Physicochemical Properties Of Aqueous Solutions Research Articles

Modulation of physical properties of microfluidized whey protein fibrils with chitosan

There is an increasing market for food and beverage products enriched in proteins and dietary fibers due to their potential health benefits. In this study, the effect of heating (85 °C, 20 min), microfluidization (20,000 psi), and pH (2 to 6.5) on the physicochemical properties of aqueous solutions containing mixtures of whey protein fibrils (7.5%; WPF) and chitosan (0.5%; CN) were examined. Heating of the mixed systems increased their turbidity and apparent viscosity, which was attributed to the formation of protein-rich particles. Interestingly, heating the mixed systems and then applying microfluidization led to phase separation and a lower apparent viscosity, which was attributed to high-pressure disruption of the whey protein fibrils. The pH of the systems significantly influenced their appearance, turbidity, particle size, and apparent viscosity, with high turbidity and viscosity, and large particle size occurring from pH 3.5 to 5.5. These effects were attributed to protein aggregation close to its isoelectric point (pH 5) coupled with electrostatic attraction between anionic groups on the whey protein and cationic groups on the chitosan. The addition of chitosan increased the net isoelectric point from pH 5 for pure whey protein to pH 6 for the mixed system. Overall, this study showed that the appearance and rheological properties of protein-dietary fiber mixtures could be manipulated by heating, microfluidization, and pH adjustment. This information may be useful for designing protein and fiber enriched food and beverage products with desirable physical and sensory properties.

Physicochemical Properties of Aqueous Solutions of Binary Mixtures of Lignin Derivatives and Sodium Dodecyl Sulfate

Physicochemical properties of aqueous solutions of binary mixtures of lignosulfonates and sodium dodecyl sulfate were studied. Introduction of sodium dodecyl sulfate into solutions of high-molecular-mass lignosulfonates at certain ratios causes macrophase separation of the systems with the formation of loose precipitates. A synergistic effect of a decrease in the surface tension is observed in the mixed solutions. This effect increases with increasing lignosulfonate molecular mass and temperature. The revealed relationships are caused by hydrophobic interactions of hydrocarbon radicals of sodium dodecyl sulfate with hydrophobic segments of lignosulfonate polymer chains with the formation of micellar associates. Aqueous solutions of binary mixtures of lignosulfonates (сLS ≥ 0.2 g dm–3) and sodium dodecyl sulfate (сDSNa ≥ 0.08 g dm–3) can be recommended for use as surfactant formulations for high-temperature autoclave leaching of polymetal ores.

±Water: Demonstration of Water Properties, Depending on its Electrical Potential

The aim of this work is to demonstrate that the physicochemical properties of water depend on its electric charge (potential). It is also shown that the physico-chemical properties of aqueous solutions depend very much on the electric charge (potential) of the water on which these solutions are prepared.

Physicochemical properties of aqueous solutions of L-aspartic acid containing chitosan

Physicochemical properties of aqueous solutions of L-aspartic acid with and without addition of chitosan have been studied by conductometry, potentiometry, refractometry, tensiometry, and viscosimetry. It has been shown that aspartic acid molecules take a cyclic configuration stabilized by hydrogen bonds in aqueous solution at c > 0.04 g/dL (298 K). The interaction of chitosan with aspartic acid results in the formation of the polymeric salt that dissociates in aqueous solution to give chitosan polycation [~(NH3)+] and aspartate counterions. The addition of chitosan to solutions of L-aspartic acid results in progressive increase in the surface tension, absorbance, and refractive index as well as the change in hydrodynamic properties of the macromolecules. The polymeric salt exhibits polyelectrolyte properties in dilute aqueous solutions. The increase in temperature impairs the thermodynamic quality of the solvent for chitosan leading to the shrinkage of the polymer coils and, hence, to the decrease in the intrinsic viscosity of the system.

Determination of optimal conditions for electrodeposition of Tin(II) in the presence of Alizarin Red S.

A detailed physicochemical properties of aqueous solutions of alizarin red S − tin (II) chloride, has been thoroughly investigated by extensively exploring the effect of pH, concentration and temperature on the optimal conditions for the formation of tin (II)-alizarin red S (ARS-Sn II) complex. UV-Vis spectra, electrical conductivity and pH method were also used to characterize the final product. The stoichiometry of the reaction complex formation was determined via different referential methods. It was observed that, the reaction complex was formed when the concentrations were smaller than a certain limit (10−5 M). Adjusting the pH of the reaction (typically from 3.7 to 6.0) also resulted in the formation of the complex. The formed complex was highly stable in dark conditions (absence of sunlight) and at ambient temperature. Without the use of additives and by employing the investigated optimal conditions (i.e. pH: 5.0, i: 6 mA/cm2, t: 5 min, C: 0.1 M, d: 1.273 × 10−4 cm), electrodeposition of tin (II) was demonstrated to be successful.

Why physicochemical properties of aqueous solutions of various compounds are linearly interrelated

Analysis of physicochemical properties, such as water activity, osmotic coefficients, surface tension, viscosity, and relative permittivity, of aqueous solutions of different inorganic salts, organic compounds, and polymers shows that these properties are linearly interrelated and this interrelationship may be described as: Yi1(ci1)=k1+k2Yi2(ci2)+k3Yi3(ci3), where Yi1(ci1), Yi2(ci2), and Yi3(ci3) are properties of aqueous solutions of individual compounds 1, 2, and 3 at the same ith concentration i of each compound (ci1=ci2 = ci3); k1, k2, and k3 are constants. The relationship holds for various concentrations of compounds provided properties of aqueous solutions of the individual compounds are compared at the same concentration of each compound. Similar interrelationships are established also between different properties of aqueous solutions of any given compound. It is suggested that the reason for these relationships is that all physicochemical properties of aqueous solutions of any compound display different aspects and peculiarities of intermolecular water-water interactions affected by the presence of the compound, its nature, and concentration. The different types of water-water interactions in aqueous solutions may be quantified with the solvatochromic dyes. The solvent dipolarity/polarizability, π*, hydrogen bond donor acidity, α, and hydrogen bond acceptor basicity, β of water reported previously for aqueous solutions of organic compounds and polymers as well as those obtained for solutions of inorganic salts are linearly interrelated likely due to the cooperativity of intermolecular interactions in water. It is shown that any physicochemical property of aqueous solution of a given salt, organic compound, or polymer may be described by linear combination of two solvent features, π* and α, or in some cases by a single solvent feature. This fact explains the reason for the existence of the aforementioned linear interrelationships between the physicochemical properties of aqueous solutions of different compounds.

Protonation–deprotonation and structural dynamics of antidiabetic drug metformin

Since the late 1950s, metformin is the worldwide first-line pharmacologic treatment for type 2 diabetes. Beyond the fact that the mode of action of this drug has always been very difficult to elucidate, little is known about its physicochemical properties in aqueous solution. Herein, we focus on the protonation–deprotonation features of metformin by using jointly Raman scattering and theoretical calculations. Vibrational markers evidence the fact that within a wide pH interval extended at either side of the physiological one, i.e. ∼7±4, metformin is mainly monoprotonated. Although the biprotonated form appears as major population at very low pH values (<1.5), Raman markers of neutral species do not dominate even at very high pH values (>13), presumably because of the extreme basicity of metformin as described by recent NMR measurements. Density functional theory calculations using both explicit and implicit hydration models, have led to presume a possible coexistence of two possible monoprotonated forms in aqueous environment. In conclusion, the biophysical features of this molecule and the amount used in clinical practice might certainly explain the pleiotropic actions toward several targets where metformin could be a permanent cationic partner, a proton donor/acceptor, as well as a good candidate for stabilizing the so-called π→π interactions.

Lysine-based oligomeric surfactants with cyanuric chloride: synthesis and micellization properties

Two lysine-based oligomeric surfactants 2C12LyNa2 and 3C12LyNa3 were synthesized using cyanuric chloride and Ne-lauroyl-l-lysine. Their physicochemical properties of aqueous solutions were determined by surface tension and conductivity as well as dynamic light scattering (DLS) and transmission electron microscopy (TEM) measurements. From the results of surface tension and conductivity measurements, the critical micelle concentration decreases by one order of magnitude with increasing degree of oligomerization. 3C12LyNa3 and 2C12LyNa2 tend to form premicellar aggregates in solution at a sufficiently low concentration. In addition, their interface behaviors such as adsorption and micellization are reflected by parameters such as the minimum surface area per molecule (Amin), adsorption efficiency and effectiveness (pC20), maximum surface excess concentration (Γmax), and standard free energy for micellization and adsorption (ΔGmic∘, ΔGads°). The Amin value of 2C12LyNa2 and 3C12LyNa3 is two times that of the monomeric surfactant sodium Ne-lauroyl-l-lysine (C12LyNa). With increasing degree of oligomerization, pC20 increases, which follows the reverse order for ΔGmic° and ΔGads°. TEM results showed that C12LyNa forms slightly entangled rod-like micelles. 2C12LyNa2 and 3C12LyNa2 can self-assemble into regular spherical assemblies; DLS showed that with increasing degree of oligomerization for 2C12LyNa2 and 3C12LyNa3, the diameters of the spherical aggregates decrease and the hydrophobic interaction and hydrogen bonding become stronger.

Self-organization and physicochemical properties of aqueous solutions of the antibodies to interferon gamma at ultrahigh dilution

It has been recently shown that manifestation of nonmonotonic concentration dependences of physicochemical properties of highly diluted solutions (10 –20 –10 –6 mol/L) of biologically active compounds (BACs) correlating with their bioeffects is caused by formation and rearrangement of nanoobjects (100– 400 nm), referred to as nanoassociates (see review [1] and references therein). It has been revealed that nanoassociates are initiated by a solute under certain conditions, the most essential among which are the presence of external electromagnetic fields, the defi� nite structure of the solute, and the procedure of prep� aration of solutions. In highly diluted BAC solutions kept in a permalloy container, i.e., at reduced levels of external physical fields, nanoassociates are not formed and the properties of solutions correspond to the prop� erties of the solvent, water. Based on analysis of data

The relationship between self-organization, physicochemical properties, and biological activity of low-concentration solutions of p-aminobenzoic acid

The self-organization and the physicochemical properties of aqueous solutions (1•10–11—1•10–2 mol L–1) of p-aminobenzoic acid (PABA) kept both under ambient conditions and in the absence of external physical fields were studied by dynamic light scattering and conductometry. It was shown that in aqueous solutions of PABA in the 1•10–10—1•10–3 mol L–1 concentration range, nanosized molecular assemblies (supramolecular domains and nanoassociates) of 100—300 nm size, stable in the temperature range of 25—40 °C, are formed. In the low-concentration range, PABA concentrations in aqueous solutions of 10–10—10–9 mol L–1 and 10–5—10–4 mol L–1 are optimal for waste water treatment.

Epoxidized poly(N‐isopropyl acrylamide)‐b‐epoHTPB‐b‐poly(N‐isopropyl acrylamide) triblock copolymer micelle nanoparticles for 10‐hydroxycamptothecin drug release

ABSTRACTThermoresponsive poly(N‐isopropyl acrylamide) (PNIPAM)‐block‐hydroxy‐terminated polybutadine‐block‐PNIPAM triblock copolymers were synthesized by atom transfer radical polymerization; this was followed by the in situ epoxidation reaction of peracetic acid. The copolymers were characterized by 1H‐NMR, Fourier transform infrared spectroscopy, and size exclusion chromatography measurements, and their physicochemical properties in aqueous solution were investigated by surface tension measurement, fluorescent spectrometry, ultraviolet–visible transmittance, transmission electron microscopy observations, dynamic light scattering, and so on. The experimental results indicate that the epoxidized copolymer micelle aggregates retained a spherical core–shell micelle structure similar to the control sample. However, they possessed a decreased critical aggregate concentration (CAC), increased hydrodynamic diameters, and a high aggregation number and cloud point because of the incorporation of epoxy groups and so on. In particular, the epoxidized copolymer micelles assumed an improved loading capacity and entrapment efficiency of the drug, a preferable drug‐release profiles without an initial burst release, and a low cytotoxicity. Therefore, they were more suitable for the loading and delivery of the hydrophobic drug as a controlled release drug carrier. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41877.

Physicochemical properties of aqueous solutions of sodium glycinate in the non-precipitation regime from 298.15 to 343.15 K

The physicochemical properties, including the density, viscosity, and refractive index of aqueous solutions of sodium glycinate as a solvent for CO2 absorption in the non-precipitation regime were measured under the wide temperature range of 298.15 to 343.15K. The concentration of the sodium glycinate in an aqueous form in the non-precipitation regime was identified up to 2.0mol·L−1. The coefficients of thermal expansion values were estimated from measured density data. It was found that, the densities, viscosities and refractive indices of the aqueous sodium glycinate decrease with an increase in temperature, whereas with increasing sodium glycinate concentration in the solution, all three properties increase. Thermal expansion coefficients slightly increase with rising temperature and concentration. The measured values of density, viscosity and refractive index were correlated as a function of temperature by using the least squares method. The predicted data obtained from correlation equations for all measured properties were in fairly good agreement with the experimental data.

Aqueous electrolyte solution modelling: Some limitations of the Pitzer equations

Despite intense efforts, general thermodynamic modelling of aqueous electrolyte solutions still presents a difficult challenge, with no obvious method of choice. Even though the Pitzer equations seemingly provide a well-established theoretical framework applicable to many chemical systems over a wide range of temperatures and pressures, they are not as widely adopted as their early promise might have suggested. This is strikingly illustrated by the simultaneous appearance in the literature of numerous, different (and potentially incompatible) Pitzer models alongside a proliferation of alternative theoretical approaches with inferior capabilities.To better understand this problem, the ability of the Pitzer equations to represent the physicochemical properties of aqueous solutions has been systematically investigated for exemplar electrolyte systems. Pitzer ion-interaction parameters have been calculated for selected systems by least-squares regression analysis of published solution data for activity coefficients, osmotic coefficients, relative enthalpies, heat capacities, volumes and densities to high temperatures and pressures. Although satisfactory fits can be achieved when the ranges of conditions are carefully chosen and when sufficient data are available to constrain the regression, the fits obtained tend otherwise to be unsatisfactory. The Pitzer equations do not cope well with gaps and other deficiencies in the regressed data. Profound difficulties, poorly recognized hitherto, can also arise because of variation in the sensitivity of the Pitzer functions to values for different physicochemical properties when these are combined. Given the dimensionality of numerous related thermodynamic properties, all changing as functions of composition, temperature and pressure, these problems are difficult to detect, let alone address, especially in multicomponent systems. The growing practice of improving fits simply by adding basis functions (thereby increasing the number of adjustable parameters) should be deprecated because it increases the likelihood of error propagation, introduces subjectivity, makes independent verification difficult and has deleterious implications for both automated data processing and for consistency between thermodynamic models.

Density and sound speed study of hydration of 1-butyl-3-methylimidazolium based amino acid ionic liquids in aqueous solutions

Amino acid ionic liquids (AAILs) have huge potential in the field of protein chemistry, enzymatic reactions, templates for synthetic study etc. which is due to their distinctive properties like unique acid-base characteristics, tunable hydrophobicity, hydrogen bonding ability and strong hydration effects. To explore the field of bio-ionic liquids for its real life applications and sustainable technology development, it is essential to have better understanding of these newly researched liquid salts in life’s most chosen medium, i.e. in aqueous medium, through study of their physicochemical properties in aqueous solutions. In this context, we are reporting herewith measurements and analysis of volumetric properties in the temperature range of (293.15 to 313.25)K and acoustic properties at 298.15K in the concentration range of (0.05 to 0.5)mol·kg−1 for aqueous solutions of 1-butyl-3-methylimidazolium [Bmim] based amino acid ionic liquids, prepared from glycine, l-alanine, l-valine, l-leucine and l-isoleucine. The experimental density and sound speed data were used to obtain apparent, partial and limiting molar volumes as well as isentropic and isothermal compressibility properties. These data have been further used to understand electrostriction as well as concentration dependence of internal pressure. The hydration numbers for AAILs in aqueous medium were estimated from compressibility data using Passynski method and the estimated ionic hydration numbers are compared with those obtained using activity data. The results are explained in terms of cooperative hydration effects, hydrophobic interactions, kosmotropic behavior of AAILs, etc.

Physicochemical properties of aqueous solution of 1-methylimidazolium acetate ionic liquid at several temperatures

Densities (ρ) and viscosities (η) of 1-methylimidazolium acetate ([Mim]Ac) protic ionic liquid+water mixture were measured at T=(293.15, 298.15, 303.15, 308.15 and 313.15) K under atmospheric pressure. Refractive indices (nD) and electrical conductivities (κ) of the above-mentioned system over the entire composition range were measured at 298.15K. Excess molar volumes (VE), viscosity deviations (Δη) and refractive index deviations (ΔnD) were obtained from the experimental data and fitted to the Redlich–Kister equation with satisfactory results. The results show that VE values of the system are negative over the whole composition range, whereas Δη and ΔnD values are positive. Other volumetric properties such as apparent molar volumes (Vϕi), partial molar volumes (V¯m,i) and excess partial molar volumes (V¯m,iE) of the system were calculated from the density data. The concentration dependence of κ was fitted according to the empirical Casteel–Amis equation. The measured and derived properties were employed to investigate the intermolecular interactions of the system.

Pulsed Electrical Discharges in Water: Can Non-volatile Compounds Diffuse into the Plasma Channel?

The objective of this research effort is to develop a more comprehensive understanding of how molecules get degraded in plasma during an electrical discharge in water. The study correlates the intensity of hydroxyl (OH) radicals in the plasma and physicochemical properties of aqueous solutions of methanol, ethanol, acetonitrile, acetone, dimethyl sulfoxide (DMSO), dimethyl formamide (DMF), phenol, hydroquinone, caffeine, and bisphenol A (BPA). To determine the tendency of the used compounds to penetrate the plasma, their vapor pressures, Henry’s constants, aqueous solubilities, reaction rate constants with OH radicals, and octanol–water partition coefficients are compared and correlated with plasma spectroscopic and hydrogen peroxide (H2O2) measurements. OH radicals are precursors to the formation of hydrogen peroxide and any compound that diffuses into the plasma will react with and lower the intensity of OH radicals and therefore the concentration of hydrogen peroxide in the bulk liquid. Optical emission spectroscopy (OES) reveals that all the used compounds diffuse inside the plasma channel regardless of their vapor pressure where they get oxidized (primarily by OH radicals) and thermally degraded. Results also indicate that hydrophobicity (i.e., octanol–water partition coefficient) is the most important property that determines a compound’s tendency to diffuse inside the plasma channel; hydrophobic compounds readily penetrate the plasma whereas hydrophilic compounds tend to stay in the bulk liquid. The rate of formation of hydrogen peroxide is independent of the type of the compound present in the bulk liquid which confirms that this molecule is formed at the plasma interface.

Comparative study of the physicochemical properties of aqueous solutions of the hydrocarbon and fluorocarbon surfactants and their ternary mixtures

Speed of sound and density of aqueous solutions of hydrocarbon p-(1,1,3,3-tetramethylbutyl) phenoxypoly(ethyleneglycols) (Triton X-100 (TX100), Triton X-165 (TX165)) and fluorocarbon (Zonyl FSN-100 (FSN100), Zonyl FSO-100 (FSO100)) surfactants as well as their ternary mixtures were measured at 293K. Taking into account these values and the literature data of the surface tension and viscosity of the studied systems, the values of the isentropic compressibility, apparent specific adiabatic compressibility, hydration number, apparent specific volume and Jones Dole’s A and B-coefficients were determined. For the systems containing FSO100 also the values of dB/dT were determined on the basis of the values of viscosity measured at different temperatures. Next, the calculated thermodynamic properties have been discussed in the term of intermolecular interactions between the components of the mixtures.

Physicochemical Properties of Aqueous Solutions of Sodium l-Prolinate as an Absorbent for CO2 Removal

The physicochemical properties such as density, viscosity, and refractive index of aqueous solutions of sodium l-prolinate (SP) as a solvent for CO2 capture was measured. These properties were measured at different temperatures from (298.15 to 343.15) K. The mass fractions of SP were 0.05, 0.10, 0.20, 0.30, and 0.40. The coefficient of thermal expansion was calculated from the experimental density values in the same temperature range. The analysis of experimental results shows that the densities, viscosities, and refractive indices of the aqueous solutions of SP increase with an increase in the mass fraction in the solution, and decrease with increasing temperature. The thermal expansion coefficient slightly increases with increasing temperature and concentration. The experimental data of density, viscosity, and refractive index were correlated by the least-squares method as a function of temperature. The predicted data were estimated from correlation coefficients for all measured properties and reported ...

ChemInform Abstract: New Tetra‐ and Octa‐Functionalized Phthalocyanines: Methods of Synthesis and Physicochemical Properties in Aqueous Solutions and on Solid Substrates. Review

AbstractReview: 94 refs.

Ionic liquid induced alterations in the physicochemical properties of aqueous solutions of sodium dodecylsulfate (SDS)

Changes in the micellization behavior of an anionic surfactant sodium dodecylsulfate (SDS) in aqueous solutions have been investigated at varying concentration of hydrophobic ionic liquid 3-methy-1-pentylimidazolium hexafluorophosphate [C5mim][PF6] using techniques like conductometry, densiometry and speed of sound at a temperature range of 298.15–318.15K. Critical micelle concentration (cmc) of SDS increases upon addition of [C5mim][PF6], which is also evidenced from fluorescence spectra of pyrene probe. Presence of solvophobic interactions is proposed to be the reason for these observations.