Conductometric Method Research Articles

Solvent Effect on Stability and Thermodynamic Behavior of Complex of 18-Crown-6 with Hydroxyl Ammonium Cation

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

Self-Aggregation Phenomenon of Promazine Hydrochloride Under the Influence of Sodium Cholate/Sodium Deoxycholate in Aqueous Medium

Herein, we have examined the interaction between promazine hydrochloride (PMZ) with bile salts (sodium cholate (NaC) and sodium deoxycholate (NaDC)) at different temperatures and compositions using conductometric method. The critical micelle concentration (cmc) value of pure PMZ and bile salts were also evaluated by tensiometric method. The cmc values attained by the two methods are close to each other. Various physicochemical parameters like cmc, ideal cmc (cmcid), degree of dissociation of counterion (g), micellar mole fractions of bile salt (, , ), micellar mole fraction of bile salt in ideal state (), interaction parameter (βm), activity coefficients (f1, f2), standard Gibbs free energy (), enthalpy (), entropy of micellization (), and excess free energy of mixing (ΔGex) of the mixed micelles have been evaluated and discussed in detail using Clint's, Rubingh's, Motomura's, and Rodenas's models. NaDC is more efficient in decreasing the cmc of PMZ as compared to NaC because it binds strongly to PMZ ions and more decreases the head group area of drug. On the whole, this lesson might find application in the fundamental science of the physical chemistry of amphiphilic systems, as well as in the research of drug delivery system.

Thermodynamic study of the complexation of Cd2+ cation with 1,4,10-trioxa-7,13-diazacyclopentadecane (Kryptofix 21) in acetonitrile and its binary mixtures with methanol and ethyl aacetate

The complexation processes between Cd2+ cation and a macrocyclic ligand, 1,4,10-trioxa-7,13-diazacyclopentadecane (Kryptofix 21) were studied by the conductometric method in pure acetonitrile and acetonitrile-methanol and acetonitrile-ethyl acetate binary mixtures at different temperatures. In some cases, the stoichiometry of the complex formed between Kryptofix 21 with Cd2+ cation is 1 : 1 [M L], whereas in some solvent systems 1 : 2 [ML2] and 1 : 3 [ML3] complexes are formed in addition to [ML]. The thermodynamic parameters (ΔSc0, ΔHc0) for the formation of the Kryptofix 21-Cd2+ complex were obtained from the temperature dependence of the stability constant of the [ML] complex. The complexation reaction between Cd2+ and Kryptofix 21 is athermic or exothermic, depending on the solvent system.

Effect of salt and urea on complexation behavior of pharmaceutical excipient gelatin with phenothiazine drug promazine hydrochloride

An evaluation of the interactions of cationic phenothiazine drug promazine hydrochloride (PMZ) with gelatin in aqueous solution as well as in the presence of 50mM NaCl and 100mM urea, investigated through different physicochemical measurements is presented in the present study using conductometric method. PMZ is used for the control of mania and schizophrenia. The drug interacts with gelatin similar to the interaction of surfactants and polymers. The plots of specific conductivity versus concentration of the drug were nonlinear with three different linear regions with two clear breaks. The first break point, i.e., critical aggregation concentration (cac), appeared well below the typical critical micelle concentration (cmc). The second break point is considered as polymer saturation point (psp) that is akin to cmc. The cac value decreases on increasing the gelatin concentration, whereas the psp value increases for all fixed concentrations (%w/v) of gelatin which is a clear signal of the interaction of the drug with gelatin. As inorganic salts increase the ionic strength, the solubility of amphiphile (drug) is lowered by ionic screening effects, ensuing in a greater tendency to aggregates at lower concentration. As a result, both the cac and psp/cmc values decrease. By the addition of urea an increase in the surface charge of the micelles was observed followed by halt of the aggregation of the drug hence both the cac and psp/cmc values increase. Free energies of aggregation (ΔGagg), micellization (ΔGmic), polymer saturation (∆Gpsp) and transfer (ΔGt) were also evaluated.

Modeling the binary system Mn(NO3)2–H2O with the extended universal quasichemical (UNIQUAC) model

In this study, new experimental data for the binary system of Mn(NO3)2–H2O are presented in the temperature range from −29°C to 35°C at atmospheric pressure using the conductometric method, this synthetic method is an accurate experimental procedure in the determination of the solubility of salts in aqueous solutions.Thermodynamic modeling for the binary system of Mn(NO3)2–H2O is also presented based on this new experimental solubility data and some modification on the available data bank.Model parameters for this system were determined and revisited; these parameters are generally valid in the entire range of temperature and composition of the salt.

Conductometric Studies of the Thermodynamics for Complexation of 1,1-Diethyl-3-(4-methoxybenzoyl)thiourea and Cobalt(II) Cation in Aqueous Binary Mixtures of Polar Organic Solvents

The complexation reaction of Co2+ (M) and the 1,1-diethyl-3-(4-methoxybenzoyl)thiourea (L) ligand in the binary mixtures: acetonitrile–dimethylsulfoxide (MeCN–DMSO), acetonitrile–dichloromethane (MeCN–DCM), water–dimethylsulfoxide (H2O–DMSO) and acetonitrile–water (MeCN–H2O), was investigated using a conductometric method at temperatures of (288.15, 298.15, 308.15 and 318.15) K. In all cases, the conductance data showed that the stoichiometry of the neutral complex formed between M and L is 1:3 [M:3L], which indicates that the Co2+ ion was oxidized to Co3+ during the reaction. The best estimate of the stability constant, log10 K f, = 3.31 for the [CoL3] complex, was observed with the MeCN–DCM (20:80 %) binary mixture at 298.15 K. The values of the thermodynamic parameters (i.e., $$ \Delta G_{\text{c}}^{^\circ } $$ and $$ \Delta S_{\text{c}}^{^\circ } $$ ) for the formation of the [CoL3] complex were obtained from the temperature dependence of the stability constant via van’t Hoff plots. The results show that, in most cases, the [CoL3] complexes are enthalpy destabilized but entropy stabilized. The values and signs of the thermodynamic parameters are affected by the nature and composition of the mixed solvents but are independent of the temperature.

FTIR metabolomic fingerprint reveals different modes of action exerted by structural variants of N-alkyltropinium bromide surfactants on Escherichia coli and Listeria innocua cells.

Surfactants are extremely important agents to clean and sanitize various environments. Their biocidal activity is a key factor determined by the interactions between amphiphile structure and the target microbial cells. The object of this study was to analyze the interactions between four structural variants of N-alkyltropinium bromide surfactants with the Gram negative Escherichia coli and the Gram positive Listeria innocua bacteria. Microbiological and conductometric methods with a previously described FTIR bioassay were used to assess the metabolomic damage exerted by these compounds. All surfactants tested showed more biocidal activity in L. innocua than in E. coli. N-tetradecyltropinium bromide was the most effective compound against both species, while all the other variants had a reduced efficacy as biocides, mainly against E. coli cells. In general, the most prominent metabolomic response was observed for the constituents of the cell envelope in the fatty acids (W1) and amides (W2) regions and at the wavenumbers referred to peptidoglycan (W2 and W3 regions). This response was particularly strong and negative in L. innocua, when cells were challenged by N-tetradecyltropinium bromide, and by the variant with a smaller head and a 12C tail (N-dodecylquinuclidinium bromide). Tail length was critical for microbial inhibition especially when acting against E. coli, maybe due the complex nature of Gram negative cell envelope. Statistical analysis allowed us to correlate the induced mortality with the metabolomic cell response, highlighting two different modes of action. In general, gaining insights in the interactions between fine structural properties of surfactants and the microbial diversity can allow tailoring these compounds for the various operative conditions.

Sensitive Spectrophotometric and Conductometric Methods for the Determination of Candesartan Using Acidic Dyes

Two simple, sensitive, accurate, rapid spectrophotometric and conductometric methods were developed for the determination of candesartan (CAND) in raw material and in its pharmaceutical preparation. The proposed methods depend upon the reaction of bromocresol green (BCG) or bromocresol purple (BCP) with candesartan in phosphate buffered solution to form stable colored ion-pair complex, which was extracted in chloroform. The yellow colored complexes were determined at λmax 415, 405 nm with BCG, BCP, respectively. Using conductometric titration, candesartan could be evaluated in acetone. The optimizations of various experimental conditions were described. The results obtained showed good recover of 100.14 (n=6) with relative standard deviation of 0.62 (n=6). Applications of the proposed methods to representative pharmaceutical formulations are successfully presented compared with official methods.

Statistical Modeling of Environmental Factors on Microbial Urea Hydrolysis Process for Biocement Production

Calcium carbonate is a widely used raw material by many industries. It can be precipitated through microbial process within soil pores as cementitious bonding agent between grains for geotechnical applications. It is called microbially induced calcium carbonate precipitation (MICP). Designing an appropriate biogrout material for injection into soil is essential for controlling the amount, type, time, and place of the biocement production within pores. For this purpose, understanding the active reactions and the kinetics of bacterial growth and urea hydrolysis is necessary. A conductometric method and spectrophotometry were used in this study to, respectively, monitor the urea hydrolysis reaction progress and bacterial growth inS. pasteurii-inoculated urea-NB-NH4Cl solution at different level of the environmental factors that are initial cell concentration, urea concentration, and temperature. Variation in conductivity of the solution versus logarithmic scale of time was depicted as microbial ureolysis characteristic curve (MUCC) through which lag duration, specific rate, and potential of urea hydrolysis at each condition were obtained. Central composite face-centered (CCF) design, which is one of the response surface methodologies, was employed to statistically fit polynomial models explaining the bacterial growth and the characteristics obtained from MUCCs in terms of the environmental factors and their interactions. An optimization analysis based on the urea-normalized responses was also carried out.

Software and Hardware System for Gradient of Ion Concentration Measuring

Several topical physicochemical issues in the area of high-molecular compounds and biophysics requires real-time registration of the spatial distribution of low-molecular ions. A device utilizing conductometric method based on high-frequency electrode pairs switching in traveling wave mode is proposed for the spatial distribution of low-molecular ion study. Technical features, advantages and applications of the device is described. Results of device testing are presented.

Dynamic saturation curve measurement in liquid composite molding by heat transfer analysis

In Liquid Composite Molding (LCM) processes the saturation of the reinforcement by the resin may induce the creation of porosity in the preform affecting the final properties of the composite. The purpose of this work concerns the development of an experimental protocol and the associated modeling to identify the dynamic saturation curve during filling by taking advantage of sharp contrasts of thermal properties existing between dry and fully-saturated reinforcement. To identify saturation, several injections were performed with a laboratory RTM mold for which thermal design allows accurate control of heat transfer. Several heat flux sensors were used to identify the saturation curve. Sensitivity analysis proves the feasibility of the method. The results are compared with a conductometric method with good agreement. Evolution of residual voids identified for several flow rates are also consistent with those expected according to the capillary number.

ELECTROCHEMICAL PROPERTIES OF AMINOMETHANESULPHONIC ACID – WATER SYSTEM

The aminomethanesulphonic acid (AMSA) – water system has been investigated by рН– and conductometric methods in the temperature range 298 – 313 K. The temperature and concentration dependences on the AMSA ionization constant and temperature dependence on the molar conductivity of aqueous solutions have been determinated.

Physicochemical Properties of Amphiphilic Drug and Anionic Surfactant Mixtures: Experimental and Theoretical Approach

Herein, we have reported the mixed micelle formation of amphiphilic phenothiazine drug promethazine hydrochloride (PMT) and anionic surfactant sodium bis(2-ethylhexyl)sulfosuccinate (AOT) mixtures at different compositions and temperatures (288.15, 293.15, 298.15, 303.15, and 308.15 K). A conductometric method is used to evaluate the critical micelle concentration (CMC) of binary mixtures. An attractive interaction between PMT and AOT mixed systems was indicated by the experimental and ideal critical micelle concentration (CMC and CMCid) values. The micellar mole fraction of anionic surfactant (, , , and ) was evaluated by different proposed models, and they prove the greater contribution of AOT in mixed micelle and increase with the increase in AOT concentration. Activity coefficients (f 1 and f 2) calculated by all recommended models were found to be always less than unity, signifying nonideality in the mixed systems. Different thermodynamic parameters have also been evaluated using the respective CMC values as a function of temperature. values were always found to be negative for all the systems; however, for pure drug as well as PMT–AOT mixed systems is negative at lower temperatures and positive at higher temperatures. The values are positive at all temperatures but their magnitude is higher at T = 303.15 K and above.

Thermodynamic study of complex formation between Kryptofix-5 and Sn2+ in several individual and binary non-aqueous solvents using a conductometric method

The complex formation between 1,13-bis(8-quinolyl)-1,4,7,10,13-pentaoxatridecane (Kryptofix-5) and Sn2+ ions was studied in pure acetonitrile (AN), dimethylformamide (DMF), 1,4-dioxane (DOX), and methanol (MeOH) and in acetonitrile-1,4-dioxane (AN-DOX), acetonitrile-dichloromethane (AN-DCM), acetonitrile-methanol (AN-MeOH), and acetonitrile-dimethylformamide (AN-DMF) binary mixed solvent solutions at different temperatures using conductometric method. 1: 1 [ML] complex is formed between the metal cation and ligand in most solvent systems but in the cases of AN-MeOH (MeOH = 90 mol %) binary mixture and in pure MeOH a 2: 1 [M2L] complex was observed, that is the stoichiometry of complexes may be changed by the nature of the medium. The stability order of the (Kryptofix-5·Sn)2+ complex in the studied binary mixed solvent solutions at 25°C was found to be AN-DOX > AN-DCM > AN-MeOH > AN-DMF and in the case of pure solvents at 25°C the sequence was the following: AN > DMF > DOX. A non-linear behavior was observed for changes of logK f of (Kryptofix-5·Sn)2+ complex versus the composition of the binary mixed solvents, which was explained in terms of solvent-solvent intractions and also by the preferential solvation of the f species involved in the complexation reaction. The values of standard enthalpy changes (ΔH c ○ ) for complexation reactions were obtained from the slope of the Van’t Hoff plots and the changes in standard entropy (ΔS c ○ ) were calculated from the relationship ΔG c, 298.15 ○ = ΔH c ○ − 298.15ΔS c ○ . The results show that in most cases, the (Kryptofix-5·Sn)2+ complex is both enthalpy and entropy stabilized.

Study of complex formation of 5,5′-(2E, 2′E)-2,2′-(ethane-1,2-diylidene)bis(hydrazine-1-yl-2-ylidene)bis(4-amino-4H-1,2,4-triazole-3-thiol) (HYT) macrocyclic ligand with Cd2+ cation in non-aqueous solution by spectroscopic and conductometric methods

In this paper the complexation reaction of the 5,5′-(2E,2′E)-2,2′-(ethane-1,2-diylidene)bis(hydrazine-1-yl-2-ylidene)bis(4-amino-4H-1,2,4-triazole-3-thiol) ligand (HYT) with Cd2+ education was studied in some binary mixtures of methanol (MeOH), n-propanol (PrOH) and dimethyl-formamide (DMF) at different temperatures using the conductometry and spectrophotometry. The stability constants of the complex was determined using a GENPLOT computer program. The conductance data and absorbance-mole ratio plots show that in all solvent systems, the stoichiometry of the complex formed between (HYT) and Cd2+ cation is 1: 1. The obtained results show that the stability of (HYT)-Cd complex is sensitive to the mixed solvents composition. The values of thermodynamic parameters (ΔG ∘, ΔH ∘, and ΔS ∘) for formation of (HYT)-Cd complex were obtained from temperature dependence of the stability constant using the van’t Hoff plots. The results show that in most cases, the complex are enthalpy destabilized but entropy stabilized and the complex formation is affected by pH, time, temperature and the nature of the solvent.

Thermodynamic study of complex formation between Ce3+ and cryptand 222 in some binary mixed nonaqueous solvents

The stoichiometry, stability and the thermodynamic parameters of complex formation between cerium(III) cation and cryptand 222 (4,7,13,16,21,24-hexaoxa-1,10-diazabycyclo[8.8.8]-hexacosane) were studied by conductometric titration method in some binary solvent mixtures of dimethylformamide (DMF), 1,2-dichloroethane (DCE), ethyl acetate (EtOAc) and methyl acetate (MeOAc) with methanol (MeOH), at 288, 298, 308, and 318 K. A model based on 1: 1 stoichiometry has been used to analyze the conductivity data. The data have been fitted according to a non-linear least-squares analysis that provide the stability constant, K f, for the cation-ligand inclusion complex. The results revealed that the stability order of [Ce(cryptand 222)]3+ complex changes with the nature and composition of the solvent system. A non-linear relationship was observed between the stability constant (logK f) of [Ce(cryptand 222)]3+ complex versus the composition of the binary mixed solvent. Standard thermodynamic values were obtained from temperature dependence of the stability constant of the complex, show that the studied complexation process is mainly entropy governed and are influenced by the nature and composition of the binary mixed solvent solutions.

Conductometric Method of Measuring the Level of Molten Sodium

A conductometric method of measuring the level of molten sodium without the elements of the level gauge entering the tank is considered.

Chemistry of Metal Picramates - Part II (Copper and Silver )

Copper and silver picramates have been prepared and their compositions have been established by micro-analysis. This has been further confirmed by conductometric and potentiometric methods. I.R. studies of metal picramates show-H/sub 2/ N->M coordination where M is copper and silver. Various explosive properties of these picramates have also been studied.

Removal of Cadmium(II) from Aqueous Solutions by Calcium Alginate Beads

Sorption of Cd(II) ions from dilute aqueous solutions by alginate beads has been studied. The measurements were run at 25°C at a fixed pH of 5.0. Equilibrium sorption isotherms have been determined over a wide cadmium concentration range of 0.3-3 mmol/dm3. The Langmuir equation has been found to adequately describe experimental results, and the equilibrium constants depended on the alginate content in the beads. The values of the maximum sorption capacity of Cd(II) ions have been found to decrease with increasing alginate content in the beads. Effective diffusivity (De) of the cadmium compounds was also calculated in the beads. The study was carried out using two methods: a shrinking core model (SCM) method and a newly developed method named conductometric. The conductometric method turned out to be a simple and effective one for calculation of effective diffusivity of Cd(II) in alginate sorbents. The De values obtained by the two methods depended on the alginate content in the beads. However, the SCM method, in contrast to the conductometric one, gave the De values increasing with increasing alginate level in the beads and higher than the molecular diffusivity of Cd(II), this being inconsistent with the mechanism of diffusion in porous carriers. For this reason, the conductometric method can be considered as one giving more reliable results than the SCM method. Moreover, the retardation coefficients of the diffusion in the alginate beads were calculated. Enhanced content of the biopolymer in the beads caused retardation of Cd(II) diffusion in the beads owing to decreasing of calculated retardation coefficients with increasing alginate contents in the beads.

Effect of solvent on complexation between Y3+ cation and 4,13-diaza-18-crown-6 in some binary mixed non-aqueous solvents

The complexation reaction of 4,13-diaza-18-crown-6 (DA18C6) with Y3+ cation was studied in some binary mixed solvent solutions of acetonitrile (AN) with methanol (MeOH), ethanol (EtOH), 2-propanol (2-PrOH) and methyl acetate (MeOAc) at different temperatures by conductometric method. The obtained data show that in all studied solutions the stoichiometry of the complex formed between DA18C6 and Y3+ cation is 1: 1 [ML], but in the case of pure MeOAc, a 2: 1 [ML2] complex is formed in solution upon addition of the ligand to the metal salt solution, and further addition of the ligand results in formation of a M2L2 complex in solution. This results show that the stoichiometry of the composition of the macrocyclic complexes may be affected by the nature of the solvent system. The results obtained in this study show that the stability constant of the resulting 1: 1 [ML] complex in the binary solvent solutions decreases in the order: AN-MeOAc > AN-2PrOH > AN-MeOH > AN-EtOH. A non-linear relationship was observed between the stability constant (logKf) of [Y(DA18C6)]3+ complex with the composition of the binary mixed solvent solutions. The corresponding standard thermodynamic parameters (H°c, Δ S°c) for 1: 1 [ML] complexation reaction between DA18C6 and Y3+ cation were obtained from temperature dependence of the stability constant of the complex. The results show that, in all solvent systems, the (DAI8C6.Y)3+ complex is entropy stabilized, but from enthalpy point of view, depending on the solvent system, it is stabilized or destabilized and the result show that the values of both thermodynamic quantities change with the nature and composition of the binary mixed solvent solutions.