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Liposomal preparations play an important role as formulations for transdermal drug delivery; however, the electrical conductivity of these systems is sparingly evaluated. The aim of the study was to outline the range of the values of electrical conductivity values that may be recorded in the future pharmaceutical systems in the context of their viscosity. The electrical conductivity, measured by a conductivity probe of k = 1.0 cm−1, and the dynamic viscosity of liposomal and non-liposomal systems with naproxen sodium, embedded into a methylcellulose hydrophilic gel (0.25%), were compared with data from preparations without naproxen sodium in a range reflecting the naproxen sodium concentrations 0.1·10−2–9.5·10−2 mol/L. The specific conductivity covered a 1.5 μS·cm−1–5616.0 μS·cm−1 range, whereas the viscosity ranged from 0.9 to 9.4 mPa·s. The naproxen sodium highly influenced the electrical conductivity, whereas the dynamic viscosity was a moderate factor. The observed phenomena may be ascribed to the high mobility of sodium ions recruited from naproxen sodium and the relatively low concentrations of applied methylcellulose. The assembly of lecithin in liposomes may have lowered the specific conductivity of the systems with naproxen sodium. These measurements will be further developed for implementation as simple assays of the concentrations of active pharmaceutical ingredient in release experiments of preparations proposed for dermatological applications. [ABSTRACT FROM AUTHOR]

The development of chemical sensor devices operating in non-contact mode is of primary interest due to the demand from various industries for a fast, simple and inexpensive determination of chemical composition in different media in a non-invasive way. One of the promising directions for the development of analytical devices with such characteristics is the use of high-frequency electrical signals. The paper discusses the evolution of high-frequency contactless conductometry method, likewise other methods and devices operating on similar physical principles (dielectric spectroscopy, microwave sensors, C4D detectors). [ABSTRACT FROM AUTHOR]

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A thiosemicarbazide derivative as (E)-4-ethyl-1-(1-(naphthalen-1-yl) ethylidene) thiosemicarbazide (HAN) was synthesized then characterized to prepare [Co(HAN)Cl2·(H2O)2], [Ni(HAN)Cl2·(H2O)2]. H2O, and [Cd(HAN)Cl2] 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 4T1g → 4T1g(P)(ʋ2) and 4T1g → 4A2g(F)(ʋ3) and 3A2g → 3T1g(P,υ3) and 3A2g → 3T1g(F,υ2), 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.

One of the important molecules in homeostasis, especially for hormone metabolism, cellular membrane production, and vitamin D synthesis is cholesterol. However, studies showed that increased levels of this molecule would be associated with increased incidence of cardiovascular diseases including heart failure and myocardial infarction (MI). Thus, the measurement of the blood level of cholesterol is an important step for early detection and prevention of several diseases. Electrochemical sensors with high accuracy could be useful for the detection of cholesterol in body fluids. Due to the outstanding chemical and physical properties that nanoparticles possess, they are perfectly suited for the development of new and improved sensing devices. In particular, electrochemical sensors and biosensors are two types of sensing devices that could benefit from the use of nanoparticles. Many different kinds of nanoparticles, such as metal nanoparticles, oxide nanoparticles, semiconductor nanoparticles, and even composite nanoparticles, have found widespread application in electrochemical sensors and biosensors, respectively. This review has covered a variety of electrochemical biosensors for cholesterol detection, including conductometric, amperometric, and potentiometric-based biosensors, as well as their detection techniques and limitations. [ABSTRACT FROM AUTHOR]

In this paper, a microconductometric sensor has been designed, based on a chitosan composite including alcohol dehydrogenase—and its cofactor—and gold nanoparticles, and was calibrated by differential measurements in the headspace of aqueous solutions of ethanol. The role of gold nanoparticles (GNPs) was crucial in improving the analytical performance of the ethanol sensor in terms of response time, sensitivity, selectivity, and reproducibility. The response time was reduced to 10 s, compared to 21 s without GNPs. The sensitivity was 416 µS/cm (v/v%)−1 which is 11.3 times higher than without GNPs. The selectivity factor versus methanol was 8.3, three times higher than without GNPs. The relative standard deviation (RSD) obtained with the same sensor was 2%, whereas it was found to be 12% without GNPs. When the air from the operator's mouth was analyzed just after rinsing with an antiseptic mouthwash, the ethanol content was very high (3.5 v/v%). The background level was reached only after rinsing with water. [ABSTRACT FROM AUTHOR]

High dilutions of solutions containing extremely small amounts of the initial substance can modify the biological effects of the initial substance molecules. Using terahertz spectroscopy, we studied the possibility of modifying the physicochemical properties of the initial substance by adding high dilutions of high-molecular-weight (IFNγ) and low-molecular-weight (Na2SO4) compounds. In addition, the modifying effect produced by high dilutions of a low-molecular electrolyte (a solution of Na2SO4 salt) on the initial substance was confirmed by conductometry. This method allows measuring electrical conductivity that also depends on the physicochemical properties of the solution, namely, the number of ions and velocity of their movement. Statistically significant differences were shown between terahertz and conductometric characteristics of the initial solution (inorganic salt Na2SO4 or a protein IFNγ) and a solution, where high dilutions of the same substances were added in different concentrations. Interestingly, the differences were more pronounced for the biological molecule. Thus, it has been shown that high dilutions can change the properties of the initial solution; the effect is more pronounced for the protein solution. [ABSTRACT FROM AUTHOR]

Parabens are frequently used in cosmetics and their high quantities in wastewater are detrimental to the ecosystem. The effect of sonication, light aid and a combination of both on nano-sized zinc oxide-mediated degradation of methylparaben (MP) was investigated using electronic spectroscopy and differential conductometry. The time-dependent absorption at λmax of MP (i.e. 254 nm) was used to monitor the system. The degradation process that followed pseudo-first-order kinetics was augmented by the presence of ZnO. Light exposure gave better results than sonication; however, a negative synergy was observed under the combined catalysis. This limitation was overcome using constant sonication time, a high amount of catalyst and variable light exposure duration. Conductivity measurements revealed an excess of free radical or neutral species. X-ray diffraction analysis (XRD) indicated a wurtzite hexagonal structure and crystallite size of 39 nm for ZnO NPs. In Fourier transform infrared spectrum, the Zn-O band was observed at 618 cm−1.

Owing to their surface active properties, surfactants have numerous applications in different fields of life. In the present research work, the solubilization of reactive red 2 (RR2) has been studied in single and mixed micellar systems (MMS) using UV-visible spectroscopy and electrical conductivity measurements. The interaction of RR2 with ionic micelles of cetylpyridinium chloride (CPC) was investigated. In order to probe the interaction of RR2 in MMS, mixtures of CPC and TX-114 (Triton X-114, a nonionic surfactant) were used. UV-visible spectroscopy has been used to obtain the degree of solubilization of RR2 in terms of the partition coefficient (Kc) and Gibbs free energy of partitioning (ΔG°p). Electrical conductivity data have been employed to detect the critical micelle concentration (CMC) of the surfactant systems in the presence of RR2 and, accordingly, to calculate the thermodynamic parameters of the micellization. From the obtained data, it is concluded that the micellization is spontaneous at all studied temperatures. Moreover, the micellization was observed to be driven by both enthalpy and entropy. The results also indicated that MMS have better solubilizing power than single micellar solutions. [ABSTRACT FROM AUTHOR]

The object of study is a differential two-electrode conductivity cell with a calculated constant, designed for the practical realization of the unit of length – a meter in national measurement standards of electrolytic conductivity of liquids. The differential cell consists of two tubes of the same diameter but different lengths. The article presents an idealized model for calculating cell constants and determining electrolytic conductivity. The presence of holes for filling the cell, causing a distortion of the uniformity of the current density distribution in the middle of the cell, and a significant dielectric permeability of aqueous solutions lead to significant errors when measuring the resistance of liquid columns. The article presents mathematical expressions for calculating two types of corrections. First, the correction caused by the distortion of the field uniformity due to the presence of the inlet and outlet holes of the cell. Secondly, the correction caused by the presence of bias currents in aqueous solutions of electrolytes. The appearance of a differential cell based on two tubes with a diameter of 9 mm and a length of 50 and 100 mm, respectively, which is being tested as a part of the national measurement standard of Ukraine, is given. References 7, figures 5, tables 2. [ABSTRACT FROM AUTHOR]

The complexation of cefotaxime with an anionic polysaccharide, sodium alginate, in aqueous solutions with different pH values was studied by conductometry and by UV and IR spectroscopy. The compositions and stability constants of the complexes were determined. At pH 2.0, 5.6, and 7.2, the composition of the complex of cefotaxime with alginate corresponds to the [cefotaxime] : [alginate] molar ratio of 4.0 : 1.0, 2.3 : 1.0, and 1.0 : 1.0, respectively. The cefotaxime–alginate complex is most stable in strongly acidic media. [ABSTRACT FROM AUTHOR]

The objective of this study was to reexamine the general statement declaring that cationic and anionic species cannot be compatible in cosmetic products. This research demonstrated that there are considerable differences between the binding of cationic preservatives and various anionic compounds used in cosmetics, depending on the anionic functional group. Sulfate- and sulfonate-based molecules showed significantly stronger interactions with cationic surfactants than carboxylate-based anionic surfactants: This difference of affinity could reach a ratio of 1 to 10. We validated that conductimetry and isothermal titration calorimetry (ITC) can be used as predictive tools to determine the molecular interactions between any cationic and anionic species. Consequently, the correlation between compatible and incompatible cationic/anionic mixtures were verified and their corresponding anti-microbial activity using the challenge test was assessed. [ABSTRACT FROM AUTHOR]

Nickel hydroxides are widely used as electrochemically active substances in alkaline batteries and hybrid supercapacitors; they can be used for electrocatalysis, in electrochemical sensors, and as pigments. Knowledge of the formation mechanism of nickel hydroxides is necessary for developing and optimizing targeted synthesis methods. The thermal effects of processes in the formation of nickel hydroxide from nitrate were studied by the calorimetry method. The mechanism of precipitate formation was investigated by the method of simultaneous potentiometric (with a glass universal electrode) and conductometric titration. The nickel content in the samples obtained at the determined NaOH/Ni2+ ratios was investigated by the chemical method of trilonometry after preliminary dissolution. Calorimetric investigations showed that the reaction of nickel nitrate with NaOH was exothermic with ΔНreaction=‒28328.5 J/mol. The exothermic nature of the NaOH dilution process was revealed with ΔНdilution =‒2454 J/mol. According to the results of potentiometric titration, the formation of a basic salt of the NiOHNO3 type was not detected. Analysis of the results of conductometric titration revealed a two-stage chemical mechanism for the formation of nickel hydroxide from nitrate. At the first stage, which had a high rate, due to the liquid-phase reaction of the nickel cation with the hydroxyl anion, a primary precipitate of the composition Ni(OH)1.87(NO3)0.13 was formed. In the second stage, as a result of a slow topochemical reaction of the primary precipitate with hydroxyl anions, nitrate ions were displaced from the precipitate to form nickel hydroxide. These data are confirmed by the analysis of precipitate obtained at NaOH/Ni2+ ratios of 1.87 and 2.2: the Ni content was 52.95 % and 55.63 %, corresponding to the formulas Ni(OH)1.87(NO3)0.13∙0.68H2O and Ni(OH)2∙0.71H2O. This clearly indicated that the primary precipitate was nitratedoped α-Ni(OH)2 and the final precipitate corresponded to the α-modification of nickel hydroxide. [ABSTRACT FROM AUTHOR]

A study is performed of the interaction between 2(4)-aminopyridines (2(4)-AP) and Pd(II), Pt(II), Pt(IV) and accompanying ions Ni(II), Co(II), Fe(II, III), Cu(II) in aqueous solutions close to the conditions of their extraction isolation and separation. It is shown that platinum metal ions form stable neutral and cationic complexes with both 2-AP and 4-AP that can be isolated from aqueous solutions. The tendency to form cationic complexes diminishes in the order Pd(II) > Pt(II) > Pt(IV) and 4-AP > 2-AP. With the exception of Cu(II), ions of 3d-elements do not form stable complexes under these conditions. Cu(II) forms complexes with 2(4)-AP that are subject to hydrolysis when isolated from aqueous solutions. Features of 2(4)-AP when interacting with metal ions are discussed. It is proposed that analogs of 2(4)-AP with long hydrocarbon radicals be used for the extraction concentration of platinum metals from hydrometallurgical solutions of complex composition. [ABSTRACT FROM AUTHOR]

Copyright of Innotec is the property of Laboratorio Tecnologico del Uruguay 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 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]

In this work, we explore the analytical potential of a simple inexpensive sensor device based on the evolution of the high-frequency contactless conductometry method. This method was developed in the middle of the 20th century as one of the options to assess the electrical conductivity of samples, and it employed electrical signals registered at a specific, single AC frequency. The method did not find a wide application since the analytical signal in the developed systems was a complex function of many factors (sample conductivity, capacitive characteristics, dielectric permittivity, and magnetic properties), which was difficult to be mathematically processed. We came back to this technology with the following in mind: (1) modern electronic components enable the design of such measuring devices in a very-low-cost manner and allow registering the response signal in a whole range of AC frequencies; (2) the application of modern machine learning tools to process these signals allows for the extraction of qualitative and quantitative information about the samples. It was found that the detector has numerous capabilities such as the quantification of inorganic salts in individual aqueous solutions and in complex mixtures, the quantification of dielectric constants of organic solvents, and distinguishing the cultures of various bacteria and cancer cells.

In this paper, a microconductometric sensor has been designed, based on a chitosan composite including alcohol dehydrogenase—and its cofactor—and gold nanoparticles, and was calibrated by differential measurements in the headspace of aqueous solutions of ethanol. The role of gold nanoparticles (GNPs) was crucial in improving the analytical performance of the ethanol sensor in terms of response time, sensitivity, selectivity, and reproducibility. The response time was reduced to 10 s, compared to 21 s without GNPs. The sensitivity was 416 µS/cm (v/v%)−1 which is 11.3 times higher than without GNPs. The selectivity factor versus methanol was 8.3, three times higher than without GNPs. The relative standard deviation (RSD) obtained with the same sensor was 2%, whereas it was found to be 12% without GNPs. When the air from the operator’s mouth was analyzed just after rinsing with an antiseptic mouthwash, the ethanol content was very high (3.5 v/v%). The background level was reached only after rinsing with water.

The microwave‐assisted synthesis technique, one of the pioneers of green chemistry, was used to synthesize aromatic thiadiazole crown ethers in this study. Thiadiazole crown ethers were synthesized by the cyclization reaction of 2‐amino‐5‐mercapto‐1,3,4‐thiadiazole and mono‐di‐tri‐tetra ethylene glycol dichloride compounds using the SN2 reaction mechanism in acetonitrile solvent and the presence of cesium carbonate base. FT‐IR, 1H‐NMR, 13C‐NMR, LC‐MS/MS spectroscopic techniques, and elemental analysis were used to characterize the synthesized compounds after purification. Furthermore, the conductivity behaviour of the synthesized compounds against metal salts (NaCl, KCl, MgCl2, CaCl2, ZnCl2, FeSO4, AgNO3, CoCl2) was determined using Job′s Plot technique, which was adapted to conductometry. Interactions between ligands and ions were investigated. According to conductometric data, thiadiazole crown ethers showed significant complexations; M1 and M4 with Ca2+, M2 with Fe2+, and M3 with Co2+ ions. [ABSTRACT FROM AUTHOR]

In this article, a mathematical model was developed to describe and optimize the configuration of the urea biosensor. The biosensor is based on interdigitated gold microelectrodes modified with a urease enzyme membrane. The model presented here focuses on the enzymatic reaction and/or diffusion phenomena that occur in the enzyme membrane and in the diffusion layer. Numerical resolution of differential equations was performed using the finite difference technique. The mathematical model was validated using experimental biosensor data. The responses of the biosensor to various conditions were simulated to guide experiments, improve analytical performance, and reduce development costs. [ABSTRACT FROM AUTHOR]

A simple algorithm for determining the set of parameters of the equivalent circuits of the impedance of a planar conductometric transducer with an interdigital comb topology, consisting of interelectrode and Faraday impedances is proposed. The frequency characteristics of the impedance parameters of the transducer samples and the electrical equivalent with averaged values of the parameters have been studied. A technique for determining the parameters of a three-element equivalent circuit, including solution resistance, double layer capacitance, and charge transfer resistance, has been developed and tested on a series of transducer samples. The optimal operating frequencies of the impedance-measuring channel are determined, and its schemes are developed. A technique for estimating the parameters of the Warburg impedance of transducer samples is demonstrated. The results obtained in the work make it possible to determine the optimal operating frequency range of biosensor systems and reduce errors from the influence of the Faraday impedance. The possibility of extending the functions of such transducers by using the near-electrode layer impedance parameters as informative ones is shown. [ABSTRACT FROM AUTHOR]

Owing to their surface active properties, surfactants have numerous applications in different fields of life. In the present research work, the solubilization of reactive red 2 (RR2) has been studied in single and mixed micellar systems (MMS) using UV-visible spectroscopy and electrical conductivity measurements. The interaction of RR2 with ionic micelles of cetylpyridinium chloride (CPC) was investigated. In order to probe the interaction of RR2 in MMS, mixtures of CPC and TX-114 (Triton X-114, a nonionic surfactant) were used. UV-visible spectroscopy has been used to obtain the degree of solubilization of RR2 in terms of the partition coefficient (Kc) and Gibbs free energy of partitioning (ΔG°p). Electrical conductivity data have been employed to detect the critical micelle concentration (CMC) of the surfactant systems in the presence of RR2 and, accordingly, to calculate the thermodynamic parameters of the micellization. From the obtained data, it is concluded that the micellization is spontaneous at all studied temperatures. Moreover, the micellization was observed to be driven by both enthalpy and entropy. The results also indicated that MMS have better solubilizing power than single micellar solutions.

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. [ABSTRACT FROM AUTHOR]

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.

This paper describes the design and characterization of a reconfigurable, multi-technique electrochemical biosensor designed for direct integration into smartphone and wearable technologies to enable remote and accurate personal health monitoring. By repurposing components from one mode to the next, the biosensor's potentiostat is able reconfigure itself into three different measurements modes to perform amperometric, potentiometric, and impedance spectroscopic tests all with minimal redundant devices. A [Formula: see text] PCB prototype of the module was developed with discrete components and tested using Google's Project Ara modular smartphone. The amperometric mode has a ±1 nA to [Formula: see text] measurement range. When used to detect pH, the potentiometric mode achieves a resolution of < 0.08 pH units. In impedance measurement mode, the device can measure 50 Ω-10 [Formula: see text] and has been shown to have of phase error. This prototype was used to perform several point-of-care health tracking assays suitable for use with mobile devices: 1) Blood glucose tests were conducted and shown to cover the diagnostic range for Diabetic patients (  ∼  200 mg/dL). 2) Lactoferrin, a biomarker for urinary tract infections, was detected with a limit of detection of approximately 1 ng/mL. 3) pH tests of sweat were conducted to track dehydration during exercise. 4) EIS was used to determine the concentration of NeutrAvidin via a label-free assay.

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 complexation between CE and Mn+ in water + acetonitrile binary solvent system (20, 40, 60 and 80%; v/v) at 298.15 K to 328.15 K by conductometric technique. Kf values for all complexes were found to be decreased with enhancement of temperature. Complexes associated with Zn2+ exhibit a trend of Kf: 24C8 + Zn2+ > 18C6 + Zn2+ in 20% solvent composition (water-acetonitrile) and order of 18C6 + Zn2+ > 24C8 + Zn2+ was found for 80% solvent composition. However, logarithm values of Kf for the Cu2+ complexes were found to obey the order of 24C8 > 18C6 almost for all compositions except with a few exceptions. Δ G o was found to be negative indicating spontaneous complexation between CE and Mn+. [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 micellar properties of two common surfactants, namely sodiumdodecyl sulphate (SDS) which is of anionic character and dodecyltriamonium bromide (DTAB) of cationic type alongwith 12-2-12 gemini surfactant which was produced in aqueous solutions of 0.001, 0.005 and 0.01 mol·kg-1 aqueous solutions of metformin hydrochloride (Mfm-HCl) (antidiabetic drug) at 25, 35 and 45 degree Celsius has been analyzed through conductometry. The obtained conductivity data has been used to determine one of the most important characteristic of surfactants known critical micelle concentration (CMC); the concentration above which micelles are formed. The variation in CMC with content of metformin hydrochloride has been compensated in terms of hydrophobic interactions. The drug has been found to diminish the CMC of both types of surfactants (conventional and synthesized). In terms of the hydrophilic/hydrophobic interactions existing in the system, the effect of temperature on the micellization behaviour of these discussed surfactants has also been studied. Moreover, energetics of micellization has also been discussed by using phsedo-phase separation model for all the studied systems in terms of thermodynamic parameters viz. standard enthalpy, ΔHom free energy, ΔGom and entropy, ΔSom of micellization and viewed in terms of different interactions that may exist in the system. The influence on the micro polarity of micellar environment has been discussed by pyrene probe fluorescence technique and used to determine CMC which has been discovered to have a strong resemblance to conductivity studies. [ABSTRACT FROM AUTHOR]

Parabens are frequently used in cosmetics and their high quantities in wastewater are detrimental to the ecosystem. The effect of sonication, light aid and a combination of both on nano-sized zinc oxide-mediated degradation of methylparaben (MP) was investigated using electronic spectroscopy and differential conductometry. The time-dependent absorption at λmax of MP (i.e. 254 nm) was used to monitor the system. The degradation process that followed pseudo-first-order kinetics was augmented by the presence of ZnO. Light exposure gave better results than sonication; however, a negative synergy was observed under the combined catalysis. This limitation was overcome using constant sonication time, a high amount of catalyst and variable light exposure duration. Conductivity measurements revealed an excess of free radical or neutral species. X-ray diffraction analysis (XRD) indicated a wurtzite hexagonal structure and crystallite size of 39 nm for ZnO NPs. In Fourier transform infrared spectrum, the Zn-O band was observed at 618 cm−1. [ABSTRACT FROM AUTHOR]

The conductometric study of ligand structure influence on the Pb(II) complexation with crown ethers in different solvents has been investigated. In this paper, the complexation reaction of macrocyclic ligand, 18-crown-6 (18C6), dibenzo-18-crown-6 (DB18C6), and Pb(II) cation was studied in different solvents: dichloromethane (DCM) and 1,2-dichloroethane (1,2-DCE). The effects of surfactant structure (Triton X-100 and Triton X-45) on the conductivity of the Pb(II) complex with 18-crown-6 and dibenzo-18-crown-6 ether have been investigated. The conductance data showed that the stoichiometry of the complexes in most cases is 1:1(ML). It is also demonstrated that the influence of crown ethers is deeply affected by the organic solvent used. In the solvents studied, the stability of the resulting complexes showed higher stability in dichloromethane comparing with 1,2- dichloroethane. Macrocyclic ligand 18-crown-6 showed more suitable for complexation of Pb(II) ions compared to dibenzo-18-crown-6. Adding a surfactant affected the higher absolute values of the conductivity of systems, but not the change in the stoichiometric ratio between a metal ion and macrocyclic ligand.

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.

The objective of this study was to reexamine the general statement declaring that cationic and anionic species cannot be compatible in cosmetic products. This research demonstrated that there are considerable differences between the binding of cationic preservatives and various anionic compounds used in cosmetics, depending on the anionic functional group. Sulfate- and sulfonate-based molecules showed significantly stronger interactions with cationic surfactants than carboxylate-based anionic surfactants: This difference of affinity could reach a ratio of 1 to 10. We validated that conductimetry and isothermal titration calorimetry (ITC) can be used as predictive tools to determine the molecular interactions between any cationic and anionic species. Consequently, the correlation between compatible and incompatible cationic/anionic mixtures were verified and their corresponding anti-microbial activity using the challenge test was assessed.

The technical legal acts that regulate the quality and safety parameters of mineral waters out were analyzed. Seven samples of mineral waters produced in Belarus, Russia, and Georgia were studied. Analysis for heavy metals (Zn, Cd, Pb, Cu, and Hg) was performed by stripping voltammetry, for sulfates, by spectrophotometry, and for total mineralization, by conductometry. The pH values were measured by direct potentiometry. Comparative safety assessment of packaged mineral waters was performed. [ABSTRACT FROM AUTHOR]

Dopamine is a biologically active chemical that performs a number of vital functions as a hormone and neurotransmitter. Therefore, the determination of dopamine concentration in the human body is important for biomedical research. The content of dopamine in the blood varies depending on the age of a healthy person and can serve as a prognostic marker of many diseases. The aim of this work was to develop a new enzyme conductometric biosensor for the determination of dopamine in aqueous samples and to study the biosensor's analytical characteristics. The conductometric method of analysis with differential measurement mode was used in the work. Two pairs of gold interdigitated electrodes deposited on a sitall substrate were used as a conductometric transducer. The biorecognition element of the biosensor was based on laccase immobilized by glutaraldehyde cross‐linking. The optimal conditions of laccase immobilization were selected. The influence of solution parameters (ionic strength, pH, buffer capacity) on the biosensor work was investigated. The biosensors demonstrated high sensitivity to dopamine (minimum limit of detection −7.8 μM) with the linear range up to 1 mM. The biosensor was highly selective and reusable. The proposed biosensor was tested regarding the possibility of its long‐term storage under different conditions. The developed conductometric biosensor was proven to be suitable for measuring dopamine concentration in biological and pharmaceutical samples. [ABSTRACT FROM AUTHOR]

The paper presents the results of a study of errors arising in the presence of radial displacements in a conductometric differential cell with a removable central part, in the process of measuring the electrolytic conductivity of solutions. The analysis of the component of the measurement error of the cell resistance, caused by the presence of displacement at the cell joint, as a systematic error is carried out. This error is caused by the appearance of additional resistance of the solution column in the cell due to a decrease in the cross-sectional area at the joint with a radial displacement and a corresponding change in the path of electric current flow in the cell. This additional resistance is estimated using computer cell modeling and finite element method. To describe the joint of the displaced cell parts, the parameter KJ is used, which depends on the diameter of the tubes and the magnitude of the displacement. Expressions for the errors and dependences for KJ are obtained, with the help of which it is possible to estimate the component of the error in measuring the resistance for real cells due to radial displacements. The results of the work can be used to estimate the component of the measurement error of electrolytic conductivity due to the presence of radial displacements of a known value for real cells. This will make it possible to ascertain whether or not this source of error should be taken into account when estimation the measurement uncertainty of electrolytic conductivity with the known characteristics of the cell fixing devices. [ABSTRACT FROM AUTHOR]

This article demonstrates an instrumented mouthguard capable of non-invasively monitoring salivary uric acid (SUA) levels. The enzyme (uricase)-modified screen printed electrode system has been integrated onto a mouthguard platform along with anatomically-miniaturized instrumentation electronics featuring a potentiostat, microcontroller, and a Bluetooth Low Energy (BLE) transceiver. Unlike RFID-based biosensing systems, which require large proximal power sources, the developed platform enables real-time wireless transmission of the sensed information to standard smartphones, laptops, and other consumer electronics for on-demand processing, diagnostics, or storage. The mouthguard biosensor system offers high sensitivity, selectivity, and stability towards uric acid detection in human saliva, covering the concentration ranges for both healthy people and hyperuricemia patients. The new wireless mouthguard biosensor system is able to monitor SUA level in real-time and continuous fashion, and can be readily expanded to an array of sensors for different analytes to enable an attractive wearable monitoring system for diverse health and fitness applications.

The effect of acetonitrile (ACN) on the micellization of a cationic surfactant, cetyltrimethylammonium bromide (CTAB), in aqueous solutions at different temperatures was studied. The critical micellar concentration (CMC) as well as the degree of counter ion dissociation (a) of CTAB in aqueous ACN mixtures (10-20 % v/v) at various temperatures (291.2-298.2 K) were determined by electrical conductivity measurements, while steady-state fluorescence measurements were used to determine several CMCs (for comparison) and a micellar aggregation number (Nagg) as well. At a fixed temperature, both an increase in CMC and a decrease in Nagg were observed for an increase in ACN in the solvent mixture. With a temperature increase, CMC values increased for 10 % (v/v) ACN, while for both 15 % and 20 % (v/v) ACN, CMC values were a minimum at T = 295.2 K with a temperature increase. In addition, some aspects related to the Krafft temperature behavior of CTAB in the examined micellar systems are discussed.

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. [ABSTRACT FROM AUTHOR]

The effect of acetonitrile (ACN) on the micellization of a cationic surfactant, cetyltrimethylammonium bromide (CTAB), in aqueous solutions at different temperatures was studied. The critical micellar concentration (CMC) as well as the degree of counter ion dissociation () of CTAB in aqueous ACN mixtures (1020 % v/v) at various temperatures (291.2298.2 K) were determined by electrical conductivity measurements, while steady-state fluorescence measurements were used to determine several CMCs (for comparison) and a micellar aggregation number (Nagg) as well. At a fixed temperature, both an increase in CMC and a decrease in Nagg were observed for an increase in ACN in the solvent mixture. With a temperature increase, CMC values increased for 10 % (v/v) ACN, while for both 15 % and 20 % (v/v) ACN, CMC values were a minimum at T = 295.2 K with a temperature increase. In addition, some aspects related to the Krafft temperature behavior of CTAB in the examined micellar systems are discussed. [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]

Introduction: Phenol is considered to be an important pollutant in the environment and is steadier than other aromatic compounds in industrial treatment. There are several methods for detecting phenol in the wastes. In spite of the high accuracy of these methods, they are time consuming and complex. The utilization of enzymatic biosensors for the identification of phenolic compounds is one of the options and successful techniques. However, the weaknesses of enzymes and high financial expenses cannot be ignored. One of the alternative solutions to overcome the shortcomings of working with enzymes is the utilization of microbial cells in biosensors. In this study, microbial cells were used to design a reasonable and accurate biosensor. Materials and Methods: In this survey, designing of a biosensor was examined using a phenol consuming bacterium. Pseudomonas.GSN23 was acclimatized to high phenol concentrations and immobilized by forming physical and chemical links on working electrodes (glassy carbon and gold interdigitated microelectrodes).Two electrochemical methods (square wave voltammetry and conductometric) were utilized to measure the phenol. Results: In the presence of 1 gram per liter phenol, as the only source of carbon and energy, Pseudomonas. GSN23 consumed 73% of the initial phenol concentration at 32 hours and phenol consumed completely at 72 hours. This bacterium had positive and repeatable responses in conductometric method for phenol detection in the range of 1-300 milligram per liter. The phenol selectivity of the designed biosensor was estimated 5 times more than other aromatic compounds. Conclusion: Microbial biosensors are practical, stable and resistant to the changes of the experimental media. In this study, Pseudomonas.GSN23 was utilized as a phenol consuming bacterium and by conductivity measurement; repeatable responses were acquired in detecting this contaminant.

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. [ABSTRACT FROM AUTHOR]

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