Wanwan Ma

Molecular imprinted polymers based on magnetic chitosan with different deep eutectic solvent monomers for the selective separation of catechins in black tea

Two types of molecular‐imprinted polymers‐based magnetic chitosan with facile deep eutectic solvent‐functional monomers (Fe3O4‐CTS@DES‐MIPs) were synthesized and applied as adsorbents in magnetic solid‐phase extraction (MSPE) for the selective recognition and separation of (+)‐catechin, (−)‐epicatechin, and (−)‐epigallocatechin gallate in black tea. The obtained Fe3O4‐CTS@DES‐MIPs were characterized by Fourier transform infrared spectroscopy and field emission scanning electron microscopy. The selective recognition ability was examined by adsorption experiments. The actual amounts of (+)‐catechin, (−)‐epicatechin, and (−)‐epigallocatechin gallate extracted from black tea using Fe3O4‐CTS@DES‐MIPs by the MSPE method were 13.10, 6.32, and 8.76 mg/g, respectively. In addition, the magnetic Fe3O4‐CTS@DES‐MIPs showed outstanding recognition and selectivity. Therefore, it can be used to separate bioactive compounds from black tea. The new‐type of DES adopted as the functional monomer in this paper provides a new perspective for the recognition and separation of bioactive compounds.

Exploration of a ternary deep eutectic solvent of methyltriphenylphosphonium bromide/chalcone/formic acid for the selective recognition of rutin and quercetin in Herba Artemisiae Scopariae

Methyltriphenylphosphonium bromide/chalcone/formic acid, a green ternary deep eutectic solvent, was applied as a functional monomer and dummy template simultaneously in the synthesis of a new molecularly imprinted polymer. Ternary deep eutectic solvent based molecularly imprinted polymers are used as a solid-phase extraction sorbent in the separation and purification of rutin and quercetin from Herba Artemisiae Scopariae combined with high-performance liquid chromatography. Fourier transform infrared spectroscopy and field-emission scanning electron microscopy were applied to characterize the deep eutectic solvent based molecularly imprinted polymers synthesized using different molar ratios of chalcone. The static and competitive adsorption tests were performed to examine the recognition ability of the molecularly imprinted polymers to rutin and quercetin. The ternary deep eutectic solvent consisting of formic acid/chalcone/methyltriphenylphosphonium bromide (1:0.05:0.5) had the best molecular recognition effect. After optimization of the washing solvents (methanol/water, 1:9) and eluting solvents (acetonitrile/acetic acid, 9:1), a reliable analytical method was developed for strong recognition towards rutin and quercetin in Herba Artemisiae Scopariae with satisfactory extraction recoveries (rutin: 92.48%, quercetin: 94.23%). Overall, the chalcone ternary deep eutectic solvent-based molecularly imprinted polymer coupled with solid-phase extraction is an effective method for the selective purification of multiple bioactive compounds in complex samples.

Determination of deep eutectic solvents as eco-friendly catalysts for biodiesel esterification from an alcohol-palmitic acid mixture

Deep eutectic solvents (DESs) were prepared by mixing a quaternary salt as a hydrogen bond acceptor with a hydrogen bond donor. In this study, DESs had an excellent effect as a solvent-catalyst for the esterification of palmitic acid and methanol. This method was found to be safe, mild, simple, and eco-friendly. A range of DESs with different mixing ratios were used to optimize the preparation of methyl palmitate. Other factors, such as temperature, time and DESs/methanol ratio, were also examined. The optimal DES was prepared from tetrabutyl ammonium chloride and acetic acid (1 : 2); the methanol and palmitic acid sample to DES ratio was 1 : 0.5 (v/v). The reaction was optimized at a methanol/palmitic acid ratio of 10 : 1 (mol/mol) at 60 °C for 60 min. The yield was 94.3% under the optimized conditions. Therefore, DESs can be developed as a catalyst for the esterification of palmitic acid for obtaining methyl palmitate as biodiesel, and have potential applicability in other biodiesel pretreatments.

An effective separation and purification of rutin and scoparone from Herba Artemisiae Scopariae by solid-phase extraction cartridges packed with an ionic liquid-based silica

ABSTRACT Five types of ionic liquid-based silica were synthesized as solid-phase extraction (SPE) sorbents for separation and purification of bioactive compounds, that is, rutin and scoparone extracted from Herba Artemisiae Scopariae. The SilprBImCl material with the highest adsorption capacity was selected as the sorbent for SPE packing. Ethyl acetate and water were found to be suitable washing and eluting solvents, respectively. SilprBImCl was then applied to multi-phase extraction, and its superiority as a sorbent over the commercial cartridge was proven with high rutin and scoparone recoveries of 90.5% and 83.9%, respectively. This highlights the potential of ionic liquid-based silica materials applied to SPE and MPE.

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

ABSTRACT 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. GRAPHICAL ABSTRACT

Retention of Large Biological Molecules by Size-Exclusion Chromatography

ABSTRACT Size-exclusion chromatography has been developed for the separation of large biological molecules including proteins, polymers, peptides, nucleic acids, and polysaccharide according to their molecular size. This study determined the retention factors for dextran (5, 25, 50, 270, 670, and 1100 kDa) and polysaccharides, such as fucoidan, alginic acid, and laminarin, in the size-exclusion chromatography stationary phase. In addition, the molecular weights and retention factor of three polysaccharides were calculated from the dextran standard curve. The largest retention factor was 4.26 using the size-exclusion chromatography columns (5 kDa dextran). The molecular weights of fucoidan, alginic acid, and laminarin were determined to be 250, 200, and 5 to 64 kDa, respectively.

Determination of Polysaccharides in Undaria pinnatifida by Ionic Liquid-Modified Silica Gel Size Exclusion Chromatography

ABSTRACT Ionic liquid-modified silica particles with a large pore size were synthesized and used as the stationary phase for size exclusion chromatography coupled with a refractive index detector for the determination of polysaccharides, such as fucoidan, alginic acid, and laminarin from Undaria pinnatifida (seaweed). The molecular weight of polysaccharide was determined by a dextran standard curve (5–1100 kDa). The ionic liquid-modified silica column exhibited excellent size exclusion properties in separating laminarin from other components. The 1-butyl-3-methyl-imidazolium bis-(trifluoromethylsulfonyl)-amino silica column has superior resolution in laminarin separation than the other columns because the amino-group in ionic liquid provide π–π interactions due to aromaticity of the ring structure, which enhances the effect of the hydroxyl group in the target compound separation. The concentrations of polysaccharides were calculated using a standard linear equation to be 0.332–0.484 mg/g of fucoidan, 0.207–0.301 mg/g of alginic acid, and 0.154–0.297 mg/g of laminarin.

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

ABSTRACT 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.

Characterization of Deep Eutectic Solvents for Dispersive Liquid–Liquid Microextraction for Phenolics

ABSTRACT Dispersive liquid–liquid microextraction using deep eutectic solvents, as novel extraction solvents, was developed for the separation, preconcentration, and determination of chlorophenol, 2,3-dihydroxybenzoic acid, p-cresol, 4-chlorophenol, 2,4-dichlorophenol, and 2,4,6-trichlorophenol in vegetable oil. Seven deep eutectic solvents composed of choline chloride and different hydrogen bond donors (ethyl glycol, glycerol, 1,2-butanediol, 1,4-butanediol, 1,6-hexanediol, urea, and acetic acid) were characterized. The deep eutectic solvents formed by choline chloride-1,6-hexanediol in a 1:2 molar ratio provided the highest extraction efficiency. The sonication time, deep eutectic solvent volume, and disperser solvent were optimized. Under the optimal conditions of a sonication time of 11 min, a deep eutectic solvent volume of 90 µL, and acetone as the disperser solvent, extraction recoveries from 76.1 to 88.3% were obtained with 8.46 to 9.46 enrichment factors and the limits of detection exceeding 0.1 µg/mL with the relative standard deviations from 1.0 to 3.5%. This method using dispersive liquid–liquid microextraction with deep eutectic solvents is simple and provides high enrichment.