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This study reports a novel microfluidic platform for rapid and long-ranged concentration of rare-pathogen from human blood for subsequent on-chip surface-enhanced Raman spectroscopy (SERS) identification/discrimination of bacteria based on their detected fingerprints. Using a hybrid electrokinetic mechanism, bacteria can be concentrated at the stagnation area on the SERS-active roughened electrode, while blood cells were excluded away from this region at the center of concentric circular electrodes. This electrokinetic approach performs isolation and concentration of bacteria in about three minutes; the density factor is increased approximately a thousand fold in a local area of ~5000 μm(2) from a low bacteria concentration of 5 × 10(3) CFU/ml. Besides, three genera of bacteria, S. aureus, E. coli, and P. aeruginosa that are found in most of the isolated infections in bacteremia were successfully identified in less than one minute on-chip without the use of any antibody/chemical immobilization and reaction processes.

This study reports a novel microfluidic platform for rapid and long-ranged concentration of rare-pathogen from human blood for subsequent on-chip surface-enhanced Raman spectroscopy (SERS) identification/discrimination of bacteria based on their detected fingerprints. Using a hybrid electrokinetic mechanism, bacteria can be concentrated at the stagnation area on the SERS-active roughened electrode, while blood cells were excluded away from this region at the center of concentric circular electrodes. This electrokinetic approach performs isolation and concentration of bacteria in about three minutes; the density factor is increased approximately a thousand fold in a local area of ~5000 μm(2) from a low bacteria concentration of 5 × 10(3) CFU/ml. Besides, three genera of bacteria, S. aureus, E. coli, and P. aeruginosa that are found in most of the isolated infections in bacteremia were successfully identified in less than one minute on-chip without the use of any antibody/chemical immobilization and reaction processes.

The reported work is an attempt to explore the most appropriate micellar media for the solubilization of organic dye, Allura Red (AR). The micellar solution of anionic surfactant i.e. sodium dodecyl sulphate, SDS and mixed micellar solutions of SDS and cetyltrimethylammonium bromide, CTAB (cationic surfactant) have been employed for said purpose. The values of partition coefficient, Kx and Gibbs free energy change of partition, ΔGp decide the suitable composition of surfactant solution with the highest solubilizing power. The said parameters have been determined from data of UV/Visible spectroscopy while thermodynamic parameters (ΔGm, ΔHm and ΔSm) have been calculated from specific conductivity data. The effect of the presence of various concentrations of CTAB i.e. 0.1, 0.2 and 0.4 mM has been observed to find the most suitable concentration of CTAB that produces a maximum increase in the solubilizing capacity of SDS solution. [ABSTRACT FROM AUTHOR]

We measured the quantum-confined Stark effect (QCSE) of several types of fluorescent colloidal semiconductor quantum dots and nanorods at the single molecule level at room temperature. These measurements demonstrate the possible utility of these nanoparticles for local electric field (voltage) sensing on the nanoscale. Here we show that charge separation across one (or more) heterostructure interface(s) with type-II band alignment (and the associated induced dipole) is crucial for an enhanced QCSE. To further gain insight into the experimental results, we numerically solved the Schrödinger and Poisson equations under self-consistent field approximation, including dielectric inhomogeneities. Both calculations and experiments suggest that the degree of initial charge separation (and the associated exciton binding energy) determines the magnitude of the QCSE in these structures.

Determination of the extractive behavior of ionic species from lateritic ore leachates is complex, since the leachates are pregnant with tens of different ions in, as a rule, multiple oxide states. To examine the possible pathways of intrinsic electrochemical extraction of the crucial elements Ni and Co, it was necessary to make model solutions of these elements and to subject them to electrochemical examination techniques in order to obtain a benchmark. Beside Ni and Co, the model system for Fe had to be evaluated. Iron, as a dominant ore component by far, is the main interfering factor in the extraction processes of Ni and Co in rather low amounts from leaching solution. The leachate examination results were compared to separate model solutions, as well as to their combinations in concentrations and to pH values comparable to those of the leachate. The separation of the leachate components was initially performed by continuous increase in pH upon leaching with NaOH solution, and afterwards the pH-adjusted solutions were subjected to electrochemical investigation. With the purpose of connecting and quantifying the visual changes in leachate upon increase in pH, conductometric measurements were performed. Reactions of oxidation/precipitations were indicated, which led to the essential Fe removal by precipitation. Resulting solutions were found suitable for Ni and Co electrochemical extraction.

Operational control of parameters of electrolytes (first of all–of specific electric conductivity), is an important electrochemical technology. The methods of measurement of electric conductivity of electrolytes is a subject of permanent discussions because of complexity of physical-and-chemical processes accompanying ion transport and of electrolyte polarization near surfaces of electrodes and of electrochemical processes on the electrodes surfaces. Actual highand low-frequency conductometric methods require relatively expensive equipment and are not free of methodological flaws. In this paper a new method of electric resistance of liquid electrolytes is described and substantiated. It is based on automatic performance of a series of measurements of electrolyte resistance at DC, data processing and extrapolation of an appropriate dependence to threshold voltage at measurement cell plates. The character of functions approximating resistance-applied voltage dependence and method of resistance determination are substantiated. The measurements of specific resistance of some electrolytes were performed. The advantages of the proposed method and measuring device are their simplicity, cheapness, reliability and, consequently, wider possibility to utilize it at technological lines and processes, even at such sites of production processes where such a control was impractical earlier. The method can be widely used for express-diagnostics of electrolytes in such areas as electrochemical energy storage, medicine, agriculture, chemical industry, food production.

The complexation reaction between some heavy metal ions such as: Ag+, Co2+, Hg2+, Zn2+, Ni2+, Cu2+, Cd2+, Mn2+, Cr3+, Fe3+ and Pb2+ with 2,3-dimethyl-1,2-dihydro-8H-pyrazolo[5,1-a]isoindol-8-one, ligand in acetonitrile as nonaqueous solvents at 25 ºC were investigated by spectrophotometric and conductometric methods. The formation constants (kf) of the 1:1 (metal ion to ligand) complexes were calculated by computer fitting of the absorbance-mole ratio data, and molar conductance-mole ratio data at 25 ºC using the KINFIT program, and found that complexes to vary in acetonitrile solvent in the order of Zn2+> Ag+> Cr3+> Ni2+> Hg2+> Fe3+> Cu2+> Cd2+> Co2+> Mn2+> Pb2+. DOI: http://dx.doi.org/10.17807/orbital.v10i6.1141

Metal ions play a key role in living systems and are used to perform different physiological activities in our body. Complexation of drugs with metal ions is known to influence the bioavailability and other pharmacokinetic properties of drugs. In the present work, complexation of two essential cations, Mg2+ and Ca2+ with zidovudine (AZT), the first approved antiretroviral drug for human immunodeficiency virus (HIV) has been studied by conductometry and spectrophotometry. The plots of molar conductance versus the mole ratio of [AZT]/[M2+], Job’s method of continuous variation and mole ratio method showed the stoichiometry to be 1:1 (M2+:AZT) for both the cations. The metal ion-AZT complexes formed through the nitrogen of the azide group were further ascertained by liquid chromatography-mass spectrometric analysis. The formation constants of the complexes as evaluated by the conductance method and the Rose-Drago method were in good agreement. The values of thermodynamic parameters (∆H and ∆S) for the formation of complexes were obtained from the Van’t Hoff plots. The results revealed that both the complexation reactions were spontaneous, endothermic and entropy stabilized.

The conductance behavior of Zn2+ and Cu2+ and their complexes with two ligands (crown ethers) have been inspected in 10, 20, 30, and 40% DMF–water mixed solvent at 298.15, 308.15, 318.15, and 328.15 K. The conductance study indicates a 1 : 1 complexation mode amongst the metal ions and ligands hereby studied. The order of stability constants with crown ethers was found to be Cu(II) > Zn(II). The stability constant for Zn2+ ion with crown ether complexes in 10 and 40 wt % solvent composition varies in the order of benzo-18-crown-6 > benzo-15-crown-5. The stability constant for Cu2+ ion with crown ether complexes in 10% solvent composition varies in the order of benzo-18-crown-6 > benzo-15-crown-5, and for 40% solvent composition, it is benzo-18-crown-6 > benzo-15-crown-5. The enthalpy and the entropy of complexation were estimated from the variation of stability constants with respect to the variation of temperature. The observed results elicit that the complexation is enthalpy stabilized, but entropy destabilized. [ABSTRACT FROM AUTHOR]

In the current study, the results of the conductometric work of the complexation reaction of Kryptofix5 (Scheme 1) with Al3+, Cu2+, Ca2+, and Fe3+ cations are studied in acetonitrile–ethanol (AN–EtOH) binary non-aqueous solvents. In all cases, the achieved results reveal that the stoichiometry of the complexes formed between the ligand and Al3+, Cu2+, Ca2+, and Fe3+ metal cations is 1 : 1 [ML] complex. GENPLOT (the computer program) calculates the stability constants of complexes of (Kryptofix5 · M)n+. The selectivity order of Kryptofix5 ligand for the studied metal cations in pure AN and AN–EtOH (AN = 50 mol %) binary mixed solvent at 15°C is found to be Ca2+ > Fe3+ > Cu2+ > Al3+ and Cu2+ > Fe3+ > Ca2+ > Al3+, respectively. As a result, the selectivity order of the ligand for the metal cations shows independence from the nature and composition of the mixed binary solvent. By using the Van't Hoff plots, the thermodynamic parameters ( , ) value for 1 : 1 complexes are calculated from the temperature due to the stability constants of the complexes. The achieved findings reveal that the thermodynamics of the complexation reaction is affected by the nature and composition of the mixed solvents, and the complexation processes entropy and enthalpy are stabilized in most cases. [ABSTRACT FROM AUTHOR]

Copyright of Sensor Electronics & Microsystems Technologies / Sensorna Elektronika i Microsystemni Tekhnologii is the property of I. I. Mechnikov Odessa National University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Recommendations are given concerning the terminology of methods used in electroanalytical chemistry. Fundamental terms in electrochemistry are reproduced from previous PAC Recommendations, and new and updated material is added for terms in electroanalytical chemistry, classification of electrode systems, and electroanalytical techniques. [ABSTRACT FROM AUTHOR]

The complexation responses between Kryptofix22DD, with Ag+ cation, was gathered in methanol-acetonitrile (MeOH-AN), tetrahydrofuran-acetonitrile (THF-AN) tetrahydrofuran-methanol (THF-MeOH) and methanol- dimethyl formamide (MeOH-DMF) binary non-aqueous dissolvable arrangements at various temperatures utilizing impact measurement conduction strategy. Measurement conduction information shows that on the whole cases, Note that the measurement of complex elements is this Metal cation articulated between the macrocyclic and the ligand is 1:1 [ML].Experimental results indicate that in any event, the complex the reactants formed between the Ag+ and the Kryptofix22DD macrocyclic ligand is 1:1 (ML). The qualities the development constants of the complex have been amassed by plotting the molar conductivity bends-utilizing program, GENPLOT. A nonlinear relationship they were found in some spot complex's continuity constant (logKf) and binary solvent composition. Standard thermodynamic parameter values were found (ΔHc° and ΔSc°) Van't Hoff diagrams have been found to use the complex according to temperature parameters. The results indicate that these thermodynamic quantities depend on the solutions of the nature and composition of the binary solvents. [ABSTRACT FROM AUTHOR]

The structures of a protein-polysaccharide composite hydrogel and its modifications prepared using carbon nanotubes (CNTs) were studied by small-angle X-ray scattering and scanning electron microscopy. A correlation between the morphology and physicochemical properties of the hydrogels is demonstrated taking the specific electrical conductivity of the hydrogels as an example. It is shown that the specific electrical conductivity is unambiguously related to the structure of the systems studied, viz., the higher the density of cross-links between biopolymer chains the lower the conductivity, and vice versa. It is found that the addition of CNTs to K-carrageenan—gelatin composite hydrogels can lead to either increase or decrease in their electrical conductivity. [ABSTRACT FROM AUTHOR]

The complexation reaction between salen (Bis(salicylidene)ethylenediamine) and Cu(II) cations in methanol (MeOH), 2-propanol (2-PrOH), acetonitrile (AN), tetrahydrofuran (THF), and chloroform (CHCl3) as nonaqueous solvents at 25º C has been investigated. The stoichiometry and formation constants of complexes have been determined spectrophotometrically and conductometrically by method of continuous variations and mole ration method. The stoichiometry of Cu(II)-salen complexes in all solvents were 1:1 (ML) type using the two methods. By method of continuous variation, chloroform > 2-propanol > methanol ~ acetonitrile ~ tetrahydrofuran. However, by mole ratio method, the order of stability was as follows: chloroform ~ tetrahydrofuran > 2-propanol > methanol ~ acetonitrile. The resulting average of pKf values in each solvent using the two spectrophotometric methods was as follows: 7.40, 6.89, 6.8, 6.22, and 6.18 for chloroform, 2-propanol, tetrahydrofuran, acetonitrile, and methanol, respectively. The Cu(II) cation formed a more stable complex with salen in chloroform. However, the less stable complex was in methanol. [ABSTRACT FROM AUTHOR]

Copyright of Technical Electrodynamics / Tekhnichna Elektrodynamika is the property of National Academy of Sciences of Ukraine, Institute of Electrodynamics and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

• 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]

The complexation reaction between Y3+ 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 Y3+ 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 [M2:L] and also a 2:2 [M2:L2] complexes are formed in solution. The results show that the stoichiometry of the complex formed between 4′NB18C6 and Y3+ 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 (logKf) 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 logKf of the (4′NB18C6.Y)3+ complex versus the composition of the binary mixed solvents. The values of standard thermodynamic quantities (ΔH°c and ΔS°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.

In this study, the complexation reaction between Cu2+, Zn2+ and Ag+ cations with 1,8-dihydroxyanthraquinone (DHAQ) and 1- (methylamino) anthraquinone (MAAQ) was studied in (AN/MeOH) binary mixtures at different temperatures using conductometry method. The conductivity data indicates in all cases, the stoichiometry of the complexes is [ML]1:1 except for the complex formation reaction between Cu2+ cation and DHAQ ligand in pure methanol and in AN/MeOH (mol% AN = 75) binary solutions was obtained [M2L] 2:1. The stability constants of complexes were calculated using Genplot software and non–linear fitting of conductometric data. Also, the experimental data show that the selectivity order of DHAQ and MAAQ for Cu2+, Zn2+ and Ag+ cations, in addition to the ligand, changes with mole fraction of a component of the solvent in AN/MeOH binary mixtures. The value of &DeltaHºc for formation of complexes was obtained from temperature dependence of the stability constants of the complexes using the Van't Hoff plots and linear fitting using mentioned software. The results showed the complexation reaction between Cu2+, Zn2+ and Ag+ cations with DHAQ and MAAQ in this binary mixtures are endothermic and, in all cases the resulting complexes are entropy stabilized but enthalpy destabilized. Also, the T&DeltaSºc versus &DeltaHºc plot of all thermodynamic data indicated a fairly good linear correlation indicating the existence of the enthalpy– entropy compensation in the complexation reactions.

Water stability of eight samples of extruded salmon feeds was first determined by applying two gravimetric methods developed by the authors: gravimetric static and wet sieving method. Then, the conductometric method, primarily developed for investigation of nutrient leaching of feed into the water by the authors, was used for each sample. The aim of this study was to evaluate the potential of the conductometric measurement as a technique for determining water stability of extruded fish feed. In order to find any correlation between the results of two gravimetric tests and conductometric method, correlation analysis was employed. The results of static and wet sieving method were expressed as water stability index, which was expressed as the percent of remained dry matter of sample after being disintegrated in the water. The results of conductometric method were shown as conductivity curves for each sample, giving the insight in rate of nutrient leaching during the time. The obtained values of water conductivity showed no significant (p < 0.05) correlation with the results of static water method, while there was a negative significant (p < 0.05) correlation with the results of wet sieving method during first four hours of pellets soaking in water. The highest correlation coefficients were obtained within the first hour of conductivity measurement, demonstrating that proposed conductometric method had a potential to be applied as a rapid and simple method for determination and relative comparison of salmon feed water stability.[ Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III46012 and Grant no. TR31011]

A thiosemicarbazide derivative as ( E )-4-ethyl-1-(1-(naphthalen-1-yl) ethylidene) thiosemicarbazide (HAN) was synthesized then characterized to prepare [Co(HAN)Cl 2 ·(H 2 O) 2 ], [Ni(HAN)Cl 2 ·(H 2 O) 2 ]. H 2 O, and [Cd(HAN)Cl 2 ] complexes. According to spectral and analytical data we could confirm the neutral bidentate mode of bonding via (C]S) and (C]N) groups to form 1:1 M ratio within the three complexes. The octahedral geometry was suggested for Co(II) and Ni(II) complexes according to electronic transitions assigned to 4 T 1g → 4 T 1g (P)(ʋ 2 ) and 4 T 1g → 4 A 2g (F)(ʋ 3 ) and 3 A 2g → 3 T 1g (P,υ 3 ) and 3 A 2g → 3 T 1g (F,υ 2 ), respectively. The values of nephelauetic ratio (β) in the ligand field parameters detect the ionic nature of new M-L bonds. The molecular ion peaks appeared in the mass spectra of two selected complexes confirming their molecular formulae. The conductometric study was performed for Cd(II) ion solution during variable additions of HAN to calculate association and formation constant of Cd(II)-HAN complex. DFT/B3LYP method was used to optimize the structures of the compounds and confirm the binding mode of the ligand. The distribution of C(5) = N(17) and C(13) = S(19) groups asserts their priority in coordination. Hirshfeld crystal properties were obtained via normalized contact distance (dnorm) and shape index in which the nitrogen atoms act as the best contact points in crystal packing. The biological screening was carried out against microbial strains as well as methyl green/DNA test. In vitro, the superiority of the ligand was clearly recorded in its biological effectiveness. In silico methods were implemented to confirm the activity of the ligand and to recognize the interaction features. The bioavailability, pharmacokinetics and drug-likeness were evaluated via Swiss-link. The data detect the ability of the ligand to penetrate barrier of brain (BBB) but not absorbed in gastrointestinal tract. Pharmit link and molecular docking were utilized to investigate the interaction of HAN with 1bna, 425d and 2k4l proteins. The best intercalation with protein pockets was observed with 2k4l protein, and searching the MolPort library detects a drug analog of MolPort-002-894-701. Finally, the results suggest the biological efficiency of the ligand, which may be asserted by specialists through intensive in-vivo studies., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Author. Published by Elsevier Ltd.)

The complexation process between Y3+ cation and kryptofix 22DD was studied in ethyl acetate–dimethylformamide (EtOAc–DMF), ethyl acetate–methanol (EtOAc–MeOH), ethyl acetate–nitromethane (EtOAc–NM) and ethyl acetate–dimethylsulfoxide (EtOAc–DMSO) binary mixtures at different temperatures by using conductometric method. The conductance data show that in most cases, the stoichiometry of the complex formed between the macrocyclic ligand and the Y3+ cation is 1 : 1 [ML]. But in some systems such as, in the case of EtOAc–DMSO (90 mol % DMSO) binary solvent solution, in addition to formation of a 1 : 1 (ML) complex, a 1 : 2 (ML2) complex is formed in solution, which shows that the stoichoimetry of complexes may be changed by the nature of the medium. The stability order of (kryptofix 22DD · Y)3+complex in the studied binary solvent solutions at 25°C was found to be: EtOAc–MeOH > EtOAc–DMF > EtOAc–DMSO and in the case of pure non-aqueous solvents at 25°C it was: EtOAc > MeOH > DMF ∼ NM. A density functional theory (DFT) study of the interaction of yttrium(III) cation with kryptofix 22DD in the liquid phase for the pure organic solvents was performed. The results are in reasonably good agreement with the experimental data. A non-linear behavior was observed for changes of log Kf of (kryptofix 22DD · Y)3+ complex versus the composition of the binary mixed solvents, which was explained in terms of solvent–solvent interactions and also the preferential solvation of the species involved in the complexation reaction. [ABSTRACT FROM AUTHOR]

A conductometric system with a multipumping module and a gas-diffusion cell has been developed to determine free and total sulfur dioxide (SO2) in wine. The developed method has two protocols to determine both types of SO2 using the same system. For free SO2, sulfite is converted to H2SO4 by acidification and diffusion with H2O2 in an acceptor channel. The sample was previously hydrolyzed by mixing the sample with NaOH and heated at 70 °C prior making the determination of total SO2 in order to break the bonds of the combined SO2. Free and total SO2 were determined in the ranges of 2.5–25.4 and 10.2–76.2 mg L−1 with a sample throughput of 13 and 12 h−1, respectively. The calibration curves of free and total SO2 were in the range of ΔG (mS cm−1) = (–1.0242 ± 0.2871) + (0.6613 ± 0.0201) [SO2, mg L−1], r2 of 0.997 and ΔG (mS cm−1) = (–0.5850 ± 0.1678) + (0.1236 ± 0.0033) [SO2, mg L−1], r2 of 0.997. The proposed automated method is simple and easy to apply for the determination of SO2 in wine using simple reagents. [ABSTRACT FROM AUTHOR]

It is known, that conductivity of liquid media as well as biological objects directly related to the mobility of ions, which in turn depends on electric field strength. This article describes general principles and applications of method and hand-made conductometry device for measurement conductivity of a single biological cells and liquid media in pulsed electric field with rising strength. The device allows to determine the conductivity in the range 0.1-105 µS/cm (with an error about 3%) in the field strengths 0-10 kV/cm, pulse duration 50 µs, repetition period 5-10 s. Conductometric measurements were carried out on mouse and cow oocytes in 0.3 M solution of sucrose and some 0.3M aqueous solutions: xylitol, sorbitol, mannitol, glucose, sucrose, conventional distillate and deionized apyrogenic water. It was found that with rising in the field strength, the conductivity of cells first increases gradually and almost linearly in the range 0.2-1.3 kV/cm, and then sharper and finally exponentially, with strength more 2.8 kV/cm and 3.3 kV/cm for mouse and cow oocytes respectively, i.e., electric breakdown of the cell membrane occurs. The conductivity of liquid media is almost independent of the field strength, but small variations in some media have shown the presence of conductive impurities in them, which are absent in the solvent. Thus, the cell conductivity changes in rising field strength can detect and investigate all stages of membrane electroporation (reversible and irreversible electric breakdown) and the method can serve for estimating the purity of the initial reagents as well as quality control of other liquid media. [ABSTRACT FROM AUTHOR]

Dissociation and complexation with Cu(II) cation is studied for phosphoryl-containing podands (tetrabasic 1,5-bis[2-(dioxyphosphoryl)-4-ethylphenoxy]acidic-type-3-oxapentane (H4LP) and dibasic 1,5-bis[2-(oxyethoxyphosphoryl)-4-ethylphenoxy]-pentane (H2LP)) and their carbonyl analog (polyether dibasic acid 1,5-bis[2-(oxycarbonylphenoxy)]oxapentane (H2LC) in water in the presence of 5% dimethylformamide potentiometrically, spectrophotometrically, and conductometrically. Phosphoryl podands exhibit good complexing properties and can selectively bind metal cations. The dissociation constants are determined and the distribution diagram of ionized species of the compounds under study depending on pH is plotted. The molar ratio between the metal and podand in all complexes is found to be 1 : 1. The stability constants of complexes with Cu2+ cation are calculated. The most stable copper(II) complexes are formed with the tetrabasic podand. [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]

Coolant flow mixing processes with different temperatures and concentrations of diluted additives widely known in nuclear power units operation. In some cases these processes make essential impact on the resource and behavior of the nuclear unit during transient and emergency situations. The aim of the study was creation of measurement system and test facility to carry out basic tests and to embed spatial conductometry method in investigation practice of turbulent coolant flows. In the course of investigation measurement system with sensors and experimental facility was designed, several first tests were carried out. A special attention was dedicated to calibration and clarification of conductometry sensor application methodologies in studies of turbulent flow characteristics. Investigations involved method of electrically contrast tracer jet with concurrent flow in closed channel of round crosssection. The measurements include both averaged and unsteady realizations of measurement signal. Experimental data processing shows good agreement with other tests acquired from another measurement systems based on different physical principles. Calibration functions were acquired, methodical basis of spatial conductometry measurement system application was created. Gathered experience of spatial sensor application made it possible to formulate the principles of further investigation that involve large-scale models of nuclear unit equipment. Spatial wire-mesh sensors proved to be a perspective type of eddy resolving measurement devices.

Aim. The development of sensible, economical and expressive method of quantitative determination of organic acids in complex poly herbal extraction counted on izovaleric acid with the use of digital technologies. Materials and methods. Model complex poly herbal extraction of sedative action was chosen as a research object. Extraction is composed of these medical plants: Valeriana officinalis L., Crataégus, Melissa officinalis L., Hypericum, Mentha piperita L., Húmulus lúpulus, Viburnum. Based on chemical composition of plant components, we consider that main pharmacologically active compounds, which can be found in complex poly herbal extraction are: polyphenolic substances (flavonoids), which are contained in Crataégus, Viburnum, Hypericum, Mentha piperita L., Húmulus lúpulus; also organic acids, including izovaleric acid, which are contained in Valeriana officinalis L., Mentha piperita L., Melissa officinalis L., Viburnum; the aminoacid are contained in Valeriana officinalis L. For the determination of organic acids content in low concentration we applied instrumental method of analysis, namely conductometry titration which consisted in the dependences of water solution conductivity of complex poly herbal extraction on composition of organic acids. Result. The got analytical dependences, which describes tangent lines to the conductometry curve before and after the point of equivalence, allow to determine the volume of solution expended on titration and carry out procedure of quantitative determination of organic acids in the digital mode. Conclusion. The proposed method enables to determine the point of equivalence and carry out quantitative determination of organic acids counted on izovaleric acid with the use of digital technologies, that allows to computerize the method on the whole.

Conductivity of two micellar systems was measured in order to determine critical micelle concentration (CMC) of cetyltrimethylammonium bromide (CTAB). Those systems were: CTin water and CTin binary mixture acetonitrile (ACN)-water. Conductivity (κ)-concentration (c) data were treated by four different methods: conventional method, differential methods (first and second derivative) and method of integration (methods A-D, respectively). As CTin water micellar system shows a sharp transition between premicellar and postmicellar part of the κ/c curve, any of the applied methods gives reliable CMC values and there is no statistically significant difference between them. However, for CTin ACN-water mixture micellar system the integration method for CMC determination is recommended due to a weak curvature of κ/c plot.

The complexation reaction between hydroxyl ammonium (HONH3+ ) cation with 18-crown-6 (18C6) ligand was studied in dimethylsulfoxide – water (DMSO-H2O), methanol – water (MeOH-H2O) and dimethylformamid – methanol (DMF-MeOH), binary solutions at different temperatures using conductometric method. The obtained results show that the stoichiometry of the complex formed between HONH3+ cation with (18C6 ) in all of the binary mixed solvents is 1:1[ML], as well as, these results show that the nature and the composition of the solvent systems are important factors that are effective on the stability of the complex formed between the macrocyclic ligand and metal cation in solutions. A non-linear behavior was observed for changes of stability constants of the complex versus the composition of the binary mixed solvents. The values of thermodynamic parameters show that the thermodynamics of complexation reaction is affected by the nature and composition of the mixed solvents and the complex is entropy stabilized, but enthalpy destabilized in most compositions of binary solutions.

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]

The complexation reaction between some heavy metal ions such as: Ag+, Co2+, Hg2+, Zn2+, Ni2+, Cu2+, Cd2+, Mn2+, Cr3+, Fe3+ and Pb2+ with 2,3-dimethyl-1,2-dihydro-8H-pyrazolo[5,1-a]isoindol-8-one, ligand in acetonitrile as nonaqueous solvents at 25 °C were investigated by spectrophotometric and conductometric methods. The formation constants (kf) of the 1:1 (metal ion to ligand) complexes were calculated by computer fitting of the absorbance-mole ratio data, and molar conductance-mole ratio data at 25 °C using the KINFIT program, and found that complexes to vary in acetonitrile solvent in the order of Zn2+> Ag+> Cr3+> Ni2+> Hg2+> Fe3+> Cu2+> Cd2+> Co2+> Mn2+> Pb2+. [ABSTRACT FROM AUTHOR]

The Krafft temperature (ТKr) of 1-alkyl-4-aza-1-azoniabicyclo[2.2.2]octane bromides (Alk = n-CnH2n + 1, n = 14, 16, 18) (D-n) and complexes of them with transition metals [Cu(II), Ni(II), Co(II), La(III)] in water is determined via conductometry and compared their corresponding acyclic analogs (alkyltrimethylammonium bromides). The dependence of the complexes’ ТKr on the structure of the inorganic salts and the hydrophobicity of ligands is established. It is shown that the complexation of D-n with metal nitrates and the shortening of the ligand hydrocarbon radical reduce ТKr. [ABSTRACT FROM AUTHOR]

We compile here electronic ion track etching effects, such as capacitive-type currents, current spike emission, phase shift, rectification and background currents that eventually emerge upon application of sinusoidal alternating voltages across thin, aged swift heavy ion-irradiated polymer foils during etching. Both capacitive-type currents and current spike emission occur as long as obstacles still prevent a smooth continuous charge carrier passage across the foils. In the case of sufficiently high applied electric fields, these obstacles are overcome by spike emission. These effects vanish upon etchant breakthrough. Subsequent transmitted currents are usually of Ohmic type, but shortly after breakthrough (during the track’ core etching) often still exhibit deviations such as strong positive phase shifts. They stem from very slow charge carrier mobility across the etched ion tracks due to retarding trapping/detrapping processes. Upon etching the track’s penumbra, one occasionally observes a split-up into two transmitted current components, one with positive and another one with negative phase shifts. Usually, these phase shifts vanish when bulk etching starts. Current rectification upon track etching is a very frequent phenomenon. Rectification uses to inverse when core etching ends and penumbra etching begins. When the latter ends, rectification largely vanishes. Occasionally, some residual rectification remains which we attribute to the aged polymeric bulk itself. Last not least, we still consider background currents which often emerge transiently during track etching. We could assign them clearly to differences in the electrochemical potential of the liquids on both sides of the etched polymer foils. Transient relaxation effects during the track etching cause their eventually chaotic behaviour. [ABSTRACT FROM AUTHOR]

Spectroscopic and conductometric approach was employed to study the effect of aromatic amino acid-tyrosine on the micellisation of hexadecyltrimethylammonium bromide and sodium dodecyl sulphate in aqueous medium. Tyrosine was used as an additive as well as a probe while recording the UV-visible spectrum. A simple experiment was performed were the conductivity and UV-visible spectrum of amino acid was utilised to determine the effect of increasing amphiphile concentration. The critical micelle concentration and various thermodynamic parameters such as Gibbs free energy of micellisation,, enthalpy of micellisation,, entropy,, Gibbs free energy of transfer values,, hydrophobic free energy,, free energy associated with surface contribution,, etc. were calculated to find the effect of this amino acid on the solubilisation, interaction, and aggregation process in aqueous medium. [ABSTRACT FROM PUBLISHER]

Micelles are of increasing importance as versatile carriers for hydrophobic substances and nanoprobes for a wide range of pharmaceutical, diagnostic, medical, and therapeutic applications. A key parameter indicating the formation and stability of micelles is the critical micelle concentration (CMC). In this respect, we determined the CMC of common anionic, cationic, and non-ionic surfactants fluorometrically using different fluorescent probes and fluorescence parameters for signal detection and compared the results with conductometric and surface tension measurements. Based upon these results, requirements, advantages, and pitfalls of each method are discussed. Our study underlines the versatility of fluorometric methods that do not impose specific requirements on surfactants and are especially suited for the quantification of very low CMC values. Conductivity and surface tension measurements yield smaller uncertainties particularly for high CMC values, yet are more time- and substance consuming and not suitable for every surfactant. [ABSTRACT FROM AUTHOR]