Conductometric Method Research Articles

Study of complex formation process between 4′-nitrobenzo-18-crown-6 and yttrium(III) cation in some binary mixed non-aqueous solvents using the conductometry method

The complexation reaction between Y3+ cation and macrocyclic ligand, 4′-nitrobenzo-18-crown-6 (4′NB18C6), was studied in acetonitrile–methanol (AN–MeOH), acetonitrile–1,2-dichloroethane (AN–DCE), acetonitrile–dimethylformamide (AN–DMF) and acetonitrile–ethylacetate (AN–EtOAc) binary mixed solvent solutions at different temperatures using the conductometric method. The conductance data show that in most cases, the stoichiometry of the complex formed between 4′NB18C6 and Y3+ cation is 1:1 [M:L], but in the case of AN-DCE binary solution (mol% DCE=50) at 15, 25 and 35°C, a 2:1 [M2:L] and also a 2:2 [M2:L2] complexes are formed in solution. The results show that the stoichiometry of the complex formed between 4′NB18C6 and Y3+ cation changes with the composition of the mixed solvents and even with temperature. The stability constant of the 1:1 complex was determined using a computer program, GENPLOT. The stability order of (4′NB18C6.Y)3+ complex in pure studied solvents at 25°C was found to be: EtOAc>AN>MeOH>DMF and in the case of the mixed solvent solutions with 25mol percent of AN at 25°C was: AN-DCE>AN-EtOAc>AN-MeOH∼AN-DMF. The values of stability constant (logKf) of (4′NB18C6.Y)3+ complex which were obtained from conductometric data, show that the stability of the complex is not only affected by the nature and composition of the solvent system, but it is also influenced by the temperature. In all cases, a non-linear behavior is observed for changes of logKf of the (4′NB18C6.Y)3+ complex versus the composition of the binary mixed solvents. The values of standard thermodynamic quantities (ΔH°c and ΔS°c) for the complexation process which were obtained from temperature dependence of the stability constant of (4′NB18C6.Y)3+ complex, show that depending on the solvent system, in most cases, the complex is enthalpy and also entropy stabilized, but in some cases, it is stabilized or destabilized from these view points.

Effect of non-aqueous binary solution on stoichiometry and stability constant of complexes formation between 4,4′,4″,4‴-(porphine-5,10,15,20-tetrayl) tetrakis (benzoic acid) and 15-crown-5 with Fe2+, Cu2+, and Zn2+ cations using conductometric method

In this study, the effect of acetonitrile (AN)—dimethylsulfoxide (DMSO) binary solutions on the complexation reaction between Fe2+, Cu2+, and Zn2+ cations with 4,4′,4″,4‴-(porphine-5,10,15,20-tetrayl) tetrakis (benzoic acid) (TBAP) and 15-crown-5 (15C5) ligands has been studied at different temperatures using conductometric method. The stability constant of complexes is obtained from fitting of molar conductivity data using GENPLOT computer program, also in all cases, the stoichiometry of the complexes was obtained 1: 1 [M: L]. The results show that the order of stability constant for (TBAP.Cu2+), (TBAP.Zn2+), (15C5.Cu2+) and (15C5.Zn2+) complexes in pure organic solvents is: AN > DMSO. A non-linear behavior was observed for changes of the stability constant of complexes versus the composition of AN-DMSO binary solutions. The selectivity order of 15C5 ligand for these cations in AN-DMSO (AN = 25, 50 and 75 mol %) binary solutions was obtained: Fe2+ > Cu2+ > Zn2+ but in the case of TBAP ligand in AN-DMSO (AN = 50 and 75 mol %) binary solutions were found: Fe2+ > Zn2+ > Cu2+. The values of thermodynamic parameters (ΔHC°) and (ΔSC°) for formation of complexes were obtained from temperature dependence of stability constants of complexes using the Van’t Hoff plots. Moreover, the results show a non-monotonic relationship between these thermodynamic quantities and the solvent composition.

New water soluble bis-imidazolium salts with a saldach scaffold: Synthesis, characterization and in vitro cytotoxicity/bactericidal studies

A series of water-soluble bis-imidazolium salts of the type H2(iPr)2saldach(1,2-Me2Im+-X−)2 (4) and their mononuclear complexes [M(III)Cl{(iPr)2saldach(1,2-Me2Im+-X−)2}] (M=Mn, 5; Fe, 6), (X=Cl, a; PF6, b; BF4, c), where saldach=N,N′-bis(salicylidene)-(±)-trans-1,2-diaminocyclohexane, have been synthesized and characterized using elemental analysis, electronic, spectral, magnetic as well as conductometric methods and MALDI-TOF-, ESI-MS. All complexes possess a distorted square pyramidal coordination geometry with MN2O2Cl chromophore, as revealed by the elemental, spectral and literature data. These salts have been evaluated for in vitro cytotoxicity against HepG-2 and MCF-7 cell lines. Among them, 4c (IC50=22.17μM) exhibited potency against MCF-7. The bactericidal efficacy of 4a–c was screened against a panel of common pathogenic bacteria. Compound 4a was found to be the most potent antibacterial agent and could inhibit all the bacterial strains more effectively than standard antibiotics.

Conductometric study of complexation reaction of 4′-nitrobenzo-15-crown-5 with Mn+2, Co+2, Y+3, and ZrO+2 cations in acetonitrile, methanol and their binary solvent solutions

The complexation reactions of Mn2+, Co2+, Y3+, and ZrO2+ cations with the macrocyclic ligand, 4′-nitrobenz-15-crown-5 (4′-NB15C5), in acetonitrile (AN), methanol and AN-MeOH binary mixtures have been studied at various temperatures using the conductometric method. The conductance data stand for the Me : L stoichiometric ratio 1 : 1. Values of the formation constants of the complexes were accumulated by plotting molar conductivity curves using the computer program, GENPLOT. The order of stability of the metal-ion complexes in pure AN at 15°C was found to be: (4′-NB15C5 · ZrO)2+ > (4′-NB15C5 · Mn)2+ ≈ (4′-NB15C5 · Co)2+ > (4′-NB15C5 · Y)3+. In the case of AN-MeOH binary solvent solutions with 50 and 75 mole percent of AN at the same temperature, the sequence of stability of the complexes was the following: (4′-NB15C5 · Mn)2+ > (4′-NB15C5 · ZrO)2+ ≈ (4′-NB15C5 · Co)2+ 〉 (4′-NB15C5 · Y)3+, and (4′-NB15C5 · Mn)2+ > (4′-NB15C5 · Y)3+ ≈ (4′-NB15C5 · Co)2+ > (4′-NB15C5 · ZrO)2+, respectively. The complexes formed are entropy stabilized in all cases.

DEVELOPMENT OF NEWER CONDUCTOMETRIC METHOD FOR ESTIMATION OF TELMISARTAN IN PURE AND FORMULATION

Objective of the present study is to develop simple, easily accessible, economic, newer conductometric method of estimation for Telmisartan. Telmisartan is weak acid due to presence of acidic functional group which can be estimated by conductometric method in alcoholic media. The developed method was validated according to ICH guidelines for parameters like accuracy, precision, specificity, ruggedness, robustness and percentage recovery. Results: The Relative Standard Deviation was 0.701677; recovery was 98-100%. Tablet formulations were used as sample for estimation and the results are found to be well within the specified limit. Conclusion: Therefore developed method can used for estimation of Telmisatan in pure or in formulations. Key words: Conductometry, Telmisartan, Estimation, Weak acid.

A novel, rapid and automated conductometric method to evaluate surfactant–cells interactions by means of critical micellar concentration analysis

Conductometry is widely used to determine critical micellar concentration and micellar aggregates surface properties of amphiphiles. Current conductivity experiments of surfactant solutions are typically carried out by manual pipetting, yielding some tens reading points within a couple of hours. In order to study the properties of surfactant–cells interactions, each amphiphile must be tested in different conditions against several types of cells. This calls for complex experimental designs making the application of current methods seriously time consuming, especially because long experiments risk to determine alterations of cells, independently of the surfactant action. In this paper we present a novel, accurate and rapid automated procedure to obtain conductometric curves with several hundreds reading points within tens of minutes. The method was validated with surfactant solutions alone and in combination with Saccharomyces cerevisiae cells. An easy-to use R script, calculates conductometric parameters and their statistical significance with a graphic interface to visualize data and results. The validations showed that indeed the procedure works in the same manner with surfactant alone or in combination with cells, yielding around 1000 reading points within 20min and with high accuracy, as determined by the regression analysis.

Spectrophotometric and Conductometric Studies on the Interaction of Anionic Dye Eosin-Y with Cationic Micelles

In this paper, spectrophotometric and conductometric methods were used to study the interaction phenomenon between oppositely charged anionic Eosin-Y and cationic surfactants; dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, cetyltrimethylammonium bromide, cetylpyridinium bromide and cetylpyridinium chloride. Conductivity measurements of surfactants were performed and the degree of micellar ionization was determined in the absence and presence of Eosin-Y. The ionization degree and counterion binding parameter obtained from conductivity data are used to evaluate the interaction mechanism of Eosin-Y in wide range of different hydrophobic cationic microenvironments as well. The absorption spectra were used to quantify the binding constants by means of Benesi-Hildebrand equation. Comparison of the binding degree of Eosin-Y to micelles indicates a direct correlation between binding constant and hydrophobicity. The micellar properties of cationic surfactants at levels below and above their CMCs in aqueous and in the presence of Eosin-Y were also studied using conductivity and spectrophotometry. It was observed that the CMC values of cationic surfactants decreased in the presence of Eosin-Y. The spectrophotometric behavior of Eosin-Y in water-EOH mixture of varying composition was also monitored in order to gain more information about the localization of Eosin-Y in cationic micelles.

Thermodynamic studies on metal complexes of Co2+, Ni2+, Cu2+ and Cd2+ with 8-hydroxy 5-quinolinesulfonic acid in water, methanol and water-methanol binary solvent systems at 303.15 K, 313.15 K and 323.15 K by conductometric method

Thermodynamic studies on metal complexes of Co2+, Ni2+, Cu2+ and Cd2+ with 8-hydroxy 5-quinolinesulfonic acid in water, methanol and water-methanol binary solvent systems at 303.15 K, 313.15 K and 323.15 K by conductometric method

Thermodynamic studies on metal complexes of Co2+, Ni2+, Cu2+ and Cd2+ with 8-hydroxy 5-quinolinesulfonic acid in water, methanol and water-methanol binary solvent systems at 303.15 K, 313.15 K and 323.15 K by conductometric method

Thermodynamic studies on metal complexes of Co2+, Ni2+, Cu2+ and Cd2+ with 8-hydroxy 5-quinolinesulfonic acid in water, methanol and water-methanol binary solvent systems at 303.15 K, 313.15 K and 323.15 K by conductometric method

Increase in electrolythic cell indices

The results of applied research of electrolytic cells with various constructions process parameters and electrochemical systems check by means of electrolysis current control are represented. The results of back EMF and electrolytic cell resistance control techniques implementation are considered. At the Private Joint Stock Company “Zavod Poluprovodnikov” (“Semiconductor Plant”) (Zaporozhye) the hydrogen electrolytic cell electrochemical parameters control through conductometric method application with use of aluminum electrolytic production experimental results, obtained at the PJSC “ZAlK, is introduced. On the ground of aluminum electrolytic production results the hydrogen electrolytic cell control techniques have been designed and introduced. After all technical arrangements have been carried out, their implementation made it possible to reduce the hydrogen production power consumption from 5,6 to 5,3 kW/h, an save 800 000 UAH for each electrolytic cell annually.The new electrolysis current control techniques, aiming at electrolytic cell technological parameters control and improvement in the supervision process quality are currently discussed.

Thermodynamic and Interfacial Properties of DTABr/CTABr Mixed Surfactant Systems in Ethanolamine/Water Mixtures: A Conductometry Study

Mixed-micelle formation in the binary mixtures of dodecyltrimethylammonium bromide (DTABr) and cetyltrimethylammonium bromide (CTABr) surfactants in water-ethanolamine mixed solvent systems has been studied by conductometric method in the temperature range of 298.1 to 313.1 K at 5 K intervals. It was observed that the presence of ethanolamine forced the formation of mixed micelle to lower total surfactant concentration than in water only. The synergistic interaction was quantitatively investigated using the theoretical models of Clint and Rubingh. The interaction parameter β12 was negative at all the mole fractions of DTABr in the surfactant mixtures indicating a strong synergistic interaction, with the presence of ethanolamine in the solvent system resulting in a more enhanced synergism in micelle formation than in water only. The free energy of micellization ΔGM values was more negative in water-ethanolamine mixed solvent system than in pure water indicating more spontaneity in mixed micelle formation in the presence of ethanolamine than in pure water.

Determination of the thermodynamic parameters, stoichiometry, and stability constants for complex formation of dicyclohexyl-18-crown-6 and 15-crown-5 with Y3+, La3+, and Hg2+ cations in binary solutions

The complexation of Y3+, La3+, and nd Hg2+ cations with macrocyclic ligands, dicyclohexyl-18-crown-6 (DCH18C6) and 15-crown-5 (15C5) have been studied in acetonitrile (AN)-N,N-dimethylformamide (DMF) binary solutions at different temperatures using conductometric method. The conductance data revealed 1: 1 [ML] stoichiometry for most complexes in pure DMF and AN-DMF binary solutions, except for the (DCH18C6-Y3+) complex in pure AN (1: 2, [ML2]). The stability constants of DCH18C6-La3+ and 15C5-La3+ in pure AN were higher than in pure DMF at all temperatures. Nonlinear behavior was observed for the stability constants of complexes against the composition of AN-DMF binary solutions at all temperatures. The minimum log Kf value for the 15C5-La3+ complex in AN-DMF binary solutions was obtained at χAN = 0.5, which may be due to negative excess viscosities ηE of AN-DMF mixtures over the whole composition range with a minimum value of χAN = 0.5. Moreover, the selectivity order of DCH18C6 and 15C5 for Y3+, La3+, and Hg2+ cations 25°C depended on the AN-DMF ratio. The thermodynamic parameters (ΔHC0) for complex formation were obtained from the temperature dependences of the stability constants of the complexes using the van’t Hoff plots, and the standard entropy (ΔSC0) was calculated from the relationship: ΔGC, 298.150 = ΔHC0 − 298.15ΔSC0.

English

A simple, precise and low cost conductometric method for the determination of alfuzosin hydrochloride and fexofenadine hydrochloride in pure form and pharmaceutical formulations using sodium tetraphenylborate has been described. The method is based on the formation of ion association complex of cations coming from the cited drugs with tetraphenylborate anions and the conductance of the solution is measured as a function of the volume of titrant. Various experimental conditions were evaluated. The described procedures allowed the determination of the studied drugs in double distilled water in the range of 2.13 - 10.65 and 2.50 - 13.45 mg of alfuzosin hydrochloride and fexofenadine hydrochloride, respectively. Statistical treatment of the experimental results indicates that the method is precise and accurate. The accuracy of the method is indicated by the excellent recovery 99.85-102.49 and 99.80-100.48% for alfuzosin hydrochloride and fexofenadine hydrochloride, respectively, and the precision is supported by the low relative standard deviation < 3.04%. The method was further applied successively to pharmaceutical formulations, the proposed method offering a high degree of accuracy and precision when compared to potentiometric pharmacopoeial methods.

Investigations of ternary complexes of Co(II) and Ni(II) with oxydiacetate anion and 1,10-phenanthroline or 2,2′-bipyridine in solutions

AbstractPotentiometric (PT) and conductometric (CT) titration methods have been used to determine the stoichiometry and formation constants in water for a series of ternary complexes of Co(II) and Ni(II) involving the oxydiacetate anion (ODA) and 1,10-phenanthroline (phen) or 2,2′-bipyridine (bipy) ligands, namely [Co(ODA)(phen)(H2O)], [Co(ODA)(bpy)(H2O)], [Ni(ODA)(phen)(H2O)] and [Ni(ODA)(bpy)(H2O)]. The ternary complex formation process was found to take place in a stepwise manner in which the oxydiacetate ligand acts as a primary ligand and the phen or bipy ligands act as auxiliary ones. The stability of the ternary complexes formed is discussed in the relation to the corresponding binary ones. Furthermore, the kinetics of the substitution reactions of the aqua ligands in the coordination sphere of the Ni-ODA and Co-ODA complexes to phen or bipy were studied by the stopped-flow method. The kinetic measurements were performed in the 288–303 K temperature range, at a constant concentration of phen or bipy and at seven different concentrations of the binary complexes (4–7 mM). The influence of experimental conditions and the kind of the auxiliary ligands (phen/bipy) on the substitution rate was discussed.

Effect of magnetic field on property of a non-aqueous solvent upon complex formation between kryptofix 22DD with yttrium (III) cation

To understand the effect of a magnetized solvent upon complexation processes between the metal ions and the ligands, we studied the complexation reaction between Y+3 cation with the kryptofix 22DD, in non-magnetized and magnetized methanol solvents at different temperatures using the conductometric method. Addition of kryptofix 22DD to the cation solution causes a continuous increase in the molar conductivities which indicates that the mobility of the complexed cation is higher than the uncomplexed one in both non-magnetized and magnetized methanol solvents. The conductance data show that the stoichiometry of the complex formed between the ligand and Y3+ cation is 1:1(M:L). The value of stability constant of (kryptofix 22DD.Y)3+ complex was determined from conductometric data using a non-linear least-square program (GENPLOT). The results obtained in this investigation, show that the stability constant of the complex decreases when we use magnetized methanol solvent.

Aggregation properties and thermodynamics of micellization of gemini surfactants with diethyl ether spacer in water and water–organic solvent mixed media

The aggregation properties and thermodynamics of micellization of three cationic gemini surfactants (n–EO1–n) containing diethyl ether spacer group with varying carbon number (n=12, 14 and 16) in the hydrophobic tails have been studied in water and water–organic solvents mixed media over the range of temperature (298.15 to 328.15)K using the conductometric method. Ethylene glycol (EG) and 1,4-dioxane (DO) were used as organic co-solvents with three different volume percentages due to their unique nature than other solvents. With increasing tail length, the critical micellar concentration (cmc) of gemini surfactants decreased. The effect of the diethyl ether spacer group on aggregation behaviour has been compared with other reported spacer groups. The micellization process is delayed in the presence of organic co-solvents as compared to pure water giving a positive value for the Gibbs energy of transfer (ΔGtranso). The degree of counter ion dissociation (α) increases with increasing tail length of gemini surfactants. It also increases with increase in the percentage of organic co-solvents and it is more prominent in DO–WR than EG–WR mixed media. The standard Gibbs energy of micellization (ΔGmo) is found to increase with increasing volume percentage of an organic co-solvent and also with decrease in the chain length of gemini surfactants. The ΔGmo has been correlated with Gordon parameter. The ΔGmo increases with increasing temperature which is more prominent in the presence of high percentage of an organic co-solvent and also in the presence of an organic co-solvent with less polarity. The enthalpies of micellization in all cases are exothermic in nature. The compensation between the enthalpy and entropy for the formation of micellar aggregates has been observed.

The effect of sodium dodecyl sulphate on Furosemide — A cardiovascular drug in water–methanol at different temperature

Different kinds of interactions have been critically assessed in order to understand the effect of methanol (MeOH) on sodium dodecyl sulphate (SDS) containing different concentrations of Furosemide with the help of densimetric and conductometric methods. A number of physico-chemical parameters viz. apparent molar volume, apparent molar adiabatic compressibility, standard enthalpy of micellization, standard entropy of micellization and standard free energy of micellization have been calculated from experimentally measured density, velocity of sound and critical micelle concentration (CMC). The CMC has been calculated from conductivity studies. The behaviour of these parameters suggests hydrophobic hydration of the surfactant molecules in a pre-micellar region and their cooperative self-association in a micellar region. The application of the Lumry–Rajender enthalpy–entropy compensation model to the present thermodynamic parameters has also been done to calculate compensation temperature Tc, which lies in the range 270–300K suggesting solvent induced synergistic behaviour. The plot of apparent molar volume (ϕv) vs. (SDS) at different concentrations of Furosemide in 8.0mol% aqueous solution of MeOH at 303K is shown in Fig. (A) which clearly indicates the dominance of electrostatic interaction in the pre-micellar region. The data were found to be in qualitative accordance indicating the existence of intermolecular hydrophobic as well electrostatic interactions between the surfactant, MeOH and drug.

ДИАГНОСТИКА УСТОЙЧИВОСТИ СОРТОВ ЯРОВОЙ ПШЕНИЦЫ И ЯЧМЕНЯ К ОБЫКНОВЕННОЙ КОРНЕВОЙ ГНИЛИ КОНДУКТОМЕТРИЧЕСКИМ МЕТОДОМ

Resistance to stresses is known to be under the plant genes control. In winter cereals which are sensitive to a rot pathogen Bipolaris sorokiniana Schoem., the metabolic processes, i.e. the energy accumulation, respiration intensity, enzymatic activity, polysaccharide and amino acids synthesis, K input, cell membrane intactness, change significantly. As a result, a part of intracellular electrolytes are lost. A variety resistance (tolerance) is usually evaluated as the yield loss which indicates an agronomic resistance to disease, and by estimating the physiological, biochemical and biophysical parameters during early vegetation which reflect a biological resistance. We used a conductometric method to estimate the resistance of 15 winter wheat and winter rye varieties under plant inoculation with B. sorokiniana Schoem. in a climatic chamber, and then the 4 winter wheat varieties with contrast characteristics in that test were examined in pot trials. The correlations between different indexes of early plant reaction to biotic stress were shown to be really tight and reliable. It was revealed that the electrophysical parameters of leaf cell membranes changed equal to root and sprouts length in 14-day seedlings, and to their biomass as an integral growth index. Thus, the electrophisical parameters are adequate to biometric, psychopathological, physiological parameters and yield losses, and can be used as the indicators for plant resistance to stress caused by B. sorokiniana Schoem. infection.

Thermodynamic study of complex formation between 3,5-di iodo-hydroxy quinoline and Zn2+, Ni2+ and Co2+ cations in some binary solvents using a conductometric method

The complexation reactions between 3,5-di iodo-8-hydroxy quinoline (IQN) and Zn2+, Ni2+ and Co2+ were studied in dimethylformamide (DMF)-ethanol (EtOH) binary solvent systems at different temperatures using a conductometric method. The stoichiometry of complexes was established 1:1. It was found that the stability of complexes formed between cations and this ligand increases with increases temperature. The standard enthalpies and standard entropies of complexes were obtained from the temperature dependence of stability constants. The results obtained by conductometric technique show that there is an inverse relationship between the formation constants of complexes and donor number of solvents. In all cases, the formation constants increased with increasing amounts of EtOH versus DMF in these binary systems. The standard enthalpy and standard entropies of complexes were obtained from the temperature dependence of stability constant. In all cases, ΔH° was positive and ΔS° was negative. The selectivity order for IQN complexes among various neat studied solvents varies in the order: Zn–IQN2+› Ni–IQN2+›Co–IQN2+.

Electrochemical versus Spectrophotometric Assessment of Antioxidant Activity of Hop (Humulus lupulus L.) Products and Individual Compounds

Antioxidant (AO) activity of extracts of hop cones (Serbian domestic varieties) and commercial hop products (Saaz, Spalter, Spalter select, and Magnum pellets) was determined by parallel application of recently developed direct current (DC) polarographic and widely used DPPH assay. Correlations between 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) scavenging and total phenolics (TPC) determined by the Folin-Ciocalteu assay (FC) (0.99), and between H2O2 scavenging (HPS) and humulone content (H) determined by conductometric method (0.94), total resins (TR) (0.85), and hop storage index (HIS) (-0.90), were found statistically significant at p < 0.05 level while complete lack of HPS correlation with TPC and DPPH was observed. To obtain an insight into differences between results of AO assays applied, activity of individual compounds, prevalent hop phenolics, and bitter acids was determined. By far superior HPS activity of humulone was followed by catechin, quercetin, xanthohumol, lupulone, and rutin. In contrast, DPPH scavenging activity of phenolics (quercetin > catechin > rutin > xantohumol) was found substantially higher than activity of bitter acids. According to ferric reducing antioxidant power (FRAP) and scavenging of 2,2-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS), higher AO activity was ascribed to phenolics, while almost neglecting humulone. Besides reliability, low cost, and an easy-to-handle procedure, an ability to recognize humulone as the major contributor of hop AO activity could allow DC polarographic assay to be applied in analysis of various hop-derived products.