Cosolvent Fraction Research Articles

Regeneration of conventional and emerging PFAS-selective anion exchange resins used to treat PFAS-contaminated waters

Anion exchange resins (AERs) have emerged as a promising separation technology to remediate PFAS-contaminated waters due to their improved selectivities and capacities in comparison to legacy activated carbon adsorbents. Presently, site managers choose between AER systems employing resins defined as being ‘regenerable’ with relatively low PFAS selectivity, and PFAS-selective resins that are marketed as ‘single-use’ media intended for disposal upon PFAS breakthrough. However, the potential for these highly-selective adsorbents to be regenerated and/or reused remains poorly characterized. This study presents a comprehensive evaluation of the efficacy of various regenerant solution constituents, mixtures, and operational considerations on the regenerability of both ‘regenerable’ and ‘PFAS-selective’ AERs that were loaded during a pilot treatment study of PFAS-contaminated groundwater. Batch screening of regenerant solution constituents found that both classes of resins may be effectively regenerated using combinations of salt brine and organic cosolvent, with high cosolvent fractions being necessary for PFAS-selective AERs. While neither brine-only nor solvent-only regenerant solutions led to effective PFAS desorption, the efficacy of regeneration with brine/cosolvent mixtures varied with salt type and cosolvent composition. Chloride salts outperformed sulfate and bicarbonate salts, cosolvent efficacy depended on the volume fraction and type used, and highly non-polar solutions led to optimal PFAS desorption. Continuous-flow regeneration experiments showed near-complete PFAS desorption from regenerable AERs using 10 bed volumes (BVs) of 70 % methanolic brine solutions, whereas PFAS-selective resins required more bed volumes (30) of brines with higher methanol content (90 %) or a more hydrophobic cosolvent (n-propanol); increasing regenerant empty-bed contact time had minimal effect on PFAS desorption. > 90 % methanol recovery from the resulting waste regenerant mixtures was accomplished with negligible PFAS contamination using distillation, leaving a minimal volume of a PFAS-concentrated still bottoms waste that may be further treated for PFAS destruction. Life cycle analyses revealed that groundwater treatment using PFAS-selective AERs operated in a regenerable mode have lower environmental impacts and costs than systems using conventional regenerable AERs, and lower treatment costs than systems operated using PFAS-selective resins in a single-use mode. Although counterintuitive, these findings stem from the fact that higher cosolvent requirements for regeneration of PFAS-selective resins lead to greater internal recycling of regenerant solutions and much lower volumes of residual waste still bottoms that require off-site incineration or disposal.

Compatibility versus reaction diffusion: Factors that determine the heterogeneity of polymerized adhesive networks

ObjectivesHeterogeneity and phase separation during network polymerization is a major issue contributing to the failure of dental adhesives. This study investigates how the ratio of hydrophobic crosslinkers to hydrophilic comonomer (C/H ratio), as well as cosolvent fraction (ethanol/water) influences the degree of heterogeneity and proclivity for phase separation in a series of model adhesive formulations. MethodsTwelve formulations were investigated, with 4 different C/H ratios (7:1, 2.2:1, 1:1, 0.5:1) and 3 different overall cosolvent fractions (0, 10 and 20 wt%). The heterogeneity and phase behavior were characterized using Fourier Transform Infrared Spectroscopy (FT-IR), dynamic mechanical analysis (DMA), small-angle x-ray scattering (SAXS) and atomic force microscopy (AFM). ResultsIn resins without cosolvent, all characterizations confirm reduced heterogeneity as C/H ratio decreases. However, when 10 or 20 wt% of cosolvent is included in the adhesive formulation, a higher degree of heterogeneity and even distinct phase separation with domains ranging from a few hundreds of nanometers to a few micrometers in size form. This is particularly noticeable at lower C/H ratios, which is surprising as HEMA is commonly considered a compatibilizer between hydrophobic crosslinkers and aqueous (co)solvents. SignificanceOur experiments demonstrate that formulations with lower C/H ratio and thus a lower viscosity experience later onsets of diffusion limitations during polymerization, which favors thermodynamically driven phase separation. Therefore, to determine or predict the resulting phase structure of adhesive materials, it is necessary to consider the kinetics and diffusion constraints during the formation of the polymer network and not just the compatibility of resin constituents.

Ether-type co-solvents of excellence for aqueous base-free Pt-catalyzed oxidation of concentrated 5-(hydroxymethyl)furfural to 2,5-furandicarboxylic acid

The biomass-derived 5-(hydroxymethyl)furfural (5-HMF) is readily converted in water to 2,5-furandicarboxyl acid (FDCA) that is well known as a renewable diacid monomer. However, the limited solubility of FDCA in water posed serious challenges to process development. Herein, the base-free Pt-catalyzed oxidation of 5-HMF was explored in aqueous binary solvent systems containing organic co-solvents such as dimethyl sulfoxide, N,N-dimethylformamide, gamma-valerolactone, dioxane, diethylene glycol dimethyl ether, and 1,2-dimethoxyethane (DME). The FDCA solubility and 5-HMF oxidation performance were investigated in co-solvent/H2O systems with different co-solvent fractions. When correlated with the solvatochromic parameters of co-solvents, the FDCA yield appeared to be in harmony with their polarizability and hydrogen bonding acceptance ability. Thus, infrared spectra were collected with three systems such as co-solvent/H2O, 5-HMF in co-solvent, and 5-HMF in co-solvent/H2O. The employed co-solvent was found to have different abilities to interact with the O–H and C=O moieties of 5-HMF via H-bonding and dipole-induced dipole attraction (related with the polarizability), respectively. Consequently, a high FDCA yield was achieved using three ether-type co-solvents in which these interactions are relatively weak. In a continuous-flow pattern for the base-free oxidation of 3 wt% 5-HMF solution, a FDCA yield of >98 % was achieved with 60 wt% DME/H2O under the optimized conditions.

The dissolution mechanism, molecular dynamics simulation and thermodynamic analysis of nirmatrelvir (treatment of COVID-19) in aqueous ethanol mixtures

This research investigates the cosolvent effect of nirmatrelvir (treatment of COVID-19) in ethanol + water mixtures. The result shows that the maximum solubility in mole fraction is 8.313 × 10−2 at the ethanol mass fraction of 80%, which is greater than that in pure water. The solvent effect analysis indicates that the hydrogen bond acidity (HBA) of solvent has the greatest impact on the solubility of nirmatrelvir solubility. The negative preferential solvation values in water-rich regions indicate that nirmatrelvir molecules are preferentially solvated by water molecules. With the rising mass fraction of cosolvent, ethanol disrupts the ordered structure of water molecules in solution through hydrogen bonding, allowing nirmatrelvir molecules to be preferentially solvated by ethanol. Nonetheless, nirmatrelvir molecules are preferentially solvated by water again in ethanol-rich regions. Through molecular dynamics calculations (MD), it could be found that the dissolution behavior is consistent with its calculated by solvation free energy calculation. Furthermore, the tall and sharp peak of the RDF plots of O···H-O (ethanol/water) and N-H···O (ethanol/water) were attained at 1.50–2.50 Å, indicating that ethanol and water molecules form a regular and definite coordination sphere around the nirmatrelvir moiety at the distance of 1.50–2.50 Å through hydrogen bonding form. Additionally, the correlation fitting was performed for the solubility data through the Jouyban-Acree model and its derivative models. Moreover, “Apparent thermodynamic analysis” of nirmatrelvir dissolution process in aqueous ethanol mixtures including entropy, enthalpy and Gibbs free energy were completed.

Solubility measurement of syringic acid, trans-cinnamic acid, p-coumaric acid, and vanillin constituent of Deverra DC. genus in (ethyl acetate + ethyl alcohol) mixtures: Thermodynamic modeling and preferential solvation

This work aims firstly to measure the solubility of four natural phenolic compounds (syringic acid, trans-cinnamic acid, p-coumaric acid, and vanillin) present in Deverra DC. Genus in (ethyl alcohol + ethyl acetate) using the gravimetric method from 283.15 to 323.15 K at normal pressure and then to analyze the solubility using the Jouyban-Acree and van't Hoff-Jouyban-Acree models. Secondly, based on the obtained solubility data, the preferential solvation parameters (δx1,3) of four natural phenolic compounds (PhC) in double solvent mixtures of ethyl alcohol (1) + ethyl acetate (2) were calculated using the inverse Kirkwood-Buff integrals method. The δx1,3 numbers differ indirectly with the co-solvent (1) fraction in all the binary mixtures. For the ethyl alcohol (1) + ethyl acetate (2) systems, the δx1,3 values are negative in ethyl acetate-rich mixtures and positive in constituents (x1) ranging from 0.59 to 1 for syringic acid, 0.51 to 0.63 trans-cinnamic acid, and 0.48 to 0.63 for vanillin in the mole fraction of ethyl alcohol. However, for the ethyl alcohol (1) + ethyl acetate (2) +p-coumaric acid (3) mixtures comprising 0 <x1 < 0.63, the values of δx1,3 are positive. This indicates that the co-solvent preferentially dissolved p-coumaric acid. The positive amounts of δx1,3 obtained are because the phenolic molecules that interact with the hydrogen acceptor groups existing in the co-solvent have higher acidic properties.

Hydrophilic interaction liquid chromatography with methanol-water eluent on a zeolite

BackgroundHydrophilic interaction chromatography (HILIC) works with organic solvent-water mixtures as eluent and is based on the formation of a water enriched liquid phase on the surface of a hydrophilic stationary phase. Hydrophilic solutes are retained on that stagnant water-rich film depending on the difference of solvation compared to the mobile phase composition. However, the enhancement of selectivity by increasing the fraction of organic cosolvent is coupled with a limitation the analyte solubility, and the improvement of the HILIC principle by new hydrophilic stationary phases is the remaining option. ResultsY-zeolite (faujasite, FAU type) in the Na+-form with an average particle diameter of 5 μm was used as packing material in a 125 mm long HPLC column. The chromatographic response of the column was tested in methanol-water mixtures as eluent after injection of several aliphatic alcohols, polyols and monosaccharides with eluent conditions where no separation occurs on diol functionalized silica. On the zeolite the retention time increases according to ethylene glycol < glycerol < erythritol < sorbitol < inositol. The separation principle is explained to be superposed by two effects: firstly, a partition equilibrium between the water-rich phase in the zeolite micropores exists, and secondly, selective interactions with the inner crystalline pore surface and fixed-position Na+ ions, both serving to enhance the selectivity. Furthermore, arabinose and fructose monosaccharides could be separated into their tautomeric forms. Only upon increasing the temperature from 20 to 60 °C the tautomeric pattern merges into a single peak. Significance and noveltyInstead of the stagnant water rich surface layer, zeolite micropores now take over that function. As a result, the selectivity among polyols and between α/β-arabinopyranose and β-fructopyranose/β-fructofuranose tautomers is extraordinary superior towards conventional hydrophilic interaction liquid chromatography (HILIC).

Cellulose-cellulose composite membranes for ultrafiltration

Research and development towards sustainable chemistry includes also the development of new materials and the exploration of new ways to fabricate them. In this work, composite membranes were fabricated from fully biodegradable materials (cellulose) through a simple and scalable process, i.e., a combination of film casting, nonsolvent-induced phase separation and lamination, in which only environmentally friendly solvents are used. Filter paper was utilized as support material. Cellulose was dissolved in a mixture of an ionic liquid (1-ethyl or 1-butyl-3-methylimidazolium acetate) with a co-solvent (dimethylsulfoxide, DMSO) and used for casting the barrier layer. The influence of pre-wetting the filter paper with different liquids (water, glycerine, DMSO) was investigated. It was found that using DMSO as impregnation liquid improved both, the membrane separation performance and the strength of the lamination between the cellulose barrier layer and the filter paper as demonstrated by adhesion tests. Barrier layer thickness could be reduced to a few μm by appropriate cast film thickness. Membrane separation performance in terms of permeance and solute rejection could also be adjusted by the choice of cellulose concentration and co-solvent fraction in the casting solution. The applicability of the cellulose-cellulose composite membranes in ultrafiltration (UF) of aqueous or organic solvent-based mixtures was evaluated with dextran or polyethylene glycol and polyethylene oxide, respectively, as test solutes. Molecular weight cut-off data for one specific UF membrane type were ∼100 kDa, ∼170 kDa, or ∼390 kDa in water, dimethylformamide or DMSO. All results obtained in this study indicate that the novel membranes have potential as a more sustainable alternative material for various relevant separations.

Equilibrium solubility and modeling of Glibenclamide in cosolvent mixtures of Methanol, n-Propanol, Isopropanol, and Acetonitrile + Water

Equilibrium solubility of glibenclamide (GCM) in aqueous solutions of methanol, n-propanol, isopropanol, and acetonitrile were studied by static technique at temperatures ranging from 288.15 K to 323.15 K under p = 101.3 kPa. When the composition of cosolvent was constant in the four mixed solvents, GCM solubility increased with the rising temperature. When the temperature was fixed, the GCM mole fraction solubility showed positive dependence on the increasing mass fraction of methanol in methanol + water mixture. While in solutions of n-propanol + water, isopropanol + water, and acetonitrile + water, it first increased as the mass fraction of cosolvent (w) added, at around w = 0.9, the solubility reached a maximum value and then it descended. Thermodynamic models like Jouyban−Acree model, modified Apelblat−Jouyban−Acree model, and CNIBS/R-K model were taken to correlate the equilibrium mole fraction solubility of GCM in four solvent mixtures. The maximum RAD and the RMSD values calculated by the CNIBS/R-K model were found in the mixture of methanol + water and didn’t exceeded 7.4 × 10−2 and 1.48 × 10−5, respectively. However, the maximum RAD values obtained by the Jouyban−Acree and modified Apelblat−Jouyban−Acree model were found in the mixture of acetonitrile + water and didn’t exceeded 5.57 × 10−2 and 5.55 × 10−2, respectively. The RMSD all didn’t exceeded 2.54 × 10−5. Hence, the Jouyban−Acree model and modified Apelblat−Jouyban−Acree model are shown to be superior to the CNIBS/R-K model in this work. The experimental data and model parameters obtained will be helpful for the preparation and purification of GCM.

Implementation of a choline bis(trifluoromethylsulfonyl)imide aqueous electrolyte for low temperature EDLCs enabled by a cosolvent

We report a carbon/carbon capacitor based on micro/mesoporous carbon electrodes with cost-effective and eco-friendly aqueous choline bis(trifluoromethylsulfonyl)imide (ChTFSI) electrolyte with a cosolvent enabling low-temperature operation down to −30 °C. For this purpose, a MgO-templated hierarchical carbon (MP98B) with an average mesopore diameter of 3.5 nm was prepared by pyrolysis of magnesium citrate hydrate at 900 °C. To reach lower temperatures, the melting point and viscosity of the aqueous electrolyte were reduced by mixing water (W) with an organic solvent (methanol, M, or isopropanol, I) of high dielectric constant and low viscosity. 5 mol kg−1 (5 m) ChTFSI in an optimized volume fraction of cosolvent, M0.75W0.25, and I0.75W0.25, showed the highest conductivity; the higher conductivity in M0.75W0.25 (22.8 and 3.1 mS cm−1 at 20 and −30 °C, respectively) than in I0.75W0.25 (8.5 and 0.5 mS cm−1 at 20 and −30 °C, respectively) is attributed to the lower viscosity of the M0.75W0.25 solution. The electrochemical stability window (ESW) of 5 m ChTFSI in M0.75W0.25 and I0.75W0.25 (1.6 V) on an MP98B electrode was determined by applying the S-method. Meanwhile, by adjusting the mass ratio of the two electrodes, a MP98B/MP98B capacitor using the 5 m electrolyte in M0.75W0.25 could operate with a good life span up to 1.6 V while exhibiting a better charge propagation, greater specific capacitance, and higher specific energy than in I0.75W0.25.

Thermodynamic data measurement and analysis of organoaluminum supported by β-diketimine ligand in several solvents

Organoaluminum compounds are supported by β-diketimine ligands were widely used in organic synthesis, homogeneous catalysis and other fields due to their unique structure and properties. In this article, the static equilibrium method was used to determine the solubility of LAlMe2 (L = HC(CMeNAr)2, Ar = 2,6-iPr2C6H3) in four pure solvents (n-hexane, toluene, tetrahydrofuran, dichloromethane) and two binary solvent systems (n-hexane + toluene, n-hexane + dichloromethane). All operations were performed under Schlenk technology or a glove box under nitrogen atmosphere, and measurement temperature was 263.15 K to 308.15 K. The experimental results showed that the solubility of LAlMe2 gradually increased with the elevated of temperature and presents an increasing trend with the increase of the mass fraction of co-solvent in the mixed solvent. Hansen solubility parameter explained the dissolution behavior of LAlMe2. Six thermodynamic models were used to correlate the solubility data. The results showed that the Apelblat model and the Yaws model have the most extensive applicability in both pure solvent and binary solvent systems. In addition, thermodynamic parameters, such as ΔsolHo, ΔsolSo and ΔsolGo were calculated by Gibbs function and Van’t Hoff equation and the enthalpy- entropy compensation in the dissolution process was analyzed. It was concluded that dissolution is an endothermic process driven by entropy and ΔsolHo is the main factor affecting ΔsolGo.

Dl-isoprenaline hydrochloride solubility in four binary solvents at saturation: Thermodynamic analysis, Hansen solubility parameters and molecular simulation

The solubility properties of dl-isoprenaline hydrochloride (dl-IPN) in four kinds of binary-solvents systems {(n-propanol, n-butanol, 2-propoxyethanol and 2-butoxyethanol) + methanol} at temperature range of 278.15–323.15 K under 101.3 kPa was further investigated using the laser monitoring technique. According to the result about solubility of dl-IPN in these chosen binary solvents, it is obvious that dl-IPN is more soluble at higher temperature. Additionally, the solubility values of dl-IPN, in all the investigated binary solvent mixtures, is improved with increasing mass fraction of co-solvent (methanol). The Hansen solubility parameters (HSPs) interpretate reasonably the order of dl-IPN solubility in these binary-solvents systems. Furthermore, the molecular dynamic (MD) simulation is employed to describe the molecular interactions of the types solute–solvent and solvent–solvent, and the obtained results confirm that solute–solvent and solvent–solvent molecular interactions have deep impact on the solubility of dl-IPN. The obtained experimental data about the solubility of dl-IPN is fitted by five models (λh equation, Apelblat equation, Jouyban-Acree-Apelblat (J-A-A) model, Ma model and Sun model). The analysis of thermodynamic properties was based on the values of the calculated thermodynamic parameters. It can be concluded that the dl-IPN dissolution process is entropy-motivated and endothermal in all the investigated binary-solvents systems, and that the main contribution to ΔdisGo is due to enthalpy.

A Retention-Matching Strategy for Method Transfer in Supercritical Fluid Chromatography: Introducing the Isomolar Plot Approach

A strategy to match any retention shifts due to increased or decreased pressure drop during supercritical fluid chromatography (SFC) method transfer is presented. The strategy relies on adjusting the co-solvent molarity without the need to adjust the back-pressure regulator. Exact matching can be obtained with minimal changes in separation selectivity. To accomplish this, we introduce the isomolar plot approach, which shows the variation in molar co-solvent concentration depending on the mass fraction of co-solvent, pressure, and temperature, here exemplified by CO2–methanol. This plot allowed us to unify the effects of the co-solvent mass fraction and density on retention in SFC. The approach, which was verified on 12 known empirical retention models for each enantiomer of six basic pharmaceuticals, allowed us to numerically calculate the apparent retention factor for any column pressure drop. The strategy can be implemented either using a mechanistic approach if retention models are known or empirically by iteratively adjusting the co-solvent mass fraction. As a rule of thumb for the empirical approach, we found that the relative mass fraction adjustment needed is proportional to the relative change in the retention factor caused by a change in the pressure drop. Different proportionality constants were required to match retention in the case of increasing or decreasing pressure drops.

Impact of Methanol Adsorption on the Robustness of Analytical Supercritical Fluid Chromatography in Transfer from SFC to UHPSFC.

In supercritical fluid chromatography (SFC), the retention of a solute depends on the temperature, density, pressure, and cosolvent fraction. Here, we investigate how the adsorption of the cosolvent MeOH changes with pressure and temperature and how this affects the retention of several solutes. The lower the pressure, the stronger the MeOH adsorption to the stationary phase; in addition, at low pressure, perturbing the pressure results in significant changes in the amounts of MeOH adsorbed to the stationary phase. The robustness of the solute retention was lowest when operating the systems at low pressures, high temperatures, and low cosolvent fractions in the eluent. Here, we found a clear relationship between the sensitivity of MeOH adsorption to the stationary phase and the robustness of the separation system. Finally, we show that going from classical SFC to ultrahigh-performance SFC (UHPSFC), that is, separations conducted with much smaller packing diameters, results in retention factors that are more sensitive to fluctuations in the flow rate than with traditional SFC. The calculated density profiles indicate only a slight density drop over the traditional SFC column (3%, visualized as lighter → darker blue in the TOC), whereas the drop for the UHPSFC one was considerably larger (20%, visualized as dark red → light green in the TOC). The corresponding temperature drops were calculated to be 0.8 and 6.5 °C for the SFC and UHPSFC systems, respectively. These increased density and temperature drops are the underlying reasons for the decreased robustness of UHPSFC.

Systematic investigations of peak distortions due to additives in supercritical fluid chromatography

The impact of eluent components added to improve separation performance in supercritical fluid chromatography was systematically, and fundamentally, investigated. The model system comprised basic pharmaceuticals as solutes and eluents containing an amine (i.e., triethylamine, diethylamine, or isopropylamine) as additive with MeOH as the co-solvent. First, an analytical-scale study was performed, systematically investigating the impact of the additives/co-solvent on solute peak shapes and retentions, using a design of experiments approach; here, the total additive concentration in the eluent ranged between 0.021 and 0.105 % (v/v) and the MeOH fraction in the eluent between 16 and 26 % (v/v). The co-solvent fraction was found to be the most efficient tool for adjusting retentions, whereas the additive fraction was the prime tool for improving column efficiency and peak analytical performance. Next, the impacts of the amine additives on the shapes of the so-called overloaded solute elution profiles were investigated. Two principal types of preparative peak deformations appeared and were investigated in depth, analyzed using computer simulation with mechanistic modeling. The first type of deformation was due to the solute eluting too close to the additive perturbation peak, resulting in severe peak deformation caused by co-elution. The second type of deformation was also due to additive–solute interactions, but here the amine additives acted as kosmotropic agents, promoting the multilayer adsorption to the stationary phase of solutes with bulkier aryl groups.

Water‐insoluble cosolvent in aqueous two‐phase system improved the extraction of paeonol from cortex moutan

AbstractBackgroundAqueous two‐phase extraction has advantages of green extraction, high yield, good product purity and low cost. However, conventional aqueous two‐phase systems (ATPSs) are limited in extraction/separation due to high polarity. Some researchers tuned the hydrophobicity of ATPSs by addition of hydrophobic ionic liquids or polymers. We aimed to tailor the hydrophobicity of a solvent–salt–water ATPS using cosolvent for extraction of paeonol from cortex moutan.ResultsTie‐line length and compositions in the ATPS were employed for qualitative evaluation of polarity and polarity difference between the two phases. Conditions such as pH, salt type and concentration, total solvent volume fraction and cosolvent fraction were optimized. Ethyl acetate (EA) as cosolvent in ethanol–NaH2PO4–H2O (EtPO) system did not alter the first‐order kinetic extraction model, but it improved the kinetic constant and boosted the partition coefficient from 36.7 to 58.8. For both EtPO and EtPO–EA systems, both the extraction yields and partition coefficients increased when temperature increased from 11 to 37 °C. The optimized EtPO–EA system demonstrated higher extraction yield than EtPO and 70% (v/v) ethanol systems by 25.4 and 19.5%, respectively.ConclusionsThe hydrophobicity of an ATPS was successfully tuned with cosolvent for paeonol extraction. The cosolvent–salt–water two‐phase systems are promising in extraction of weakly polar components from herbs. © 2019 Society of Chemical Industry

Using solubility parameter analysis to understand delignification of poplar and rice straw with catalyzed organosolv fractionation processes

Biomass fractionation is important for the further conversion of the cellulosic fraction and the effective utilization of the lignin fraction for the production of biofuels and value-added products. Solvent properties play a crucial role on the fractionation efficiency of lignocellulosics using an organosolv fractionation process catalyzed by acidic ionic liquids (AILs). Herein, 12 organic solvents were selected as co-solvents with water based on their solubility parameters for lignin dissolution, including alcohols, alcohol ethers, lactones, and alkanolamines, in order to fractionate poplar and rice straw. Effects of fractionation liquor solubility parameters on the delignification efficiency of organosolv fractionation were investigated under the same conditions. Relative energy differences (REDs) of the co-solvent systems for lignin dissolution were closely related to the degree of delignification with adjusted coefficients of determination of 0.899 and 0.800 for poplar and rice straw processes, respectively. The application of solubility parameter analysis may provide a rational way to screen solvent or co-solvent fractionation systems for biomass fractionation process.

Investigation of robustness for supercritical fluid chromatography separation of peptides: Isocratic vs gradient mode

We investigated and compared the robustness of supercritical fluid chromatography (SFC) separations of the peptide gramicidin, using either isocratic or gradient elution. This was done using design of experiments in a design space of co-solvent fraction, water mass fraction in co-solvent, pressure, and temperature. The density of the eluent (CO2-MeOH-H2O) was experimentally determined using a Coriolis mass flow meter to calculate the volumetric flow rate required by the design. For both retention models, the most important factor was the total co-solvent fraction and water mass fraction in co-solvent. Comparing the elution modes, we found that gradient elution was more than three times more robust than isocratic elution. We also observed a relationship between the sensitivity to changes and the gradient steepness and used this to draw general conclusions beyond the studied experimental system.To test the robustness in a practical context, both the isocratic and gradient separations were transferred to another laboratory. The gradient elution was highly reproducible between laboratories, whereas the isocratic system was not. Using measurements of the actual operational conditions (not the set system conditions), the isocratic deviation was quantitatively explained using the retention model. The findings indicate the benefits of using gradient elution in SFC as well as the importance of measuring the actual operational conditions to be able to explain observed differences between laboratories when conducting method transfer.

Thermodynamics of 1-ethyl-3-methylimidazolium methylsulfate co-solvent mixtures using molecular dynamics simulation

In the present work, isothermal-isobaric (NPT) and canonical (NVT) ensemble molecular dynamics (MD) simulations have been used to calculate the binary mixture properties (excess molar heats and volumes) of 1-ethyl-3-methylimidazolium methyl sulfate [EMIM][MeSO4] with six polar covalent molecules (acetic acid, acetone, chloroform, dimethyl sulfoxide, isopropyl alcohol and methanol) over the entire composition range. Excess partial molar properties as a function of mole fraction of co-solvent were calculated by using a Redlich-Kister expansion equation. The excess molar heats and volumes for [EMIM][MeSO4] with all the six co-solvents were all negative over the entire composition range. The size and structure of these molecules, as well as the nature of interaction between the mixture components seems to play a major role in the observed effects. These results have been interpreted in terms of hydrogen bonding and intermolecular interactions between ionic liquid ions and co-solvent molecules via radial distribution functions. The results showed that hydrogen bond interactions between ionic liquid and co-solvents play a major role in the volumetric and energetic properties of the mixtures. Further, radial distribution functions suggest that ionic liquid ions aggregate at higher concentrations of co-solvents.

Multicomponent inverse modeling of supercritical fluid extraction of carotenoids, chlorophyll A, ergosterol and lipids from microalgae

The fundamentals of analyte extractable fraction, solubility, partitioning and mass transfer resistance in supercritical fluid extraction were studied using inverse modeling. These phenomena are essential for understanding, predicting and optimizing the supercritical fluid extraction process. Carotenoids, chlorophyll A, ergosterol and total lipids were extracted from the microalgae Chlorella sp. The analytes were measured continuously in-line and on-line using UV/Vis absorption spectroscopy measurements and by evaporative light scattering detection. Various pressures, temperatures, flow rates and fractions of ethanol as a co-solvent were evaluated. The extractable fraction of carotenoids, chlorophyll A and total lipids were dependent on the co-solvent fraction in the extraction phase. The additional amount that could be extracted by using more co-solvent followed a normal distribution, indicating that analytes should not simply be categorized into weakly or strongly bound. The characteristics of diminishing extraction rates over time was accounted for by analyte partitioning rather than intra-particle diffusion limitations.

Equilibrium solubility and preferential solvation of 1,1′-sulfonylbis(4-aminobenzene) in binary aqueous solutions of n -propanol, isopropanol and 1,4-dioxane

Abstract The equilibrium solubility of 1,1′-sulfonylbis(4-aminobenzene) (dapsone) in neat solvents of n-propanol, isopropanol 1,4-dioxane and water and in cosolvent mixtures of n-propanol + water, isopropanol + water and 1,4-dioxane + water were determined experimentally by the saturation shake-flask method within the temperature range from 278.15 K to 323.15 K under atmospheric pressure of 101.0 kPa. The mole fraction solubility of dapsone increased with increasing temperature and mass fraction of cosolvent in each binary system. At the same temperature and mass fraction of the organic solvent, the solubility of dapsone was greater in (1,4-dioxane + water) than in the other two cosolvent mixtures. The type and extent of solvent effect was analyzed by KAT-LSER approach. The obtained solubility was mathematically represented by using the Jouyban-Acree model, van’t Hoff-Jouyban-Acree model and Apelblat-Jouyban-Acree model obtaining average relative deviations lower than 4.88% and root-mean-square deviation lower than 5.86 × 10−4 for correlative studies. Positive values of the apparent dissolution enthalpy illustrated that the dissolution process of dapsone in these mixed solvents was endothermic. Furthermore, the preferential solvation parameters were derived from their thermodynamic solution properties by means of the inverse Kirkwood–Buff integrals. The preferential solvation parameters for n-propanol, isopropanol or 1,4-dioxane (δx1,3) were negative in water-rich mixtures but positive in compositions from 0.24 (0.19, 0.18) in mole fraction of n-propanol (isopropanol or 1,4-dioxane) to neat n-propanol (isopropanol or 1,4-dioxane). It was conjecturable that in former case the hydrophobic hydration around phenyl groups could play a more relevant role than hydrophilic hydration.