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We have investigated the behaviour of change of molar conductivity of mixtures of two crown ethers (CE) (18-Crown-6; 18C6 and 24-Crown-8; 24C8) and metal ions (Mn+) (Zn2+ and Cu2+) and the complexa...

Physicochemical properties of the iron(II) 2-naphthalenesulfonate complex with 4-amino-1,2,4-triazole ([Fe(NH2trz)3](ns)2·2H2O (I)) are studied. The complex exhibits the 1A1 ↔ 5T2 spin crossover. Complex I and the initial compound for its preparation, Fe(ns)2 (II), are studied by static magnetic susceptibility, conductometry, spectrophotometry, and cyclic voltammetry methods. The μeff(T) dependence for I shows that the spin transition is abrupt both in the initial complex and in the DMF solution. Forward and inverse spin crossover temperatures are determined.

The mixed ligand lanthanum complexes have been synthesized using polydentate ligands. The (2Z)-2-(N-hydroxyimino)-1,2-diphenylethan-1-ol (cupron) was used as a primary ligand and L-isolucine, L-threonine, L-lysine and L-glycine were used as secondary ligands for the synthesis. Conductometry, elemental analysis, magnetic susceptibility measurements, complexometric estimation, UV-Visible spectroscopy, FTIR spectroscopy, thermal analysis and XRD methods were used for structural interpretation of all synthesized complexes. All complexes were solid and white and slight yellow in colour. They are non-electrolytic and diamagnetic in nature, as confirmed by conductometric and magnetic susceptibility methods respectively. All the complexes were synthesized by combination of lanthanum metal ion, primary ligand and secondary ligands in 1:2:1 ratio which was confirmed by elemental analysis. During reaction between lanthanum ion, primary ligand and secondary ligands there was transition of electrons which was confirmed by UV-Visible spectroscopy. Identification of functional group in the complexes was carried out and confirmed by FTIR spectroscopy. The decomposition temperature and thermal behaviour of the complexes have been concluded by thermal and XRD techniques. Tube dilution and agar cup methods have been employed to study antibacterial activities of all synthesized lanthanum complexes. The inhibition potential was seen to some extent.

A conductometric transducer is proposed for the first time for the detection of ethanol vapor. This ethanol microsensor is prepared by encapsulation of alcohol dehydrogenase (ADH) in chitosan. Interdigitated electrodes fabricated by silicon technology were used. The electrodeposition of chitosan allows the addressing of the chitosan film on the microconductometric devices and to encapsulate ADH and nicotinamide adenine dinucleotide (NAD+), which was monitored by FTIR. The analytical performance of the ethanol microsensor was determined in gaseous methanol, ethanol, and acetone samples, collected from the headspace above aqueous solutions of known concentration. The response time (tRec) of the sensor varies from 7 to 21 s from lower concentrations to higher concentrations. The detection limit is 0.12v/v % in the gas phase, corresponding to 0.22 M in the liquid phase. The relative standard deviation for the same sensor is from 12% for lower concentrations to 2% for higher concentrations. The ethanol sensor presents 2.6 times lower sensitivity for methanol and 28.3 times lower sensitivity for acetone. A detection of ethanol in the headspace of a red wine sample lead to an alcohol content in good agreement with the value given by the producer.

Association of sodium dodecyl sulfate (SDS) ionic surfactant in concentration range of 1–100 mmol L−1 in binary water—ethanol media with alcohol volume concentrations of 0–92.3 vol.% was studied by conductometry and nuclear magnetic resonance spectrometry. The dynamic properties of surfactant solutions including self-diffusion processes and diffusive transfer of charges in SDS solutions under alteration of solvent micro-heterogeneous structure were studied. The transformation of structure and size of SDS associates upon change of ethanol content in the solution was discussed. The correlation between SDS association processes and changes in micro-heterogeneous structure of binary solvent was analyzed.

In the work, the possibility of using nanoparticles of gold (AuNPs) to upgrade bioselective elements of biosensors in order to improve their analytical characteristics is considered. The bioselective elements of biosensors based on acetylcholinesterase (AChE), butyryl cholinesterase (BuChE) and glucose oxidase (GOD) were used as an experimental model. Immobilization of enzymes on the surfaces of conductometric transducers was performed by the crosslinking of corresponding enzymes using glutaraldehyde. The conditions of immobilization of AChE with gold nanoparticles were optimized. Thus, we determined the optimal values of concentration of crosslinking agent (glutaraldehyde), duration of immobilization, the enzyme to AuNPs ratio, the AuNPs concentration and size. The performance characteristics of the biosensors based on enzymes and AuNPs were investigated and compared with the characteristics of biosensors based on enzymes only. It was also examined how the addition of AuNPs to the bioselective element of biosensors affects the biosensor stability. In particular, the reproducibility of preparation and continuous operation of biosensors was tested as well as their stability at storage. It was shown that the presence of AuNPs in the composition of bioselective elements can improve some characteristics of biosensors, which may be promising for further study and use.

Protomicelles represent a new concept of colloid science relevant to micelle-like aggregates of surfactants in solutions. In contrast to ordinary micelles, their formation requires no critical micelle concentration (CMC) and proceeds gradually through the adsorption of surfactant molecules or ions on a solubilization core at concentrations much lower than the CMC. A completely formed protomicelle looks like an ordinary solubilisate-containing micelle. Protomicelles can be formed on phthalocyanine monomers and dimers. In this work, the role of protomicelles in monomerization of crown-substituted magnesium phthalocyaninate (I) in aqueous sodium dodecyl sulfate (II) solutions has been studied spectrophotometrically at compound I concentrations of 0.38 and 1.2 μМ. Empirical methods have been developed for determining a new parameter, monomerization concentration (concentration of II required to initiate the monomerization of I), and it has been shown that the monomerization concentration decreases with an increase in the concentration of I. Another new parameter defined as the concentration of II corresponding to nearly complete monomerization of I has been studied in comparison with the CMC of II. For this purpose, the CMC has, for the first time, being measured (by conductometry) in the presence of protomicelles. The latter circumstance has been shown to decrease the CMC. At the same time, it has been revealed that the concentration corresponding to the completion of monomerization in the studied system nearly coincides with the CMC.

Interactions within mixtures of the phenothiazine drug promethazine hydrochloride (PMH) and cationic hydrotropes ortho-toluidine hydrochloride (o-TDH) and para-toluidine hydrochloride (p-TDH) were investigated at different ratios and temperatures via conductometry to understand various physicochemical properties. Critical micelle concentration (cmc) was less than values of cmcid (cmc in ideal mixed system), indicating significant interaction among the studied constituents in solution mixtures. The cmc of pure PMH was also determined by measuring the surface tension for comparison. A variety of micellization thermodynamic parameters (Gibbs free energy [ΔG 0 ], change in standard enthalpy [ΔG 0 ], and change in entropy [ΔG 0 ]) were computed using conductometry. The micellar mole fraction (X 1 , X 1 , and X 1 ) of hydrotropes estimated by various theoretical models (Rubingh, Rodenas, and Motomura) was assessed, and the results showed a greater contribution of hydrotropes in mixed micelles along with their values increasing via an increase in mole fraction (α1) of hydrotropes (o-TDH/p-TDH). Negative β values suggest extremely favorable attractive interaction/synergism, as declines occurred in the whole quantity of amphiphile used for the desired purpose, leading to a drop of expenditure along with ecological concern. Obtained activity coefficients (f1 and f2) were always beneath unity, meaning nonideality was found between PMH and o-TDH/p-TDH. Like the conductivity method, the UV-visible and FT-IR techniques also demonstrate the interaction between the PMH and o-TDH/p-TDH.

The determination of free acidity and uranium in a radioactive uranyl nitrate solution inside a hot cell has to be done remotely. It generally involves the addition of complexing agents or the application of sophisticated analytical methods and modelling. To make the analyses uncomplicated, a simple acid–base conductometric titration method was developed to determine the free acidity and the uranium concentration simultaneously. Uranyl nitrate solutions containing nitric acid from 0.02 to 0.83 mmol and uranium from 0.32 to 15.90 mg per aliquot were determined by this method. The precision and accuracy of the method were found to be within ± 5%. For the titrations carried out at higher temperatures, the bias was found to be within ± 10%.

In this research, conductometry was applied as a rapid method to screen functional ligands of cadmium ion-imprinted polymers for the first time. To better understand the binding mechanisms of Cd(II) to nucleoside monophosphates (NMPs), isothermal titration calorimetry (ITC) and nuclear magnetic resonance spectroscopy (NMR) experiments were carried out. First, the magnitude of conductivity change, Δσ, was found to be proportional to the ligand’s binding capacity to cadmium, and the ΔσGMP ≈ ΔσdGMP = 103.5 μs $$\cdot $$ cm−1. Second, the ITC experiments indicated that the coordination binding of Cd(II) and guanosine monophosphate (GMP) in 4-(2-hydroxyerhyl)piperazine-1-erhanesulfonic acid (HEPES)/boric acid buffers were demonstrated as different thermodynamic process: an exothermic process (ΔH = -1.446 kcal $$\cdot $$ mol−1) in HEPES, and an exothermic process (ΔH = − 1.495 kcal $$\cdot $$ mol−1) followed by an endothermic one (ΔH = 1.383 kcal mol−1) in boric acid. In contrast, the formation of the Cd(II)–uridine monophosphate (UMP) system was an endothermic process in both buffers. NMR experiments indicated that the shift Δδ of the GMP’s proton signals were different, especially for H1: 0.37 ppm in HEPES, and 0.03 ppm in boric acid. Referring to the results of ITC experiments, the major Cd(II) binding sites of GMP in HEPES buffer was the guanosine group, and phosphate group was another site in the boric acid buffer. By contrast, the major Cd(II) binding site of UMP was the phosphate group in both buffers. In general, investigating the functional ligand–cadmium binding mechanism has provided important theoretical and experimental guidance for the subsequent preparation of cadmium ion-imprinted materials.

A spectrophotometric method for the determination of Cu (II) ions with N- (2-hydroxybenzoyl) -N '- (p-tosyl) hydrazine (GBSH) in ammonia media has been developed. The optimal conditions for the formation of a complex compound are found: the wavelength of maximum light absorption; pH complexation; optimal time for color development; the amount of photometric reagent. Under optimal conditions of complexation of GBSG with Cu (Ⅱ) ions (λ = 401 nm, pH = 9.2, τ = 30 minutes, VGBSG = 3.75 ml), a calibration graph is constructed. The Bouguer-Lambert-Beer law is fulfilled in the range from 0.13 to 1.59 mg Cu (II) / 25 ml. The true molar light absorption coefficient of the complex compound of HBSG with Cu (Ⅱ) ions in the ammonia medium was 1480. The molar ratios in the solution of the complex compound were determined by the methods of saturation, shift of equilibria and conductometric titration - [Cu (Ⅱ)]: [HBSG] = 1: 1. According to Babko's method, the conditional constant of stability of the GBSG complex with Cu (Ⅱ) ions was calculated and it was 4.4 × 1010. The reproducibility and relative error of the developed photometric technique were determined by the method of mathematical statistics.

Interfacial separation of components of extractants based on di-(2-ethylhexyl)phosphoric acid (di-2EHPA) in toluene and a mixture of di-2EHPA with trioctylamine in toluene has been studied in the course of treatment with aqueous sodium hydroxide solutions yielding an organic phase and an aqueous colloidal solution of di-2EHPA sodium salt. Conditions have been found for the isolation of almost pure di-2EHPA and toluene, as well as di-2EHPA and a trioctylamine solution in toluene. The aqueous colloidal solutions have been studied by conductometry, dynamic light scattering, and 1H-NMR spectroscopy. The considered systems are promising to be used in hydrometallurgy for improving parameters of extraction of metals and their concentrating in re-extracts.

The possibility of determining the anionic surfactant alkylbenzenesulfonic acid by various methods: potentiometric and conductometric titration with sodium hydroxide, conductometric titration with cationic surfactants (tetrabutylammonium bromide, cetyltrimethylammonium bromide) and spectrophotometry in the UV region, was considered. The acid-base titration method allows to determine the alkylbenzenesulfonic acid concentration in pure aqeous solutions. The content of anionic surfactant in the presence of nitric acid can be determined by conductometric titration with cetyltrimethylammonium bromide. The optimal conditions for alkylbenzenesulfonic acid spectrophotometric determination (light absorption maxima, linearity range of the calibration graph, molar absorption coefficient) have been established.

Introduction. The majority of ionic chromatographic methods approved in our country for assessing the quality and chemical safety of water for the content of controlled anions and cations are developed using conductometry. However, quantitative determination of micro concentrations of cations and anions in drinking water and other water bodies against the background of macro concentrations of other components due to their interfering influence by the method of conductometric ion-chromatographic analysis is not possible. Material and methods. The tap water in Nothern East Administrative district of Moscow was used. The “Stayer” ion chromatograph with amperometric and conductometric detectors and separating columns was used. The column Phenomenex Star Ion A-300 100/4.6 was used for the determination of iodide. The column Shodex IC SI-52 4E 250/4, 6 was used for the determination of nitrite. The column Shodex IC YS-50 150/4.6 was used for the determination of bivalent iron. Results. Chromatograms of ion chromatographic analysis with amperometric and conductometric detections of tap water with different contents of target ions are presented. It is shown that it is impossible to determine the target components using the standard method with conductometric detection. The content of accompanying ions (chlorides, nitrates, and sulfates), exceeding the concentration of nitrite and iodide by tens of thousands of times, was not prevented by the determination. Discussion. The high efficiency of the proposed method for determining iodides, nitrites, and bivalent iron is provided due to their anode discharge in the electrochemical cell of the detector. Interfering components (chloride, nitrate, phosphate, and sulfate) neither participate in the anodic oxidation process and nor generate an electrical signal; that allows determining micro concentration of nitrite and iodide ions and bivalent iron in virtually any aqueous system containing an excess of chlorides, nitrates, sulfates. Conclusion. Authors proposed a highly sensitive ion - chromatographic amperometric determination of iodide, nitrite ions and bivalent iron in water and other water bodies. It allows eliminating the interfering influence of macro concentrations of accompanying components. The determination is performed by direct insertion of the sample into the chromatographic system.

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.

This work is the first attempt to study the physicochemical properties of ionogels - quasi-solid hybrid materials formed by ionic liquids (ILs) − 1-butyl-3-methylimidazolium (BMIm+) salts with dicyanamide- (DCA−), bis(trifluoromethylsulfonyl)imide- (TFSI−), and trifluoromethanesulfonate- (Otf−) anions - and halloysite, a powdered clay filler with nanotube particles (at the IL:Hal molar ratio of 2:1) in order to find possible new applications of ionic liquids and industrial minerals. The electron microscopy, TG, and DSC analysis, FTIR spectroscopy, X-ray diffraction analysis, conductometry and cyclic voltammetry methods are used to investigate the anion effect on the IL interaction with halloysite. It has, for the first time, been found that the distinguishing feature of halloysite interaction with an IL determining the structural changes in the clay mineral and electrochemical characteristics of the ionogels is partial dehydration of the clay and absorption of the released water by the ionic liquid. It is shown that the halloysite dehydration effect depends on the IL hydrophilicity determined by the anion type, corresponds to the series: BMImDCA > BMImOtf > BMImTFSI. The electrochemical and thermal behaviour of ILs confined within a halloysite matrix differs from that of bulk ILs and is controlled by the anion type. Temperature dependences of the structural resistance of the halloysite filler are radically different for the ILs with high and low hydrophilicity. The effects resulting from the formation of halloysite-based ionogels can be of interest to those who develop quasi-solid ionic conductors that can work within a wide temperature range.

The forming and study of cationic surfactant/polyelectrolyte (PE) polymer colloid systems has been done at different concentrations of an amphiphilic compound and fixed polymer concentration. An imidazolium amphiphilic compound with a tetradecyl radical (IA-14) served as the surfactant; polyacrylic acid (PAA) characterized by a molecular weight of 1800 Da was used as component of the polymer. The aggregation characteristics of the systems have been examined via tensiometry, conductometry and fluorescence spectroscopy. It is shown that introducing of polyelectrolyte initiates the formation of polymer colloid complexes (PCC) at a 50 times lower concentration than the one required for an individual IA-14 system. Dynamic light scattering analysis has shown that the values of the hydrodynamic parameters of PCC lied in the range of 100–120 nm and did not depend on the concentration of the PE or the surfactant. It has been estimated via electrophoretic light scattering that electrostatic interactions make the main contribution to the formation of complexes.

Exploratory, regression, and neural network analysis of the stability constants of crown ether [12C4, 16C5, (CH3)216C5, DB21C7, DB24C8, DCH24C8, DB30C10] 1 : 1 complexes with alkaline (Li+, Na+, K+, Cs+, Rb+), alkaline-earth (Ca2+, Sr2+, Ba2+), and heavy (Ag+, Tl+, Co2+, Cu2+, Pb2+) metals and NH4+ in water and organic solvents (methanol, acetonitrile, acetone, N,N-dimethylformamide, nitrobenzene, nitromethane, 1,2-dichloroethane, propylene carbonate) at 298.15 K obtained via conductometry has been performed. Factor, cluster, discriminant, canonical, decision tree, regression, and neural network models of clustering, approximation, and prediction of thermodynamic constants of the complexation depending on the properties of the ligand, the cation, and the solvent have been developed. The trained MLP 7-5-5 Multilayer Perceptron Cluster has completely confirmed the k-means clustering. Independent data on the stability constants of coronates have demonstrated the predictive capacity of the trained perceptron-approximator MLP 7-7-1.

Two simple, accurate, sensitive and precise conductometric methods were developed for determination of trospium chloride in pure form and in pharmaceutical formulations. It is based on using two precipitating reagents; Phosphomolybdic acid (PMA) and Silver nitrate (AgNO3). The mean recovery for Silver nitrate is in the range (98-100.95%) and for Phosphomolybdic acid in the range (98-101.69%). A molar ratio has been determined conductometrically for the two reagents, revealed (1/1) for (drug/reagent). The proposed methods were validated and successfully applied for the determination of the studied drug in pure form and in its pharmaceutical preparation. The results of the proposed methods were compared to the results of reported method with no significant difference between them.

Reactions of FeSO4 precursor with thiosemicarbazones Hatc-R, where R is ethyl (Et) or phenyl (Ph), led to the formation of homoleptic iron(III) complexes of the type [Fe(atc-R)2]HSO4. The characterization of the compounds was performed by spectroscopy techniques, such as FTIR, UV–Vis, besides elemental analysis, conductometry, voltammetry and magnetic susceptibility measurement. The crystalline structure of [Fe(atc-Ph)2]HSO4·H2O was determined by single-crystal X-ray diffraction and revealed the oxidation of the Fe(II) centre to Fe(III) upon complexation of the monoanionic N,N,S-tridentate thiosemicarbazonate ligands. The magnetic susceptibility results showed the paramagnetic property of the iron(III) complexes in the extension of 1 unpaired electron. The electrochemical analyses showed a nearly reversible process of the iron complex, which is slightly influenced by the peripheral substituent groups at the N(4) position of the atc-R1− ligands. Hirshfeld surface analysis revealed that the supramolecular structure of [Fe(atc-Ph)2]HSO4·H2O is stabilized mainly by H···H, C···H/H···C and O···H/H···O interactions.

Composites of chitosan Bombyx mori with hydroxyapatite – (Ca10(PO4)6(OH)2) were obtained and their interaction in aqueous solutions was studied. The composition and structure of composites obtained at various mass ratios were studied. The possibility of controlling the composition and morphology of composites by varying the ratios of the initial reagents was shown. FITR and UV spectroscopic methods were used to investigate the structure of composites. The results of XRDA studies have shown that depending on the CS/HA ratio, CS/HA crystals with sizes from 6.9 to 20.4 nm were formed in the system. Using the methods of potentiometry, conductometry and viscometric measurements the equivalent composition of the composite was determined, which is CS/HA-70:30 mass %. It was found that nanostructured composites with minimum sizes from 2 to 15 nm were obtained under the selected synthesis conditions. The obtained data are applied interest for the prevention and treatment of osteomolyosis, osteoporosis and bone replacement of living organisms.

The direct use of lignin results in the synthesis and production of low-value materials. Therefore, the chemical modification of lignin increases not only its reactivity, but also improves its compatibility and better dispersion in the lignin-based polymeric materials where lignin acts as a good substitute for oil-based polyols. Systematic studies were conducted in the present work. Hydroxymethylated lignin (HML) was synthesized via its reaction with formaldehyde, and functional groups present in the sol fraction of HML were then quantitatively investigated by aqueous potentiometric/conductometry titration prior to any further modification and by 1HNMR and FTIR techniques after reacting with α-bromoisobutyryl bromide, resulting in brominated HML (BHML). To calculate moles of hydroxyl groups per gram of HML, 1HNMR of BHML was recorded in the presence of a given amount of N,N-dimethylformamide as an internal standard. It was found that the number of hydroxyl groups increases from 6.44 mmol/g in the lignin to 7.77 mmol/g in the HML. The moles of phenolic hydroxyl and carboxyl groups per gram of HML were calculated using aqueous titration. It was found that the moles of phenolic hydroxyl groups in the HML decrease by 19.8% compared to lignin. Due to poor solubility of the HML in tetrahydrofuran, BHML was used in the GPC analysis, from which the number average molecular weight ($$\bar{M}_{\rm{n}}$$) of the HML was obtained after some calculations to be 1014 g/mol. It was observed that modification of lignin with formaldehyde increases not only its functional groups but also increases its molecular weight by creating methylene bridges between the two lignin molecules.

In this study, the grafting of 1-methyl-3-phenylpropylamine (1-M-3-PP) on cellulose nanocrystals (CNCs) via a two-step reaction route was investigated and compared with physico-chemical surface adsorption. The first step involved subjecting CNCs to a 2,2,6,6-Tetramethyl-1-piperidinyloxy (TEMPO)-mediated oxidation. The carboxylic groups present on recovered oxidized TEMPO-CNC were quantified by several characterization methods (conductometric titration, elemental analysis, and X-ray photoelectron spectroscopy), and a degree of oxidation close to 0.2 was found. The second step was an amidation reaction carried out in an aqueous medium under mild conditions and in the presence of N-(3-dimethylaminopropyl)-N′-ethylcarbodiimide (EDC)/N-hydroxysuccinimide (NHS) as catalyst. The recovered modified CNCs after amidation reaction with 1-M-3-PP (CNC-1-M-3-PP) were extensively washed and then characterized. The amount of grafted molecules was determined by several techniques like X-ray photoelectron spectroscopy (XPS), and the calculated degree of substitution was found to be close to 0.05 with respect to the bulk CNC. This low amount is sufficient to enhance the modified CNC dispersion and their colloidal stabilization in organic solvents, allowing the preparation of nanocomposites. Furthermore, such CNC-1-M-3-PP units with aromatic molecules attached to it can find applications in barrier materials in which the sorption of aromatic molecules can be very useful.

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.

The isohydricity conditions are formulated for D+T systems composed of titrand D and titrant T, mixed according to titrimetric mode; only acid-base equilibria are involved there. The original method of dissociation constants determination, based on the isohydricity principle, is presented and confirmed experimentally. The pH titrations in the system of isohydric solutions are also put in context with conductometric titrations.

The present review is concerned with application possibility of tristimulus colorimetry method and argumentation of theoretical basis, and experimental approach of tristimulus colorimetry functions values use as analytical response in studies of acid-base equilibria in solutions of multifunctional organic compounds. A conceptual model is proposed, it is based on the change in tristimulus colorimetry function values in the ionization of functional groups of multifunctional compounds. The definitions of the corresponding terms are described. It has been established that use tristimulus colorimetry functions value as analytical response allows differentiating similar in acid-base characteristics functional groups, to determine the corresponding values of the ionization constants and to build a holistic picture about existing acid-base equilibria in a wide range of acidity of the medium. The values of tristimulus colorimetry functions of the specific and total color difference, the yellowness index, as well as the principles of their calculation within different color spaces by the example of polyfunctional compounds (about 50), namely different classes of dyes (azo-, triphenylmethane, xanthene, anthraquinone and pyrilium derivatives). It is established that all specified functions are suitable for the determination of p Kа , and the use of functions of full color difference makes it possible to simplify the mathematical apparatus for processing experimental data. The advantages of tristimulus colorimetry method before classical instrumental methods (spectrophotometry, potentiometry, conductometry) of studying acid-base equilibria in solutions of polyfunctional compounds are shown.

As a way of finding value-added materials from waste medium density fiberboard (MDF), this study characterized cellulose nanocrystals (CNCs) isolated by ammonium persulfate (APS) oxidation using recycled MDF fibers. Chemical composition of the recycled MDF fibers was done to quantify α-cellulose, hemicellulose, lignin, nitrogen, ash and extractives. The APS oxidation was performed at 60 °C for 16 h, followed by ultrasonication, which resulted in a CNC yield of 11%. Transmission electron microscope images showed that rod-like CNCs had an average length and diameter of 167±47 nm and 8.24±2.28 nm, respectively, which gave an aspect ratio of about 20. The conductometric titration of aqueous CNCs suspension resulted in a carboxyl content of 0.24 mmol/g and the degree of oxidation was 0.04. Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy clearly showed the presence of carboxyl group on the CNCs prepared by the APS oxidation. The change of pH of the aqueous CNC suspension from 4 to 7 converted the carboxyl group to sodium carboxylate group. These results showed that the APS oxidation was facile and CNCs had a one-step preparation method, and thus suggested an optimization of the oxidation condition in future.

A combination of a long exposure to ultraviolet (UV) radiation and the extraction of radiolysis and photolysis products from tracks makes it possible to create ion-selective membranes from polyethylene terephthalate (PET) films irradiated with heavy ions. These membranes exhibit high selectivity for singly charged cations and high transport characteristics in the electrodialysis mode. The aim of this study is to analyze the mechanisms of the transformation of latent tracks into a system of through pores of the subnanometer range in more detail. Polyethylene terephthalate films are irradiated with accelerated Xe and Bi ions with energy losses in the polymer of 11 and 18 keV/nm, respectively. The evolution of the free volume and the accumulation of carboxyl groups in the irradiated films at different stages of the treatment are studied using gravimetry, IR and UV spectroscopy, conductometry, and electron microscopy methods. It is found that the properties of the resulting membranes depend on several critical parameters, which include, in addition to temperature during extraction, the energy loss of the bombarding ion, the pH of the solution used for extraction, and ion fluence. Dramatic changes in the membrane properties are observed at ion fluences at which individual tracks begin to overlap.

The nonexchange sorption of diverse electrolytes by an MK-40 sulfonic cation-exchange membrane has been studied by conductometry without separating solution and membrane phases. The data of sorption experiments performed within the framework of the two-phase microheterogeneous model of an ion-exchange material have been used to find the Donnan constant for the MK-40 membrane in solutions of electrolytes, namely, HCl, NaOH, NaCl, MgCl2, CaCl2, and BaCl2. The concentration of an electrolyte sorbed by the membrane has been determined as depending on the nature and concentration of an equilibrium solution. Factors that have the most significant effect on the concentration of a sorbed electrolyte and the Donnan constant, such as the specific moisture capacity of the membrane and the nature and charge of counter- and coions, have been studied. The volume fractions of the gel and equilibrium solution phases have been determined by two methods, i.e., from the experimental data on the membrane specific conductivity in solutions of different natures and concentrations and from the data on the nonexchange sorption calculated within the microheterogeneous model of the membrane structure. It has been shown that the Donnan constant may be calculated for the MK-40 membrane in the salt solutions by a simplified method from the data on the sorption of an electrolyte of only one concentration, provided that the volume fractions of the conducting phases in the membrane are known.

Background: Common methods for identifying the infectious bacteria in human urine are mainly time-consuming and costly. Therefore, the most reliable method for detecting the urinary tract infections is the urine culture, which requires at least 48 hours to identify infectious factors. Objectives: It is important to detect the bacteria in urine rapidly, simply, and accurately. Materials and Methods: In this work, the variations in the electrical conductivity and dielectric coefficient of the urine sample due to changes in the concentration of infectious bacteria have been studied. Furthermore, an appropriate measurement system was prepared for impedancemetry and conductometry. Results: We showed that the detection time was reduced to about an hour. Finally, the accuracy of the device for diagnosis and precision of measurement were evaluated and compared by the detection method for bacterial culture. Conclusion: In this work, the detection time was reduced to about 1 hour.

The electrophoretic mobility of Ag and Au nanoparticles in n-hexadecane-chloroform mixtures was studied as a function of the chloroform content (from 0 to 100 vol%). The nanoparticles were stabilized by sodium bis-(2-ethylhexyl)sulfosuccinate (AOT, Aerosol OT) with a concentration of 2.5 × 10-4 mol L-1. The obtained organosols were characterized by phase analysis light scattering, dynamic light scattering, transmission electron microscopy, diffusion-ordered spectroscopy of nuclear magnetic resonance, spectrophotometry and conductometry. The electrophoretic mobility of the nanoparticles sharply increased from 0 to 3.6 × 10-9 m2 V-1 s-1 with increasing chloroform content. The growth of the mobility was caused by an increase in the concentration of solvated AOT ions, which formed by the disproportionation reaction from uncharged molecules. Low concentrations of AOT and a considerable zeta potential (up to ∼100 mV) made it possible to use the obtained organosols for the formation of electrostatically bound aggregates of Ag and Au with negatively charged SiO2 nanoparticles.

Effect of various stimuli (concentration, pH, temperature and salt) have been investigated, in aqueous isosorbide (sugar based) spacer based cationic gemini surfactant with hexadecyl chain (16-Isb-16), using spectroscopic and physico-chemical techniques (dynamic light scattering, DLS; nuclear magnetic resonance, NMR; transmission electron microscopy, TEM; polarizing optical microscopy; POM; zeta (ζ)-potential; count rate; pH and conductometry). An interesting phenomenon of micelle to vesicle transition (MVT) has been observed upon dilution. pH sensitive systems, including micelles and vesicles, are found in the solution without changing the pH externally. For external pH change (in the acidic range), DLS data revealed that vesicles are present near the neutral pH. The morphological transitions were confirmed by TEM and POM. ζ data show the conversion of positively charged aggregates to neutral ones. MVT has also been checked by increasing the temperature or adding a salt (NaCl, NaBr, NaNO3 or sodium salicylate; NaSal). Heating induces a transition from micelles to vesicles near ∼40–45 °C while salt addition causes a reverse effect (vesicle to micelle). The transition has been found to be dependent on concentration/nature of salt. The study provides a simple and effective way of tuning the micellar morphology. Keywords: Isosorbide, Cationic gemini surfactant, Micelle-Vesicle-Micelle Transition (MVMT), 1H NMR, TEM, Dynamic light scattering

In this study, an ionic liquid (IL), 1-butyl-3-methylimidazolium acetate, was used to prepare ionogels with microcrystalline cellulose (MCC) and halloysite (Hal). SEM, XRD, TG, DSC, FTIR spectroscopy, conductometry and mechanical tests were used to study the morphology, structure, thermal behaviour and electrophysical and mechanical characteristics of synthesised ionogels. XRD analysis showed a slight decrease in the interlayer space of halloysite in ionogels containing MCC, which may have been associated with the removal of residual water molecules resulting from hydrophilic IL anions and polymer macromolecules. A change in conductivity and glass-transition temperature of the ionic liquid was revealed due to intercalation into halloysite (a confinement effect) and modification with cellulose. For triple IL/Hal/MCC ionogels, the characteristic thermal degradation temperatures were higher than the corresponding values for IL/Hal composites. This indicates that the synthesised IL/Hal/MCC ionogels are characterised by a greater thermal stability than those of IL/Hal systems.

The aim of the work is to provide a comparative study of influence of ionic radii of neodymium and scandium ions on their sorption process from corresponding sulfates by individual ion exchangers Amberlite IR120, AB-17-8 and interpolymer system Amberlite IR120-AB-17-8. Experiments were carried out by using the following physicochemical methods of analysis: conductometry, pH-metry, colorimetry, and atomic-emission spectroscopy. Ion exchangers in the interpolymer system undergo remote interactions with a further transition into highly ionized state. There is the formation of optimal conformation in the structure of the initial ion exchangers. A significant increase of ionization of the ion-exchange resins occurs at molar ratio of Amberlite IR120:AB-17-8 = 5:1. A significant increase of sorption properties is observed at this ratio due to the mutual activation of ion exchangers. The average growth of sorption properties in interpolymer system Amberlite IR120:AB-17-8 = 5:1 is over 90% comparatively to Amberlite IR120 and almost 170% comparatively to AB-17-8 for neodymium ions sorption, for scandium ions sorption the growth is over 65% comparatively to Amberlite IR120 and almost 90% comparatively to AB-17-8. A possible reason for higher sorption of neodymium ions in comparison with scandium ions is maximum conformity of globes of internode links of Amberlite IR120 and AB-17-8 after activation to sizes of neodymium sulfate in an aqueous medium.