscopy, and the rebinding mechanism of the molecularly imprinted polymer for sulfonamides was studied. A static equilibrium experiment revealed that the as‐obtained molecularly imprinted polymer had higher molecular recognition for sulfonamides (e.g., sulfamethoxazole, sulfamonomethoxine, and sulfadiazine) in methanol; however, its adsorption of interferent (e.g., diphenylamine, metronidazole, 2,4‐dichlorophenol, and m‐dihydroxybenzene) was quite low. ¹H NMR spectroscopy indicated that the excellent recognition performance of the imprinted polymer was based primarily on hydrogen bond, electrostatic and π‐π interactions. Furthermore, the molecularly imprinted polymer can be employed as a solid phase extraction sorbent to effectively extract sulfamethoxazole from a mixed solution. Combined with high‐performance liquid chromatography analysis, a valid molecularly imprinted polymer‐solid phase extraction protocol was established for extraction and detection of trace sulfamethoxazole in spiked soil and sediment samples, and with a recovery that ranged from 93–107%, and a relative standard deviation of lower than 9.7%.     

Miniaturized molecularly imprinted polymer extraction method for the gas chromatographic analysis of flavonoids

In this study, the use of monolithic molecularly imprinted polymers in a micropipette tip format allowing the simple and fast extraction of flavonoids from standard solutions and a black tea sample is demonstrated. The imprinted polymer employed quercetin, methacrylic acid or 4‐vinylpyridine, and ethylene glycol dimethacrylate as template, functional monomer, and cross‐linker, respectively. Surface morphologies of the quercetin‐imprinted polymers and the corresponding nonimprinted polymers were characterized by SEM. Extraction of flavonoid standards was performed to evaluate the selectivity and recovery with these imprinted and nonimprinted polymers. Flavonoid compositions in aliquots eluted from the tips were identified using fast GC with flame ionization detection. Maximum specific capacities of 0.2, 5.7, and 16.0 mg/g for catechin, morin, and quercetin, respectively, were obtained with the imprinted polymer prepared with methacrylic acid, with the corresponding recoveries of 99.8, 98.8, and 95.4%, respectively. Efficient extraction by the quercetin‐imprinted polymer of epicatechin, catechin, and quercetin from an apple‐flavored black tea sample was achieved, with GC–MS employed for compound identification for both the tea and extracted samples.     

Molecularly imprinted polymers for the selective extraction of tiliroside from the flowers of Edgeworthia gardneri (wall.) Meisn

Nano‐sized molecularly imprinted polymers for tiliroside were successfully prepared by a precipitation polymerization method. Acrylamide, ethylene glycol dimethacrylate, azobisisobutyronitrile, and acetonitrile/dimethyl sulfoxide were used as functional monomer, cross‐linker, initiator, and porogen, respectively. The structural features and morphological characterization of tiliroside‐imprinted polymers were characterized by Fourier transform infrared spectroscopy and scanning electron microscopy, respectively. The adsorption experiments indicated that the tiliroside‐imprinted polymers exhibited high selective recognition property to tiliroside. Scatchard analysis indicated that the homogeneous‐binding sites were formed in the polymers. The selectivity test revealed that the adsorption capacity and selectivity of polymers to tiliroside was significantly higher than that of rutin, astragalin, and kaempferol. Finally, the tiliroside‐imprinted polymers were employed as adsorbents in solid‐phase extraction for the extraction of tiliroside from the ethyl acetate extract of the flowers of Edgeworthia gardneri (wall.) Meisn. The results demonstrated that the extraction recoveries of tiliroside ranged from 69.3 to 73.5% by using tiliroside‐imprinted polymers coupled with solid‐phase extraction method. These results indicated that the tiliroside‐based molecularly imprinted solid‐phase extraction method was proven to be an effective technique for the separation and enrichment of tiliroside from natural medicines.     

Preparation of ellagic acid molecularly imprinted polymeric microspheres based on distillation–precipitation polymerization for the efficient purification of a crude extract

Molecularly imprinted polymeric microspheres with a high recognition ability toward the template molecule, ellagic acid, were synthesized based on distillation–precipitation polymerization. The as‐obtained polymers were characterized by scanning electron microscopy, infrared spectroscopy, and thermogravimetric analysis. Static, dynamic, and selective binding tests were adopted to study the binding properties and the molecular recognition ability of the prepared polymers for ellagic acid. The results indicated that the maximum static adsorption capacity of the prepared polymers toward ellagic acid was 37.07 mg/g and the adsorption equilibrium time was about 100 min when the concentration of ellagic acid was 40 mg/mL. Molecularly imprinted polymeric microspheres were also highly selective toward ellagic acid compared with its analogue quercetin. It was found that the content of ellagic acid in the pomegranate peel extract was enhanced from 23 to 86% after such molecularly imprinted solid‐phase extraction process. This work provides an efficient way for effective separation and enrichment of ellagic acid from complex matrix, which is especially valuable in industrial production.     

Deep eutectic solvents skeleton typed molecularly imprinted chitosan microsphere coated magnetic graphene oxide for solid‐phase microextraction of chlorophenols from environmental water

Novel molecularly imprinted chitosan microspheres were prepared on the surface of magnetic graphene oxide, with deep eutectic solvents both as a functional monomer and template. The prepared molecularly imprinted chitosan microspheres‐magnetic graphene oxide was characterized by scanning electron microscopy, Fourier transform infrared spectroscopy, X‐ray diffraction, Brunauer‐Emmett‐Teller surface area, thermogravimetric analysis were subsequently combined with solid‐phase micro‐extraction for simultaneous separation and enrichment of the extraction of chlorophenols from environmental water. Factors affecting the extraction efficiency of chlorophenols were optimized using response surface methodology. The actual extraction capacities under the optimal conditions (liquid to solid ratio = 3, cycles of adsorption/desorption = 5, 40°C extraction temperature, and extraction time for 35 min) were 86.90 mg/g. Compared to the traditional materials, the molecularly imprinted chitosan microspheres‐magnetic graphene oxide produced higher selectivity and extraction capacity.     

Molecularly imprinted polymer for solid-phase extraction of rutin in complicated traditional Chinese medicines

In the present work, an improved and direct approach for the preparation of molecularly imprinted polymers (MIPs) was proposed. The MIPs were prepared based on bulk polymerization by water-bath heating and ultrasonic elution of the template, using rutin as the template, acrylamide (AM) as the functional monomer and 2,2'-azobisisobutyronitrile (AIBN) as the cross linker. Molecularly imprinted polymers prepared by other elution methods, including microwave-assisted extraction and conventional Soxhlet extraction, were used for comparison and the results showed that the ultrasonic elution method is the best. The synthesized MIPs were characterized by Fourier transform infrared (FT-IR) spectroscopy and scanning electron microscopy (SEM). High performance liquid chromatography (HPLC) was used to evaluate the adsorption properties and recognition mechanism of the MIPs. Structurally similar compounds including quercetin and genistein were utilized for verifying the molecular selectivity and characterizing the recognition capability of the MIPs. The MIPs were used as a sorbent for the solid phase extraction of rutin, and the resultant cartridge showed a good extraction performance. Thus, a molecularly imprinted solid-phase extraction (MISPE) procedure for selective pre-concentration of rutin from complicated traditional Chinese medicine (TCM) samples was proposed. Various elution parameters that affect the adsorption capacity of the polymer were evaluated to optimize the selective pre-concentration of rutin. The characteristics of the MISPE method were validated by HPLC. The recoveries ranged from 85% to 91% for TCMs, which demonstrated that this MISPE-HPLC method could be applied to pre-concentrate and determinate rutin directly from complicated TCM samples in the presence of other interfering substances.     

Using natural deep eutectic solvents for the extraction of metabolites in Byrsonima intermedia leaves

Natural deep eutectic solvents have been used as an alternative to organic solvents for the extraction of plants metabolites, allowing for the extraction of compounds of different polarities, while being inexpensive, non‐toxic, and easy to prepare. This work presents the comparison of the chromatographic profiles by high‐performance liquid chromatography with diode‐array detection obtained from Byrsonima intermedia (Malpighiaceae) using five choline chloride‐based natural deep eutectic solvents, in addition to the most used traditional extraction solvents, methanol/water 7:3 and ethanol/water 7:3 v/v. A reference extract was used to tentatively identify compounds by high‐performance liquid chromatography with tandem mass spectrometry. The water content appeared to be important for the extraction efficiency and the mixture choline chloride/glycerol was shown to be the best candidate for efficiently extracting this matrix when compared with the traditional extraction media in addition to being far greener as shown by the environmental analysis tool. Seven phenolic compounds (digalloyl quinic acid, proanthocyanidin dimer, galloylproanthocyanidin dimer, quercetin‐O‐hexoside, galloyl quercetin hexoside, quercetin‐O‐pentoside, and galloyl quercetin pentoside) were tentatively identified in all extracts. Moreover, the influence of these solvents on the antioxidant activity of the extracts was studied and the results for choline chloride/glycerol extracts were very similar to that of the traditional extraction solvents.     

Molecularly imprinted spin column extraction coupled with high‐performance liquid chromatography for the selective and simple determination of trace nitrophenols in water samples

In this study, we developed a simple and selective spin column extraction technology utilizing hydrophilic molecularly imprinted polymers as the sorbents for extracting nitrophenol pollutants in water samples (the East Lake, the Yangtze River, and wastewater). The whole procedure was achieved by centrifugation of the spin column, and multiple samples were simultaneously processed with a low volume of solvent and without evaporation. Under the optimized condition, recoveries of nitrophenol compounds on the spin column packed with hydrophilic molecularly imprinted polymers ranged from 87.3 to 92.9% and an excellent purification effect was obtained. Compared with activated carbon, multi‐walled carbon nanotubes, LC‐C₁₈ sorbents, hydrophilic molecularly imprinted polymers exhibited a highly selective recognition ability for nitrophenol compounds and satisfactory sample extraction efficiency. Subsequently, the spin column extraction coupled with high‐performance liquid chromatography was established, which was found to be linear in the range of 2–1000 ng/mL for 2,4‐dinitropehnol and 2‐nitrophenol, and 6–1000 ng/mL for 4‐nitrophenol with correlation coefficients greater than 0.998. The detection limits ranged from 0.3–0.5 ng/mL. It is shown that the proposed method can be used for the determination of trace nitrophenol pollutants in complex samples, which is not only beneficial for water quality analysis but also for environmental risk assessment.     

Magnetic deep eutectic solvents molecularly imprinted polymers for the selective recognition and separation of protein

A novel and facile magnetic deep eutectic solvents (DES) molecularly imprinted polymers (MIPs) for the selective recognition and separation of Bovine hemoglobin (BHb) was prepared. The new-type DES was adopted as the functional monomer which would bring molecular imprinted technology to a new direction. The amounts of DES were optimized. The obtained magnetic DES-MIPs were characterized with fourier transform infrared spectrometry (FT-IR), thermogravimetric analysis (TGA), field emission scanning electron microscope (FESEM), dynamic light scattering (DLS), elemental analysis and vibrating sample magnetometer (VSM). The results suggested that the imprinted polymers were successfully formed and possessed a charming magnetism. The maximum adsorption capability (Q_max) and dissociation constant (K_L) were analyzed by Langmuir isotherms (R² = 0.9983) and the value were estimated to be 175.44 mg/g and 0.035 mg/mL for the imprinted particles. And the imprinted particles showed a high imprinting factor of 4.77. In addition, the magnetic DES-MIPs presented outstanding recognition specificity and selectivity so that it can be utilized to separate template protein from the mixture of proteins and real samples. Last but not least, the combination of deep eutectic solvents and molecular imprinted technology in this paper provides a new perspective for the recognition and separation of proteins.