Mixture Of Aqueous Solution Research Articles

Hydrate phase equilibria of carbon dioxide/propane gas mixture in concentrated aqueous sodium chloride solutions: Experimental data and prediction

The information on hydrate equilibrium conditions of gas hydrate formers in concentrated NaCl solutions are the prerequisites for hydrate-based desalination methods. Hydrate dissociation conditions for CO2-C3H8 mixture, as a good candidate for this application, were measured for the temperature and pressure ranges of 269–283 K and 0.3–3.4 MPa, respectively using an isochoric pressure-search method. The used gas mixture was a solution of 10 mol% C3H8 + 90 mol% CO2 and NaCl concentrations varied between 8 and 12 wt%. The promoting effect of propane was obviously observed from the experimental data. This promoting effect nearly balanced the inhibitory effect of 12 wt% NaCl. A thermodynamic model was applied to predict the experimental data using SRK, PR, and VPT EOSs. All EOSs had accurate results for prediction of CO2 hydrate equilibrium pressures, with the best result by PR EOS. The overall average absolute percent deviation (AAPD) of PR EOS in pure water and 8 wt% NaCl solution were 5.29 and 3.8 %, respectively. For gas mixture (CO2-C3H8) in pure water, the best accuracy was obtained by using SRK EOS with AAPD of 4.44 %. However, the results of VPT and PR for gas mixture in NaCl solutions, were more accurate than SRK with AAPDs equal to 7.47 and 7.75 %, respectively.

New Zwitter-Ionic Oligonucleotides: Preparation and Complementary Binding

New zwitter-ionic oligonucleotide derivatives containing 1,2,3,4-tetrahydroisoquinoline-7-sulfonyl phosphoramidate group are described. Automated synthesis of these compounds was carried out according to the β-cyanoethyl phosphoramidite scheme via the Staudinger reaction between 2-trifluoroacetyl-1,2,3,4-tetrahydroisoquinoline-7-sulfonyl azide and phosphite triester within oligonucleotide grafted to polymer support. 1,2,3,4-Tetrahydroisoquinoline-7-sulfonyl phosphoramidate group (THIQ) was stable under the conditions of standard oligonucleotide synthesis, including the removal of protective groups and cleavage of the oligonucleotide from the polymer support by treatment with a mixture of concentrated aqueous solutions of ammonia and methylamine (1 : 1) at 55°C. Oligonucleotides modified by one to five THIQ groups in various positions were obtained. The zwitter-ionic character of the obtained derivatives was reflected in their varying mobility under conditions of denaturing PAGE. The thermal stability of the duplexes of oligodeoxynucleotides containing THIQ groups with complementary DNA and RNA only slightly differed from that of natural DNA:DNA and DNA:RNA duplexes. The results reported suggest that oligonucleotides modified with zwitter-ionic THIQ groups as antisense therapeutic agents.

Degree of Dissolution of Nickel(II) Hydroxide in Mixtures of Aqueous Solutions of Ammonia and Ammonium Bicarbonate

Degree of Dissolution of Nickel(II) Hydroxide in Mixtures of Aqueous Solutions of Ammonia and Ammonium Bicarbonate

Degree of Dissolution of Nickel(II) Hydroxide in Mixtures of Aqueous Solutions of Ammonia and Ammonium Bicarbonate

The degree of dissolution of nickel(II) hydroxide in mixtures of aqueous solutions of ammonia and ammonium bicarbonate has been studied. The equilibrium between the solid and liquid phases was reached in 11–12 h after the start of experiment. Nickel(II) hydroxide showed higher solubility in the ammonia–carbonate mixture compared with aqueous solutions of ammonia and ammonium bicarbonate. The ratio of ammonium bicarbonate and ammonia concentrations in solution at which the highest degree of dissolution of Ni(OH)2 was achieved was determined. An analytical description of the ion-molecular equilibrium in the ammonia– carbonate mixture was given, and the equilibrium concentrations of molecules and ions in the system were calculated. A stoichiometric equation describing the dissolution of nickel(II) hydroxide in an ammonia–carbonate solution was given.

Физико-химические характеристики нанокомпозитов Fe3O4/TiO2 и Fe3O4/SiO2/TiO2, синтезированных гид-ротермальным пероксидным методом

In the present paper the composite materials based on Fe3O4/TiO2 and Fe3O4/SiO2/TiO2 ox-ides, synthesized by the hydrothermal peroxide method, were studied. At the first stage, magnet-ite nanoparticles were precipitated by ammonium hydroxide from a mixture of aqueous solutions of iron(II) sulfate and iron(III) chloride under continuous exposure to ultrasound, after which they were washed with distilled water. At the second stage, the resulting hydrated magnetite particles were stabilized with polyvinyl alcohol (PVA) by dispersing them under the action of ultrasound in a hot saturated aqueous PVA solution. At the third stage, the photocatalytically active particles based on titanium oxide were introduced into the composite by mixing the stabilized magnetite suspension with an aqueous solution of peroxotitanic acid (optionally introducing a sol of silicic acid), followed by hydrothermal treatment of the mixture at 180°C for 24 hours, washing, and drying under vacuum followed by calcination in a muffle furnace. The effect of the molar content of iron and titanium on the properties of the samples, the introduction of silicon dioxide into them, as well as various calcination temperatures, were studied. The photocatalytic properties of the synthesized samples during photodegradation of methyl orange and methylene blue, as well as their magnetic recovery from suspension, were studied. The physicochemical characterization of the samples was performed using high-resolution scanning electron microscopy, energy-dispersive X-ray spectroscopy, high-resolution transmission electron microscopy, powder X-ray diffraction, low-temperature nitrogen sorption porosimetry, inductively coupled plasma mass spectrometry, thermal analysis (TG–DSC), combined with mass spectrometry of gaseous thermolysis products. The optimal conditions for the synthesis of composites exhibiting the best combination of photocatalytic and magnetic properties were determined. The resulting photocatalysts can be used to purify water from dyes, followed by extraction using a magnet

Композитные магнитовосприимчивые фотокатали-заторы на основе оксидов Fe3O4/SiO2/TiO2

In the present study the composite materials based on the Fe3O4/SiO2/TiO2 oxides, synthe-sized by the sol-gel method, were investigated. At the first stage, magnetite nanoparticles were precipitated by sodium hydroxide from a mixture of aqueous solutions of iron(II) and iron(III) sulfates under continuous ultrasonic treatment, after which they were washed with distilled water and dried under vacuum. At the second stage, the resulting magnetite particles were coated with silicon oxide according to the Stober method by dispersing them under the ultrasonic treatment in a solution of tetraethoxysilane in n-propanol, followed by hydrolysis of tetraethoxysilane in the presence of aqueous ammonia, washing and drying the obtained materials under vacuum. At the third stage, photocatalytically active particles based on titanium oxide were introduced into the composite by the solvent replacement procedure via dispersing the samples in an aqueous solution of peroxotitanic acid and adding n-propanol, stirring vigorously, followed by activation based on boiling in the water/ethanol (1:1) mixture, washing and drying under vacuum. The properties of samples influenced by the citrate stabilization and separation of magnetite particles at the stage of their synthesis into “light” and “heavy” magnetic fractions, as well as calcination of samples at 450 °C, were studied. The photocatalytic properties of the synthesized samples were studied during photodegradation of methyl orange, as well as their magnetic extraction from the suspension. The physicochemical characterization of the samples was performed using a high-resolution scanning electron microscope, energy dispersive X-ray spectroscopy, X-ray powder diffraction, thermal analysis (TG–DSC), combined with mass spectrometry of gaseous thermolysis products. It has been found that the composites based on the mixed titanium-silicon oxide have a higher photocatalytic activity than the composites based on the pure titanium dioxide obtained via a similar procedure. The resulting photocatalysts can be used to purify water from dyes, followed by their extraction using a magnet.

Experimental and modeling on hydrate phase equilibrium conditions for hydrogen-containing gas mixtures in pure water and brines

Hydrate-based technology is considered as one of potential ways for hydrogen separation and storage. Additionally, it has been reported that injecting CO2/H2 mixture is an effective approach to the enhancement of natural gas hydrate exploitation. Hence the determination of hydrate formation conditions of hydrogen containing gas mixtures is of fundamental significance. A series of hydrate formation conditions of hydrogen-containing gas mixtures were then measured under 273.8 to 285.5 K and 2.61 to 10.52 MPa, including 3 binary (CH4 + H2) gas mixtures and 5 ternary (CH4 + CO2 + H2) gas mixtures in pure water, as well as 8 ternary (CH4 + CO2 + H2) gas mixtures in aqueous solutions of NaCl and Na2SO4. Meanwhile, a thermodynamic model for predicting hydrate formation conditions of hydrogen-containing systems were developed, in which Chen–Guo hydrate model was used to calculate the fugacities of guest species in hydrate phase and Patel–Teja equation of state was used to calculate the fugacities of guest components in gas phase and those of water in aqueous solutions. Two mixing rules, van der Waals mixing rule and Wang-Sandler mixing rule, were applied in parallel to determine the values of parameters of Patel–Teja equation of state. The overall average absolute deviation on formation pressure for 273 data points is 4.61 % when using Wang-Sandler mixing rule while it is 5.70 % when using van der Waals mixing rule. The experimental data and prediction method presented might be of significance for both exploitation of natural gas hydrate via injecting CO2/H2 mixture as well as the purification of hydrogen via forming hydrate.

Aqueous liquid chromatography with mobile phases of sodium dodecyl sulphate and ionic liquid

In conventional reversed-phase liquid chromatography (RPLC) with hydro-organic solvents, basic cationic solutes yield retained, broad, asymmetric peaks, owing to their interaction with free anionic silanols in the stationary phase. RPLC mobile phases to which the anionic surfactant sodium dodecyl sulphate (SDS), or an ionic liquid (IL) are added, have been proposed as solutions, since these additives are able to block the silanol effect thus improving the chromatographic performance. With these additives, it is however necessary to increase the elution strength by adding an organic solvent, such as an alcohol or acetonitrile. A novel aqueous liquid chromatographic mode (in the absence of organic solvent) is here proposed, where the mobile phases contain only a mixture of aqueous solutions of SDS and an IL derived from 1-alkyl-3-methylimidazolium associated to chloride, both environmentally friendly. When these reagents are added, the anionic surfactant adsorbed on the stationary phase is able to attract the cationic solutes, whereas the adsorbed IL cation repels them. The combination of both effects (attraction and repulsion) allows the modulation of retention, by varying the IL/SDS ratio. Given the character of the additives, a type of green liquid chromatography is achieved. In this work, the chromatographic behavior of six basic compounds of pharmaceutical interest, the β-adrenoceptor antagonists acebutolol, atenolol, carteolol, metroprolol, oxprenolol and propranolol, is examined. In order to assess the chromatographic behavior of the mixed mobile phases containing SDS and IL, changes in retention, peak profile and resolution of mixtures of the analytes were explored at varying concentration of the additives.

Electron beam irradiation applied for the detoxification and degradation of single ciprofloxacin aqueous solution and multiclass pharmaceutical quaternary mixture

The application of electron beam irradiation for detoxification and degradation of single antibiotic ciprofloxacin (CPF) and in a mixture with multiclass pharmaceuticals in aqueous solutions was carried out. Ecotoxicity assays indicated that the green algae were most sensitive to antibiotic and also that the presence of several pharmaceutical increased the toxicity. After the irradiation treatment, degradation results of single antibiotic indicated reduction of 95.86 % at 1.0 kGy. Total organic carbon decreased up to 38 % at 5.0 kGy. At lower doses (1.0 kGy), no effect in toxicity was evidenced, however, increase in toxicity for Vibrio fischeri was observed after 2.5 kGy. For Daphnia similis exposure, an increase in toxicity was noted for all applied doses. In contrast, for the green algae R. subcapitata toxicity reduction varied from 62.3 to 81.9 % at the evaluated doses. Toxicity assays to microbes E. coli and S. aureus reduced antibacterial activity of CPF after irradiation treatment. Regarding the irradiated quaternary mixture at 2.5 kGy, reduction up to 96 % was achieved for the ciprofloxacin, metformin and acetylsalicylic acid, and 81 % removal was achieved for fluoxetine. Acute assays with V. fischeri indicated no increase in toxicity, while some increase was noted for D. similis (acute effects). Nevertheless, chronic assays data indicated low toxicity reduction (14 %) with D. similis, and complete detoxification was shown for the green algae after the irradiation. In addition, decrease in antimicrobial activity was noted after the treatment. Furthermore, the in-silico model was not enough accurate for the prediction of CIP toxicity. These findings showed that electron beam irradiation can be applied for reducing the impacts of antibiotics in aquatic ecosystem. Measuring toxicity on living-organism from different trophic levels are useful tools to evaluate the interaction of mixtures and also to assess toxicity of the generated byproducts.

Non-disruptive mixing of cyclodextrins and wormlike micelles in the non-dilute regime

The encapsulation of hydrophobic molecules for different applications is of great importance, especially for pharmaceutical science, as such molecules can be used as carriers of other molecules. Among other possible molecules than can be used for encapsulation, cyclodextrins (CDs) are of particular interest as they have the ability of hosting hydrophobic molecules due to their structure which consist of a hydrophobic inner cavity and a hydrophilic outside surface. This property allows them to form inclusion complexes with amphiphilic molecules like surfactants. In this work we investigated the interaction of Cetyltrimethylammonium bromide and sodium salicylate mixtures (CTAB-NaSal) in aqueous solution with α-cyclodextrin (αCD), β-cyclodextrin (βCD) or 2-hydroxypropyl-α-cyclodextrin (HPαCD), in a regime of concentration where the CTAB-NaSal system self-assembles in wormlike micelles. Depending on CD concentration, the new system features a color change from clear to white. The rheological behavior of the new systems was measured, obtaining viscoelastic spectra and flow curves in function of CD concentration. Structural micellar changes produced by the CD incorporation were obtained and analyzed via MD simulations. The addition of CD slightly changes the typical viscoelastic behavior of the CTAB-NaSal system and maintains the Maxwellian behavior typical of wormlike micelles, although the viscosity of the solution decreases. These experimental and numerical findings show that the addition of CDs instead of disrupting the micellar structure, roughly preserve it, and produce important changes in the optical properties above a critical CD concentration due to the formation of small aggregates on the surface of the micelle. Our results are evidence of a non-disruptive interaction between self-assembled structures and CDs, giving a new type of material not only with possible encapsulation properties but also with a non-trivial rheology.

Synthesis, Self‐Aggregation, Interfacial Behavior and Interaction Studies of Non‐ Cytotoxic Caffeinium‐Based Surface Active Ionic Liquids with Sodium Dodecyl Sulfate

Caffeinium-based surface-active ionic liquids (SAILs), (1-(2-alkanoyl oxy) ethylcaffeinium bromide), [CnEcaf]Br with variable chain length (n=12, 14, 16) were synthesized and their molecular structures were explored by multiple spectral techniques. The critical micelle concentration (CMC) of pure SAILs and their mixtures with sodium dodecyl sulfate (SAIL-DS) in aqueous solution was determined by employing various techniques at 298 K. The tensiometry and dynamic light scattering (DLS) techniques have been employed to gain insight about the interfacial behavior and aggregate size of cat-anionic mixtures in aqueous solution. Interestingly, the interaction parameters ( ) showed strong synergism between these two oppositely charged molecules. Further, it was found that SAIL-DS cat-anionic mixtures exhibit excellent adsorption efficacy and are more effective in lowering the surface tension of water as compared to pure SAILs. The DLS results showed the formation of mixed-size aggregates in SAIL-DS systems. The contact angle and wetting properties of pure SAILs over the parafilm surface were also determined using a static sessile drop method. Further, MTT assay was used to determine the biocompatibility of SAILs on Human embryonic kidney (HEK-293) cell line and in-vitro anti-cancer activity on Lung cancer cells (A549). These SAILs displayed substantial cytotoxicity against cancerous cells, indicating that they could be useful in a variety of biological applications.

Tuning the ionic character of sodium dodecyl sulphate via counter-ion binding: An experimental and computational study

Solutions of surfactants exhibit remarkable features, such as a tunable amphiphilic character, which can further be varied for ionic surfactants through variations in their Coulombic interactions. These properties are very useful in many industrial applications such as in extraction, purification, and formulation processes, as detergents, wetting agents, or emulsifiers. Rather unexpectedly, the addition of tetrabutylammonium chloride ([N4,4,4,4]Cl) to solutions of the ionic surfactant of sodium dodecyl sulphate (SDS) results in the appearance of a phase transition above the lower critical solution temperature (LCST), a property usually associated with non-ionic surfactants. The aim of this study is to provide a detailed nanoscopic scenario on the interaction between SDS micelles and [N4,4,4,4]Cl moieties to better understand the nature of the LCST cloud point and how to confer it to a given ionic surfactant system. A coarse-grained molecular dynamics (CG-MD) computational framework, under the latest MARTINI 3.0 force field, was developed and validated using available literature data. The impact of [N4,4,4,4]Cl concentration in the phase of SDS micellar aqueous solutions was then characterized and compared using experimental results. Specifically, dynamic light scattering (DLS) measurements and small-angle X-ray scattering (SAXS) profiles were obtained at different [N4,4,4,4]+/[DS]- molar ratios (from 0.0 to 1.0) and compared with the CG-MD results. A good agreement between computer simulations and experimental findings was obtained, reinforcing the suitability of GC-MD to simulate complex phase behaviors. When the [N4,4,4,4]+/[DS]- molar ratio is < 0.5, a weak impact of the cation in the micellar distribution was found whereas for ratios > 0.5, the system yielded clusters of enclosed small [DS]- aggregates. Thus, the CG-MD simulations showed the formation of mixed [DS]- and [N4,4,4,4]+ aggregates with [N4,4,4,4]+ cations acting as a bridge between small [DS]- micelles. The CG-MD simulation framework developed in this work captured the role of [N4,4,4,4]+ in the micellar phase transition whilst improving the results obtained with preceding computer models for which the limitations on capturing SDS and [N4,4,4,4]Cl mixtures in aqueous solutions are also shown in detail.

Ultrasound-enhanced air-assisted liquid-liquid microextraction for the UPLC determination of organophosphorus pesticides in river water

Organophosphorus pesticide (OPP) residues in environment are harmful to ecosystem and human health. In this study, an ultrasound-enhanced air-assisted liquid–liquid microextraction (UE-AA-LLME) method was developed for ultra-high performance liquid chromatography (UPLC) determination of OPPs in water samples. The UE-AA-LLME was performed in a 1.5-mL centrifuge tube under ultrasound condition by sucking in and pushing out the mixture of aqueous solution and extraction solvent using a 2-mL syringe. After centrifugation, the sediment layer was collected and analyzed by UPLC. The parameters affecting the extraction efficiency including the type and volume of extraction solvent, pH, and extraction cycles were optimized. Under the optimized conditions, the limit of detection (LOD) of target OPPs ranged from 0.04 to 0.15 μg/L, and good linearities were acquired with correlation coefficients higher than 0.9927. The recoveries of target OPPs were evaluated to be 75.4–112.6 %, with relative standard deviations (RSDs) lower than 14.9 %. The proposed UE-AA-LLME method was successfully employed for the UPLC determination of OPPs in an urban river of Hangzhou, China. The results revealed that six OPPs were detected in the river waters at the levels of 0.06–0.54 μg/L, and the levels of OPP residues in autumn were higher than those in winter. The risk assessment suggested that there was no human health risk of OPP residues in the river water for adult and child by ingestion pathway.

Application of group method of data handling and gene expression programming for predicting solubility of CO2-N2 gas mixture in brine

The solubility of CO2-N2 gas mixtures in water is important for CO2/flue gas sequestration in aquifer. Having precise thermodynamic measurements as well as credible prediction models to utilize in innovative carbon capture and storage (CCS) systems is critical. In this study, two simple-to-use white-box models, including Gene Expression Programming (GEP) and Group Method of Data Handling (GMDH) models, have been developed using 289 experimental data to predict the solubility of CO2-N2 gas mixtures in aqueous solutions. Four tuned equations of state (EOSs), namely Peng-Robinson (PR), Soave-Redlich-Kwong (SRK), Zudkevitch-Joffe (ZJ), and Redlich-Kwong (RK), as well as the outcomes of the GEP and GMDH, were compared. The results show that the tuned EOSs perform much better than the untuned EOSs. The results show that the GMDH model has the best predictive performance such that the obtained values of root mean square error (RMSE) and coefficient of determination (R2) are 0.000564 and 0.9792, respectively. It should be noted that the GEP model also has acceptable accuracy, with RMSE and R2 values of 0.00081 and 0.9465, respectively. The SRK model obtained the best outcomes among the EOSs for the solubility of the CO2-N2 gas mixture in aqueous solution, with RMSE and R2 values of 0.00128 and 0.9561, respectively. The results also show that the solubility of CO2 in aqueous solutions is much higher than N2, and increasing the pressure increases the solubility of CO2 and N2 in aqueous solutions, while increasing the CO2 content increases and decreases the solubility of CO2 and N2, respectively. Group error analysis also shows that the developed models have less error in low values of temperature, pressure, and CO2 content. Finally, in order to validate the results of the GMDH and GEP models, the leverage technique has been utilized, which illustrated that 95% of the data are in the valid region, thus, the developed models are statistically reliable. The findings of this study can help for better understanding the solubility process of CO2 and N2 in water to overcome thermodynamic and environmental challenges.

Multifunctional quaternary ammonium surfactants with controlled release of carbonyl perfumes

The development of structurally diversified surfactants with multifunctional performance is an important task. Herein, we report a series of quaternary ammonium salts (QAS) as surfactants with hydrazone linker between a long chain and a triggered release of various fragrances. The resulting QAS with build-in aldehydes as a carrier of fragrances exhibited excellent amphiphilicity in water, their surface activity is evaluated by testing surface tension of the micelles in water with γ-CMC values ranging from 16.19 to 38.02 mN/m. Releasing performance by hydrolysis of hydrazones, meanwhile the formation of hydrazine derivatives as dynamic mixtures in acidic aqueous solutions, is investigated by headspace solid-phase micro-extraction (SPME) in combination with gas chromatography (GC) analysis, the results showed significant retention capacity for volatile aldehydes in up to 25 times higher than the neat reference of the corresponding aldehydes. The antibacterial performance of QAS is expressed by the minimum inhibitory concentration (MIC) values, along with an excellent activity on Gram-positive bacteria in the lowest concentration of 2 μg/mL. These QAS could be regarded as suitable fragrance delivery system in potential applications.

Facile preparation of graphene nitride by irradiating MHz ultrasound

The present study aimed at developing a simple sonochemical method to prepare graphene nitride from the mixture of graphite and aqueous ammonia solution. Ultrasound of 1.6 MHz was irradiated to the sample in a fabricated sonoreactor at predetermined ultrasonic power and duration. The one-pot method succeeded in the preparation of graphene nitride. The generation was proven by XPS analysis in finding N1S peak in the spectrum. Detail analysis of N1s peak suggested that the major nitrogen species was pyrrolic type. Furthermore, the presence of CO bond proved the oxidation by OH radical. The reaction product had the value of N/C as high as 0.08, which is comparable to reported values for ultrasonic preparation of graphene nitride. The fact indicates that the significance of chemical effects of MHz range ultrasound, and the finding of the simple preparation method will accelerate practical application of graphene nitride.

Low-temperature synthesis of K0.5Na0.5NbO3 ceramics in a wide temperature window via cold-sintering assisted sintering method and enhanced electrical properties

High temperatures (≥ 1100 °C) and narrow temperature window (∼ 20 °C) for sintering dense K0.5Na0.5NbO3 ceramics always deteriorate their electrical properties. Here, via cold-sintering assisted sintering method, dense K0.5Na0.5NbO3 ceramics were obtained in a wide temperature span between 800 °C and 1000 °C. An aqueous solution of NaOH and KOH mixture was used as transient liquid. Effects of liquid content (LC), molar concentration (MC) of liquid, cold-sintering temperature (TCS), and post-annealing temperature (TAN) on densification and electrical properties of the ceramics were investigated in detail. The ceramics prepared using LC = 10 wt%, MC = 10 mol/L, TCS = 350 °C, and TAN = 900 °C exhibit excellent electrical properties with d33 = 123 pC/N, εr = 609, tanδ = 0.021, Pr = 28.0 μC/cm2, Pm = 39.2 μC/cm2, and Ec = 20.3 kV/cm. Compared to the ceramics with same or similar compositions via conventional solid-state sintering, the present K0.5Na0.5NbO3 ceramics exhibit excellent electrical properties. The study endows the cold-sintering assisted sintering the successful method to prepare K0.5Na0.5NbO3 ceramics at low temperatures and in a wide temperature window.

Mechanism of oxidative destruction of polyvinyl alcohol under the action of ozone-oxygen mixture in aqueous solutions

Mechanism of oxidative destruction of polyvinyl alcohol under the action of ozone-oxygen mixture in aqueous solutions

Numerical analysis of the liquid-liquid phase separation in the antibody–human serum albumin mixtures in aqueous buffer solution

We present a theoretical study of colloidal stability of mixtures of immunoglobulin molecules and human serum albumin in aqueous buffer solution at physiological pH. The antibodies are pictured as an assembly of seven hard spheres assuming (on the average) the Y-like arrangement. Globular proteins are represented as hard spheres with attractive sites to bind immunoglobulin molecules. We use Wertheim’s thermodynamic perturbation theory to perform calculations of measurable properties. Parameters to describe the sizes of both species are taken from previous experimental studies. The immunoglobulin-human serum albumin interaction parameters were fitted on basis of the best agreement between theory and measurements, utilizing experimental data for the liquid–liquid phase separation. We calculated chemical potentials and the equation of state for the model mixture to determine the liquid–liquid part of the phase diagram. The agreement between our theoretical analysis and experimental data is in the range from qualitative to quantitative. The fitted immunoglobulin–human serum albumin attractive potential, leading the agreement with experimental data, appears to be of very short range.

Effects of Acidic Solution on the One-Step Electrodeposition of Prussian Blue Nanocrystals on Screen-Printed Carbon Electrodes Modified with Magnetite Nanoparticles

This study investigated the electrochemical synthesis of Prussian blue (PB) nanocrystals on a screen-printed carbon electrode (SPCE) modified with a thin film of magnetite nanoparticles (nano-Fe3O4) in aqueous mixture solutions of potassium hexacyanoferrate(III) and different kinds of acids. The generated PB nanocrystals exhibited varied voltammetric responses that are highly related to the characteristics and properties of acids in the mixture solution. Interestingly, in the presence of glyphosate as an organic acid, surface magnetite nanoparticles were occluded within electrogenerated Prussian blue nanocubes (PBNC), which are characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR), and cyclic voltammetry (CV). Furthermore, the possible reaction mechanism for the formation of PBNC is proposed in this study. The obtained PBNC was also evaluated as an electrocatalyst of hydrogen peroxide and applied to the detection of glyphosate.