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The presented research aimed at understanding the effect of a highly reactive pozzolan (HRP) on the early age hydration of alite (C 3 S) and tricalcium aluminate (C 3 A). Five supplementary cementitious materials of varying activity were used throughout the investigation. The hydration process was continuously monitored by examining the heat release rate of hydrating pastes (calorimetry) and the conductivity changes of alite and tricalcium aluminate hydrating suspensions (conductometry). Moreover, at specific time intervals, phase composition was analyzed using X-ray diffraction and thermal analysis, along with the liquid phase composition of hydrating suspensions (ICP-OES). The microstructure of hydration products was also observed using TEM and SEM. The results showed that the position of the 'aluminate peak' observed in the calorimetric curves is most likely the result of a synergy of two interactions: the effect of acceleration of C 3 S hydration process and the effect of HRP on the hydration of C 3 A. The lack of a linear relationship between the amount of heat released and the specific surface area indicated, that despite the significance of physical presence of SCMs, the chemical interactions within the system are more important. The C 3 A reaction is associated with the release of a large amount of heat. In a hydrating C 3 A system, the saturation of the solution with calcium hydroxide has a significant effect on the course of the reaction. During hydration in water, the degree of C 3 A reaction is greater in the presence of HRP, whereas when the system reacts in saturated calcium hydroxide, the degree of C 3 A reaction is lower. It seems that the factor accelerating the C 3 A hydration is the nucleation of products on the surface of HRP grains, leading to the formation of a larger amount of hydrated calcium sulfoaluminates, with simultaneous acceleration of C 3 A dissolution. In saturated Ca(OH) 2 , HRP promotes the formation of ettringite and, most importantly, affects its stability in the solution. Silicate ions originating from the HRP are likely incorporated into the crystallizing phases. In both environments, HRP affects the formation of hydrogarnets (C 3 AH 6). • Significance of chemical nature and surface area of SCM in understanding the filler effect. • Conductometry as a tool for the analysis of early hydration of pure clinker phases. • The role of highly reactive SCM in shaping the aluminate peak on calorimetric curve. • Highly reactive SCM promotes the formation of katoite in hydrating C3A systems. [ABSTRACT FROM AUTHOR]

• Conductometric studies of lithium dodecyl sulfate (LDS) + propranolol hydrochloride (PLH) drug in electrolytes solution. • Cloud point of TX-100 was increased due to introduction of propranolol hydrochloride. • CMC values of LDS+PLH were shown to decrease when electrolytes are present. • Cloud point (CP) of TX-100 + PLH diminishes as electrolytes concentration rises. • Thermodynamic properties for micellization/clouding processes were measured. The investigation of the assembly of lithium dodecyl sulfate (LDS) and cloudy creation of triton X-100 (TX-100) in aqueous solution of amphiphilic drug propranolol hydrochloride (PLH) has been carried out by electrical conductivity and cloud point estimation method respectively. The influences of three potassium electrolytes (KCl, K 2 SO 4 , and K 3 PO 4) on the micellization of LDS and clouding of TX-100 in presence of PLH drug have been examined. The conductivity experiments were conducted at temperatures between 288.15 and 323.15 K, with a 5 K interval. The introduction of PLH drug promotes the micelle formation of LDS up to 1 mmol kg−1 of drug. The critical micelle concentration (CMC) values of LDS in aqueous solution of PLH were shifted to lower values in aqueous electrolytes media. The cloud point (CP) of TX-100 + PLH system was observed to be increased with the rise in concentrations of PLH in aqueous medium. The reduction in the CP values of TX-100 and PLH mixed system has been attained with the enrichment of the concentrations of electrolytes and at a specific mole fraction of electrolytes, the CP values exhibited the order: CP (KCl (aq.)) > CP (K 2 SO 4 (aq.)) > CP (K 3 PO 4 (aq.)). The Gibbs free energy of assembly (Δ G m 0) appeared as negative (spontaneous assembly) whereas Δ G c 0 of clouding showed positive magnitudes indicating the nonspontaneous nature of the clouding process. The micellization of LDS demonstrate the endothermic and exothermic nature at lower and higher investigated temperature as revealed from the sign of Δ H m 0 v a l u e s.. The positive values of e n t r p o y Δ S m 0 exhibit the micellization process to be entropically driven phenomena. The phase separation of TX-100 and PLH mixed system is entropy contributed in aqueous medium while the clouding in the presence of salts is enthalpy contributed evidenced from the negative enthalpy of clouding. [ABSTRACT FROM AUTHOR]

Experimental and numerical investigations were carried out to describe the flow of a wet foam under a fence placed in the middle of a horizontal duct with a square crosssection. The aim was to characterize the foam’s flow behaviour and model it using computational fluid dynamics in complex geometrical situations such as those encountered in industrial systems as for the cleaning of food equipment. As fences affect foam structure, organization and flow dynamics, these were characterized for three different flow rate conditions. Measurements using pressure sensors, particle image velocimetry and a conductimetry technique show a reorganization of the foam downstream, with a thicker liquid film at the bottom, larger bubble sizes at the top, as well as a larger void fraction increasing from the bottom to the top. The foam revealed a viscoelastic character as would be the case for a non-Newtonian fluid when passing through the fence. Herschel–Bulkley and/or Bingham laws relating to the presence of an underlying liquid film at the bottom of the channel were selected as being appropriate for this description. After adjusting these parameters from experimental data, computational fluid dynamics analysis was carried out. Results shown a close agreement with experiments using the Herschel–Bulkley model for two very different flow regimes. [ABSTRACT FROM AUTHOR]

• The study on cationic sensitivity of inductance coil based contactless sensor. • Aqueous solutions of 16 metal cations are studied in a broad concentration range. • Sensitivity and linear response range parameters are characterized. • Response dependence of the radius and the charge of the cation are discussed. Contactless sensors for chemical analysis, based on inexpensive and widely available electronic components, are a promising alternative to existing routine laboratory methods. We have proposed a novel type of a contactless sensor, composed of three simple components: an alternate current generator, an inductance coil, and a receiver. The sample, placed into the coil as a core of the inductor, modifies the current passing through the coil. Previously, we have demonstrated that this contactless sensor may have numerous applications for chemical analysis. In this work, we have explored the performance of the coil-based measuring platform further and performed the first systematic study of the response of inductance coil sensor to metal cations in aqueous solutions. Sixteen metal cations with different charge and radii were studied. Linear response ranges, sensitivity values and the comparison between univariate and multivariate regression modeling are presented. The largest linear response range was observed for transition metal cations Ni2+, Cu2+, Pb2+ and Nd3+ (10-3 – 10-1 M), the narrowest – for Li+ and Gd3+ (10-2 – 3.2x10-1 M) with R2 values larger than 0.94. The dependence of the response on the radius and the charge of the cation are discussed. The analytical characteristics of the device show its potential in contactless and low-cost chemical analysis and set the ground for the future research. [ABSTRACT FROM AUTHOR]

This research work provides insight into the solubilization of a non-ionic drug captopril (CAP) in the micellar media of cationic surfactant cetyltrimethylammonium bromide (CTAB) and mixed micellar media of two nonionic surfactants Tween-80 and Triton X-100. CAP−surfactant interactions were analyzed by simple and differential absorption spectroscopy as well as by conductometry and the efficiency of the selected micellar system was assessed by calculating the values of partition coefficient (K x), the free energy of partition (∆ G P ), binding constant (K b) and the free energy of binding (∆ G b ). Results from differential spectroscopy depicted a noteworthy increase in the solubilization of CAP with the addition of nonionic surfactants (Tween-80 and TX-100) in the micellar solution of CTAB. Furthermore, conductometric response of micellar media has been used to calculate the degree of dissociation (β), the free energy of micellization (∆ G m ) thermodynamic parameters of micellization. [Display omitted] • TX-100 and Tween-80 enhance solubilizing capacity of CTAB micellar media. • CAP is accommodated in palisade layer of micelle. • Solubilization of CAP is exothermic and spontaneous process accompanied with increase in entropy. [ABSTRACT FROM AUTHOR]

• The interaction of SDS and CTAB with AM drug was studied by conductometric method. • The CMC values were determined as function of temperature and AM concentration. • Thermodynamic properties such as Δ G 0 , Δ H 0 and and Δ S 0 for micellization were determined. • MD simulation was made to understand the molecular interactions. • The RMSDs, electrostatic, H binding and hydrophobic interactions were determined. • The simulation and experimental results were in agreement with each other. In the present work, the interaction of sodium dodecyl sulfate and cetyl trimethyl ammonium bromide surfactants with amantadine drug in aqueous solutions was studied using conductometric measurements and molecular dynamic simulation. Conductometric data were used to determine the critical micelle concentration (CMC) values of surfactants on various amantadine aqueous solutions at T= (300.2, 310.2 and 320.2) K and 0.1 MPa. The effect of amantadine concentration (m = 0.0005, 0.0010, 0.0015 and 0.002 mol.kg −1) on CMC of sodium dodecyl sulfate and cetyl trimethyl ammonium bromide surfactants was investigated. It was observed the CMC value of sodium dodecyl sulfate surfactant increases with increasing of amantadine concentration whereas the CMC values of cetyl trimethyl ammonium bromide surfactant decrease with increasing of amantadine concentration at the same temperature. Then, the thermodynamic properties such as standard Gibbs free energy, enthalpy, and entropy for micellization in aqueous solutions were determined. In addition, molecular dynamic simulation was carried out to understand the interaction sodium dodecyl sulfate and cetyl trimethyl ammonium bromide surfactants with amantadine at the molecular level and microscopic interactions. The root-mean-square deviations and electrostatic, hydrogen binding and hydrophobic interactions were determined by MD simulations. It was seen, the electrostatic and hydrogen bonding interactions play a crucial role in sodium dodecyl sulfate and amantadine aqueous system. The obtained results showed the simulation and experimental data are in agreement with each other. [ABSTRACT FROM AUTHOR]

Abstract The newly synthesized Schiff base (HL 2 ) and its binary [ML 2 ] type of Cu(II) and Fe(III) complexes were characterized by various spectroscopic methods. The photoluminescence property of [CuL2 2 ] and [FeL2 2 ](NO 3) complexes, and HL 2 was studied in the absence and presence of Cu2+/Fe3+ ions in DMF: aqueous HEPES buffer (v: v, 1: 1, pH = 6.8). The conductance behaviors of compounds were investigated. The complexation reaction of the receptor with these ions, and the formation constants were determined in solution by spectrophotometric and conductometric method. The sensing ability of HL 2 against Cr3+, Fe3+, Ni2+, Zn2+, Cu2+, Co2+, Pb2+, Ba2+ and Ag+ ions were also evaluated in DMF: HEPES. High sensitivity and selectivity was achieved for Cu2+ and Fe3+ by UV–vis spectra in the presence of other ions, and it showed reversibility with EDTA. Job's method confirmed 2: 1 structure between HL 2 and Cu2+ and Fe3+. Receptor was applied for the ppm level detection of Fe3+ ion. Also, it sensed pH by "naked eye". Upon the addition of acid and base, its color instantly changed from yellow to colorless, corresponding to a blue shifting and disappearance in the absorption bands for acid and to orange for base. Graphical abstract Image 1 Highlights • Schiff base (HL2) and its binary Cu(II) and Fe(III) complexes were newly synthesized and characterized by various spectroscopic methods. • The photoluminescence property of [CuL22] and [FeL22](NO3) complexes, and HL2 was evaluated in the absence and presence of Cu2+/Fe3+ ions. • The complexation reaction of the receptor with these ions, and the formation constants were investigated in solution by spectrophotometric and conductometric method. • The sensing ability of HL2 against metal ions was also studied by naked eye and UV-vis spectra. [ABSTRACT FROM AUTHOR]

Abstract Non-aqueous solvents are applicable in industrial and chemical reactions as well as some analytical methods such as electrochemistry. Application of quantitative structure-electrochemistry relationship (QSER) modeling in non-aqueous media can reduce trial-and-error experiments and more accurate estimation of target properties with lower number of runs. In the current study, for the first time, QSER was applied in conductometry as a wide field in electrochemistry. The target properties for modeling were the limiting molar conductivities of three alkali metal ions (Li+, Na+, K+) in water and various organic solvents; and empirical scales of the utilized solvents were applied as the independent set of variables. R2 in training sets of Li+, Na+ and K+ models were 0.94, 0.95 and 0.90 respectively. Models also showed good prediction ability and R2 in test sets of Li+, Na+ and K+ models were 0.95, 0.94 and 0.98 respectively. In addition, more statistical evaluations were done to show the predictability and stability of proposed QSERs. One of the advantages of suggested QSER models based on solvent empirical scales is the clear meaning of the solvent scales and their ability in description of solute-solvent interactions. Based on obtained results, the impact of some solvent features such as electron-donating power, electron-donating power, dipolarity-dipolarizability, hydrogen bonding, hydrogen-bond acceptor basicity and solvent acceptor number on the conductivity of lithium, sodium and potassium ions were discussed. Highlights • Limiting molar conductivities of Li+, Na+ and K+ in different solvents was modeled. • Structure and properties of investigated organic solvents were effective on conductivity values. • Description and comparison of three models suggested for monovalent alkali metals were done. • The results can be made useful information for non-aqueous conductivity. [ABSTRACT FROM AUTHOR]

Abstract A new conductometric biosensor based on coimmobilized urease and arginase has been developed for arginine determination in pharmaceutics. First, the main parameters of the selected method of immobilization (concentrations of arginase, urease, and glutaraldehyde, time of incubation) were optimized. An influence of the solution parameters (buffer ionic strength, capacity, pH, Mn2+ concentration) on the biosensor operation was studied, working conditions were optimized. After biosensor optimization, the main analytical characteristics were as follows. The limit of detection - 2.5 μM, the linear range - 2.5–500 μM, the sensitivity to arginine 13.4 ± 2.4 μS/mM, the response time - 20 s. The signals repeatability and operational stability in continuous exploitation were studied over one working day and during one week. Additionally, the selectivity of the developed biosensor towards arginine was essayed relative to other amino acids. The developed biosensor has been used to measure arginine concentrations in some drugs. The results obtained were in high correlation with the characteristics declared by producers. Highlights • We developed a conductometric arginine biosensor based on arginase and urease. • Biosensor showed good signal reproducibility, sensitivity and selectivity. • Biosensor was used to analyze the arginine concentration in pharmaceutical samples. • Results obtained were in good correlation with concentrations declared by producers. [ABSTRACT FROM AUTHOR]

[Display omitted] • Solubilization of [Ni(dmen) 2 F 2 ].8H 2 O complex in micellar media of sodium stearate. • Partitioning and thermodynamic parameters' determination by UV–Vis spectroscopy and conductometery. • Increase in the CMC of surfactant in the presence of nickel fluoride complex. This study was aimed to investigate the physicochemical behavior, solubilization and interaction of coordination complex [Ni(dmen) 2 F 2 ].8H 2 O (NDC) with anionic surfactant sodium stearate (SS). The thermodynamic parameters of solubilization such as standard free energy (Δ G m 0), enthalpy (Δ H m 0) and entropy (Δ S m 0) changes of micellization were evaluated by using conductometric measurements. These parameters revealed that the phenomenon of micellization is entropy driven and spontaneous due to the more negative value of (Δ G m 0). The quantitative estimation of partitioning parameters such as partition coefficient (K x), binding constant (K b), standard energy of partition (Δ G part O) , and standard binding energy (Δ G bind O) revealed the complex-surfactant interaction. Spectroscopic study indicated the high degree of interaction and solubilization of NDC in SS micellar media.. The partitioning results not only governs the mechanism of solubilization but also gives understanding about the partitioning of NDC across membranes in biological systems. [ABSTRACT FROM AUTHOR]

The alternative models of ionic equilibria in acetonitrile solutions of alkaline earth percholorates in the presence of 3-hydroxyflavone (HL) were studied by conductometry at 288.15, 298.15, 308.15, 318.15, and 328.15 K. Using a procedure specially developed for this task it was shown that in the solutions containing Ca(ClO 4 ) 2 and Sr(ClO 4 ) 2 the complexation of the cation (M 2 + ) by the HL molecule leads to the formation of the doubly-charged [M(HL)] 2 + complex species. In contrast to them, in the presence of Ba(ClO 4 ) 2 HL interacts with the ion pair BaClO 4 + forming the singly-charged [BaClO 4 (HL)] + complex. The limiting equivalent conductivities as well as the constants of complexation were estimated. The latter were calculated by taking into account the ion association between cation and anion of initial salts and activity coefficients, that is the ‘true’ thermodynamic constants were found. The reliability of the proposed approach was additionally checked by analyzing artificially noised model experimental data. It was shown that the fitted parameters can be satisfactorily reproduced even at the noise level equal to 2%. The limiting equivalent conductivities of the [Ca(HL)] 2 + , [Sr(HL)] 2 + and [BaClO 4 (HL)] + complex species were interpreted in terms of the Stokes radii whose values indicate very weak solvation of the formed complexes. The variation of the constants of complexation among cations was found to be in agreement with the values of primary association constants. [ABSTRACT FROM AUTHOR]

A flow injection conductometric (FIC) system for determination of total Kjeldahl nitrogen (TKN) was developed for estimating total protein content in food. A small scale Kjeldahl digestion was performed with a short digestion time of only 20 min. The digested solution was injected into the FIC system, and TKN was converted to ammonia gas in an alkaline donor stream of the system. The gas diffused through a membrane and dissolved into an acceptor stream causing an increase in conductivity as detected by a detector and recorded as a peak. Under the optimum condition, a linear calibration graph in the range of 4.00–100.00 mg L −1 was obtained with LOD of 0.05 mg L −1 . A good precision (0.04% RSD, n = 11, 30.00 mg N L −1 ) and high sample throughput of 72 h −1 was achieved. The method was applied for determination of protein in some traditional northern Thai foods, revealing that they are good sources of proteins. [ABSTRACT FROM AUTHOR]

The complexation reaction between Y 3+ cation and macrocyclic ligand, 4′-nitrobenzo-18-crown-6 (4′NB18C6), was studied in acetonitrile–methanol (AN–MeOH), acetonitrile–1,2-dichloroethane (AN–DCE), acetonitrile–dimethylformamide (AN–DMF) and acetonitrile–ethylacetate (AN–EtOAc) binary mixed solvent solutions at different temperatures using the conductometric method. The conductance data show that in most cases, the stoichiometry of the complex formed between 4′NB18C6 and Y 3+ cation is 1:1 [M:L], but in the case of AN-DCE binary solution (mol% DCE = 50) at 15, 25 and 35 °C, a 2:1 [M 2 :L] and also a 2:2 [M 2 :L 2 ] complexes are formed in solution. The results show that the stoichiometry of the complex formed between 4′NB18C6 and Y 3+ cation changes with the composition of the mixed solvents and even with temperature. The stability constant of the 1:1 complex was determined using a computer program, GENPLOT. The stability order of (4′NB18C6.Y) 3+ complex in pure studied solvents at 25 °C was found to be: EtOAc > AN > MeOH > DMF and in the case of the mixed solvent solutions with 25 mol percent of AN at 25 °C was: AN-DCE > AN-EtOAc > AN-MeOH ∼ AN-DMF. The values of stability constant (log K f ) of (4′NB18C6.Y) 3+ complex which were obtained from conductometric data, show that the stability of the complex is not only affected by the nature and composition of the solvent system, but it is also influenced by the temperature. In all cases, a non-linear behavior is observed for changes of log K f of the (4′NB18C6.Y) 3+ complex versus the composition of the binary mixed solvents. The values of standard thermodynamic quantities (Δ H ° c and Δ S ° c ) for the complexation process which were obtained from temperature dependence of the stability constant of (4′NB18C6.Y) 3+ complex, show that depending on the solvent system, in most cases, the complex is enthalpy and also entropy stabilized, but in some cases, it is stabilized or destabilized from these view points. [ABSTRACT FROM AUTHOR]

Application of hydrocolloids is highly dependent on their structural and conformational properties. Molecular weight, macromolecular geometry, hydrophobicity and electric charge are, therefore, often researched. In the presented study, influence of sodium chloride on conformation and structure of sugar beet pectin in aqueous solutions was first time thoroughly characterized. Viscosity, surface tension, specific conductivity, zeta potential and pH of sugar beet pectin aqueous solutions were monitored and measured following the addition of sodium chloride. Relative viscosity of sugar beet pectin aqueous solutions decreased by up to 29.19% following the addition of sodium chloride. The highest decrease in relative viscosity values was noticed at the lowest sodium chloride concentrations used (0.2 g L−1 to 2 g L−1). The corresponding changes at the lowest sodium chloride concentrations used were also noticed in the obtained specific conductivity curves. Calculated diameter of sugar beet pectin macromolecule decreased by 19.98% following the addition of 10 g L−1 sodium chloride. Surface tension values of sugar beet pectin aqueous solutions were strongly influenced by the addition of sodium chloride. Decrease in zeta potential of sugar beet pectin aqueous solutions with addition of sodium chloride was observed. Presented results suggested that the addition of sodium chloride to sugar beet pectin aqueous solution could cause conformational changes of macromolecular chain suggesting possible transition from linear to globular conformation. [Display omitted] • Sodium chloride impact on SBP properties in aqueous solution was investigated. • Addition of sodium chloride strongly affected SBP viscosity characteristics. • Addition of sodium chloride decreased SBP macromolecule calculated diameter value. • Sodium chloride negatively affected surface active properties of SBP. [ABSTRACT FROM AUTHOR]

[Display omitted] • Nature of interactions of imidazolium chloride ILs with different chain length in tetraethylene glycol investigated. • Ionic association is more significant in TEG than in EG. • Process of ion pair formation is spontaneous and endothermic and entropy-driven. • [C 1 mim][Cl], [C 2 mim][Cl], [C 4 mim][Cl] and [C 6 mim][Cl] in TEG are structure-maker, while [C 0 mim][Cl] is structure-breaker. • Experimental results were supported by molecular dynamic simultations. In this work, the influence of the side chain length of five ionic liquids (ILs) containing N3-substituted 1-methylimidazolium chloride ionic liquids, [C n mim][Cl] (n = 0, 1, 2, 4, 6) on the interactions with tetraethylene glycol (TEG) was studied. Measuring the density and electrical conductivity of the IL + TEG mixtures in the temperature range (278.15–313.15) K, the values of physicochemical properties, such as apparent molar volume, apparent molar volume at infinite dilution, Masson's interaction coefficient, limiting apparent molar expansibilities, Heppler's coefficient, ion association constants, thermodynamic parameters of ion-pair formation, as well as diffusion coefficient were calculated. The results obtained from these experiments were supported by molecular dynamics (MD) simulations. In comparation with systems containing ethylene–glycol (IL + EG), the calculated free volumes in TEG are about three times higher than in EG. Therefore, assuming that the packing effect is responsible for the lower apparent molar volume at infinite dilution, values in the TEG seem reasonable. The values of ion association constants in TEG are lower than in EG. The ion association process is spontaneous for all investigated ILs in TEG solutions and entropy-driven. [ABSTRACT FROM AUTHOR]

[Display omitted] • Soap film as a low-cost sensor for headspace extraction and conductance sensing ammonia. • Soap film was manually generated on a 3D printed frame and enables rapid renewal to avoid contamination. • Micro-molar per litter level of total ammonium in solution was able to be measured. In this work, a novel, low-cost soap-film sensor for detecting ammonia in environmental water and saliva was developed. A 3D printed circular frame with two stainless steel electrodes was implemented as a carrier for a soap film. The soap film was manually generated by pulling the 3D printed frame from a mixture solution containing 20.7 g/L gelatin, 241.4 mL/L Glycerol, 34.5 mL/L Triton X-100 and 100 mM boric acid. The conductivity of the soap film was measured with a lab-made detector. For liquid sample analysis, sample and NaOH solution were mixed in a reagent bottle as the gas-diffusion vessel (GDV). The released ammonia from the reaction was then diffused into the headspace of the GDV and absorbed by the soap film. The conductivity increasing rate of the soap film was used for quantifying the ammonium concentration in sample. The analytical performance parameters were demonstrated, including a linear range of 0–500 μM, a relative standard deviation of 3.2 % (n = 10), and a limit of detection of 14 μM (0.2 mg N/L). This method showed a 90–110 % recovery rate for saliva and water samples. Compared to a reference indophenol blue method, the relative deviations of two method were less than 7.4 % (n = 33). The proposed method is easy to operate, and the device itself is compact and low cost. The soap-film sensor enables rapid renewal to avoid contamination. [ABSTRACT FROM AUTHOR]

This investigation proposes a dual-camera positioning method and the average distance in the cube (AD-Cube) method to explore the effect of three-dimensional (3D) spatial multiphase stirring. The 3D trajectories of the tracer ball were reconstructed in the stirring system using a dual-camera positioning method. The AD-Cube method for calculating the mixing uniformity within the cube region was proposed and verified by rigorous and valid numerical validation (the standard reference value was approximately 0.6617). The negative correlation coefficient between conductometry and the AD-Cube method for the evaluation of the mixing effect was −0.9118. The stirring region was equally divided into several 3D blocks, and the relationship between the whole and local was elaborated to provide more accurate information for the 3D uniformity metric. Moreover, the volume of the stirring dead zone was estimated by discrete blocking, and the influence of the stirring paddle height from the bottom and agitating motor speed on the stirring effect was studied. This study provides a theoretical basis for optimizing the parameters of a 3D stirring system, designing chemical reactors, and measuring and evaluating the 3D uniformity of stirring systems. [Display omitted] • The proposed method is based on dual-camera positioning and computational geometry. • The 3D uniformity of stirring system is characterized by the novel method. • Effectiveness of the novel method is verified on both numerical and experimental. • Evaluation indicator is established to evaluate the 3D stirring efficiency. • The method can be used in engineering fields of evaluation of 3D uniformity. [ABSTRACT FROM AUTHOR]

[Display omitted] • In water solution, cetylpyridinium and perchlorate ions form low-soluble ionic pair. • The crystallinity degree of the ionic pair samples depends upon synthetic conditions. • Signals shifts in NMR spectra of cetylpyridinium perchlorate are observed compared to the chloride. • The shifts in NMR spectra were explained by micellization and modeled by DFT. Cetylpyridinium perchlorate has been synthesized and characterized by using the differential thermal analysis (DTA), X-ray powder diffraction (XRD) techniques, Fourier transform infrared spectroscopy (FT-IR), and 1H and 13C nuclear magnetic resonance (NMR) spectroscopy. The investigated salt melts congruently at 100 °C. The DTA and XRD results indicate that the cetylpyridinium perchlorate samples synthesized at different temperatures differ in crystallinity. It has been established that the crystallinity degree of the samples affects the decomposition temperature. The highest decomposition temperature (T d = 265 °C) is observed for the sample crystallized at 20 °C. Cetylpyridinium perchlorate crystallizes in the monoclinic crystal system with the cell parameters a = 20.31 Å, b = 16.20 Å, c = 7.25 Å, β = 95.26°, Z = 4. According to the DFT calculations, the interionic interactions in the structure are characterized by electron transfer from the perchlorate anion to the cetylpyridinium cation. This explains a noticeable difference in the 1H NMR chemical shifts of the hydrogen atoms in the ortho -position (∼0.2 ppm) and the α -methylene group (∼0.1 ppm) of the DMSO solutions of the cetylpyridinium perchlorate and chloride salts micelles. The electronic structure analysis of cetylpyridinium perchlorate and cetylpyridinium chloride in terms of the "quantum theory of atoms-in-molecules" and the analysis of non-covalent interactions with the "reduced density gradient" method have revealed the presence of strong interactions between the ions in the DMSO solution. [ABSTRACT FROM AUTHOR]

[Display omitted] • The solutions of iron(II) complex with Spin-crossover were studied by methods of static magnetic susceptibility, UV and visible spectrometry and conductometry. • Solutions of the [Fe(HC(pz) 3) 2 ]ns 2 in DMFA are characterized by a high degree of dissociation by the type of 1,1-charging electrolyte. • The values of the electrolyte dissociation constant is calculated as pK = 2.3. • The activation energy of the charge transfer process is equal E a = 5815 J/mol. • Change in the spin state of the central atom of the complex in solution does not lead to changes in the nature of electrical conductivity and does not change E a. Using methods of static magnetic susceptibility, UV and visible spectrometry and conductometry, dimethylformamide solution of iron(II) complex with tris(pyrazol-1-yl)methane (HC(pz) 3) having the composition [Fe(HC(pz) 3) 2 ]ns 2 (ns = 2-naphthalene sulfonate) has been studied. In solution, as in the solid state, this compound exhibits a spin crossover of 1A 1 ↔ 5T 2 , while in solution it is shifted to a region of lower temperatures and is sharper. It is shown that at a given concentration of 2.5 × 10−4 mol/L at 298 K, the molar electrical conductivity for the [Fe(HC(pz) 3) 2 ]ns 2 complex in dimethylformamide is Λ298k = 100 ± 2 Ohm−1cm2 mol−1. Solutions of the [Fe(HC(pz) 3) 2 ]ns 2 complex in a polar aprotic solvent with high dielectric permittivity are characterized by a high degree of dissociation by the type of 1,1-charging electrolyte. The dependences of the logarithm of the electrical conductivity of the studied solutions as a function of the logarithm of concentration and of 1/T are linear. The values of the electrolyte dissociation constant, pK = 2.3, and the activation energy of the charge transfer process, E a = 5815 J/mol, are calculated. It is shown that a change in the spin state of the central atom of the complex in solution does not lead to changes in the nature of electrical conductivity and does not change E a. [ABSTRACT FROM AUTHOR]

• 112TCE and NaOH reaction kinetics was studied by simulation and experiment. • The conductometry and substrate concentration amplification method were first used. • The kinetic parameters of three parallel reactions were decoupled. • Kinetic parameters of overall and parallel reactions were obtained. Dehydrochlorination of 1,1,2-trichloroethane (112TCE) is a widely used method for preparing vinylidene chloride (VDC), which is an important polymeric monomer and intermediate of refrigerant. However, there are few reports on kinetics of this reaction system. In this work, density functional theory (DFT) calculation analyses and experiments were conducted to investigate the reaction mechanism and kinetics of 112TCE dehydrochlorination with sodium hydroxide (NaOH). DFT simulation results unveiled there were three parallel reactions which produce VDC, cis -1,2-dichloroethylene (C12DE) and trans -1,2-dichloroethylene (T12DE) respectively in the reaction process of 112TCE and NaOH. The activation energy of the reaction to produce VDC was lower than those of the other two reactions. Moreover, the kinetic parameters of the three parallel reactions, such as reaction orders, rate constants, pre-exponential factors and activation energies, were experimentally obtained by decoupling the overall reaction kinetics. All the parallel reactions are bimolecular elimination reactions and the rate expression of the intrinsic kinetics for generating VDC is d C t dt = 1.668 × 10 11 e - 75662 RT C A C B. The reaction rate is three orders of magnitude higher than those of producing C12DE and T12DE, which is consistent with the DFT simulation results. These kinetics results are useful for the process optimization and reactor design in VDC production process. [ABSTRACT FROM AUTHOR]

Herein, conductivity and surface tension measurements have been applied to investigate the mixed micellization of [C 12 C 1 pyrr][Br]/[C 14 C 1 pyrr][Br] in water/Sarcosine media at various temperatures (298.15–313.15K). The cmc* and cmc were used to define the degree of interaction between the two SAILs. In the presence of the amino acid Sarcosine, values of CMC are clearly lesser than the corresponding values in an aqueous media. The well-known Clint, Rubingh, Motomura, and Rodenas models have been employed to estimate the magnitudes of mixed micellar mole fractions (X 1), interaction parameter (β), and activity coefficients (f 1 a n d f 2). The results obtained indicate the effective participation of [C 14 C 1 pyrr][Br] in mixed micellization. At 298.15 K, tensiometric measurements have also been carried out to confirm the outcomes from conductivity analysis for all of the examined systems. The surface parameters which have been elucidated from surface tension measurement include surface tension at cmc(γ c m c ), surface pressure (Π c m c ), surface excess (Γ m a x ) and minimum area per molecule (A min), etc. All of the estimated results indicate an attractive interaction between the components of the studied mixed system. • Influence of Sarcosine on mixed micellization behavior of [C 12 C 1 pyrr][Br]/[C 14 C 1 pyrr][Br] system has been investigated. • Increasing amino acid concentration reduced CMC up to a certain value. • Various mixed micellar, surface-active and thermodynamic parameters of mixed system have been evaluated. [ABSTRACT FROM AUTHOR]

Three new binuclear Cu(II), Mn(II), Co(II) complexes [Cu 2 (L) (ClO 4 )](ClO 4 ) 2 ( 1 ), [Mn 2 (L) (ClO 4 )](ClO 4 ) 2 ( 2 ), and [Co 2 (L) (ClO 4 )](ClO 4 ) 2 ( 3 ), {L = 1,3-bis(2-((Z)-(2-aminopropylimino)methyl)phenoxy)propan-2-ol} have been synthesized. Single crystal X-ray structure analysis of complex 1 showed that the complex is binuclear and all nitrogen and oxygen atoms of ligand (N 4 O 3 ) are coordinated to two Cu(II) center ions. In addition, the crystal structure studying shows, a perchlorate ion has been bridged to the Cu(II) metal centers. However, two distorted square pyramidal Cu(II) ions are bridged asymmetrically by a perchlorate ion and oxygen of hydroxyl group of Schiff base ligand. In addition, the conductometry behaviors of all complexes were studied in acetonitrile solution. [ABSTRACT FROM AUTHOR]

A cost effective flow injection (FI) conductometric system has been developed for determination of total inorganic nitrogen (TIN). The system is aimed for evaluation of nitrogen nutrient in soil for agricultural application. Inorganic nitrogen compounds were extracted from soil according to the standard method by using potassium chloride solution as an extractant, and the extracted solution was then injected into the FI system. Nitrate and nitrite are converted to ammonium ion by an in-line reduction column packed with a Devarda's alloy. A gas diffusion unit was incorporated into the FI system to separate ammonium ion from other ions in a donor stream by forming ammonia gas that can diffuse through a PTFE membrane to re-dissolve in an acceptor stream. Conductance of the acceptor stream was directly proportional to ammonium ion concentration. Various parameters affecting reduction efficiency of the column, e.g., column diameter, column packing procedure, and column length was investigated and optimized. A linear calibration graph in the range of 2.00–60.00 mg L −1 N–NH 4 + ( y =0.123 x +0.039, R 2 =0.997) was obtained with a limit of detection of 0.47 mg L −1 . Sample throughput of 20 samples h −1 was achieved. The result of developed method was correlated with total Kjeldahl nitrogen (TKN) obtained from the Kjeldahl digestion method. The proposed method could be used as an alternative method to the Kjeldahl method for determination of TIN in soil. [ABSTRACT FROM AUTHOR]

In the present work, the conductometric measurements for complexation process between Cr 3+ cation and the macrocyclic ionophore, 4-Isopropylcalix[4]arene (IPC4) were studied in tetrahydrofuran–dimethylsulfoxide (THF–DMSO) binary non-aqueous medium at different temperatures. The results reveal that the stoichiometry of the IPC4–Cr 3+ complex in all binary mixed solvents is 1:1. A non-linear behavior was observed for changes of log K f of this complex versus the composition of the binary mixed solvents, which was explained on the basis of changes occurring in the structure of the mixed solvents and also the preferential solvation of the cation, ionophore and the resulting complex in the solution. The thermodynamic parameters (Δ H° c and Δ S° c ) for the formation of IPC4–Cr 3+ complexes were obtained from the temperature dependence of the stability constant using the van’t Hoff plots. The results obtained in this study, show that the formed complex is enthalpy destabilized, but entropy stabilized and the values of the mentioned parameters are affected strongly by the nature and composition of the binary mixed solvents. The experimental data was tested by using artificial neural network (ANN) program and was in a good agreement with the estimated data. [ABSTRACT FROM AUTHOR]

A mobile drop based approach was utilized for the conductometric determination of aqueous ammonium ion. A liquid drop was manipulated by gravity to remain or move out of a conductivity measurement zone located on a hydrophobic path. A dilute sulfuric acid drop functioned as a micro gas absorber. Gaseous NH 3 was liberated from a sample containing NH 4 + by adding NaOH and purged to flow over the absorber drop. As H + in the absorber drop was converted to NH 4 + , the conductivity decreased. The rate of the conductivity decrease thus ultimately depended on the NH 4 + concentration in the sample. While the sample could be complex, the liberation of NH 3 gas essentially freed the analyte of interest from the matrix and allowed the use of an otherwise nonselective detector. The system was applied to the determination of NH 4 + in some natural waters without prior filtration; the results agreed well with those from a manual indophenol blue method. The approach exhibited a limit of detection (LOD) of 5 μM and a relative standard deviation (RSD) of<5%. The mobile drop gave a constant volume of the gas absorbing solution and provided a cost-effective and simple analytical platform. [ABSTRACT FROM AUTHOR]

This paper presents the use of polymer coated microelectrodes for the realtime conductivity monitoring in a microchannel photoablated through the polymer without contact. Based on this strategy, a small conductometry sensor has been developed to record in time conductivity variation when an enzymatic reaction occurs through the channel. The rate constant determination, k 2 , for the dephosphorylation of organic phosphate–alkaline phosphatase–superparamagnetic beads complex using chemically different substrates such as adenosine monoesterphosphate, adenosine diphosphate and adenosine triphosphate was taken as an example to demonstrate selectivity and sensivity of the detection scheme. The k 2 value measured for each adenosine phosphate decreases from 39 to 30 s −1 in proportion with the number (3, 2 and 1) of attached phosphate moiety, thus emphasizing the steric hindrance effect on kinetics. [ABSTRACT FROM AUTHOR]

Interactions between sodium dodecyl sulfate (SDS) and methylene blue (MB) have been studied in presence of cetylpyridinium chloride (CPC) in aqueous and methanol-water binary solvents via conductometric and tensiometric methods. The experiment was conducted to see the possibility of a synergistic effect of the SDS+CPC system and changes in the interactional behavior of SDS with MB in presence of CPC. The value of the molecular interaction parameter for micellization (β M) was found to be negative from the experimental results and the value of | β M | was found to be greater than ln (CMC SDS / CMC CPC), which didn't describe synergism completely but indicated the strong striking interactions between the oppositely charged surfactants. However, the CMC of the SDS+CPC system was found to be very low as compared to the CMC of SDS alone. This result of CMC based on striking interactions between oppositely charged surfactants was used to calculate various parameters like Gibb's free energy of micellization ( ∆ G m o) , surface excess (Γ max) , minimum surface area (A min) , surface pressure π CMC , standard free energy of adsorption (∆ G ads o) , p C 20 , minimum surface free energy ( G min s) , packing parameter (P) and association equilibrium constant (K). The addition of methanol as a cosolvent enhances the CMC and α value of the SDS+CPC as well as the SDS+CPC-MB system. Correlation of ∆ G m o with different solvent parameters namely Gordon parameter (G), Reichardt's parameter (E T (30)), viscosity (η o), and solvophobic parameter (S P) has also been evaluated. [Display omitted] [ABSTRACT FROM AUTHOR]

The encapsulation of small hydrophilic molecules offers advantages for the delivery of hydrophilic food supplements and food ingredients. These advantages include: masking off-flavors, reducing astringency, and controlling release profiles. We used an internal phase separation (IPS) method for simultaneous granulation and encapsulation of a small hydrophilic food supplement in corn oil. To prove that IPS is a suitable method for the encapsulation of small hydrophilic molecules with controllable release times, we used the nutritional supplement N -acetylcysteine (NAC) as our model molecule. NAC has a variety of health and pharmaceutical benefits however it suffers from poor organoleptic properties such as a bitter aftertaste, astringency, and a strong sulfur smell. We used IPS to produce free-flowing granules containing 56–78% NAC with diameters ranging from 100 to 1000 μm. All the materials used in this process were either food safe or generally recognized as safe (GRAS). The granulated/encapsulated samples were characterized using FTIR, NMR, SEM, and LC-MS methods to confirm the presence of unreacted NAC in high loading concentrations. The kinetics of NAC release was then monitored using conductometry. The combination of hydrophilic carboxymethyl cellulose sodium salt (CMC) and hydroxypropyl methylcellulose (HPMC) gums with a hydrophobic coating such as ethyl cellulose (EC), provided an effective barrier to ensure a 5 min time window for NAC dispersion into water and drinks before the capsule starts to dissolve in water and loses more than 30 wt % of its total NAC loading. [Display omitted] • Internal phase separation was used for NAC granulation and encapsulation. • Using all GRAS materials, NAC was granulated and encapsulated in high loading. • The encapsulated samples, showed delayed NAC release in water. • The spherical granules of encapsulated NAC can be used in ready-to-mix product. [ABSTRACT FROM AUTHOR]

The interaction between cationic dye neutral red and anionic surfactant sodium dodecyl sulfate in aqueous solution was investigated using conductance measurements and spectrophotometry. Changes in the measured specific conductances of dye-surfactant solution were observed at eleven temperatures which is considered as the result of the formation of dye-surfactant ion pair. The evaluation of thermodynamic parameters was carried out using a theoretical model. The variation in the concentration of surfactant was done to monitor the spectral behaviour of the dye-surfactant system from pre-micellar to post-micellar region. The dissolution of dye-surfactant aggregates was only seen beyond this concentration. The addition of oppositely charged surfactant was made to investigate the association of the added surfactant with the surfactant in the mixture or to recover dye from the mixture of dye-surfactant. The strength of the association was further confirmed by the addition of a strong electrolyte to the dye-surfactant mixture. [ABSTRACT FROM AUTHOR]

Abstract: Twenty years has passed since the first discovery of microRNA (miRNA) lin-4 in Caenorhabditis elegans. Over the last decade, the study of miRNA biology has attracted tremendous attention. Increasing evidence has demonstrated that miRNA dysregulation could lead to a large number of genetic diseases and miRNA expressions are closely associated with the pathogenesis of most human malignancies. Recent studies have further suggested that miRNA expression profiles may serve as reliable biomarkers for cancer diagnosis, prognosis, and therapy. This provides powerful impetus and a growing demand for researchers to develop a simple analytical methodology which will allow an accurate, sensitive, selective, and cost effective miRNA analysis at point-of-care. In this regard, electrochemical methods offer many attractive characteristics and could play a leading role in future miRNA detection and quantification. This review revisits the discovery of miRNA, examines the possibility of miRNA biomarkers, discusses the conventional methods and emerging techniques for miRNA detection and quantification, and postulates future prospects in connection to electrochemical detection and quantification of miRNAs. It is hoped that this review will open new perspectives toward the development of new and novel electrochemical strategies for miRNA detection and quantification. [Copyright &y& Elsevier]

Highlights: [•] Study of interaction of RTIL with protein BSA spectroscopically. [•] Influence of RTIL on the conformation and activity of protein. [•] AutoDock blind docking simulation unveils hydrophobic interaction between RTIL–BSA. [•] Swelling of the protein instead of multimer formation with RTIL. [Copyright &y& Elsevier]

Highlights: [•] Electrical impedance spectroscopy (EIS) was used to determine CMC of ionic emulsifiers. [•] Maxwell–Wagner elements were optimized through least-squares model error minimization. [•] EIS was suitable for measuring CMC of high and low conductivity mixtures. [•] Both conductance and capacitance parameters from EIS were valid. [•] Conventional conductometry was suitable only for low conductivity mixture. [ABSTRACT FROM AUTHOR]

[Display omitted] • Adsorption, and micellization parameters of SAILs were determined.in water and in presence of amino acid studied. • CMC values of SAILs from conductance, tensiometry, and UV–Vis measurements are in good agreement. • Standard thermodynamic parameters of micellization evaluated. • Hydrophobic interaction, electrostatic repulsion and attraction of SAILs affected micellization. A series of imidazolium-based ionic liquids (ILs) with varying side alkyl chain length at N3 position which includes [C 12 mim][Br], [C 12 eim][Br], and [C 12 bim][Br] have been synthesized and characterized by 1H NMR. Then, their aggregation behavior in the presence of different concentrations of the amino acid L-Tryptophan (L-Trp) at different temperatures has been examined using conductometric, tensiometric, and UV–vis (absorption spectra) techniques. The critical micelle concentration (CMC) of ILs has been investigated in the absence and presence of amino acid to acquire a better understanding of the colloidal behavior of ILs in presence of amino acid as an external additive. The addition of amino acid is observed to reduce the CMC values of the ILs examined in an aqueous media. Likewise, applying a charged pseudo-phase model of micellization, the thermodynamic parameters of micellization, such as a change in standard free energy (ΔG m o), change in standard enthalpy (ΔH m o), and change in standard entropy (ΔS m o), have been scrutinized from the dependence of CMC on temperature. The surface tension approach was also used to evaluate interfacial characteristics. It was discovered that increasing the length of the side chain increases surface activity. All of the estimated parameters were utilized to determine the electrostatic and hydrophobic contributions of IL to the formation of micellar aggregates. [ABSTRACT FROM AUTHOR]

Abstract: We investigated the conductometric etching of heavy-ion-irradiated poly(vinylidene fluoride) (PVDF) films to study their pore growth behavior, which was estimated from radial etch rates under the application of different voltages. The plateau of the pore diameter seen in a bulk etching region was constant at an applied voltage ranging from 0.1 to 3.0V, while the breakthrough time varied considerably. Employing the first derivative of the conductometric curve, corresponding to the radial etch rate, R, enabled us to clearly analyze parameters reflecting the track structures (i.e., the maximum radial etch rate, R max, and the time for the diameter to reach the final plateau, TE ). Interestingly, these two parameters were significantly influenced by the applied voltage. There was a trend toward increasing values of R max and, in contrast, decreasing levels of TE as the applied voltage was increased. These promotional effects of the etching process can be rationalized by considering the electrophoretic migration of dissolved species in and out of each pore. Thus, conductometric etching under different voltage conditions offers the ability to control pore geometries by optimizing the etching process in the transverse direction as well as in the thickness direction. [Copyright &y& Elsevier]

Abstract: Objectives: The objectives of the present study were to quantitatively evaluate chemical permeability through human enamel/dentine using conductometry and to clarify if alternating current (AC) iontophoresis facilitates such permeability. Materials and methods: Electrical impedance of different concentrations of lidocaine hydrochloride was measured using a bipolar platinum impedance probe. A quadratic curve closely fitted to the response functions between conductance and lidocaine hydrochloride. For analysis of the passage of lidocaine hydrochloride through human enamel/dentine, eight premolars that were extracted for orthodontic treatment were sectioned at the cemento-enamel junction. The tooth crowns were held between two chambers with a double O-ring. The enamel-side chamber was filled with lidocaine hydrochloride, and the pulp-side chamber was filled with extrapure water. Two platinum plate electrodes were set at the end of each chamber to pass alternating current. A simulated interstitial pulp pressure was applied to the pulp-side chamber. The change in the concentration of lidocaine hydrochloride in the pulp-side chamber was measured every 2min using a platinum recording probe positioned at the centre of the pulp-side chamber. Passive entry without iontophoresis was used as a control. Results: The level of lidocaine hydrochloride that passed through enamel/dentine against the dentinal fluid flow increased with time. Electrical conductance (G, mho) correlated closely to the concentration (x, mmol/L) of lidocaine hydrochloride (G =2.16x 2 +0.0289x +0.000376, r 2 =0.999). Conclusions: Lidocaine hydrochloride can pass through enamel/dentine. Conductometry showed that the level of lidocaine hydrochloride that passed through enamel/dentine was increased by AC iontophoresis. [Copyright &y& Elsevier]

Abstract: The complexation reactions between octaazamacrocyclic ligand N,N′,N″,N′″-tetrakis(2-pyridylmethyl)-1,4,8,11-tetraazacyclotetradecane (tpmc) and Co2+, Ni2+, Zn2+ and Cu2+ metal cations have been studied conductometrically in acetonitrile and aqueous solutions. The conductance data exhibit different stoichiometry of the complexes in two studied solutions. In most cases 1:1 (ML) complexes were formed while in some cases 2:1 (M2L) complexes are evident. The stability constants of the resulting 1:1 complexes were determined by computer fitting of the conductance/mole ratio data. Theoretical DFT calculations were used to explain metal binding capability of tpmc ligand and the binding sequences were found to follow the order: Cu2+ ≫Ni2+ >Co2+ >Zn2+. The combination of results obtained by this theoretical approach and conductometric study successfully explains sensitivity and selectivity of recently developed tpmc based ISE and could play a guiding role in planning experiments with large macrocyclic ligands. [Copyright &y& Elsevier]

Abstract: The influence of barium as a bivalent metal cation on the molecular conformation of partially deprotonated hyaluronic acid is studied by viscosimetry and atomic force microscopy (AFM). The resulting data are compared with corresponding observations on dextran as an uncharged representative of the group of polysaccharides. Titrations monitored by rotational viscosimetry and conductometry are carried out using diluted aqueous solutions of hyaluronate and dextran, stepwise adding small amounts of a Ba2+ solution. The AFM measurements are performed on single molecules of hyaluronate and dextran in absence and presence of Ba2+ ions. The cation induced conformational changes lead to a decrease of the solution viscosity in case of the hyaluronate. The corresponding AFM micrographs reveal that Ba2+ ions induce a transformation from extended and slightly curved chains to internally linked molecules exhibiting sharp bends and significantly smaller hydrodynamic radii. In contrast, the solution viscosity and the conformation of dextran remain largely unchanged in presence of barium. [Copyright &y& Elsevier]

Abstract: The protonation constants of poly(amidoamine) dendrimer (PAMAM-NH2 G0) in an aqueous solution of sodium chloride with an ionic strength of 0.05M were determined by the potentiometric method. The interaction between PAMAM-NH2 and sodium chloride dissociated in water at room temperature was assessed by means of calorimetric and conductometric measurements. Using isothermal calorimetric titration, the number of the moles of dissociated electrolyte combined by a dendrimer mole was estimated. The conductometric measurements indicate a decrease in electrolyte conductivity in the dendrimer solution in relation to the electrolyte solution and confirm that the dendrimer investigated combines electrolyte ions. The results of DFT calculations performed for the protonated structure of PAMAM-NH3 + suggest that the chlorine atom considered is combined with terminal amino groups, which confirms the results of calorimetric and conductometric measurements. [Copyright &y& Elsevier]

Abstract: The stability constants of the complexes of cyanopyridine and aminoantipyrine with some divalent transition metal chlorides were determined at different temperatures. The thermodynamic parameters were calculated; the obtained data reveal that the complexation is an endothermic process. Also it was found that the type of bonding between the ligands and the corresponding metal ion is mainly ionic in nature. The stoichiometry of the formed complexes was found to be M:L and M:2L. The structure of some prepared complexes was confirmed by IR, 1H NMR spectra as well as elemental analysis. Thermal stability was studied using TGA technique. [Copyright &y& Elsevier]

Abstract: We investigated conductometric analysis of electro-inactive metal ions at high concentration based on nanoporous electrodes by electrochemical impedance spectroscopy (EIS). The three dimensional interconnected nanoporous Pt (L2-ePt) was found to enable significantly sensitive and selective conductometric detection of alkali and alkaline earth metal ions of high concentration at low frequency without any additional surface modification, which can be hardly done by flat Pt. The extremely large surface area of L2-ePt remarkably suppressed the electrode impedance and the pore effect was additional positive contribution to selective ion sensing by conductometry at low frequency. Importantly, L2-ePt allowed recognition of fractional ratio reversal of Na+ to K+ ions in a mixed solution at physiological concentration maintaining the constant total ionic strength. The results suggest the possibility of real time extracellular monitoring of instantaneous ion exchange near ion channels of a cell membrane such as action potential propagation along axons in a neuronal system. [Copyright &y& Elsevier]

Abstract: A new type of conductometric probe based on a molecularly imprinted membrane (MIM) for the detection of salbutamol has been designed and fabricated. The probe consists of two parallel screen-printed electrodes (SPE). One of the SPEs was coated with a molecularly imprinted membrane using salbutamol as the template, and the other was modified with a non-molecularly imprinted membrane (N-MIM). Measurements of salbutamol were conducted after the conductometric probe had been connected to a commercial portable conductometer. Multi-sample or successive detections could be easily accomplished by replacing the one-off SPE coated with the salbutamol molecularly imprinted membrane with a new one. The conductometric response of the sensor to the concentration of salbutamol displayed a linear correlation over a range from 50 to 280nM, with a detection limit of 13.5nM. The recoveries reached 92.1–98.3% based on pig urine samples. In addition, the sensor based on this new type of probe demonstrated high sensitivity and selectivity for salbutamol. [ABSTRACT FROM AUTHOR]

Abstract: Using surface tension and conductivity measurements, micellization of didodecyl dicationic dibromide Gemini surfactants of different methylene spacer lengths, 12-s-12, 2Br− (where s =2, 4-methylene groups), is investigated in water–ethylene glycol (EG) mixtures with vol. percent of EG changing within the range of 0–30. Gibbs energy of mixed micellization () is obtained from the critical micelle concentration (CMC) and degree of counter-ion dissociation (α) values. Differences in the Gibbs energies of micellization of Gemini surfactants between water and water–EG mixtures are calculated in order to monitor the influence of EG on the micellization process. We determine transfer free energy (g tr ) micelle formation for Gemini surfactants in mixed solvents using the Flory interaction parameter. CMC and micellar ionization degree increase with increase in the vol. percent of EG. The surface excess concentration (Γ max) decreases and the minimum area per surfactant molecule (A min) increases with increase in the amount of EG present in the mixture. [Copyright &y& Elsevier]

Abstract: CAE surfactants (carboxylic acid end-standing triblock copolymers of poly(ethylene oxide)–poly(propylene oxide)–poly(ethylene oxide)) are amphiphiles that are able to bind multivalent cations thermoreversibly; a property that can be used to develop new environmentally friendly separation and ion exchange applications. The analysis of the binding of multivalent ions to CAE micelles is more difficult as compared to conventional surfactants because of its thermo-responsive micellization behavior and its low CMC at room temperature. Conventional analysis techniques like conductometry and surface tensiometry are highly sensitive to temperature and are therefore very difficult to apply in surfactant solutions with strong temperature dependent micellization behavior. For this reason, binding of multivalent ions to CAE micelles has been investigated using isothermal titration calorimetry (ITC) and an alternative conductometric analysis method. Conductometry was used to construct ‘Eisenberg’ plots, which show the binding and release behavior of monovalent ions in the presence of multivalent ions. Regarding the CAE-85 (modified Pluronic P85) micellar system, both methods provide information about the exchange of multivalent cations for monovalent ions above the critical micellization temperature (CMT) of CAE-85. ITC results confirm that dehydration of multivalent ions plays a dominant role in the observed heat effect during the titration of multivalent chloride salts to CAE-85 solutions. The multivalent ions investigated in this study are Ca2+, Cu2+, Zn2+, Co2+, Mg2+, Ba2+, Mn2+ and La3+. Additionally, using the alternative conductivity approach a change in micellar shape was observed upon the addition of multivalent ions when the molar amount of cationic charges balances the molar amount of anionic carboxylate end groups of the surfactant. [Copyright &y& Elsevier]

Abstract: We describe a system for fabricating prescribed numbers of ion track nanochannels and nanowires from a few hundred down to one. It consists of two parts: first, a mobile tape transport system, which, in connection with an ion beam from a heavy-ion accelerator (nuclear charge Z above 18 and specific energy between 1 and 10MeV/nucleon) tuned down to low flux density by means of defocusing and a set of sensitive fluorescence screens, can fabricate a series of equidistant irradiation spots on a tape, whereby each spot corresponds to a preset number of ion tracks. The tape transport system uses films of 36mm width and thicknesses between 5 and 100μm. The aiming precision of the system depends on the diameter of the installed beam-defining aperture, which is between 50 and 500μm. The distance between neighboring irradiation spots on the tape is variable and typically set to 25mm. After reaching the preset number of ion counts the irradiation is terminated, the tape is marked and moved to the next position. The irradiated frames are punched out to circular membranes with the irradiation spot in the center. The second part of the setup is a compact conductometric system with 10picoampere resolution consisting of a computer controlled conductometric cell, sealing the membrane hermetically between two chemically inert half-chambers containing electrodes and filling/flushing openings, and is encased by an electrical shield and a thermal insulation. The ion tracks can be etched to a preset diameter and the system can be programmed to electroreplicate nanochannels in a prescribed sequence of magnetic/nonmagnetic metals, alloys or semiconductors. The goal of our article is to make the scientific community aware of the special features of single-ion fabrication and to demonstrate convincingly the significance of controlled etching and electro-replication. [Copyright &y& Elsevier]

Abstract: Chitosan is a polysaccharide used in a broad range of applications. Many of its unique properties come from the presence of amino groups in its structure. A proper quantification of these amino groups is very important, in order to specify if a given chitosan sample can be used in a particular application. In this work, a comparison between the determination of chitosan degree of deacetylation by conductometry and CHN elemental analysis was carried out, using a rigorous error analysis. Accurate expressions relating CHN composition, conductometric titration, and degree of deacetylation, in conjunction with their associated errors, were developed and reported in this note. Error analysis showed conductometric analysis as an inexpensive and secure method for the determination of the degree of deacetylation of chitosan. [Copyright &y& Elsevier]

Abstract: The behavior of micellization of chlorpromazine hydrochloride (CPH) as an antiemetic drug and its inclusion complex formation with β-cyclodextrin (β-CD) was studied using conductometric technique. The binding or association constant of the complexation equilibrium is evaluated from conductometric measurements by using a nonlinear regression method. The resulting K values for micellization as well as complexation are analyzed. The experiments were carried out at different temperatures. It has been found that CPH form only the 1:1 complex. The association constant values are used for evaluation of thermodynamic parameters of complexation, such as ΔG complex°, ΔH complex° and ΔS complex°. [Copyright &y& Elsevier]

• Synthesis and elucidation for Co(II) and Cu(II) complexes derived from thiazole-based ligand. • Establishing the structural formulae of the compounds via DFT/B3LYP method. • Conductometric study was performed on the complex formed in solution from nano-sized CuCl 2. • In vitro and in silico assays were performed against three carcinoma cell lines. A new thiazole-based ligand was prepared and investigated then used to preparing its Co(II) and Cu(II) complexes. All available analytical (CHN analysis & TGA) and spectral (IR, UV–Vis, 1H NMR, Mass, SEM, XRD & EDX) techniques were applied to elucidate the chemical formulae of new compounds. The ligand behaved as a neutral tetradentate towards binuclear metal ions in the two complex via N-H, two C = N and C-S groups. A tetrahedral geometry was suggested for Co(II) complex according to 4A 2 (F)→4T 1 (F)(ʋ 3) transition at 15,873 cm−1. While, a square-planer geometry was suggested for Cu(II) complex according to 2B 1g →2B 2g (ʋ 1) and 2B 1g → 2E g transitions. The magnetic moment values of the two complexes were appeared lower than the normal values, due to binuclear presence minimized electron spinning. The mass spectra of the complexes recorded their molecular ion peaks that match to the molecular formula after expel of crystal water molecules. A conductometry study was executed for the complex formed from nano-sized CuCl 2 and the ligand in solution to extract the association and formation constants as well as the M : L molar ratio. The stereo structures of the ligand and its binuclear complexes were optimized by DFT method under valence double-zeta basis set. The distribution of N(1)-N(10), C(11)-S(12) and C(15)-N(13) groups is suitable for their coordination with the two metal ions without bond strain. The in vitro assay was performed for the new compounds against HePG2, PC3 and MCF-7 cancer cell lines. The two complexes exhibited high toxicity against breast cancer cells. This result was confirmed interestingly via in silico ways as pharmacophore query and MOE-docking. The interaction parameters and docking patterns reflect the superiority of Co(II) and Cu(II) complexes in controlling breast cancer cell which agree with that obtained in vitro. [ABSTRACT FROM AUTHOR]

Abstract: A simple flow injection (FI) conductometric system with gas diffusion separation was developed for the determination of Kjeldahl nitrogen (or proteins) in milk and chicken meat. The sample was digested according to the Kjeldahl standard method and the digest was diluted and directly injected into the donor stream consisting of 4M NaOH. In alkaline medium, ammonium was converted to ammonia, which diffused through the PTFE membrane to dissolve in an acceptor stream (water). Dissociation of ammonia caused a change in conductance of the acceptor solution, which was linearly proportional to the concentration of ammonium originally present in the injected solution. A conductometric flow through cell and an amplifier circuit was fabricated, which helped improve sensitivity of the conductometric detection system. With using a plumbing Teflon tape as a gas diffusion membrane and without thermostating control of the system, a linear calibration graph in range of 10–100mgL−1 N-NH4 was obtained, with detection limit of 1mgL−1 and good precision (relative standard deviation of 0.3% for 11 replicate injections of 50mgL−1 N-NH4). The developed method was validated by the standard Kjeldahl distillation/titration method for the analysis of milk and chicken meat samples. The proposed system had sample throughput of 35h−1 and consumed much smaller amounts of chemical than the standard method (275mg vs 17.5g of NaOH per analysis, respectively). [Copyright &y& Elsevier]

We give a general overview on the application of electrochemical analysis to biosensing using nanoparticles (NPs). We describe several examples of applications of voltammetric, potentiometric, conductometric, impedimetric and scanning electrochemical microscope-based methods in NP characterization, detection and quantification. We discuss these examples in terms of sensitivity and selectivity, and other parameters of analytical performance. Using bioassay applications, we discuss the advantages of direct (without previous dissolution) vs. indirect (after dissolution or enhancement) detection of NPs using both voltammetric and potentiometric techniques. In the final part of this review, we describe the use of scanning electrochemical microscopy in characterizing and investigating intrinsic properties of metal and semiconductor NPs. This technique offers a promising approach to future bioanalytical applications, especially for single-molecule detection. The reported electrochemical methods show clear advantages for DNA and protein detection when compared to other techniques, even though application to real samples and development of final market-oriented designs are still awaited. [Copyright &y& Elsevier]

Abstract: The solubility and the micelle formation of the chiral cationic surfactant (1R,2S)-(−)-N-dodecyl-N-methylephedrinium bromide (DMEB) in aqueous solution were investigated by conductometry and titration microcalorimetry in the temperature range of 278–328K. The Krafft temperature of DMEB is T K =280K and the solubility of the surfactant at this point is 4.5mM. The cmc versus T curve passes through a shallow minimum close to room temperature. The micelle formation changes from endothermic to exothermic at this characteristic temperature. The apparent degree of dissociation of the micelles α app increases slightly as the temperature is raised. The isosteric enthalpies of micelle formation, ΔH st mic, are close to the calorimetrically measured enthalpies, ΔH mic, provided that the real degree of dissociation, α st =1, is used in the calculations. ΔH mic and the temperature dependence of ΔH mic of DMEB are markedly similar to those of sodium dodecylsulfate and dodecyltrimethylammonium bromide. The micelle formation of DMEB is favored by both enthalpy and entropy at and above room temperature. The enthalpy–entropy compensation results in a slight decrease in the Gibbs free energy on increase of the temperature. Sodium montmorillonite (M) was rendered organophilic by DMEB via ion-exchange to produce the clay/organocomplex DME-M. The swelling properties of the organoclay were investigated by XRD measurements in a variety of organic solvents. The basal spacing of DME-M varied from 1.8 to 3.5nm, depending on the nature of the solvent. DME-M is a heterogenized ephedrine derivative, which may be regarded as a potential catalyst for enantioselective organic syntheses. [Copyright &y& Elsevier]