Measured Partition Coefficients Research Articles

In Situ Measurement of Thermodynamic Partitioning in Open Hydrogels.

Thermodynamic partitioning dictates solute loading and release from a hydrogel. Design of drug delivery vehicles, cell and tissue matrices, and immunoassay scaffolds that utilize hydrogel materials is informed by an understanding of the thermodynamic partitioning properties of those hydrogels. We develop aberration-compensated laser scanning confocal microscopy (AC-LSCM), a technique that can be applied to all fluorescence microscopy-based equilibrium partition coefficient measurements where the fluorescence is uniformly distributed in the reference material (e.g., many solutes in thermodynamic equilibrium). In this paper, we use AC-LSCM to measure spatially resolved in situ equilibrium partition coefficients of various fluorescently labeled solutes in single-layer and multilayer open hydrogels. In considering a dynamic material, we scrutinize solute interactions with a UV photoactive polyacrylamide gel that incorporates a benzophenone methacrylamide backbone. We observed strong agreement with an adjusted version of Ogston's ideal size-exclusion model for spatially resolved in situ equilibrium partition coefficients across a wide range of polyacrylamide hydrogel densities (R2 = 0.98). Partition coefficients of solutes differing in hydrodynamic radius were consistent with size-based theory in the photoactive hydrogels, but exceed those in unmodified polyacrylamide gels. This observation suggests a deviation from the size-exclusion model and a shift in the thermodynamic equilibrium state of the solutes toward the gel phase. AC-LSCM also resolves differential partitioning behavior of the model solute in two-layer gels, providing insight into the transport phenomena governing the partitioning in multilaminate gel structures. Furthermore, AC-LSCM identifies and quantifies depth-dependent axial aberrations that could confound quantitation, highlighting the need for the "aberration compensated" aspect of AC-LSCM.

Abraham model correlations for solute transfer into 2-methyl-2-butanol based on measured activity coefficient and solubility data at 298.15 K

Experimental infinite dilution activity coefficients, gas-to-liquid partition coefficients and mole fraction solubilities are reported for numerous liquid and solid organic compounds dissolved in 2-methyl-2-butanol at 298.15 K. Experimental values were determined using headspace chromatographic and spectroscopic methods of analysis. Abraham model correlations were developed by combining our measured values with solubility data gathered from the published chemical literature. The mathematical correlations that we have developed described the measured partition coefficient and solubility data to within 0.14 log units (or less).

Impact of matrix variables and expertise of panelists on sensory thresholds of 1,1,6-trimethyl-1,2-dihydronaphthalene known as petrol off-flavor compound in Riesling wines

1,1,6-Trimethyl-1,2-dihydronaphthalene (TDN) is known to elicit the perception of “petrol off-flavor” in wine, most prominent in the variety Riesling. This study was focused on the impact of matrix variables such as ethanol and carbonation on the odor detection threshold of TDN. Increasing carbonation nearly doubled the detection threshold in water, however, this effect could not be observed in alcoholic matrices. Ethanol enhanced detection thresholds presumably due to diminished volatilization, which was only partially supported by measurement of partition coefficients using GC–MS. Overall, the impact of matrix changes was small ranging from 1.1 µg/L in still water to 4.0 µg/L in Riesling sparkling wine. Consumer detection threshold of 14.7 µg/L TDN determined with 156 consumers exceeded the threshold of the trained panel by a factor of five and varied by consumers’ age and gender. Rejecting a Riesling wine due to its petrol off-flavor, 60 µg/L TDN were required in a young and 91 µg/L in an eight-year-old Riesling wine. Based on analytical data for more than 250 commercial Riesling wines, geographic origin and to a smaller extent wine age contributed to large differences in TDN concentrations. About half of the investigated wines exceeded the detection threshold of the trained panel, whereas consumers would have noticed TDN in only less than 15% of the Riesling wines. Merely 3% of the wines actually exceeded the consumer rejection threshold of TDN. For both, detection and consumer rejection thresholds, the applied methodology contributed considerably to the final values, which is discussed critically.

Investigating the Phospholipid Effect on the Bioaccessibility of Rosmarinic Acid-Phospholipid Complex through a Dynamic Gastrointestinal in Vitro Model.

Phyto-phospholipid complexes have been developed as a common way of improving the oral bioavailability of poorly absorbable phyto-pharmaceuticals; however, the complexation with phospholipids can induce positive or negative effects on the bioaccessibility of such plant-derived active ingredients in different parts of the gastrointestinal tract (GIT). The purpose of this study was to investigate the effects of phospholipid complexation on the bioaccessibility of a rosmarinic acid-phospholipid complex (RA-PLC) using the TNO dynamic intestinal model-1 (TIM-1). Preparation of RA-PLC was confirmed using X-ray diffraction, Fourier-transform infrared spectroscopy, partition coefficient measurement, and Caco-2 monolayer permeation test. Bioaccessibility parameters in different GIT compartments were investigated. Complexation by phospholipids reduced the bioaccessibility of RA in jejunum compartment, while maintaining the ileum bioaccessibility. The overall bioaccessibility of RA-PLC was lower than the unformulated drug, suggesting that the improved oral absorption from a previous animal study could be considered as a net result of decreased bioaccessibility overwhelmed by enhanced intestinal permeability. This study provides insights into the effects of phospholipid on the bioaccessibility of hydrophilic compounds, and analyzes them based on the relationship between bioaccessibility, membrane permeability, and bioavailability. Additionally, TIM-1 shows promise in the evaluation of dosage forms containing materials with complicated effects on bioaccessibility.

Characterization of the solubilizing ability of tetraalkylammonium ionic liquids containing a pendant alkyl chain bearing a basic N,N-dimethylamino or N,N-dimethylaminoethoxy functionality

Infinite dilution activity coefficients and gas-to-ionic liquid partition coefficients are reported for >40 different organic compounds dissolved in N-[2-(N′,N′-dimethylamino)ethyl]-N,N-(dimethyl)-1-propanaminium bis(trifluoromethylsufonyl)imide, N-[2-(N′,N′-dimethyl-amino)ethyl]-N,N-(dimethyl)-1-butanaminium bis(trifluoromethylsufonyl)imide, N-[2-(N′,N′-dimethylamino)ethoxyethyl]-N,N-(dimethyl)-1-propanaminium bis(trifluoromethylsufonyl)imide, and N-[2-(N′,N′-dimethylamino)ethoxyethyl]-N,N-(dimethyl)-1-butanaminium bis(trifluoromethylsufonyl)imide in the temperature range from 323.15K to 373.15K. Partial molar excess enthalpies and partial molar excess entropies of solution were calculated from the temperature dependence of the infinite dilution activity coefficient assuming a van't Hoff relationship. Abraham model ionic liquid-specific correlations were determined from the measured partition coefficients. The derived mathematical expressions described the observed partition coefficients to within a standard deviation of 0.14 log units (or less).

Synthesis of a novel copolymer of block polyether macromonomer and diallyldimethylammonium chloride and its reverse demulsification performance

Produced fluid from polymer flooding is a complicated mixture of water/crude oil emulsion and crude oil/water emulsion. During the treatment of produced fluid, both demulsifier and reverse demulsifier are added into the oil water separator and the function of reverse demulsifier is to reduce the oil content in crude oil/water emulsion for relieving the load of oily wastewater treatment. In this paper, a novel reverse demulsifier was prepared by copolymerization of block polyether macromonomer (PEP-65) and diallyldimethylammonium chloride (DM). Its synthesis condition was optimized by using three indexes including product stability, the effect on dehydration of water/crude oil emulsion and oil removal of crude oil/water emulsion. The best copolymer of PEP-65 and DM (PDMP) had no negative effect on the dehydration of water/crude oil emulsion and had a more than three times of oil removal of crude oil/water emulsion than that of commercial reverse demulsifier. In addition, measurement of partition coefficient, interfacial tension, interfacial dilational modulus and dual polarization interferometry (DPI) test were carried out for investigating the reverse demulsification properties of PDMP. We found that PDMP had better interface activity, higher interface adsorption mass and lower interfacial dilational modulus than that of commercial reverse demulsifier.

Generalized molecular solvation in non-aqueous solutions by a single parameter implicit solvation scheme.

In computer simulations of solvation effects on chemical reactions, continuum modeling techniques regain popularity as a way to efficiently circumvent an otherwise costly sampling of solvent degrees of freedom. As effective techniques, such implicit solvation models always depend on a number of parameters that need to be determined earlier. In the past, the focus lay mostly on an accurate parametrization of water models. Yet, non-aqueous solvents have recently attracted increasing attention, in particular, for the design of battery materials. To this end, we present a systematic parametrization protocol for the Self-Consistent Continuum Solvation (SCCS) model resulting in optimized parameters for 67 non-aqueous solvents. Our parametrization is based on a collection of ≈6000 experimentally measured partition coefficients, which we collected in the Solv@TUM database presented here. The accuracy of our optimized SCCS model is comparable to the well-known universal continuum solvation model (SMx) family of methods, while relying on only a single fit parameter and thereby largely reducing statistical noise. Furthermore, slightly modifying the non-electrostatic terms of the model, we present the SCCS-P solvation model as a more accurate alternative, in particular, for aromatic solutes. Finally, we show that SCCS parameters can, to a good degree of accuracy, also be predicted for solvents outside the database using merely the dielectric bulk permittivity of the solvent of choice.

Estimating n-octanol-water partition coefficients for neutral highly hydrophobic chemicals using measured n-butanol-water partition coefficients

Direct measurement of the n-octanol partition coefficients (KOW) for highly hydrophobic organic chemicals is extremely difficult because of the extremely low concentrations present in the water phase. n-Butanol/water partition coefficients (KBW) are generally much lower than KOW due to the increased solubility of solute in the alcohol saturated aqueous phase, and therefore become easier to measure. We measured the KBW for 25 neutral organic chemicals having measured log KOWs ranging from 2 to 9 and 4 additional highly hydrophobic chemicals, with unmeasured KOWs, having estimated log KOWs ranging from 6 to 18. The measured log KBW and log KOW values were linearly related, r2 = 0.978, and using the regression developed from the data, KOWs were predicted for the 4 highly hydrophobic chemicals with unmeasured KOWs. The resulting predictions were orders of magnitude lower than those predicted by a variety of computational models and suggests the estimates of KOW in the literature for highly hydrophobic chemicals (i.e., log KOW greater than 10) are likely incorrect by several orders of magnitude.

Assessment of VOC absorption in hydrophobic ionic liquids: Measurement of partition and diffusion coefficients and simulation of a packed column

Partition coefficients of toluene and dichloromethane (DCM) in 23 hydrophobic ionic liquids (ILs), which can be used potentially for the physical absorption of volatile organic compounds (VOCs), were measured at 298 K. The partition coefficients, expressed as Henry’s law constants, were 400–1300 times for toluene and 10–47 times for DCM lower in the selected ILs than in water. Thus, the toluene and DCM diffusion coefficients were measured in three high potential hydrophobic ILs and in [Bmim][NTf2] using a thermogravimetric microbalance. Diffusivity measurements were performed at 298 K for toluene and between 278 and 308 K for DCM. Diffusion coefficients in ILs, ranging between 1 and 4 × 10−11 m2 s−1, were from 18 to 90 times lower than in water at 298 K. The diffusion coefficients were correlated to the temperature, the solute molar volume, the IL viscosity and molar volume with an average error of 4.2%. Finally, a 3 m industrial packed column was simulated for the removal of DCM and toluene in [AllylEt2S][NTf2] and [bmim][NTf2], which both present moderate viscosities of nearly 50 mPa s at 293 K. The overall mass-transfer coefficient, the removal efficiency and the pressure drop were calculated and compared to those obtained using other heavy solvents (a silicon oil and di-(2-ethylhexyl) adipate). This prospective simulation has demonstrated a good potential of ionic liquids for the toluene removal. Nonetheless, the DCM removal efficiencies simulated were lower than 44%. It suggests that even more efficient ionic liquids can be tuned and synthesized in the future for this specific application.

Thermodynamic study of aqueous two-phase systems containing biocompatible cholinium aminoate ionic-liquids and polyethylene glycol di-methyl ether 250 and their performances for bovine serum albumin separation

Aqueous two-phase systems, ATPSs, are known as an interesting media for the separation and purification of vital biomolecules in biotechnology applications. From this viewpoint, the ambition of this work is investigating ability of cholinium aminoate ([Ch][AA]) as novel, low toxic and high biodegradable ionic liquids, including of cholinium glycinate ([Ch][Gly]), cholinium prolinate ([Ch][l-Pro]) and cholinium valinate ([Ch][l-Val]) for inducing ATPSs with polyethylene glycol di-methyl ether 250, PEGDME250, and then evaluating their performances for partitioning of bovine serum albumin, BSA, as a model protein. For achieving this purpose, binodal curves and tie-lines were experimentally measured at T = (298.15, 308.15 and 318.15) K under atmospheric pressure (≈85 kPa) for all of the aforementioned systems. The influences of ionic liquid anion and temperature were searched systematically on the binodal curve and tie-lines. The phase splitting ability in these systems was assessed by utilizing the effective exclude volume theory from which the locations of binodals may be predicted and the Setschenow-type equation which provides salting-out coefficients by fitting the experimental tie-lines to this equation. Two empirical equations including of Merchuk equation were applied in order to represent the binodal data. Moreover, the Othmer-Tobias and Bancraft, Osmotic virial equations and two versions of NRTL models (m- or e-NRTL) were selected to correlate the tie-lines. In addition, the partition behaviour of BSA was studied by measuring of partition coefficient and extraction efficiency in the mentioned systems. The measured partition coefficients for BSA were discussed on the basis of physiochemical properties of amino acids involved in ionic liquid structure.

Lipid, water, and protein composition to facilitate kinetic modeling of the auditory pathway

Environments combining JP-8 jet fuel exposure with heightened ambient noise may accelerate hearing loss induced by noise. To reduce animal use and facilitate kinetic modeling of this military aviation fuel, tissue-specific parameters are required, including water, protein, and lipid content. However, tissues involved in hearing, including cochlea, brainstem, frontal, and temporal lobe, have not been characterized before. Therefore, water content was determined by lyophilization of rat auditory tissues and the protein of the freeze dried remainder was quantified using a bicinchoninic acid assay. Lipids were extracted from fresh-frozen rat auditory tissues and separated into neutral lipids, free fatty acids, neutral phospholipids, and acidic phospholipids using solid phase extraction. Phospholipid fractions were confirmed by 31 P nuclear magnetic resonance analysis showing distinct phospholipid profiles. Lipid content in reference tissues, such as kidney and adipose, confirmed literature values. For the first time, lipid content in the rat auditory pathway was determined showing that total lipid content was lowest in cochlea and highest in brainstem compared with frontal and temporal lobes. Auditory tissues displayed distinct lipid fraction profiles. The information on water, protein, and lipid composition is necessary to validate algorithms used in mathematical models and predict partitioning of chemicals of future interest into these tissues. This research may reduce the use of animals to measure partition coefficients for prospective physiological models.

Detection of tris(2,3-dibromopropyl) phosphate and other organophosphorous compounds in Arctic rivers.

The flame-retardant tris(2,3-dibromopropyl) phosphate (TDBrPP) was in the 1970s banned for uses in textiles that may be in contact with the skin, owing to strong suspicions that the substance was a human carcinogen. The substance is looked for but rarely detected in samples from the built and natural environments, but there are indications that TDBrPP is still in use. Here, we report the measurement of a polymer-water partition coefficient (Kpw) for two types of silicone rubber (SR), allowing quantitative estimation of freely dissolved concentrations of TDBrPP by passive sampling in water. We found levels of 100 to 200pg/L in two Arctic rivers that were sampled during a 2014-2015 survey of contamination using passive samplers in Norwegian and Russian rivers draining into the Barents Sea. We also report the widespread presence of other organophosphorus flame retardants in this survey of eight rivers that drain into the Barents Sea.

Specifics of Non‐Specific Drug‐Membrane Interactions Affecting Drug Action and Disposition: Membrane Permeability, Location and Orientation

ObjectiveMembrane partitioning of drugs to a discrete energy favorable location, orientation, and conformation is critical for drug binding to membrane receptors such as GPCRs and ion‐channels, membrane‐bound enzymes such as cytochrome P450s, and efflux transporters such as P‐glycoprotein, affecting drug action and disposition. The location of nonspecific binding sites for a drug molecule within the membrane lipid bilayer have been shown to affect how that drug approaches its specific binding site on a membrane associated receptor; and thus knowledge of the orientation and conformation it adopts in the bilayer may be crucial in understanding its action at the binding site. The traditional methods for assessing the ‘lipophilicity’ of drugs such as measurement of partition coefficients in 1‐octanol/buffer system are inadequate for many drugs. The anisotropic bilayer structure, in contrast to an isotropic surrogate phases has very different physical and chemical characteristics as a function of distance along the bilayer normal axis, including higher surface‐to‐volume ratio. The process of drug partitioning within the membrane appears to exploit these differences in achieving an energetically favorable location, orientation, and conformation. Our previous study (Mol. Pharmaceutics, 2014, 11, 3577–3595) reported a good agreement between experimentally determined bilayer locations of 27 chemicals and that of predicted using a novel surrogate system containing hexadecane/diacetyl phosphatidylcholine (C16/DAcPC) that mimics the phospholipid bilayer more realistically than 1‐octanol/buffer system. This present study investigates the free energy of lipid bilayer partitioning, membrane location and orientation of these molecules using atomistic molecular dynamic simulations.MethodsThe membrane partitioning characteristics of the studied chemicals (the potential mean force, PMF along the bilayer normal, time average locations and orientations) were investigated in dimyristoyl phosphatidylcholine (DMPC) model membrane system by Umbrella Sampling molecular dynamic simulations, using GPU version of NAMD2.12. The model membrane system and chemicals were parameterized using the CHARMM36 and CGenFF force fields respectively.ResultsThe results from the PMF calculations and atomistic details of interactions from MD trajectory analysis revealed a close agreement with the predicted time‐average location and orientation for majority of the studied chemicals by the surrogate (C16/DAcPC) system. However, the assumption that molecules partition in extended conformation and thus consideration of only extended conformations in head/core interface poses resulted in erroneous omission of critical poses identified during MD for some compounds.ConclusionsThe obtained results from this study supports that the C16/DAcPC surrogate system accounts for majority of the drug‐membrane interactions and more closely mimic the phospholipid bilayer than the traditional systems. This study also reveals a critical deficiency in the existing interface pose generation method that warrants improvement, and suggests combining MD simulation as an essential tool for investigating membrane‐drug interactions.Support or Funding InformationWashington State UniversityThis abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.

FRET Detects the Size of Nanodomains for Coexisting Liquid-Disordered and Liquid-Ordered Phases

Biomembranes with as few as three lipid components can form coexisting liquid-disordered (Ld) and liquid-ordered (Lo) phases. In the coexistence region of Ld and Lo phases, the lipid mixtures 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC)/1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC)/chol or brain sphingomyelin (bSM)/DOPC/chol form micron-scale domains that are easily visualized with light microscopy. Although large domains are not observed in the mixtures DSPC/1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC)/chol and bSM/POPC/chol, lateral heterogeneity is nevertheless detected using techniques with nanometer-scale spatial resolution. We propose a simple and accessible method to measure domain sizes below optical resolution (∼200 nm). We measured nanodomain size for the latter two mixtures by combining experimental Förster resonance energy transfer data with a Monte-Carlo-based analysis. We found a domain radius of 7.5−10 nm for DSPC/POPC/chol, similar to values obtained previously by neutron scattering, and ∼5 nm for bSM/POPC/chol, slightly smaller than measurable by neutron scattering. These analyses also detect the domain-size transition that is observed by fluorescence microscopy in the four-component lipid mixture bSM/DOPC/POPC/chol. Accurate measurements of fluorescent-probe partition coefficients are especially important for the analysis; therefore, we exploit three different methods to measure the partition coefficient of fluorescent molecules between Ld and Lo phases.

Infinite Dilution Activity Coefficients and Gas-to-Liquid Partition Coefficients of Organic Solutes Dissolved in 1-Benzylpyridinium Bis(Trifluoromethylsulfonyl)Imide and 1-Cyclohexylmethyl-1-Methylpyrrolidinium Bis(Trifluoromethylsulfonyl)Imide

Infinite dilution activity coefficients and gas-to-ionic liquid partition coefficients were measured for a chemically diverse set of 48 or more organic solute probes dissolved in the ionic liquids 1-benzylpyridinium bis(trifluoromethylsulfonyl)imide ([BzPy][Tf2N]) and 1-cyclohexylmethyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide ([ChxmPyrr][Tf2N]) in the temperature range from 323.15 to 373.15 K using inverse gas chromatography. Selectivities and capacities for different separation problems were calculated from the measured chromatographic data. The measured partition coefficients were correlated using mathematical equations based on the Abraham general solvation parameter model. The derived Abraham model correlations back-calculated the observed partition coefficients to within 0.12 log10 units.

Measuring Partition Coefficient between Liquid-Disordered (LD) and Liquid-Ordered Phases. Why are Phase Diagrams Important to Know?

We study and exploit methods to measure the partition coefficient of fluorescent molecules between liquid-disordered (Ld) and liquid-ordered (Lo) phases in 3 or 4-components lipid mixtures. A trajectory is created of 60-70 different lipid composition samples along a thermodynamic tieline, and the fluorescence signal of a single probe is measured for each sample. To determinate the partition coefficient, the single dye fluorescence is fitted by a hyperbolic curve based on the fraction of Ld or Lo phase. Because self-quenching could disturb the fluorescence profile along the tieline, we develop a self-quenching correction and formulate an equation to account for this effect. Briefly, we first studied how the fluorescence self-quenching behaves for increased dye concentration. Then we applied this correction along the tieline, since the dye concentration and the self-quenching effects vary with the fraction of Ld and Lo phases. Without this correction for fluorescence self-quenching, significant partition coefficient errors can occur. We show experiments using different dye concentrations where our corrected equation conveys the same partition coefficient measurement. We tested dyes that favor Ld phase, TopFluorPC and C12:0DiI, and TopFluor Ceramide that favors the Lo phase. We also compare our results to partition coefficient measurements using giant unilamellar vesicles (GUVs). We call attention to how well-resolved phase diagrams can be crucial for any measurement of the partition coefficient.

Experimental partition determination of octanol-water coefficients of ferrocene derivatives using square wave voltammetry techniques

An electrochemical method based on square wave voltammetry was developed for the measurement of octanol-water partition coefficient, LogP, for ten ferrocene derivatives. Measured LogP values ranged over two orders of magnitude, between 2.18 for 1- ferrocenylethanol and 4.38 for ferrocenyl-2-nitrophenyl. The measured LogP values were compared with those obtained by theoretical calculations developed on the basis of the adaptation of the Rekker method. The correlation coefficient of 0.992 for the comparison of experimental LogP values with those obtained by theoretical calculations indicates an excellent agreement.Keywords: Partition coefficients, log P, ferrocene derivatives, square wave voltammetry.

Salt partitioning between water and high-pressure ices. Implication for the dynamics and habitability of icy moons and water-rich planetary bodies

Water-rich planetary bodies including large icy moons and ocean exoplanets may host a deep liquid water ocean underlying a high-pressure icy mantle. The latter is often considered as a limitation to the habitability of the uppermost ocean because it would limit the availability of nutrients resulting from the hydrothermal alteration of the silicate mantle located beneath the deep ice layer. To assess the effects of salts on the physical properties of high-pressure ices and therefore the possible chemical exchanges and habitability inside H2O-rich planetary bodies, we measured partitioning coefficients and densities in the H2O–RbI system up to 450 K and 4 GPa; RbI standing as an experimentally amenable analog of NaCl in the H2O-salt solutions. We measured the partitioning coefficient of RbI between the aqueous fluid and ices VI and VII, using in-situ Synchrotron X-ray Fluorescence (XRF). With in-situ X-ray diffraction, we measured the unit-cell parameters and the densities of the high-pressure ice phases in equilibrium with the aqueous fluid, at pressures and temperatures relevant to the interior of planetary bodies. We conclude that RbI is strongly incompatible towards ice VI with a partitioning coefficient Kd(VI-L)=5.0(±2.1)⋅10−3 and moderately incompatible towards ice VII, Kd(VII-L)=0.12(±0.05). RbI significantly increases the unit-cell volume of ice VI and VII by ca. 1%. This implies that RbI-poor ice VI is buoyant compared to H2O ice VI while RbI-enriched ice VII is denser than H2O ice VII. These new experimental results might profoundly impact the internal dynamics of water-rich planetary bodies. For instance, an icy mantle at moderate conditions of pressure and temperature will consist of buoyant ice VI with low concentration of salt, and would likely induce an upwelling current of solutes towards the above liquid ocean. In contrast, a deep and/or thick icy mantle of ice VII will be enriched in salt and hence would form a stable chemical boundary layer on top of the silicate mantle. Such a contrasted dynamics in the aqueous–ice VI–ice VII system would greatly influence the migration of nutrients towards the uppermost liquid ocean, thus controlling the habitability of moderate to large H2O-rich planetary bodies in our solar system (e.g., Ganymede, Titan, Calisto) and beyond.

Partitioning of Alkali Metal Salts and Boric Acid from Aqueous Phase into the Polyamide Active Layers of Reverse Osmosis Membranes.

The partition coefficient of solutes into the polyamide active layer of reverse osmosis (RO) membranes is one of the three membrane properties (together with solute diffusion coefficient and active layer thickness) that determine solute permeation. However, no well-established method exists to measure solute partition coefficients into polyamide active layers. Further, the few studies that measured partition coefficients for inorganic salts report values significantly higher than one (∼3-8), which is contrary to expectations from Donnan theory and the observed high rejection of salts. As such, we developed a benchtop method to determine solute partition coefficients into the polyamide active layers of RO membranes. The method uses a quartz crystal microbalance (QCM) to measure the change in the mass of the active layer caused by the uptake of the partitioned solutes. The method was evaluated using several inorganic salts (alkali metal salts of chloride) and a weak acid of common concern in water desalination (boric acid). All partition coefficients were found to be lower than 1, in general agreement with expectations from Donnan theory. Results reported in this study advance the fundamental understanding of contaminant transport through RO membranes, and can be used in future studies to decouple the contributions of contaminant partitioning and diffusion to contaminant permeation.

X線イメージングと蛍光X線分析を利用したFe-Cr-Ni-Mo合金の溶質分配係数のその場測定

X線イメージングと蛍光X線分析を利用したFe-Cr-Ni-Mo合金の溶質分配係数のその場測定