Conductometric Method Research Articles

A Novel Method for Combination of Ionic Conductivity and pH-metry Methods for the Determination of the Aqueous Solubility of a New Diisopropylammonium Hydrogenmaleate Crystalline Molecule

Dissociation constant, solubility, and thermodynamic data are very important physicochemical parameters for biological substances and their knowledge is of fundamental importance for the validation of drugs. In addition to their low cost and accessibility, Conductometric and pH-metric methods seem to be particularly suitable for the determination of these parameters given the often weak acidic or basic nature of drugs. These parameters were determined for a new synthesized diisopropylammonium hydrogenmaleate (iPr2NH2-MA) crystalline molecule. Conductometric and pH-metric methods were used for this characterization. The pH-metric method lead to pKa1 = 3.6, pKa2 = 6.7 and pKa3 = 7.5, while the conductometric method made it possible to determine two pKa values which are pKa1 = 3.5 and pKa3 = 7.8. The values of the thermodynamic parameters calculated for the enthalpy change (∆rH0) and the entropy change (∆S) of the iPr2NH2-MA acidic dissociation reaction are of the order of ∆H = 25. 36 ± 0.06 kJ.mol-1 and ∆S = 6.08 ± 0.18 kJ.mol-1.K-1. In addition, the Gibbs free energy change (ΔG) of the molecule decreased as a function of temperature. The solubility varied between 1 and 84 mg mL-1 for pH values comprised between 3.5 and 8.5 and reached its maximum Smax = 84 mg mL-1 at pH 5.6. The dissociation process was found to be is non-spontaneous, endothermic and entropically favorable. These results demonstrated on the one hand the reliability and effectiveness of the Conductometric and pH-metric methods for the characterization of molecules with acidic and/or basic sites, and on the other hand the excellent physical and chemical properties of diisopropylammonium hydrogenmaleate (iPr2NH2-MA) crystalline molecule.

Continuous flow microfluidic system with magnetic nanoparticles for the spectrophotometric quantification of urea in urine and plasma samples.

Urea, synthesized exclusively in the liver, is primarily transported through the bloodstream to the kidneys, where it is excreted in urine, accounting for 80-90% of nitrogen excretion in humans. Elevated blood urea levels, indicative of kidney dysfunction, make it a crucial biomarker for assessing renal function. Previous studies on urea detection using microdevices have largely focused on conductometric methods. In this study, we demonstrated the application of a continuous flow miniaturized system for rapid spectrophotometric urea quantification using polydimethylsiloxane (PDMS) microdevices. The microdevice featured two distinct zones: an enzymatic reaction zone, where urease-conjugated magnetic nanoparticles were immobilized, and a detection zone, where reagents were incorporated to produce a colored reaction product via a modified Berthelot reaction. Integrating magnetic nanoparticles as a solid support for the enzyme enabled the reuse of PDMS microdevices without compromising the analytical signal. Spectrophotometric detection was performed in an additional microdevice acting as a microflow cell coupled with optical fibers. A calibration curve was constructed using urea standards diluted in phosphate buffer solution (PBS), yielding a linear range of 0.12-3.00 mg dL-1. The method demonstrated detection and quantification limits of 0.04 mg dL-1 and 0.12 mg dL-1, respectively. Precision and accuracy assessments yielded a repeatability of 0.90% and intermediate precision of 4.52%, with recovery rates near 100%. The method was applied to plasma and urine samples, showing urea concentrations within normal physiological ranges and an analysis throughput of 36 measurements per hour.

Antimicrobial and aggregation properties of asymmetric gemini surfactants based on 1-(2-hydroxypropyl)-4-ethyl piperazine and alkyl bromides

Asymmetric gemini surfactants were synthesized by the quaternization reaction of 1-(2-hydroxypropyl)-4-ethyl piperazine with (C9, C10, C12, and C14) alkyl bromides. The surface tension of their aqueous solutions was determined by the Du Nouy ring method and the conductometric method of specific electrical conductivity. According to the concentration dependence graphs of surface tension and specific electrical conductivity, critical micelle concentration – CMC, degree of association of the counterion – β, surface area occupied by the head group of the surfactant – Amin, maximum surface excess concentration – Γmax, effectiveness or surface pressure –πCMC, adsorption efficiency – pC20 were calculated, and the change of these parameters depending on the length of the alkyl chain was determined. Simultaneously, variations in Gibbs free energies of micellization and adsorption processes were computed. The diameters of aggregates formed by asymmetric gemini surfactants in water were determined by the DLS method. Antimicrobial abilities of asymmetric gemini surfactants against gram positive and gram negative bacteria and fungi were defined by the disk diffusion method.

Determination of Critical Micelle Concentration (CMC) of Sodium Stearate Solution in Distilled Water

Surfactant is an organic compound having polar and nonpolar parts. The specific conductivity of sodium stearate surfactant in double distilled water has been studied by conductometric method at three temperatures (298.15, 308.15, and 318.15) K. conductivity of the surfactant increases with increase in temperature and concentration of solution. Critical Micelle Concentration (CMC) of sodium stearate was determined attemperature 298.15 K is 0.00095Mol/lit using the easy plot software. FESEM image shows themorphological structure of the sodium stearate surfactant.

Mass insulation enhancement of cork stoppers through heat treatment: experimental measurements, modeling, and optimization

Natural cork stoppers, used as bottle sealers for high-end products such as ingredients and flavorings, belong to the highest class in terms of cork quality. Various studies have been carried out to examine the solute diffusion in cork using conventional methods. However, the investigations were limited to natural cork stoppers that had been boiled and cut in a single direction. In this study, the anisotropic cylindrical shape of cork samples was modeled, considering various cutting directions. Additionally, we subjected the stoppers to boiling then to an optimal THT cycle to improve the cork's mechanical qualities. The optimal thermal cycle is determined using TGA analysis. IR and SEM tests are employed to verify the enhancements in the cork. The apparent mass diffusion coefficient (Dapp) is determined by the calibration of the model with the experimental data acquired via the conductometric method. The coefficient values are optimized using the Bat algorithm with a relative error of 10–5. The Dapp was found to be better for the treated cork grown in the Jijel region than for the cork Medea, which is better than of Skikda cork. Regarding the impact of the cutting direction on the Jijel's cork, the results indicate that the mass insulation is higher when the treated stoppers are cut in the tangential-longitudinal direction (DJTLt=4,12.10-13m2s-1) compared to the tangential-radial direction (DJTRt=7,75.10-13m2s-1) and the longitudinal-radial direction (DJLRt=8,53.10-13m2s-1). The treatment, which serves as a solution for the cork industry, showed an improvement in mass insulation 13-fold greater than the natural cork.

Investigation of micellization and thermodynamic properties of cationic gemini surfactant (12-2-O-2-12) in the presence of organic solvents

The micellization behaviour and thermodynamic properties of synthesized cationic gemini surfactant (12-2-O-12-12), N,N′-didodecyl-N,N,N′,N′-tetramethyl-N,N′-(oxybis(ethane-2,1-diyl))-diammonium dibromide were studied in the presence of organic solvents for four different temperatures (25, 30, 35 and 40 °C). Aqueous solutions of 10 % and 20 % methanol (MeOH), ethanol (EtOH), isopropanol (IPOH) and dimethyl sulfoxide (DMSO) were used as solvents. The critical micelle concentration (CMC) of cationic gemini surfactant and the degree of counterion dissociation (α) were determined by the conductometric method. Using the CMC and α values for each of the four temperatures, the values of the standard Gibbs free energy (ΔGmo), Gibbs free energy of transfer (ΔGm,transo), enthalpy (ΔHmo), and entropy (ΔSmo) of micellization were calculated. It was observed that the CMC and α values increased with increasing solvent percentage and temperature. It was found that in all cases, the standard Gibbs free energy and enthalpy values were negative while both the micellization entropy and the standard Gibbs free energy of transfer are positive. Negative Gibbs free energy values indicated that micellization was a spontaneous situation, while positive entropy values indicated the existence of a disordered situation. The positive ΔGm,transo values show that the presence of solvents makes the environment unfavorable for micelle formation.

Valorization of Fine-Fraction CDW in Binary Pozzolanic CDW/Bamboo Leaf Ash Mixtures for the Elaboration of New Ternary Low-Carbon Cement

This paper presents the characterization of a binary mixture of construction and demolition waste (CDW) and bamboo leaf ash (BLAsh) calcined at 600 °C (novel mixture) and the study of its pozzolanic behavior. Different dosages in a pozzolan/Ca(OH)2 system were employed. The aim is the valorization of fine-fraction CDW that achieves a more reactive binary mixture and allows an adequate use of CDW as waste, as CDW is a material of limited use due to its low pozzolanic activity. The pozzolanic behavior of the mixture was analyzed using the conductometric method, which measures the electrical conductivity in the CDW + BLAsh/CH solution versus reaction time. With the application of a kinetic–diffusive mathematical model, the kinetic parameters of the pozzolanic reaction were quantified. This allowed a quantitative evaluation of the pozzolanic activity based on the values of these parameters. To validate these results, other experimental techniques were used: X-ray diffraction, thermogravimetry and scanning electron microscopy. Also, mechanical compressive strength assays were carried out. The results show an increase in the pozzolanic activity of binary mixes of CDW + BLAsh for all the dosages used in comparison to the pozzolanic activity of CDW alone. The quantitative assessment (kinetic parameters) shows that the binary mixture CDW50 + BLAsh50 is the most reactive (reaction rate constant of 7.88 × 10−1 h−1) and is superior to the mixtures CDW60 + BLAsh40 and CDW70 + BLAs30. Compressive strength tests show higher strength values for the ternary mixes (OPC + CDW + BLAsh) compared to the binary mixes (OPC + CDW). In view of the results, the binary blend of pozzolans CDW + BLAsh is suitable for the manufacture of future low-carbon ternary cements.

Assessment of drought resistance of grain sorghum samples by the conductometric method

Assessment of drought resistance of grain sorghum samples by the conductometric method

Cytotoxicity and bioavailability assessment from micellar system based Thiamine-Phospholipid complexes

Poor absorption (3–5 %) of thiamine hydrochloride (TH), is primarily concerned with impaired permeability across intestinal mucosa. To modulate the permeability of TH, a phospholipid (PL) interaction-based hydrophobic complex of thiamine was investigated. Using the solvent evaporation approach, thiamine-phospholipid complexes (TPCs) were prepared between free bases of thiamine and PLs in the weight ratio (1:1, 1:2, and 2:1) and characterized using FTIR, spectrophotometry, XRD, and conductometric methods. Electrical conductivity and partition coefficient studies demonstrated that TPCs were hydrophobic transformations formed via PL interaction with a free thiamine base. TPCs were embedded into the micellar system (Tween20/Ethanol), characterized by electrical conductivities and zeta-sizing studies, and exploited in its micellar delivery system design. TPC 1:1 & 1:2 had much lower conductivity than TH and its physical mixture (TH/PL) in the Tween20/Ethanol environment diluted with an aqueous phase. The average size of micellar systems loaded with TPC (10 % w/w) was within the range of 12–25 nm, and conductivity was in the range of 122-130µS/cm. In vitro release characterization from complexes and their micellar systems in HCl 1.2, phosphate buffer (PB) 6.8, and bidistilled water showed a delayed release pattern. TPC modulated the intestinal permeability of thiamine as revealed from ex vivo studies. TPC (1:1) and its micellar system produced significant differences in drug permeability (p < 0.001) compared to TH and physical mixture. Pharmacokinetic assessment of the micellar system of complexes in Wistar rats showed that the TPC (1:1) loaded micellar system produced a 2.4-fold enhancement of AUC(0−24) over (TH) followed by oral administration. Assessment of cell viability in mouse fibroblast cell line (L929) culture showed that TPC or micellar system did not inhibit cell growth and was safe at various concentration levels. TPc complexes developed using phospholipid complexation yield hydrophobic transformation in TH and their micellar system-based delivery modulates the intestinal permeability and bioavailability enhancement.

USE OF ETHOXYLATED ALCOHOLS WITH ANIONIC SURFACTANTS FOR ENHANCED RECOVERY

The article is devoted to the development of surfactant compositions, including a number of known anionic surfactants, in formulations with new types of nonionic surfactants - fatty alcohols with an increased degree of ethoxylation. The solubilizing properties of new types of fatty ethoxylated alcohols have been exploited during formulation development. A conductometric method was used to control the assembly of the formulations. After evaluating the stability of the resulting compositions, physicochemical properties were evaluated, including thermal stability and corrosiveness. The freezing point of the compositions was evaluated at temperatures down to minus 40 °C. The search for stable compositions was carried out for aggressive application conditions: at 90 ° C for models of mineralized formation waters having a total amount of dissolved salts in the range of 100-300 g/l. Ranges including critical concentrations of formulations at which colloidal structures are stable and exhibit maximum surface activity were evaluated. When determining the interfacial tension at the surfactant-hydrocarbon liquid solution boundary, a number of developed compositions showed ultra-low interfacial tension (less than 0.01 mN/m). Biodegradability was evaluated for compositions showing the best properties. According to the results of the assessment, biodegradability was more than 98 %, which reduces environmental risks. The results obtained by the authors show that a number of compositions collected by conductometric method are stable under aggressive conditions and can be used in the field of chemical methods for increasing oil recovery. The resulting compositions were adapted to reduce human factors in subsequent applications. The results reflect the potential of these approaches in adapting and selecting surfactant compositions for chemical waterflooding to enhance oil recovery. The development of technologies for the ethoxylation of higher fatty alcohols allows the manufacturability of processes for the production, collection and treatment of oil and gas. The development of practices for the use of new chemical technologies will expand the capabilities of subsoil users and reduce the risks associated with the use of large-scale chemical products.

Conductometric and Thermodynamic Studies of Selected Imidazolium Chloride Ionic Liquids in N,N-Dimethylformamide at Temperatures from 278.15 to 313.15 K.

This scientific article presents research on the electrical conductivity of imidazole-derived ionic liquids (1-methylimidazolium chloride, 1-ethyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, 1-hexyl-3-methylimidazolium chloride and 1-methyl-3-octylimidazolium chloride) in the temperature range of 278.15-313.15 K in N,N-Dimethylformamide. The measurement methods employed relied mainly on conductometric measurements, enabling precise monitoring of the conductivity changes as a function of temperature. Experiments were conducted at various temperature values, which provided a comprehensive picture of the conducting properties of the investigated ionic liquids. The focus of the study was the analysis of the conductometric results, which were used to determine the conductivity function as a function of temperature. Based on the obtained data, a detailed analysis of association constants (KA) and thermodynamic parameters such as enthalpy (∆H0), entropy (∆S0), Gibbs free energy (∆G0), Eyring activation enthalpy for charge transport (ΔHλ‡) and diffusion processes (D0) was carried out. The conductometric method proved to be an extremely effective tool for accurately determining these parameters, significantly contributing to the understanding of the properties of imidazole-derived ionic liquids in the investigated temperature range. As a result, the obtained results not only provide new insights into the electrical conductivity of the studied ionic liquids but also broaden our knowledge of their thermodynamic behavior under different temperature conditions. These studies may have significant implications for the field of ionic liquid chemistry and may be applied in the design of modern materials with desired conducting properties.

Quantitative Estimation of Vanillin content in various brands of Vanilla Flavored Custard Powder by Conductometry

A facile and cost effective conductometric method for quantitative estimation of vanillin content in various locally available brands of vanilla custard powders was performed. Background of the study was conducted taking the base of varied consumption of flavored foods. Vanillin being the choice of flavored desserts in the local region of Telangana, few brands of custard powder were analyzed conductometrically. The milk proteins were removed by precipitation using Saturated copper sulphate and the vanillin content of the various vanilla flavoured custard powder was extracted by liquid-liquid extraction using methanol as solvent.Then the extracted analyte was titrated aganist 0.00105 M NaOH (Standardized).The observed conductance readings on Y-axis and volume of NaOH added on X-axis was taken and plotted a graph and end point determined graphically at 3.5mL,4mL and 3.5mL for product-1, product-2 and product-3.The amount of vanillin content in various locally available brands of vanilla flavoured custard powders was determined. And all the data obtained in this study was within the limits according to FDA. This method is well suited for routine lab analysis and easy to perform when compared to spectroscopic methods.

Biocomposite Materials Derived from Andropogon halepensis: Eco-Design and Biophysical Evaluation.

This research work presents a "green" strategy of weed valorization for developing silver nanoparticles (AgNPs) with promising interesting applications. Two types of AgNPs were phyto-synthesized using an aqueous leaf extract of the weed Andropogon halepensis L. Phyto-manufacturing of AgNPs was achieved by two bio-reactions, in which the volume ratio of (phyto-extract)/(silver salt solution) was varied. The size and physical stability of Andropogon-AgNPs were evaluated by means of DLS and zeta potential measurements, respectively. The phyto-developed nanoparticles presented good free radicals-scavenging properties (investigated via a chemiluminescence technique) and also urease inhibitory activity (evaluated using the conductometric method). Andropogon-AgNPs could be promising candidates for various bio-applications, such as acting as an antioxidant coating for the development of multifunctional materials. Thus, the Andropogon-derived samples were used to treat spider silk from the spider Pholcus phalangioides, and then, the obtained "green" materials were characterized by spectral (UV-Vis absorption, FTIR ATR, and EDX) and morphological (SEM) analyses. These results could be exploited to design novel bioactive materials with applications in the biomedical field.

Synthesis and study of Arginin-containing iron and cobalt chelates

Synthesis conditions have been established and arginin-containing iron and cobalt chelate compounds with general formula: Me(Arg)n(CH3COO)2·mH2O, where Me = Fe, Co; Arg – neutral arginin molecule, n = 1÷3; m = 1÷4 have been synthesized. Synthesized chelates have been studied using a number of physical and chemical methods. In particular, the content has been established via trace element analysis, while individuality has been identified using melting temperature measurement and diffractographic method. According to study of qualitative solubility chelates are well soluble in water, though they are poorly soluble in organic solvents. Using the conductometric method there has been calculated the dissociation constant of chelate compound containing solutions. On the basis of preliminary trial tests conducted with a purpose of biological activity study, there has been expressed an opinion that entry of arginin-containing iron and cobalt chelates into composition of broilers’ combined feed premixes has had a positive impact on poultry live weight gain and poultry survival rate. An opinion on the reasonability of basic tests conduction has been given in order to determine the doses of arginin-containing iron and cobalt chelate compounds optimal for broilers.

Effect of pH of Medium and Initial Salt Quantity on Release Behaviour of Potassium Chloride from Leached Poly(vinyl alcohol)/Glutaraldehyde

The purpose of present work is to study the release kinetics of KCl from leached poly(vinyl alcohol)/glutaraldehyde (PVA/GA) hydrogelsinto demineralized water under various pH conditions. The PVA/GA hydrogels, which was prepared by mixing method, were leachedseveral times using demineralized water. The physico-chemical properties of the hydrogels were investigated using FT-IR and SEMtechniques. The release kinetics of KCl from the hydrogel into the demineralized water at various pH conditions and initial quantity ofKCl inside the hydrogel were studied using conductometric method. It was found that the trapped residual inside the hydrogel matrix can be well removed by repeated leaching. The pH of medium affects the rate of release and the amount of KCl at equilibrium conditions. The kinetics of KCl desorption into the media follows pseudo first-order kinetics, which indicates that the release kinetics is controlled by the initial amount of KCl in the PVA/GA matrix.

Use of the Conductometric Method for Measuring the Moisture Content of Flax Sraw

The results and particularities of using the conductometric method for measuring the moisture content of the retted flax straw in rolls are presented. The optimal form of the primary detector for the moisture meter of flax rolls has been selected. The structure and operating principle of the developed device is shown.

Smoothing Methods for Continuous Permeation Data Measured Discretely Designated for Quick Evaluation of Barrier Materials

Information concerning barrier properties of materials used for production of personal protective equipment fundamentally not only affects their useful properties, but also supports the end users’ decisions. Data obtained from measurements by standardized methods have to be processed by appropriate statistical methods. The article deals with numerical and statistical methods of reconstruction of a continuous curve out of discretely measured data. These mathematical models are proposed as an extension to the manual measurement of a conductometric method. Behaviour of these models is demonstrated on two chemical warfare agent simulants, however, the proposed methodology is universal and can be applied also to chemicals which have no conductivity. The parametric and nonparametric models are studied in the curve reconstruction, as well as in the calculation of subsequent characteristics, for example, a lag-time. The nonparametric model shows the best results which are in accordance with an expert’s estimate.

Sustainable and renewable hydrogen production from recycled aluminum

The whole world has been suffering strong consequences related to climate change. The intense use of fossil fuels in the chemical and automotive industries have put the environment in jeopardy. Thus, the industry has achieved a point of no return and it is urgent the development of renewable and sustainable technologies. Hydrogen has been pointed as a key component of the new era in industry since it can be produced in a clean and sustainable way. Currently the development of hydrogen fuel cells technology has put the automotive sector ahead of the chemical industries in relation to studies regarding the hydrogen production. Chemical industries produce hydrogen with technologies reliant on fossil fuels while the automotive sector has been looking for renewable forms of hydrogen generation. Trains powered by hydrogen fuel cells are a reality in Europe, for instance. Hydrogen generation technological advances must match the pace of the development of fuel cells electrical vehicles in order to the environmental goals and widespread application of fuel cell systems to be achieved. The present study addresses the hydrogen generation from the spontaneous reaction between aluminum and aqueous solution of sodium hydroxide. Aluminum is a metal that presents high exergetic value and can be recycled several times without losing its thermo-mechanical properties. That makes the use of aluminum especially appealing. It will make hydrogen generation a cleaner and more affordable process. Our findings demonstrate that it is possible to predict the kinetic behavior of the reaction using data obtained by the conductometric method. Graphs of electrical conductivity vs time show that is possible to verify the order of the reaction. We will present concepts of kinetic, thermodynamic and transport phenomena of the reaction between solid recycled aluminum and sodium hydroxide in an aqueous solution. The knowledge acquired throughout this study will contribute to the development of a new reactor and as a consequence, a new renewable and sustainable industrial system of hydrogen generation.

Starch-Grafted Sodium Alginate-Modified Clay Composites as Environmentally Controlled-Release Materials for NPK Fertilizer

In an effort to mitigate the harm caused by the irregular use of agrochemicals, a safer release system using biopolymers is promising due to their availability, biodegradability, and eco-friendliness. Herein, controlled-release materials for NPK fertilizer were formulated using clay-based graft biopolymer composites. The clay soil sample was collected and classified through Skempton’s laboratory tests for soils and used as filler in starch-grafted sodium alginate (ST-g-SAG) with different percentages of clay. The clay-based graft biopolymer composites were synthesized via a microwave-assisted method. The biopolymer composites were characterized by FTIR, SEM, and EDS. The materials were loaded with NPK fertilizer, and a leaching test was conducted via a conductometric method to ascertain their release capacities. Biodegradation studies and the effect of humidity on the release of the NPK fertilizer were studied. Results of classification studies of the clay show Ca-montmorillonite (Ca-MMT) type. The average percent graft yield of starch-grafted sodium alginate/Ca-MMT (ST-g-SAG/Ca-MMT) was 83%. The results from FTIR and EDS showed that OH-, COO-, and CONH2 were responsible for the absorption of water. The release profile of the active NPK in the biocomposites ranged from 1% to 103%. Biodegradation results also showed a significant breakdown in biopolymer structure and mass loss. The release of active NPK from the material was humidity-responsive.

INVESTIGATION OF THE SPECIFIC ELECTRICAL CONDUCTIVITY OF RHENIUM-CONTAINING SOLUTIONS OF AMMONIUM CARBONATE AND CALCULATION OF ITS ACTIVATION ENERGY

The specific electrical conductivity dependence of aqueous solutions of ammonium carbonate and solutions of the ammonium carbonate—ammonium perrenate system on the reagents content in the range of their concentration of 0.1—1.8 mol/l for (NH4)2CO3, 0.01—0.1 mol/l for NH4ReO4 and solution temperatures in the range of 20-50 °C were investigated by the conductometric method. A linear increase in electrical conductivity with an increase in the temperature of electrolytes and a nonlinear increase with an increase in the concentration of reagents was revealed. The temperature coefficients values of electrical conductivity and the activation energy values of electrical conductivity in the studied range of concentrations and temperatures are calculated. A decrease in the activation energy of electrical conductivity with an increase in the temperature of the solution was noted. The calculated value of the activation energy of electrical conductivity indicates the diffusive nature of charge transfer.