Aqueous Organic Mixtures Research Articles

Regulation of Molecular Microheterogeneity in Electrolytes Enables Ampere-Hour-Level Aqueous LiMn2O4||Li4Ti5O12 Pouch Cells.

Aqueous batteries are attractive due to their high safety and fast reaction kinetics, but the narrow electrochemical stability window of H2O limits their applications. It is a big challenge to broaden the electrochemical operation window of aqueous electrolytes while retaining fast reaction kinetics. Here, a new organic aqueous mixture electrolyte of manipulatable (3D)molecular microheterogeneity with H2O-rich and H2O-poor domains is demonstrated. H2O-poor domains molecularly surround the reformed microclusters of H2O molecules through interfacial H-bonds, which thus not only inhibit the long-range transfer of H2O but also allow fast and consecutive Li+ transport. This new design enables low-voltage anodes reversibly cycling with aqueous-based electrolytes and high ionic conductivity of 4.5 mS cm-1. LiMn2O4||Li4Ti5O12 full cells demonstrate excellent cycling stability over 1000 cycles under various C rates and a low temperature of -20°C. 1 Ah pouch cell delivers a high energy density of 79.3Wh kg-1 and high Coulombic efficiency of 99.4% at 1 C over 200 cycles. This work provides new insights into the design of electrolytes based on the molecular microheterogeneity for rechargeable batteries.

Shungite Paste Electrodes: Basic Characterization and Initial Examples of Applicability in Electroanalysis

This article introduces a new type of carbon paste electrode prepared from black raw shungite. In powdered form, this carbonaceous material was mixed with several nonpolar binders. The resulting shungite pastes were microscopically and electrochemically characterized. Mixtures of several pasting liquids with different contents of shungite powder were tested to select the optimal composition and compared with other types of carbon paste-based electrodes made of graphite and glassy carbon powder. In terms of physical and mechanical properties, shungite paste electrodes (ShPEs) formed a composite mass being like dense pastes from glassy carbon microspheres, having harder consistency than that of traditional graphitic carbon pastes. The respective electrochemical measurements with ShPEs were based on cyclic voltammetry of ferri-/ferro-cyanide redox pairs, allowing us to evaluate some typical parameters such as electrochemically active surface area, double-layer capacitance, potential range in the working media given, heterogeneous rate constant, charge-transfer coefficient, exchange current density, and open-circuit potential. The whole study with ShPEs was then completed with three different examples of possible electroanalytical applications, confirming that the carbon paste-like configuration with powdered shungite represents an environmentally friendly (green) and low-cost electrode material with good stability in mixed aqueous-organic mixtures, and hence with interesting prospects in electroanalysis of biologically active organic compounds. It seems that similar analytical parameters of the already established variants of carbon paste electrodes can also be expected for their shungite analogues.

Thermodynamic parameters of L-carnosine dissolution and solvation in binary aqueous-organic mixtures at T = 298.15 K.

Isothermal calorimetry was used to measure the enthalpies of L-carnosine digestion in aqueous solutions of acetonitrile (AN) 1,4-dioxane (DO), acetone (AC), dimethyl sulfoxide (DMSO), ethanol EtOH), 1-propanol (1-PrOH), and 2-propanol (2-PrOH). The values of ΔsolH° obtained were combined with the standard enthalpies of L-carnosine sublimation to obtain the corresponding enthalpies of solvation ΔsolvH°. In addition, the enthalpic coefficients of pairwise interactions (hxy) of L-carnosine with organic solvent molecules and the enthalpy of transfer (ΔtrH°) from water in their mixture with the latter were calculated. It is established that the solvation of L-carnosine is weakened in a series of (H2O + EtOH) > (H2O + 1-PrOH) > (H2O + 2-PrOH). This may be due to an increase in the hydrophobicity of alcohols of the same order as well as the presence of CH3-groups within the alcohol molecule. The weakening of the solvation energy of L-carnosine by co-solvent molecules in a series of mixed solvents: (H2O + AN) < (H2O + AC) < (H2O + DO) < (H2O + DMSO) is associated both with an increase in the hydration energy of co-solvents in the same order and with their physicochemical properties. The enthalpic coefficients of water-organic solvent pairwise interactions were discovered to be linearly related to the corresponding coefficients of L-carnosine-organic solvent interactions. An increase in the polarity and acidity of an organic solvent increases the energy of pairwise interactions between L-carnosine and the organic solvent. Increasing the cohesion energy density, molar volume, and basicity of the organic solvent reduces the energy of the pairwise interactions between L-carnosine and the organic solvent.

Features of the Solvation of Glycyl-l-alanine in Various Aqueous–Organic Mixtures at T = 298.15 K

Features of the Solvation of Glycyl-<scp>l</scp>-alanine in Various Aqueous–Organic Mixtures at <i>T</i> = 298.15 K

Combination of Natural Deep Eutectic Solvents and Nano-Liquid Chromatography towards White Analytical Chemistry: A Practical Application

In this work, a green and practical analytical method based on natural deep eutectic solvents (NADES) as extraction agents and nano-liquid chromatography as a separation technique was developed. To demonstrate the applicability of the methodology, alkylphenols and bisphenol A were evaluated as model compounds in olive and sunflower oils as model fatty samples by liquid–liquid microextraction. With this aim, several NADES based on mixtures of choline chloride with glycerol, lactic, ascorbic, and citric acids or glycerol with amino acids were evaluated as potential extraction solvents. In addition, to select the most suitable stationary phase for the separation of this group of contaminants, some stationary phases were tested, including Pinnacle II phenyl, Cogent Bidentate C18™, and XBridge® C18. The last one provided the best performance with an analysis time of 11 min. To solve the problem of the compatibility of hydrophilic NADES with chromatographic systems without harming the solubility of analytes, different aqueous organic mixtures were tested. Methanol/water mixtures were the most suitable as an injection solvent. Finally, following the White Analytical Chemistry principles, different tools were used to evaluate the greenness, the practicality, and applicability of the method based on the Analytical Eco-Scale, the Analytical GREEnness metric approach, and the Blue Applicability Grade Index.

Exploring solubility and energetics: Dissolution of biologically important l-threonine in diverse aqueous organic mixtures across the temperature range of 288.15 K to 308.15 K

This research provides a thorough investigation into the solubility behavior and solution thermodynamics of l-threonine in significant organic solvent systems. The work was done on measuring the actual solubility and subsequently calculating overall transfer solvation free energetics (∆Genergetic0i) and transfer entropies (∆St0i) at a temperature of 298.15 K. These measurements were performed as l-threonine transitioned from water to different water-organic mixed solvents systems. The saturated solubilities of l-threonine were determined using the ‘gravimetric method’ at five equidistant temperatures namely 288.15 K, 293.15 K, 298.15 K, 303.15 K and 308.15 K. By analyzing the data on solubility, we further obtained the different energies involved in solvation related issues. In the case of single solvents, the nature of solubility of l-threonine was observed like: dimethylsulfoxide (DMSO) < acetonitrile (ACN) < N, N-dimethylformamide (DMF) < ethylene glycol (EG) < water (H2O), irrespective of the experimental conditions. Specifically, at 298.15 K, the solubilities of l-threonine in single solvents were found to be as follows: 0.8220 mol per kg of water, 0.3101 mol per kg of EG, 0.1337 mol per kg of DMF, 0.1107 mol per kg DMSO and 0.1188 mol per kg of ACN. This research critically examines the relationship between the experimental saturated solubility of l-threonine and the complex properties influencing its solvation energy in diverse aqueous organic solvent systems.

Zwitterion-neutral form equilibria and binding selectivity of pyridineboronic acids.

A 11B NMR study of 3-pyridineboronic acid at variable pH in water and 50 vol% aqueous dioxane confirms that the tautomeric equilibrium of the acid is shifted to the zwitterionic form in water, but to the molecular form in the mixed organic solvent. Interactions of 3- and 4-pyridineboronic acids with sialic acid, fructose and several other diols were studied by potentiometric titrations in a wide range of pH in water and water-organic mixtures. In all reaction media the stability of boronate complexes increases upon an increase in pH for neutral low acidic diols such as fructose and glucose but has the opposite trend for highly acidic sialic and lactic acids occurring as anionic species. The selectivity of pyridineboronic acids to sialate anions in an acidic medium is interpreted quantitatively by combining the pH-profiles with Brønsted type correlations for binding constants. In addition, mathematical expressions allowing one to predict the optimum pKa value of a boronic acid for the strongest binding of a given diol (sialic acid or fructose) at a given pH are suggested. The shifts in the tautomeric equilibrium induced by changing the solvent polarity in aqueous-organic mixtures are manifested in the magnitude of relative shifts of pKa of pyridineboronic acids induced by diol complexation.

On the interpretation of the unusual behavior of aqueous-organic mixtures in concentration regions with intersecting isotherms of heat capacity properties

Based on our own and some literature results, we have carried out a detailed analysis of concentration regions of the aqueous-organic mixture in which the temperature dependences of both excess molar heat capacity, CpE, and apparent molar heat capacity of each component, Cp,ϕ,i, are intersected. It is established that the ∂CpE/∂T and ∂Cp,ϕ,w/∂Tderivatives (W is water) for the {(W + hexamethylphosphoramide (HMPA)} and {(W + tert‑butanol (t-BuOH)} mixtures intersect in a rather narrow concentration interval between (0.30 and 0.35) and (0.35 and 0.40) mole fractions of the organic component, respectively. This fact we have interpreted as evidence that the decisive role in the mutually overlapping heat-capacity contributions to CpEresulting in such a situation plays the abnormal change in the isobaric molar heat capacity of W (Cp,w), which has a minimum at T ≈ 308 K, when the temperature increases.

Estimating evaporation rates and contaminant air concentrations due to small spills of non-ideal aqueous organic solvent mixtures in a controlled environment

Although small spills of non-ideal organic solvent mixtures are ubiquitous undesirable events in occupational settings, the potential risk of exposure associated with such scenarios remains insufficiently investigated. This study aimed to examine the impact of non-ideality on evaporation rates and contaminant air concentrations resulting from small spills of organic solvent mixtures. Evaporation rate constants alphas (α) were experimentally measured for five pure solvents using a gravimetric approach during solvent evaporation tests designed to simulate small spills of solvents. Two equations were used for estimating contaminants’ evaporation rates from aqueous mixtures assuming either ideal or non-ideal behavior based on the pure-chemical alpha values. A spill model also known as the well-mixed room model with exponentially decreasing emission rate was used to predict air concentrations during various spill scenarios based on the two sets of estimated evaporation rates. Model predictive performance was evaluated by comparing the estimates against real-time concentrations measured for the same scenarios. Evaluations for 12 binary non-ideal aqueous mixtures found that the estimated evaporation rates accounting for the correction by the activity coefficients of the solvents (median = 0.0318 min−1) were higher than the evaporation rates estimated without the correction factor (median = 0.00632 min−1). Model estimates using the corrected evaporation rates reasonably agreed with the measured values, with a median predicted peak concentrations-to-measured peak concentrations ratio of 0.92 (0.81 to 1.32) and a median difference between the predicted and the measured peak times of −5 min. By contrast, when the non-corrected evaporation rates were used, the median predicted peak concentrations-to-measured peak concentrations ratio was 0.31 (0.08 to 0.75) and the median difference between the predicted and the measured peak times was +33 min. Results from this study demonstrate the importance of considering the non-ideality effect for accurately estimating evaporation rates and contaminant air concentrations generated by solvent mixtures. Moreover, this study is a step further in improving knowledge of modeling exposures related to small spills of organic solvent mixtures.

Photophysical properties and aggregation behavior of diethylene glycol substituted pyropheophorbide-a in cationic surfactant solutions

The aggregation behavior of a novel amphiphilic photosensitizer - pyropheophorbide-[Formula: see text] 17-diethylene glycol ester 1 was studied in aqueous and aqueous-organic mixtures by means of steady-state absorption and fluorescence emission spectroscopy. The formation of [Formula: see text]-aggregates with a bathochromic shift of the absorption bands, weak fluorescence and resonance enhancement of the light scattering was observed in the mixed water-organic solvents. Solubilization studies in micellar cationic surfactant solutions of alkyl trimethylammonium bromides (C[Formula: see text]TAB) and alkyl triphenylphosphonium bromides (C[Formula: see text]TPPB) resulted in the most effective stabilization of the fluorescent monomolecular form of 1 in C[Formula: see text]TPPB micelles. It was shown that [Formula: see text]-aggregate formation in submicellar surfactant solutions is the initial stage of the solubilization process, which significantly increases in phosphate buffer medium at pH 7.4. Fluorescence lifetime ([Formula: see text] of 1 in DMSO was found to be 7.4 ns, fluorescence quantum yield - 34% and singlet oxygen quantum yield - 62%. The results obtained indicate the need for further studies of compound 1 solubilized in C[Formula: see text]TPPB micelles as the most promising prototype of the drug formulation for mitochondria-targeted photodynamic therapy of cancer.

Robust Nanoparticle-Derived Lubricious Antibiofilm Coating for Difficult-to-Coat Medical Devices with Intricate Geometry.

A major medical device-associated complication is the biofilm-related infection post-implantation. One promising approach to prevent this is to coat already commercialized medical devices with effective antibiofilm materials. However, developing a robust high-performance antibiofilm coating on devices with a nonflat geometry remains unmet. Here, we report the development of a facile scalable nanoparticle-based antibiofilm silver composite coating with long-term activity applicable to virtually any objects including difficult-to-coat commercially available medical devices utilizing a catecholic organic-aqueous mixture. Using a screening approach, we have identified a combination of the organic-aqueous buffer mixture which alters polycatecholamine synthesis, nanoparticle formation, and stabilization, resulting in controlled deposition of in situ formed composite silver nanoparticles in the presence of an ultra-high-molecular-weight hydrophilic polymer on diverse objects irrespective of its geometry and chemistry. Methanol-mediated synthesis of polymer-silver composite nanoparticles resulted in a biocompatible lubricious coating with high mechanical durability, long-term silver release (∼90 days), complete inhibition of bacterial adhesion, and excellent killing activity against a diverse range of bacteria over the long term. Coated catheters retained their excellent activity even after exposure to harsh mechanical challenges (rubbing, twisting, and stretching) and storage conditions (>3 months stirring in water). We confirmed its excellent bacteria-killing efficacy (>99.999%) against difficult-to-kill bacteria (Proteus mirabilis) and high biocompatibility using percutaneous catheter infection mice and subcutaneous implant rat models, respectively, in vivo. The developed coating approach opens a new avenue to transform clinically used medical devices (e.g., urinary catheters) to highly infection-resistant devices to prevent and treat implant/device-associated infections.

Recovery and Enrichment of Organic Acids from Kraft Black Liquor by an Adsorption-Based Process

Kraft black liquor (BL) is a complex multicomponent byproduct from wood pulping processes. After lignin, carbohydrate-derived carboxylic acids are the second most abundant class of organics in kraft BL and comprise a potential biomass-derived feedstock of more than 50 million tons/year globally. These acids can be valorized in biofuels and biobased chemicals production or further fractionated to produce specific high-value carboxylic acids from the mixture. However, both of these routes require a viable process to separate carboxylic acids from BL. In this work, an adsorption-based process was developed to address this challenging issue. The kraft BL stream was first pretreated to remove most of the lignin by membrane nanofiltration (NF) combined with lignin-selective adsorption. To separate organic acids from this pretreated BL, organophilic/hydrophobic granulated activated carbon (GAC) was identified as a promising adsorbent with excellent organic/inorganic selectivity and adsorption capacity (>100 mg/g GAC). We present comprehensive adsorption measurements and analysis to characterize the adsorbent and develop a viable cyclic operation scheme for the adsorption process. The GAC adsorbents show robust separation performance over 20+ cycles. We have successfully obtained concentrated aqueous organic acid mixtures with ∼95% purity from kraft BL. We propose a modified kraft process with energy-efficient BL dewatering by NF and organic acids recovery for valorization.

Extraction of anabolic steroids with aqueous-organic mixtures from hexanic solutions

The extraction of anabolic steroids (1,4-androstadiene-3,17-dione; 17α-methyltestosterone; 19-norethiocholanolone; 4-hydroxytestosterone; 4-androstene-3,17-dione; 5α-androstane-3β,17β-diol; dehydroepiandrosterone; calusterone; clostebol; methandienone; methyldienolone; nandrolone; testosterone; epitestosterone; tibolone; 19-norandrostenedione; 1-methylene-5α-androstan-3α-ol-17-one) by aqueous-organic mixtures from hexane solutions was studied at the temperature (20 ± 1) °C. Based on the experimental data obtained, the partition ratios of anabolic steroids were calculated, which were used to optimise the standard sample preparation procedure in the process of determining the compounds under study in biologically active dietary supplements and specialised sports nutrition. It was found that the most effective and selective extractants from hydrocarbon solutions are water-acetonitrile mixtures containing from 10 to 20 % by volume of water. An extraction technique has been developed for sample preparation of biologically active dietary supplements for subsequent gas chromatographic determination of anabolic steroids in them using a triple quadrupole mass spectrometric detector. The proposed method is characterised by a standard deviation of 10–15 % and a detection limit about 10 μg/kg of biologically active dietary supplements, which makes it possible to reliably determine impurities of prohibited anabolic steroids in them.

Fluoroaromatic 2H-imidazole-based push-pull fluorophores: Synthesis, theoretical studies, and application opportunities as probes for sensing the pH in saliva

A series of novel push-pull fluorophores based on 2H-imidazole scaffold bearing perfluorophenyl substituent and extended electron-donating conjugating π-system were synthesized. In particular, the Pd-catalyzed Suzuki-Miyaura coupling reactions were exploited as a main synthetic strategy to modify 4-(4-bromophenyl)-2,2-dimethyl-5-(pentafluorophenyl)-2H-imidazole with various electron-donating functionalities. The comprehensive photophysical studies were carried out for the synthesized fluorophores, including the analysis of absorbance and emission spectra and determination of absolute quantum yields. The designed compounds were found to have a strong emission in the range of 470–610 nm depending on both the nature of solvent used and the structure of electron-donating group attached to the aryl moiety. The pH effect of the aqueous-organic mixture buffer solution on the fluorescent characteristics of the synthesized compounds was established and the deprotonation-induced “turn-on” pH sensing mechanism supported by DFT calculations was proposed for the first time. Particularly, the sequence of deprotonation was confirmed, and free energies for all N-protonated and N-proton-free forms were calculated. No toxic effect on the human embryonic kidney cells (HEK-293) at concentration of ≤512 μM was observed in vitro experiments. In addition, new opportunities for the practical application of these molecular ensembles were demonstrated in case of fluorometric determination of the pH both in model solutions and real saliva probes, with 3-(4-(2,2-dimethyl-5-(pentafluorophenyl)-2H-imidazole-4-yl)phenyl)-9-phenyl-9H-carbazole being used.

A facile online multi-gear capacitively coupled contactless conductivity detector for an automatic and wide range monitoring of high salt in HPLC.

Sensing the electrolyte solution or aqueous-organic mixture has attracted much interest in chemical separation, pharmaceutical engineering, bioprocess, and biochemical experiments. However, reports on online contactless sensor with automatic and wide range sensing of high content electrolyte have been rarely presented. Herein, a facile model and theory of online multi-gear capacitively coupled contactless conductivity detection (M-C4D) sensor was proposed using one excitation electrode and multiple detection electrodes. Further, the relevant digital computation based on the M-C4D theory was developed for parameter optimization: the electrode gap of 5-150 mm, inner radius of 0.25-0.75 mm, electrode length of 10-60 mm, and frequency of 40-250 kHz using MATLAB. To demonstrate the model, theory, and digital computation, liquid chromatography (LC) was chosen as the model of bioprocess, and the sensor was designed and used as an online sensing device for the automatic monitoring of high salt elution in LC. The experiments showed that (i) the detection results were in agreement with the digital data, validating the digital computation, theory, and model of M-C4D and (ii) the monitoring data of M-C4D were in agreement with those via the traditional meter, further validating the model and theory. Finally, the developed sensor was applied to the automated detection of high salt gradient in LC. In contrast to the currently used meters and C4D, the developed M-C4D sensor had the following merits: (i) facile and automatic online detection avoiding cumbersome manual switching of detector heads, (ii) fair linear range of 0.015-20 mS cm-1 (equivalently 0.1-159 mM KCl) that does not fit the range of traditional C4D, and (iii) fair accuracy of less than 1.50% relative error. All these results indicate that the developed model, theory, and sensor have potential for the process monitoring of high content electrolytes transfer in biochemical engineering and clinic pre-warning.

Smart supramolecular photoresponsive gelator with long-alkyl chain azobenzene incorporated sugar derivatives for recycling aromatic solvents and sequestration of cationic dyes.

Phase-selective gelation of low molecular-weight photoresponsive organogelator possessing long aliphatic chain azobenzene sugar derivatives and its applications in the recycling of aromatic solvents and also the removal of cationic dyes is reported. Very low critical gelation concentration (CGC) in aromatic solvents implies that it acts as a very good gelator. The photoinduced gel-to-sol transition was attained by irradiation with UV light at 350 nm. These organogels work as a selective adsorbent for efficiently removing cationic dyes from individual aqueous dye solutions and in a mixture of cationic and anionic dye solutions show more than 95% removal within 12 h. These insights indicate that these sugar derivatives could be exploited in implementing smart materials for environmental remediation.

Entropy Effects in Intermolecular Associations of Crown-Ethers and Cyclodextrins with Amino Acids in Aqueous and in Non-Aqueous Media.

The analysis of the ratios of entropy and enthalpy characteristics and their contributions to the change in the Gibbs energy of intermolecular interactions of crown ethers and cyclodextrins with amino acids is carried out. Two different types of macrocycles were chosen for examination: crown ethers with a hydrophilic interior and cyclodextrins with a hydrophobic inner cavity and a hydrophilic exterior. The thermodynamics of complex formation of crown ethers and cyclodextrins with amino acids in water and aqueous-organic solvents of variable composition was examined. The contributions of the entropy solvation of complexes of 18-crown-6 with glycine, alanine, phenylalanine to the change in the entropy of complexation in water-ethanol and water-dimethyl sulfoxide solvents was calculated and analyzed. It was found that the ratios of the entropy and enthalpy solvation of the reagents for these systems have similar trends when moving from water to aqueous-organic mixtures. The relationship between the thermodynamic characteristics and structural features of the complexation processes between cyclodextrins and amino acids has been established. The thermodynamic enthalpy–entropy compensation effect was revealed, and its features for complexation of cyclodextrins and 18-crown-6 were considered. It was concluded that, based on the thermodynamic parameters of molecular complexation, one could judge the mode of the formation of complexes, the main driving forces of the interactions, and the degree of desolvation.

Garland, Flower, and Petals via a Hierarchical Self-Assembly of Ursane-Type Triterpenoid Uvaol.

Uvaol, a 6-6-6-6-6 pentacyclic dihydroxy ursane-type triterpenoid, is isolable from different parts of plants Plumeria rubra, Olea europaea, Nerium oleander, Lavandula pedunculta, and Malus domestica. It is also obtained by a one-step reduction of naturally occurring triterpenoid ursolic acid. Herein, we report the first self-assembly properties of uvaol in different neat organic liquids and aqueous organic binary liquid mixtures. Spontaneous self-assembly of uvaol in different neat liquids and binary liquid mixtures yielded garland, flower, and petal-like porous superstructures of nano- to micrometer dimensions. Utilization of self-assemblies has been demonstrated in generation of anticancer drug conjugates and the removal of carcinogenic and toxic chemicals.

Recent Advances of Pervaporation Separation in DMF/H2O Solutions: A Review.

N,N-dimethylformamide (DMF) is a commonly-used solvent in industry and pharmaceutics for extracting acetylene and fabricating polyacrylonitrile fibers. It is also a starting material for a variety of intermediates such as esters, pyrimidines or chlordimeforms. However, after being used, DMF can be form 5–25% spent liquors (mass fraction) that are difficult to recycle with distillation. From the point of view of energy-efficiency and environment-friendliness, an emergent separation technology, pervaporation, is broadly applied in separation of azeotropic mixtures and organic–organic mixtures, dehydration of aqueous–organic mixtures and removal of trace volatile organic compounds from aqueous solutions. Since the advances in membrane technologies to separate N,N-dimethylformamide solutions have been rarely reviewed before, hence this review mainly discusses the research progress about various membranes in separating N,N-dimethylformamide aqueous solutions. The current state of available membranes in industry and academia, and their potential advantages, limitations and applications are also reviewed.

Unified pH Measurements of Ethanol, Methanol, and Acetonitrile, and Their Mixtures with Water

Measurement of pH in aqueous-organic mixtures with different compositions is of high importance in science and technology, but it is, at the same time, challenging both from a conceptual and practical standpoint. A big part of the difficulty comes from the fundamental incomparability of conventional pH values between solvents (spH, solvent-specific scales). The recent introduction of the unified pH (pHabs) concept opens up the possibility of measuring pH, expressed as , in a way that is comparable between solvent, and, thereby, removing the conceptual problem. However, practical issues remain. This work presents the experience of the authors with measuring values in mixtures of methanol, ethanol, and acetonitrile, with water, but without the presence of buffers or other additives. The aim was to assigned values to solvent–water mixtures using differential potentiometry and the ‘pHabs-ladder’ method. Measurements were made of the potential difference between glass electrodes immersed in different solutions, separated by an ionic liquid salt bridge. Data were acquired for a series of solutions of varying solvent content. This work includes experiences related to: a selection of commercial electrodes, purity of starting material, and comparability between laboratories. Ranges of values for selected compositions of solvent–water mixtures are presented.