Enantioselective liquid-liquid extraction of valine enantiomers in the aqueous two-phase system formed by the cholinium amino acid ionic liquid copper complexes and salt

Enantioselective liquid-liquid extraction of 2-cyclohexylmandelic acid enantiomers using chiral ionic liquids

Obtaining optically pure compounds in an eco-friendly and cost-efficient manner plays an important role in human health and pharmaceutical industry. Racemic separation using multistage stereoselective liquid-liquid extraction has become one of the most practical and effective approach to access homochiral enantiomers. Currently, chiral ionic liquids (CILs) with structural designability have become a promising chiral additive and enable them as adjustable candidates for racemic separation. Herein, a high-effective stereoselective liquid-liquid extraction process composed of imidazolium cations and amino acid-derived anions as the chiral additive was established for racemic 2-cyclohexylmandelic acid (CHMA) separation. We have systematically investigated the choice of organic solvent, concentration of CIL, extraction temperature, and the pH of aqueous phase. For three-stage stereoselective extraction, the maximum enantiomeric excess (e.e.) for CHMA was reached up to 40.6%. Furthermore, the mechanism of steric effect and stereoselective capacity between the CILs and racemic CHMA was discussed and simulated. We envision that the work will facilitate the development of CILs in multistage liquid-liquid extraction and promote the large-scale production of optically pure enantiomers.

Strategies for chiral separation: from racemate to enantiomer

Chiral separation has become a crucial topic for effectively utilizing superfluous racemates synthesized by chemical means and satisfying the growing requirements for producing enantiopure chiral compounds. However, the remarkably close physical and chemical properties of enantiomers present significant obstacles, making it necessary to develop novel enantioseparation methods. This review comprehensively summaries the latest developments in the main enantioseparation methods, including preparative-scale chromatography, enantioselective liquid-liquid extraction, crystallization-based methods for chiral separation, deracemization process coupling racemization and crystallization, porous material method and membrane resolution method, focusing on significant cases involving crystallization, deracemization and membranes. Notably, potential trends and future directions are suggested based on the state-of-art "coupling" strategy, which may greatly reinvigorate the existing individual methods and facilitate the emergence of cross-cutting ideas among researchers from different enantioseparation domains.

Enantioseparation of amino acid and mandelic acid enantiomers using Josiphos-metal complexes as chiral extractants

The development of new and efficient chiral extractants has always been the research hotspot and difficulty in the field of chiral extraction. Josiphos, a famous ferrocene derivative catalyst, is employed as a chiral extractant in enantioseparation of amino acid and mandelic acid enantiomers. The influences of metal ions, organic solvents, pH of the aqueous solution, extractant concentrations, and extraction temperature on enantioselectivities are systematically studied. The result reveals that Josiphos-Pd has good capabilities to enantioseparate 4-nitro-phenylalanine (Nphe), 3-chloro-phenylglycine (Cpheg), and mandelic acid (MA) with separation factors (α) of 3.30, 2.65, and 2.18, respectively. The pH of the aqueous phase and Josiphos-Pd concentration affect the extraction significantly, whereas extraction temperature shows little influence. After optimizing by response surface method, the mathematical models for extractions are established. And the highest experimental performance factors (pf) for Nphe, Cpheg, and MA are 0.1843, 0.1335, and 0.08884, respectively.

Multiscale molecular simulations for the solvation of lignin in ionic liquids

Lignin, the second most abundant biopolymer found in nature, has emerged as a potential source of sustainable fuels, chemicals, and materials. Finding suitable solvents, as well as technologies for efficient and affordable lignin dissolution and depolymerization, are major obstacles in the conversion of lignin to value-added products. Certain ionic liquids (ILs) are capable of dissolving and depolymerizing lignin but designing and developing an effective IL for lignin dissolution remains quite challenging. To address this issue, the COnductor-like Screening MOdel for Real Solvents (COSMO-RS) model was used to screen 5670 ILs by computing logarithmic activity coefficients (ln(γ)) and excess enthalpies (H^E) of lignin, respectively. Based on the COSMO-RS computed thermodynamic properties (ln(γ) and H^E) of lignin, anions such as acetate, methyl carbonate, octanoate, glycinate, alaninate, and lysinate in combination with cations like tetraalkylammonium, tetraalkylphosphonium, and pyridinium are predicted to be suitable solvents for lignin dissolution. The dissolution properties such as interaction energy between anion and cation, viscosity, Hansen solubility parameters, dissociation constants, and Kamlet-Taft parameters of selected ILs were evaluated to assess their propensity for lignin dissolution. Furthermore, molecular dynamics (MD) simulations were performed to understand the structural and dynamic properties of tetrabutylammonium [TBA]⁺-based ILs and lignin mixtures and to shed light on the mechanisms involved in lignin dissolution. MD simulation results suggested [TBA]⁺-based ILs have the potential to dissolve lignin because of their higher contact probability and interaction energies with lignin when compared to cholinium lysinate.

Phase Behavior of Ionic Liquid-Based Aqueous Two-Phase Systems

As an environmentally friendly separation medium, the ionic liquid (IL)-based aqueous two-phase system (ATPS) is attracting long-term attention from a growing number of scientists and engineers. Phase equilibrium data of IL-based ATPSs are an important basis for the design and optimization of chemical reactions and separation processes involving ILs. This article provides the recent significant progress that has been made in the field and highlights the possible directions of future developments. The effects of each component (such as salting-out agents and ILs) on the phase behavior of IL-based ATPSs are summarized and discussed in detail. We mainly focus on the phase behavior of ATPSs by using ILs, expecting to provide meaningful and valuable information that may promote further research and application.

Protein aggregation and crystallization with ionic liquids: Insights into the influence of solvent properties

Ionic liquids (ILs) have been used in solvents for proteins in many applications, including biotechnology, pharmaceutics, and medicine due to their tunable physicochemical and biological properties. Protein aggregation is often undesirable, and predominantly occurs during bioprocesses, while the aggregation process can be reversible or irreversible and the aggregates formed can be native/non-native and soluble/insoluble. Recent studies have clearly identified key properties of ILs and IL-water mixtures related to protein performance, suggesting the use of the tailorable properties of ILs to inhibit protein aggregation, to promote protein crystallization, and to control protein aggregation pathways. This review discusses the critical properties of IL and IL-water mixtures and presents the latest understanding of the protein aggregation pathways and the development of IL systems that affect or control the protein aggregation process. Through this feature article, we hope to inspire further advances in understanding and new approaches to controlling protein behavior to optimize bioprocesses.

Enantioseparation and determination of triazole fungicides in fruit juice by aqueous biphasic system coupled with HPLC-MS/MS

The aqueous biphasic system based on choline ionic liquids and ethylene/propylene oxide copolymer coupled with high-performance liquid chromatography-tandem mass spectrometry was developed for the simultaneous determination of the enantiomers of two fungicides: myclobutanil and tebuconazole. The influence of mass fractions of ionic liquids and the copolymer on the extraction efficiency of the target fungicides was investigated. The analytes are mainly concentrated in the bottom, copolymer-rich phase. The extraction efficiencies of the selected fungicides were significantly affected by the concentrations of the copolymer, and their extraction efficiencies decreased with the higher mass fractions of the copolymer, while the mass fraction of ionic liquids had little effect on their extraction behavior. Excellent extraction efficiency was achieved using the aqueous biphasic system based on choline L-lysinate and the copolymer. At three spiked concentrations of 0.01, 0.05, and 0.1 mg/kg, the average recoveries of the selected fungicides ranged from 80 to 89%, with the relative standard deviations in the range of 2.1-5.3%. Limits of quantitation for the enantiomers of tebuconazole and myclobutanil were 0.5 and 5.0 µg/kg, respectively. The developed system could be successfully applied to the analysis of triazole fungicides residue in real samples.

Recent advances in the enantioseparation promoted by ionic liquids and their resolution mechanisms

More and more various chemical media are being applied in enantioseparation; among them, ionic liquids (ILs) have attracted the long-term attention in this decade as green designable solvents. This paper provides comprehensive overview for the applications of ILs in chiral extraction, gas chromatography, liquid chromatography, capillary electrophoresis and other techniques for enantioseparation. Additionally, the important resolution mechanisms based on ILs have also been summarized and discussed. This review focuses on the latest development of enantioseparation methods by using ILs in various modes, leading to meaningful and valuable information to related fields and thus promotes further research and application of reported methods.

Evaluation of CO2-induced azole-based switchable ionic liquid with hydrophobic/hydrophilic reversible transition as single solvent system for coupling lipid extraction and separation from wet microalgae

The utilization of microalgae as bioenergy source was limited by the excessive cost and energy consumption during the process of lipid extraction and separation. CO₂-induced switchable ionic liquids (S-ILs) with reversible hydrophobic-hydrophilic conversion were synthesized and applied for lipid extraction and separation. The reversible transition mechanism of switchable IL is due to the formation of carbamate. The novel approach based on S-ILs was developed for lipid extraction from wet microalgae, which coupled microalgae cell disruption, lipid extraction, separation, and solvent recovery process without additional solvents. The highest lipid extraction efficiencies from wet microalgae were obtained by C₆DIPA-Im, and the lipids were recovered from the extraction phase by simply bubbling CO₂. Furthermore, C₆DIPA-Im maintained more than 83.6 ± 3.6% of its initial lipid extraction efficiency after recycling five times. The S-IL based extraction and separation method provides a new strategy for sustainable bioenergy production.