Direct imaging of micrometer-thick interfaces in salt-salt aqueous biphasic systems

Unlike the interface between two immiscible electrolyte solutions (ITIES) formed between water and polar solvents, molecular understanding of the liquid-liquid interface formed for aqueous biphasic systems (ABSs) is relatively limited and mostly relies on surface tension measurements and thermodynamic models. Here, high-resolution Raman imaging is used to provide spatial and chemical resolution of the interface of lithium chloride - lithium bis(trifluoromethanesulfonyl)imide - water (LiCl-LiTFSI-water) and HCl-LiTFSI-water, prototypical salt-salt ABSs found in a range of electrochemical applications. The concentration profiles of both TFSI anions and water are found to be sigmoidal thus not showing any signs of a positive adsorption for both salts and solvent. More striking, however, is the length at which the concentration profiles extend, ranging from 11 to 2 µm with increasing concentrations, compared to a few nanometers for ITIES. We thus reveal that unlike ITIES, salt-salt ABSs do not have a molecularly sharp interface but rather form an interphase with a gradual change of environment from one phase to the other. This knowledge represents a major stepping-stone in the understanding of aqueous interfaces, key for mastering ion or electron transfer dynamics in a wide range of biological and technological settings including novel battery technologies such as membraneless redox flow and dual-ion batteries.

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.

A green miniaturized aqueous biphasic system prepared with cholinium chloride and a phosphate salt to extract and preconcentrate personal care products in wastewater samples

A miniaturized extraction/preconcentration method based on an aqueous biphasic system (μ-ABS) was developed with reagents commonly used as food additives: cholinium chloride (ChCl) as main extraction phase, K₂HPO₄ as salting-out agent, and water as the main component (being the sample for analyses). With the aim of obtaining high enrichment factors, miniaturization, and adequate analytical performance, a point in the biphasic region with the lowest amount of ChCl was selected, corresponding to 1.55% (w/w) of ChCl, 59.5% (w/w) of K₂HPO₄, and 38.95% (w/w) of water. The green μ-ABS (attending to its main elements and performance mode) was used in combination with high-performance liquid chromatography with diode-array detection (HPLC-DAD) for the determination of 9 personal care products in wastewater samples. The μ-ABS-HPLC-DAD method showed high enrichment factors (up to 100), and quantitative extraction efficiencies for those compounds containing OH groups in their structure, which can undergo hydrogen bonding with ChCl. Thus, limits of quantification down to 0.8 µg·L^-1 and extraction efficiencies between 66.4 and 108% (concentration levels of 1.3 and 13 µg·L^-1) were reached for the group of parabens and the UV-filter benzophenone-3. The method is characterized by the use of non-harmful reagents and the absence of organic solvents in the entire sample preparation procedure, while being simple, low-cost, easily compatible with HPLC, and highly efficient.

Phase Behavior of Aqueous Biphasic Systems with Choline Alkanoate Ionic Liquids and Phosphate Solutions: The Influence of pH

Aqueous biphasic systems (ABS) composed of the choline alkanoate ionic liquids (ILs) choline acetate [Cho][OAc], choline propanoate [Cho][Pro], choline butyrate [Cho][But], and choline hexanoate [Cho][Hex], mixed with K3PO4 solutions at pH 7.2 and 14.5, were prepared and their phase diagrams were compared. The ability to form ABS with alkaline K3PO4 solutions decreased in the order [Cho][OAc] ≈ [Cho][Pro] > [Cho][But] > [Cho][Hex], while with neutral K3PO4 solutions, [Cho][OAc] could not form an ABS, and the other three ILs performed similarly. All of the biphasic regions of the ABS decreased with the increase in pH. 1H-NMR data indicated anion exchange between phases in ABS at neutral pH. The ABS at neutral pH were evaluated to extract the triazine herbicides simazine, cyanazine, and atrazine, and the ABS formed by [Cho][Pro] and the pH 7.2 K3PO4 solution has shown extraction recoveries higher than 90%.

Use of the aqueous biphasic system as an alternative for concentration of Ascaris lumbricoides eggs, with non-toxic separation of faecal residues and fats

OBJECTIVES

Human enteroparasites are considered a serious public health problem in underdeveloped countries located in world regions with tropical, subtropical and equatorial climates. These parasites are commonly diagnosed by the Parasitological Examination of Faeces (PEF), performed by conventional techniques and/or commercial kits that result in tests with low-to-moderate sensitivity, due to the use of destructive chemical solvents to parasite structures, and to present excess adipose substance and digestive residues in their microscopic slides. In order to improve the efficacy of these tests/examinations, this study aimed to investigate a new alternative for the PEF, with the use of Aqueous Biphasic System (ABS).

METHODS

For this, four ABSs containing poly (ethylene glycol), PEG (PEG-4000 and PEG-6000), dipotassium phosphate and sodium citrate at different concentrations in the biphasic systems were evaluated with faecal samples containing eggs of Ascaris lumbricoides.

RESULTS

The ABS consisting of PEG-4000 and dipotassium phosphate, at concentrations of 55% w/w and 20% w/w, respectively, achieved 100% satisfactory results compared to the conventional TF-Test technique in terms of preservation and concentration of A. lumbricoides eggs, with adequate separation of digestive residues, without using a centrifuge or chemical solvents that may cause harm to the parasites.

CONCLUSIONS

This study presents ABS as a new low-cost technical principle for the detection of parasite eggs in PEF. The new technique is simple, fast, non-toxic, not harmful to the parasite and does not require a centrifuge.

Extraction and Separation of Eight Ginsenosides from Flower Buds of Panax Ginseng Using Aqueous Ionic Liquid-Based Ultrasonic-Assisted Extraction Coupled with an Aqueous Biphasic System

Ionic liquids (ILs) are recognized as a possible replacement of traditional organic solvents, and ILs have been widely applied to extract various compounds. The present work aims to extract ginsenosides from Panax ginseng flower buds using aqueous ionic liquid based ultrasonic assisted extraction (IL-UAE). The extraction yields of 1-alkyl-3-methylimidazolium ionic liquids with different anions and alkyl chains were evaluated. The extraction parameters of eight ginsenosides were optimized by utilizing response surface methodology (RSM). The model demonstrated that a high yield of total ginsenosides could be obtained using IL-UAE, and the optimum extraction parameters were 0.23 M [C₄mim][BF₄], ultrasonic time of 23 min, temperature of extraction set to 30 °C, and liquid-solid ratio of 31:1. After that, an aqueous biphasic system (ABS) was used to separate ginsenosides further. The nature and concentration of salt, as well as the value of pH in ionic liquid were evaluated, and the optimal conditions (6.0 mL IL extract, 3 g NaH₂PO₄, and pH 5.0) were obtained. The preconcentration factor was 2.58, and extraction efficiency reached 64.53%. The results indicate that as a simple and efficient method, an IL-UAE-ABS can be considered as a promising method for extracting and separating the natural active compounds from medicinal herbs.

The role of ionic liquid [C4 C1 im]Br as an adjuvant on the two-phase formation and the extraction of l-phenylalanine in ABS composed of PEG400 and potassium citrate at different temperatures

The potential of {polyethylene glycol 400 + potassium citrate} aqueous biphasic system (ABS) with ionic liquid (IL) 1-butyl-3-methylimidazolium bromide ([C₄ C₁ im]Br) as an adjuvant is examined for the extraction of l-phenylalanine (Phe), as a model biomolecule, at different temperatures and system compositions. The binodal curves and liquid-liquid equilibrium data were determined by the addition of 5 wt% IL to investigate its effect on phase diagrams and Phe partition coefficients. The results indicate that binodal curves of systems with and without IL are more deviated from each other with decreasing temperature. Moreover, IL has a high tendency to partition into the PEG-rich phase. This tendency increases with increasing temperature and system compositions. For Phe, the partition coefficients obtained in this work (K_Phe ≈ 5.5-81.2) are significantly higher than those observed in other conventional PEG-inorganic salt ABS (K_Phe ≈ 0.5-2.5), water-immiscible ILs two-phase extraction systems (K_Phe ≈ 0.02-1.2), or even, in the IL-based ABS with the same IL as the main phase-forming component (K_Phe ≈ 3.2). The phase hydrophobicity, salting-out and π⋯π stacking seem to be the main driving forces to affect the extraction aptitude of the studied ABS for Phe. Furthermore, the performance of using [C₄ C₁ im]Br as adjuvant to improve the partition of Phe in the studied ABS at different temperatures seems to be ruled by the differences in the phases hydrophobicities. Finally, the experimental tie lines and partition coefficients are accurately correlated using the NRTL model. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 2018 © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:1149-1166, 2018.

Liquid-liquid extraction of antimicrobial peptide P34 by aqueous two-phase and micellar systems

Antimicrobial peptide P34 is a promising biopreservative for utilization in the food industry. In this work, aqueous biphasic systems (ABS) and aqueous biphasic micellar systems (ABMS) were studied as prestep for purification of peptide P34. The ABS was prepared with polyethylene glycol (PEG) and inorganic salts and the ABMS with Triton X-114 was chosen as the phase-forming surfactant. Results indicate that peptide P34 partitions preferentially to PEG-rich phase and extraction with ammonium sulfate [(NH₄)₂SO₄], yielding a 75% recovery of the antimicrobial activity, specific activity of 1,530 antimicrobial units per mg of protein, and purification fold of 2.48. Protein partition coefficient and partition coefficient for the biological activity with (NH₄)₂SO₄ system were 0.48 and 64, respectively. Addition of sodium chloride did not affect recovery, but decreased protein amount in the PEG-rich phase, indicating a higher partition of biomolecules. ABMS did not yield good recovery of antimicrobial activity. Purification fold using PEG-(NH₄)₂SO₄ and 1.0 mol l^-1 sodium chloride was twice higher than that obtained by conventional protocol, indicating a successful utilization of ABS as a step for purification of peptide P34.

Extraction, Preconcentration and Isolation of Flavonoids from Apocynum venetum L. Leaves Using Ionic Liquid-Based Ultrasonic-Assisted Extraction Coupled with an Aqueous Biphasic System

BACKGROUND

Ionic liquids (ILs) are considered as green solvents, and widely applied for the extraction of various compounds.

METHODS

The present research focuses on the extraction of flavonoids from Apocynum venetum L. leaves by ultrasound-assisted extraction (UAE). Several major influencing factors were optimized. Then, an aqueous biphasic system (ABS) was applied for further isolation of flavonoids.

RESULTS

The flavonoids were mainly distributed in the top phase, while impurities were extracted to the bottom phase. The parameters influencing the extraction, namely type and concentration of salt, temperature, and pH, were studied in detail. Under optimized conditions (72.43% IL extract, 28.57% (NH4)2SO4, 25 °C temperature, pH 4.5), the preconcentration factor and extraction efficiency were found to be 3.78% and 93.35%, respectively.

CONCLUSIONS

This simple and efficient methodology is expected to see great use in the extraction and isolation of pharmaceutically active components from medicinal plant resources.

Production and extraction of sugars from switchgrass hydrolyzed in ionic liquids

BACKGROUND

The use of Ionic liquids (ILs) as biomass solvents is considered to be an attractive alternative for the pretreatment of lignocellulosic biomass. Acid catalysts have been used previously to hydrolyze polysaccharides into fermentable sugars during IL pretreatment. This could potentially provide a means of liberating fermentable sugars from biomass without the use of costly enzymes. However, the separation of the sugars from the aqueous IL and recovery of IL is challenging and imperative to make this process viable.

RESULTS

Aqueous alkaline solutions are used to induce the formation of a biphasic system to recover sugars produced from the acid catalyzed hydrolysis of switchgrass in imidazolium-based ILs. The amount of sugar produced from this process was proportional to the extent of biomass solubilized. Pretreatment at high temperatures (e.g., 160°C, 1.5 h) was more effective in producing glucose. Sugar extraction into the alkali phase was dependent on both the amount of sugar produced by acidolysis and the alkali concentration in the aqueous extractant phase. Maximum yields of 53% glucose and 88% xylose are recovered in the alkali phase, based on the amounts present in the initial biomass. The partition coefficients of glucose and xylose between the IL and alkali phases can be accurately predicted using molecular dynamics simulations.

CONCLUSIONS

This biphasic system may enable the facile recycling of IL and rapid recovery of the sugars, and provides an alternative route to the production of monomeric sugars from biomass that eliminates the need for enzymatic saccharification and also reduces the amount of water required.