Ionic Strength Values Research Articles

New thermodynamic insights into pregabalin interactions with H+, Na+, Mg2+, Ca2+, Cu2+, Zn2+: Equilibrium constants, enthalpy changes and sequestering ability

The thermodynamics of the interaction between (S)-(+)-3-aminomethyl-5-methylhexanoic acid (pregabalin) and protons was studied potentiometrically at different temperatures (288.15 ≤ T/K ≤ 310.15), ionic strengths (0.16 ≤ I/mol kg−1(H2O) ≤ 0.97, NaCl), (0.11 ≤ I/mol kg−1(H2O) ≤ 1.11, (C2H5)4NI), (0.10 ≤ I/mol kg−1(H2O) ≤ 1.03, NaClO4, only at T = 298.15 K). The protonation constants at infinite dilution and the corresponding enthalpy change values were determined, as well as their parameters for the dependence on the temperature and ionic strength. The results showed that the protonation reactions are exothermic, and that the entropic contribution is the driving force of the processes.Formation constants of pregabalin (L) with Zn2+, Cu2+, Ca2+, and Mg2+ were determined in NaCl(aq) at different ionic strength values, at 298.15 K. Different speciation models were proposed for the various metal/Pregabalin systems: ZnHL2+, ZnLOH0(aq), CuL+, CuL20(aq), CaL+, CaHL2+, and MgL+, depending on the different acid-base properties of the metals and the possible formation of sparingly soluble species. The modelling of the thermodynamic formation parameters respect to the temperature and ionic strength variation was carried out by using both the Specific Ion Interaction Theory (SIT) and an extended Debye-Hückel type equation.Being Pregabalin an emerging contaminant, it was interesting to investigate its distribution in presence of the investigated metal cations in aqueous solution simulating both biological fluid (urine) and natural water (seawater).

De Novo Design and Characterization of Amphiphilic Peptides with Basic Side Chains for Tailored Interfacial Chemistries.

Lysine-leucine (LK) peptides have been used as model systems and platforms for 2D material design for decades. LK peptides are amphiphilic sequences designed to bind and fold at hydrophobic surfaces through hydrophobic leucine side chains and hydrophilic lysine side chains extending into the aqueous subphase. The hydrophobic periodicity of the sequence dictates the secondary structure at the interface. This robust design makes them ideal candidates for controlling interfacial chemistry. This study presents the de novo design and characterization of two novel peptides: LRα14 and LHα14, which substitute lysine with arginine and histidine, respectively, in the helical LKα14 sequence. This modification is intended to expand the LK peptide platform to a new basic interfacial chemistry. We explore the stability of the new LRα14 and LHα14 designs with respect to changes in pH and salt concentration in bulk solution and at the interface using circular dichroism (UV-CD) and vibrational sum-frequency generation spectroscopy, respectively. Notably, the structural stability of the peptides remains unaffected across a wide range of pH and ionic strength values. At the same time, the variation of side-chain chemistry leads to a wide spectrum of interfacial water structures. By extension of the LK platform to include arginine and histidine, this study broadens the toolbox for designing tailored interfacial chemistries with applications in material and biomedical sciences.

Complex conductivity as a tool to investigate the electrical behavior between graphene oxide and reduced graphene in supercapacitors: Correlation between the electrical properties

The storage mechanisms of solid-solid supercapacitors based on graphene oxide (rGO/GO/rGO) were explored by Zhang Q et al. (Zhang et al., 2014) [1], using Density Functional Theory (DFT) and Impedance Spectroscopy (EIS) to elucidate the unusual capacitive behavior of GO sandwich films. Their study revealed alternating charged layers without diffusion zones. Analysis of complex impedance (Z*) data, ranging from 10−3 to 3.106 Hz, was conducted using an equivalent circuit, though this was limited to Nyquist plot data.To further investigate charge storage mechanisms, the current study delved deeper into complex impedance (Z*) and conductivity (σ*). A theoretical approach identified relaxation processes in the imaginary parts of (Z″) and (σ'') across frequencies. Extrapolation up to 3.10^9 Hz and deconvolution confirmed three distinct relaxation processes in Z* and σ*, similar to Cole-Cole relaxation, which describes Maxwell-Wagner-Sillars (MWS) relaxation. This reflects local electrical interactions between active sites on molecular chains and counterions, creating induced dipolar moments or diffusion processes.The identified relaxations at low, medium, and high frequencies correspond well with DFT results, attributed to specific regions: graphene oxide (GO), the (rGO/GO) interface, and reduced graphene (rGO). Key parameters extracted from each relaxation, such as relaxation time, ionic strength, and conductivity values at different frequencies, showed good correlation. This approach, based on deep conductivity (σ*) analysis, effectively highlighted the charge conduction and storage mechanisms in rGO/GO/rGO supercapacitor films.

Two approaches to prepare cationic lignin‐based adsorbents for efficient removal of phosphate ion from wastewater

AbstractIn this work, two types of cationic lignin‐based adsorbents (AL‐METAC and AL‐GTA) were prepared through free radical polymerization or etherification reaction of alkali lignin with 2,3‐epoxypropyl‐3‐trimethylammonium chloride or methylacrylloxyethyl trimethyl ammonium chloride (METAC). The contents of quaternary ammonium groups in the adsorbents were adjusted by changing the dosages of 2,3‐epoxypropyl‐3‐trimethylammonium chloride and METAC to fabricate the adsorbents with excellent adsorption capacity. The structures, aqueous solubility, and physical properties of adsorbents were analyzed. Meanwhile, the effects of adsorbents dosage, pH value of solution, temperature, and ionic strength on the adsorption capacity of adsorbents were also analyzed. These two types of adsorbents exhibited outstanding affinity for phosphate, with a maximum removal efficiency of 51.8 and 73.2 mg/g, respectively. The adsorption processes followed pseudo‐second‐order and Langmuir models well. In addition, the AL‐GTA exhibited higher removal efficiency than AL‐METAC. Moreover, the AL‐METAC and AL‐GTA still retained 69.7% and 69.0% adsorption capacity after four times regeneration. The fabricated lignin‐based adsorbents have potential applications in the removal of phosphate from wastewater, which would promote the high‐value application of lignin.

Engineering of chimeric enzymes with expanded tolerance to ionic strength.

Antimicrobial resistance poses a significant global threat, reaching dangerously high levels as reported by the World Health Organization. The emergence and rapid spread of new resistance mechanisms, coupled with the absence of effective treatments in recent decades, have led to thousands of deaths annually from infections caused by drug-resistant microorganisms. Consequently, there is an urgent need for the development of new compounds capable of combating antibiotic-resistant bacteria. A promising class of molecules exhibiting potent bactericidal effects is peptidoglycan hydrolases. Previously, we cloned and characterized the biochemical properties of the M23 catalytic domain of the EnpA (EnpACD) protein from Enterococcus faecalis. Unlike other enzymes within the M23 family, EnpACD demonstrates broad specificity. However, its activity is constrained under low ionic strength conditions. In this study, we present the engineering of three chimeric enzymes comprising EnpACD fused with three distinct SH3b cell wall-binding domains. These chimeras exhibit enhanced tolerance to environmental conditions and sustained activity in bovine and human serum. Furthermore, our findings demonstrate that the addition of SH3b domains influences the activity of the chimeric enzymes, thereby expanding their potential applications in combating antimicrobial resistance.IMPORTANCEThese studies demonstrate that the addition of the SH3b-binding domain to the EnpACD results in generation of chimeras with a broader tolerance to ionic strength and pH values, enabling them to remain active over a wider range of conditions. Such approach offers a relatively straightforward method for obtaining antibacterial enzymes with tailored properties and emphasizes the potential for proteins' engineering with enhanced functionality, contributing to the ongoing efforts to address antimicrobial resistance effectively.

Cadmium Sorption on Alumina Nanoparticles and Mixtures of Alumina and Smectite: An Experimental and Modelling Study

Cadmium (Cd) is one of the most toxic transition metals for living organisms. Thus, effective measures to remediate Cd from water and soils need to be developed. Cd immobilization by alumina and mixtures of alumina and smectite have been analyzed experimentally and theoretically by sorption experiments and sorption modelling, respectively. Removal of aqueous Cd was dependent on pH and Cd concentration, being maximal for pH > 7.5. A two-site non-electrostatic sorption model for Cd sorption on alumina was developed and it successfully reproduced the experimental Cd immobilization on alumina. Cd sorption on mixtures of alumina and smectite were depending on pH, ionic strength, and alumina content in the mixture. Cd removal in mixtures increased with alumina content at high pH and ionic strength values. However, Cd sorption decreased with increasing alumina content under acidic conditions and low ionic strength. This effect was the result of alumina dissolution and the release of Al3+ into the suspension at low pH values. Modelling of Cd sorption on mixtures of alumina and smectite was performed by considering the individual Cd sorption models for alumina and smectite. It could be shown that the contributions of the individual sorption models were additive in the model for the mixtures when the competition of Al3+ with Cd2+ for cation exchange sites in smectite was included.

Enrichment of surface charge contributes to the stability of surface nanobubbles

Surface nanobubbles are spontaneously formed at the interface between hydrophobic surfaces and aqueous solutions, which show extraordinarily longer lifetime than that was predicted by the classical thermodynamics model. In the present work, by using a surface plasmon resonance microscopy (SPRM) to quantitatively measure the dissolution kinetics of individual surface nanobubbles in real time, we explored the effects of ionic strength and pH value on the dissolution rates (lifetime) of nanobubbles. The results revealed that nanobubbles could exist stably for a long time in low-concentration electrolyte solutions or high-concentration non-electrolyte solutions, while they dissolved quickly in high-concentration electrolyte solutions. With the increase of ionic strength, the dissolution rates were accelerated by 2–3 orders of magnitude, and thus the lifespan of these surface nanobubbles was significantly shortened. In addition to ionic strength, it was further found that, with the increase of acidity or alkalinity of the solution, the dissolution rates of the surface nanobubbles were faster than that in neutral solution. These results demonstrated that the interfacial charge enrichment significantly contributed to the extraordinary stability of the surface nanobubbles.

CITRIC ACID–SODIUM CITRATE–WATER SOLUTIONS ACID-BASE AND ELECTROCHEMICAL BEHAVIOR

The protolytic equilibria in the system citric acid (H3Cit)–sodium citrate (Na3Cit)–water at a total content of citrates forms (citric acid, dihydrocitrate (H2Cit-), hydrocitrate (HCit2-) and citrate (Cit3-) anions) 1.0 mol/l have been studied by pH- and conductometric methods in the temperature range 293 ÷ 313 K. The first concentration ranges at which pH – lg(νH3Cit/νNa3Cit) and κ – CNa+/Ccit functions are linear correspond to the H3Cit/H2Cit- buffer system; the second ones – to H3Cit/H2Cit- and H2Cit-/HCit2-; the third ones to – HCit2-/Cit3- buffer system. The investigated solutions ion-molecular composition and ionic strength (m, mol/l) have been calculated using the mathematical model taking into account the law of mass action, material balance for citrates and electrical neutrality principle. The ionic strength concentration dependences have a complex character due to the ion-molecular composition multicomponent nature for the studied solutions. The ionic strength values are directly proportional to the ratio [Na+]/CCit in the concentration intervals 0 ≤ [Na+]/CCit ≤ 1.0 and 2.0 ≤ [Na+]/CCit ≤ 3.0. In the concentration range 1.0 ≤ [Na+]/CCit ≤ 2.0, the values of m = 1.15 ± 0.27 mol/l) weakly depend on the [Na+]/CCit ratio and practically do not depend on temperature. Citric acid concentration and thermodynamic constants for the first, second, and third dissociation stages have been determined. The obtained data on the acid-base and electrochemical characteristics of the solutions HOC3H4(COOH)3 – HOC3H4(COONa)3 – H2O(СCit = 1.0 mol/l; СNa+ = 0 ÷ 1.0 mol/l) can be used in chemical analysis, microbiological and biochemical studies, and the acidity data of the solutions studied can simulate chemisorption of acidic (SO2) and/or basic (NH3) gases.

Insight into Ionic Strength-Induced Solubilization of Myofibrillar Proteins from Silver Carp (Hypophthalmichthys molitrix): Structural Changes and 4D Label-Free Proteomics Analysis.

In this study, changes in the physical, structural, and assembly characteristics of silver carp myofibrillar proteins (MPs) at different ionic strength (I) values were investigated. Moreover, the differential proteomic profile of soluble MPs was analyzed using 4D proteomics based on timsTOF Pro mass spectrometry. Solubility of MPs significantly increased at high I (>0.3), and the increase in I enhanced the apparent viscosity, fluorescence intensity, surface hydrophobicity, and α-helix content of MPs solution. Particle size and sodium dodecyl sulfate-polyacrylamide gel electrophoresis patterns also supported the solubility profiles. Transmission electron microscopy and atomic force microscopy observations revealed the morphological assembly and disassembly of MPs under different I conditions. Finally, proteomic analysis revealed the evolution law of salt-induced solubilization of MPs and the critical molecular characteristics in different I environments. The number of differentially abundant proteins (DAPs) decreased with the increase of I, and most DAPs related to the muscle filament sliding, contraction and assembly, actinin binding, and actin filament binding. The soluble abundance of myosin and some structural proteins was dependent on I, and structural proteins in the Z-disk and M-band might contribute to the solubilization of myosin. Our findings provide insightful information about the impact of common I on the solubility pattern of MPs from freshwater fish.

Multi-attribute analysis of adeno-associated virus by size exclusion chromatography with fluorescence and triple-wavelength UV detection

Adeno-associated virus (AAV) is the leading platform for in vivo gene therapy to treat numerous genetic diseases. Comprehensive analysis of the AAV particles is essential to ensure desired safety and efficacy. An array of techniques is required to evaluate their critical quality attributes. However, many of these techniques are expensive, time-consuming, labour-intensive, and varying in accuracy. Size exclusion chromatography coupled with fluorescence and triple-wavelength ultraviolet detection (SEC-FLD-TWUV) and incorporating an aromatic amino acid of tryptophan as an internal standard offers a simple, rapid, and reliable approach for simultaneous multi-attribute analysis of AAVs. In the current study, we demonstrate its capability for AAV characterization and quantification, that includes capsid concentration, empty to full capsid ratio, vector genome concentration, and the presence of aggregates or fragments. All were performed in 20-min chromatographic runs with minimal sample handling. Data analysis involves the assessment of intrinsic fluorescence and UV absorbance of samples at three wavelengths that can be utilised to determine the content of the capsid protein and genome copy number. The separation efficiency using SEC columns with different pore sizes, and elution buffers of varying compositions, ionic strength, and pH values was also evaluated. This SEC-FLD-TWUV method may serve as a powerful yet cost-effective tool for responsive quality evaluation of AAVs. This may enhance performance, robustness, and safety of bioprocessing for AAV vectors to be used in gene therapy.

Tuning surface interactions on MgFe2O4 nanoparticles to induce interfacial hyperactivation in Candida rugosa lipase immobilization

Lipase adsorption on solid supports can be mediated by a precise balance of electrostatic and hydrophobic interactions. A suitable fine-tuning could allow the immobilized enzyme to display high catalytic activity. The objective of this work was to investigate how pH and ionic strength fluctuations affected protein-support interactions during immobilization via physical adsorption of a Candida rugosa lipase (CRL) on MgFe2O5. The highest amount of immobilized protein (IP) was measured at pH 4, and an ionic strength of 90 mM. However, these immobilization conditions did not register the highest hydrolytic activity (HA) in the biocatalyst (CRLa@MgFe2O4), finding the best values also at acidic pH but with a slight shift towards higher values of ionic strength around 110 mM. These findings were confirmed when the adsorption isotherms were examined under different immobilization conditions so that the maximum measurements of IP did not coincide with that of HA. Furthermore, when the recovered activity was examined, a strong interfacial hyperactivation of the lipase was detected towards acidic pH and highly charged surrounding environments. Spectroscopic studies, as well as in silico molecular docking analyses, revealed a considerable involvement of surface hydrophobic protein-carrier interactions, with aromatic aminoacids, especially phenylalanine residues, playing an important role. In light of these findings, this study significantly contributes to the body of knowledge and a better understanding of the factors that influence the lipase immobilization process on magnetic inorganic oxide nanoparticle surfaces.

Thermodynamic insights into Trans-Aconitate interactions with H+, Cd2+, Mn2+, and Pb2+: Equilibrium constants, enthalpy changes and sequestering ability

The thermodynamics of interaction of trans‐aconitate (L3-) with proton, sodium and potassium cations was studied by means of potentiometric titration performed at different temperatures, ionic strengths, and aqueous ionic media (NaCl, KCl and (C2H5)4NI). Three protonation constants and corresponding enthalpy changes are reported at infinite dilution together with their dependence parameters on temperature and ionic strength according to van’t Hoff and Extended Debye Hückel equations, respectively. Enthalpy changes resulted slightly endothermic at infinite dilution and values decrease with increasing ionic strength. Proton binding resulted always entropic in nature. Weak association constants of Na+/L3- and K+/L3- species were determined using the pure water model approach. Formation constants of trans‐aconitate with Cd2+, Pb2+ and Mn2+ were determined in KCl(aq) at different ionic strength values and at 298.15 K. Three complex species were found with all metal cations (ML-, MHL0(aq), MH2L+), whose formation constant values at infinite dilution and at T = 298.15 K were log β = 4.54, 9.94, 13.77 for cadmium, 5.00, 10.57, 14.81 for manganese and 4.97, 10.44, 14.13 for lead. The as found values resulted unexpectedly high. The sequestering ability of trans‐aconitate towards M2+ was evaluated by determining pL0.5 (the ligand total concentration required to bind 50% of the metal cation), and the results show that, throughout the investigated pH range, trans‐aconitate shows the highest sequestering ability towards Mn2+. Data reported in this paper were critically compared to other tricarboxylic acid, namely citric and tricarballylic acid.

ROLE OF ION PAIRS AND ACTIVITY IN ESTIMATION OF IONIC STRENGTH FROM ELECTRICAL CONDUCTIVITY OF IRRIGATION WATER

This study was carried out in Erbil governorate, Iraq during 2020 to estimate the regression relations between the ionic strength of 354 water samples and their electrical conductivity then influence of correcting ion pairs and activity on this relation. Results indicated that electrical conductivity regards as an accurate measure of ionic strength for irrigation water. Correcting ion pairs plus activity had a great effect on the regression values between ionic strength values and electrical conductivity of the studied water samples. Highly significant correlation coefficient was recorded between ionic strength and electrical conductivity before correction and after correcting ion pairs and ion pairs plus activity with the correlation coefficient values of (r= 0.99**, 0.93** and 0.97**) respectively. Correcting ion pairs and ion pairs plus activity caused a decrease in the slope of the regression from 0.0157 to 0.0104 and 0.0047 respectively. Neglecting intercept values from the regression line caused an increase in the slope of regression relation to 0.0112 and 0.0058 for correcting ion pairs and ion pairs plus activity respectively.

Effects of size and surface charge on the sedimentation of nanoplastics in freshwater

The environmental issues caused by nanoplastics (NPs) are increasingly noticeable. Environmental behavior study of the NPs could provide vital information for their environmental impact assessment. However, associations between NPs' inherent properties and their sedimentation behaviors were seldom investigated. In this study, six types of PSNPs (polystyrene nanoplastics) with different charges (positive and negative) and particle sizes (20–50 nm, 150–190 nm and 220–250 nm) were synthesized, and their sedimentations under different environmental factors, (e.g., pH value, ionic strength (IS), electrolyte type and natural organic matter) were investigated. Results displayed that both particle size and surface charge would affect the sedimentation of PSNPs. The maximum sedimentation ratio of 26.48% was obtained in positive charged PSNPs with size of 20–50 nm, while the minimum sedimentation ratio of 1.02% was obtained in negative charged PSNPs with size of 220–250 nm at pH 7.6. The pH value shift (range of 5–10) triggered negligible changes of sedimentation ratio, the average particle size and the Zeta potential. Small size PSNPs (20–50 nm) showed higher sensitivity to IS, electrolyte type and HA condition than large size PSNPs. At high IS value (ISCaCl2 = 30 mM or ISNaCl = 100 mM), the sedimentation ratios of the PSNPs all increased differently according to their properties, and the sedimentation promoting effect of CaCl2 was more significant on negative charged PSNPs than positive charged PSNPs. When ISCaCl2 increased from 0.9 to 9 mM, the sedimentation ratios of negative charged PSNPs increased by 0.53%–23.49%, while that of positive charged PSNPs increased by less than 10%. Besides, humic acid (HA) addition (1–10 mg/L) would lead to a stable suspension status for PSNPs in water with different degree and perhaps different mechanism due to their charge characteristics. These results showed new light on influence factor studies of NPs' sedimentation and would be helpful for further knowledge of NPs’ environmental behaviors.

Geochemical evaluation of mud volcanic sediment and water in Northern Borneo: A baseline study

A comprehensive geochemical investigation was carried out to characterise the sediment and water seeping out from mud volcano, in Kampung Meritam, Limbang, northern Borneo. Chemical analysis included major oxides, trace metals, rare earth elements, and major ions. Interpretation of results reveals that the geochemical composition of sediment samples is originated from sedimentary provenance particularly Setap Shale, which is the dominant Formation present in this region. The concentration of trace elements and major oxides were used to identify the origin and weathering nature of sediment. SiO2 is the dominant major oxide present in the sediment samples with an average concentration of 58.24%. Whereas for trace metals, Ba is dominating with an average concentration of 263ppm. Environmental pollution indices such as contamination factor, geoaccumulation index, and enrichment factor were used to assess the contamination level of mud volcanic sediments. Hydrochemistry of mud volcano suggests that the water is derived from ionic enriched solute, indicated by Na-Cl water type. The average concentration of Na+ and Cl- is 987 mg/L and 10457.50 mg/L. The ionic ratios suggest that water-rock interaction including carbonate mineral dissolution is the predominant process that controls the water chemistry. Gibbs diagram shows that the water is influenced by the dissolution of evaporite minerals. Thermodynamic stability and saturation index were used to evaluate the mineral stability and saturation condition during weathering. Ca2+ and Mg2+ were released into the water due to the reverse ion exchange process, which was supported by XRD results. Higher ionic strength and Log pCO2 values suggest longer residence time of water in the aquifer matrix and therefore significant dissolution of enriched solute due to the intensive water-rock interaction. The outcome of this study would provide the basis for a better understanding on the geochemical characteristics of Meritam mud volcano in Northern Borneo.

The Adsorption Efficiency of Regenerable Chitosan-TiO2 Composite Films in Removing 2,4-Dinitrophenol from Water.

In this work, the great performance of chitosan-based films blended with TiO2 (CH/TiO2) is presented to adsorb the hazardous pollutant 2,4-dinitrophenol (DNP) from water. The DNP was successfully removed, with a high adsorption %: CH/TiO2 exhibited a maximum adsorption capacity of 900 mg/g. For pursuing the proposed aim, UV-Vis spectroscopy was considered a powerful tool for monitoring the presence of DNP in purposely contaminated water. Swelling measurements were employed to infer more information about the interactions between chitosan and DNP, demonstrating the presence of electrostatic forces, deeply investigated by performing adsorption measurements by changing DNP solutions' ionic strength and pH values. The thermodynamics, adsorption isotherms, and kinetics were also studied, suggesting the DNP adsorption's heterogeneous character onto chitosan films. The applicability of pseudo-first- and pseudo-second-order kinetic equations confirmed the finding, further detailed by the Weber-Morris model. Finally, the adsorbent regeneration was exploited, and the possibility of inducing DNP desorption was investigated. For this purpose, suitable experiments were conducted using a saline solution that induced the DNP release, favoring the adsorbent reuse. In particular, 10 adsorption/desorption cycles were performed, evidencing the great ability of this material that does not lose its efficiency. As an alternative approach, the pollutant photodegradation by using Advanced Oxidation Processes, allowed by the presence of TiO2, was preliminary investigated, opening a novel horizon in the use of chitosan-based materials for environmental applications.

Empirical models to determine ions concentrations in lithium brines with high ionic strength

Argentina Puna brines are complex systems in which ions such as Na+, K+, Li+, Mg2+, Ca2+, SO42−, and B4O72− are presents. To obtain lithium carbonate from brines, they must be treated in order to increase its lithium concentrations and to eliminate the others ions that are presents in the brines. During concentration some salts can reach their solubility products (kps) and crystallize, producing different solid-liquid equilibriums. In order to design and select the process to purify the brine before lithium salts precipitation, it is necessary to know the other ions concentrations.Ion concentrations in solutions can be calculated based on the salts coefficient activities using Pitzer's model and its modifications. These methods have the restriction that can only be applied to solutions with ionic strength values up to 6 molal. The state of the art shows that the approach to study the equilibrium in complex system is to consider it as binary, ternary, quaternary and quinary systems. When ionic strength values are higher than 6 m the systems studied are binaries or have symmetrical ions.Brines of the Argentina Puna have, in general, initial ionic strength values around 6 molal and it increases when the brine is concentrated by evaporation, so the available thermodynamical models cannot be used to determine, beforehand, the final composition of a certain brine. In this work four different brines from four different Puna plateau in Argentina were evaporated to several degrees and ionic strength was calculated from the chemical brine's composition after each evaporation test. Ionic strength was found to correlate with the percentage of eliminated water following two different simple mathematical models, depending on the initial sulphate concentration of the brine and the possibility of its precipitation. Models to estimate the concentration of diluted ions of commercial value such as Li+, K+, and Mg2+ as function of ionic strength were also proposed. Ion concentrations could be modeled as function of the amount of eliminated water, once the correct relationship between this parameter and the ionic strength of the brine is established. These models correlate accurately ionic strength and ion concentrations for an ionic strength range from 4.8 to 15.4 molal; corresponding to percentages of water evaporated from 0% up to 60%.With these models it is possible to calculate beforehand the final ions concentrations after a given percentage of evaporated water. It allows to design brines processing and select the purification techniques without exhausting and time-consuming tests. Nowadays there are no tools that allows to do that, in consequence, each company must perform rigorous and numerous tests with its brines. Results of these work show that ionic strength is the parameter that unified brines behavior even if initial composition could be different. In consequence, it could be used as a parameter to describe brine behavior during evaporations.

Copper-Guanosine Nanorods (Cu-Guo NRs) as a Laccase Mimicking Nanozyme for Colorimetric Detection of Rutin

Inspired by laccase activity, herein, Cu-guanosine nanorods (Cu-Guo NRs) have been synthesized for the first time through a simple procedure. The activity of the Cu-Guo NR as the laccase mimicking nanozyme has been examined in the colorimetric sensing of rutin (Rtn) by a novel and simple spectrophotometric method. The distinct changes in the absorbance signal intensity of Rtn and a distinguished red shift under the optimum condition based on pH and ionic strength values confirmed the formation of the oxidized form of Rtn (o-quinone) via laccase-like nanozyme activity of Cu-Guo NRs. A vivid and concentration-dependent color variation from green to dark yellow led to the visual detection of Rtn in a broad concentration range from 770 nM to 54.46 µM with a limit of detection (LOD) of 114 nM. The proposed methodology was successfully applied for the fast tracing of Rtn in the presence of certain common interfering species and various complex samples such as propolis dry extract, human biofluids, and dietary supplement tablets, with satisfactory precision. The sensitivity and selectivity of the developed sensor, which are bonuses in addition to rapid, on-site, cost-effective, and naked-eye determination of Rtn, hold great promise to provide technical support for routine analysis in the real world.

Structure and stability of nickel(II) complexes with cryptand[2.2.2

The values of the stability constants of the mononuclear, protonated and binuclear complexes of nickel(II) with cryptand [2.2.2] were determined using potentiometric titration at ionic strength value µ→0 and temperature of 298 K. The structure and the most important geometric characteristics of Ni2 + cryptates were optimized via quantum chemical calculations performed in vacuo .

Edible Oleogels Fabricated by Dispersing Cellulose Particles in Oil Phase: Effects from the Water Addition

A new strategy to fabricate edible oleogels had been developed in this work, using natural cellulose particles as gelator and water as secondary fluid. Effect of the content of cellulose particles and second fluid on the formation of oleogels were investigated, and a qualitative phase diagram was constructed. Consideration has also focused on the influence of second fluid (ionic strength, pH and sucrose). Results showed that the cellulose particles could form a network in oil phase through the capillary force originated from the secondary fluid. A denser and more uniform network provided the oleogels higher centrifugal stability against oil loss. The viscoelastic properties of oleogels could be enhanced by increasing the ionic strength (10–100 mM), sucrose concentration (10–20 wt%) and pH value (2.0–5.0) of the second fluid. These results suggested that the capillary force of the gel network could be modulated by the composition and pH of secondary fluid. The considerable gel strength and economical manufacturing process give the oleogels great application potential. • Edible oleogels were prepared using a simple and economical process. • Using natural cellulose particles as gelator and water as the second fluid. • Cellulose particles could form a network in oil phase through the capillary force. • Strength of the oleogels could be modulated by the water phase.