Ternary liquid—liquid equilibria for acetonitrile—ethanol—cyclohexane and acetonitrile—2-propanol—cyclohexane

Liquid—liquid equilibrium data were obtained for two ternary systems: acetonitrile— ethanol—cyclohexane at 40°C, and acetonitrile—2-propanol—cyclohexane at 50°C. Binary vapor—Liquid equilibrium data were measured for acetonitrile—2-propanol at 50°C. The binary parameters of the Zeta and effective Zeta equations were evaluated from equilibrium data for binary pairs. The parameters obtained were used to predict the ternary liquid—liquid equilibrium data for six systems involving the present systems and the ternary vapor—liquid equilibrium data for one completely miscible system and two partially miscible systems without adding any ternary parameter. A heterogeneous area calculated by the Zeta equation is in general too large and does not decrease appreciably with increasing values of the third parameter ζ of the Zeta equation. However, the effective Zeta equation works much better than the original Zeta equation in data reduction.     

Excess enthalpies and complex formation of acetonitrile with acetone,chloroform, and benzene

Excess enthalpies of binary systems of acetonitrile—acetone, chloroform—acetone and chloroform—benzene, and ternary systems of acetonitrile—chloroform—acetone and acetonitrile—chloroform—benzene are reported at 25°C. The results are analyzed with thermodynamic association theory for complex ternary liquid mixtures. The theory involves two types of self-association of acetonitrile, formation and binary complexes for component pairs of a ternary system, and a nonspecific interaction term expressed by the NRTL equation between various chemical species.     

Ternary liquid—liquid equilibria and their representation by modified NRTL equations

Experimental liquid—liquid equilibrium data are reported for the systems acetonitrile—acetone—cyclohexane at 318.15 K and acetonitrile—methyl acetate—cyclohexane at 313.15 K. Two modified forms of the NRTL equation proposed by Renon are presented by substituting local surface fractions for local mole fractions and further by including Guggenheim's combinatorial entropy for athermal mixtures whose molecules differ in size and shape. The resultant equations involve three adjustable parameters and are extended to multicomponent systems without adding ternary (or higher) parameters. Calculated results of vapor—liquid and liquid—liquid equilibria for typical binary and ternary mixtures are presented.     

Isothermal vapor—liquid equilibrium of ternary mixtures formed by 1-propanol,acetonitrile and benzene

Vapor—liquid equilibrium data are presented for the ternary system 1-propanol-acetonitrile-benzene, at 45°C. The experimental vapor—liquid equilibrium results of the three constituent binary systems are well reproduced with the UNIQUAC associated-solution model and the ternary results are compared with those calculated from the model with binary parameters alone. Ternary prediction of liquid—liquid equilibria is given for the 1-propanol-acetonitrile-n-hexane and 1-propanol—acetonitrile-n-heptane systems at 25°C.     

Excess enthalpies of binary and ternary mixtures of acetonitrile with methanol,ethanol and benzene

Excess molar enthalpies are measured for the binary mixtures methanol—acetonitrile and ethanol—acetonitrile at 25 and 35°C and for the ternary mixtures methanol—acetonitrile—benzene and ethanol—acetonitrile—benzene at 25°C using an isothermal dilution calorimeter. The binary results are well reproduced with an association model which contains four equilibrium constants for the association of alcohol, two equilibrium constants for that of acetonitrile, and two solvation equilibrium constants between alcohol and acetonitrile molecules. The ternary results are compared with those calculated from the model with binary parameters.     

The prediction of isothermal phase equilibria for non-ideal multicomponent mixtures from heats of mixing

A method is presented for predicting both vapor—liquid and liquid—liquid equilibria for multicomponent mixtures using heat of mixing data for the constituent binary pairs together with pure component vapor pressures. Its application to two highly non-ideal hydrocarbon ternary systems is discussed. The parameters of the hybrid local composition model of Renon and Prausnitz, known as the NRTL equation, were evaluated from heat of mixing data for the three binary pairs in each of the two ternary systems. The parameters thus obtained were used in the multicomponent form of the NRTL equation to predict the ternary vapor—liquid equilibrium data for the completely miscible system cyclohexane(1)—n-heptane(2)—touluene(3) and for the partially miscible system acetonitrile(1)—benzene(2)—n-heptane(3) without the need for any ternary or higher order parameters.This method predicted compositions of the single phase region of the partially miscible ternary system with a standard deviation of 10%. It also predicted compositions for the fully miscible system with a standard deviation of 4.6%. Total pressure curves for the partially miscible and miscible ternaries were predicted with standard deviations of 6.6% and 4.5% respectively. Poor predictions of the binodal curve for the partially miscible region were obtained. The method offers a means of predicting the whole range of ternary phase equilibria for miscible systems.     

On the thermodynamics of alcohol solutions. Phase equilibria of binary and ternary mixtures containing any number of alcohols

Nagata, I., 1985. On the thermodynamics of alcohol solutions. Phase equilibria of binary and ternary mixtures containing any number of alcohols. Fluid Phase Equilibria, 19: 153–174.Binary vapor—liquid and liquid—liquid equilibrium data for alcohol solutions includin one or two alcohols are correlated with the UNIQUAC associated solution theory (Nagata and Kawamura). The theory uses pure liquid association constants determined by the method of Brandani and a single value of the enthalpy of the hydrogen bond equal to ?23.2 kJ mol ^?1 for pure alcohols. For alcohol-active nonassociating component mixtures and alcohol—alcohol mixtures the theory involves additional solvation constants. The theory is extended to contain ternary mixtures with any number of alcohols. Ternary predictions of vapor—liquid and liquid—liquid equilibria are performed using only binary parameters. Good agreement is obtained between calculated and experimental results for many representative mixtures.     

Association Model and Its Representation of Phase Equilibria and Excess Enthalpies of Alcohol, Aniline, and Acetonitrile Mixtures

An association model is presented to describe vapor–liquid equilibria,liquid–liquid equilibria, and excess enthalpies of binary and ternary liquid solutionscontaining alcohols, aniline, and/or acetonitrile using the concepts of linearself-association of associated components and of solvation between unlike molecules.Calculated results also show that the model works well in representing thethermodynamic properties for alcohol + aniline, alcohol + acetonitrile, andalcohol + alcohol mixtures.     

Phase diagram for the hexane-acetonitrile-tri-<Emphasis Type="Italic">n</Emphasis>-butyl phosphate-solvated thorium(IV) nitrate ternary liquid system

Phase diagrams of the hexane-acetonitrile-[Th(NO₃)₄(TBP)₂] liquid ternary system were studied at various temperatures. The system consists of two pairs of incompletely miscible liquids: hexane-acetonitrile and [Th(NO₃)₄(TBP)₂]-hexane. The two-liquid field in the [Th(NO₃)₄(TBP)₂]-hexane system decreases with increasing temperature; the upper critical solution temperature T _cr = 337.85 ± 0.25 K. The temperature effect on the immiscibility field in the hexane-acetonitrile system is insignificant. The title ternary liquid system is characterized by two homogeneous liquid fields and one two-phase liquid field at T < 338 K. One phase is depleted of acetonitrile and contains variable proportions of [Th(NO₃)₄(TBP)₂] and hexane; the other contains variable proportions of acetonitrile and [Th(NO₃)₄(TBP)₂] and a small proportion of hexane. With rising temperature, the two-phase field narrows and deforms, whereas the homogeneous liquid fields expand. At T > 338 K, the system transforms into a ternary liquid system with one pair of incompletely miscible liquids (hexane-acetonitrile).     

The prediction of isobaric phase equilibria for non-ideal multicomponent mixtures from heat of mixing data

A method for predicting isobaric binary and ternary vapor—liquid equilibrium data using only isothermal binary heat of mixing data and pure component vapor pressure data is presented. Three binary and two ternary hydrocarbon liquid mixtures were studied. The method consists of evaluating the parameters of the NRTL equation from isothermal heat of mixing data for the constituent binary pairs. These parameters are then used in the multicomponent NRTL equation to compute isobaric vapor—liquid equilibrium data for the ternary mixture. No ternary or higher order interaction terms are needed in the ternary calculations because of the nature of the NRTL equation. NRTL parameters derived from heat of mixing data at one temperature can be used to predict vapor—liquid equilibrium data at other temperatures up to the boiling temperature of the liquid mixture.For the systems studied this method predicted the composition of the vapor phase with a standard deviation ranging from 1–8% for the binary systems and from 4–12% for the ternary systems.     

Liquid—liquid equilibria of ternary systems of 1-hexene/hexane and extraction solvents

Olefins and paraffins are important basic chemical raw materials with so similar molecular structure and volatility that their separation is a difficult and energy-consuming process. Liquid—liquid equilibrium (LLE) data were determined for ternary systems of: 1-hexene + hexane + solvent at 25°C, 30°C, and 35°C, and N-formylmorpholine (NFM), N-methyl-2-pyrrolidone (NMP), γ-butyrolactone (GBL), and 1-methylimidazole (1-MEI) as the solvents studied. Liquid—liquid equilibrium data for each system were correlated to the NRTL (Non-Random Two Liquid) equation and the interaction parameters presented. The calculated results agree well with the experimental data.     

An experimental study of three- and four-phase equilibria for isopropanol—water—carbon dioxide mixtures at elevated pressures

Compositions and molar volumes of the three phases in liquid—liquid—gas equilibrium are reported for ternary mixtures of isopropanol, water and CO₂ at elevated pressures and at temperatures of 50 and 60°C. Phase compositions and molar volumes were also obtained for three-phase, liquid—liquid—liquid equilibrium and four-phase, liquid—liquid—liquid—gas equilibrium at 40°C. Gas—liquid and liquid—liquid critical endpoints, which represent pressure bounds on the liquid—liquid—gas region at 60°C, were determined from observations of critical opalescence.The phase behavior exhibited by the isopropanol—water—CO₂ system is quite complex, particularly at conditions near the critical point of CO₂. These conditions are well within the range of operating conditions proposed for supercritical-fluid extraction of organic compounds from water using CO₂. Therefore, the existence of multiple coexisting phases can be an important factor in designing and operating such extraction processes.     

Prediction of ternary phase equilibria from binary data

The two-parameter UNIQUAC equation is modified to give better results of vapor—liquid and liquid—liquid equilibria for a variety of binary systems. The proposed equation is easily extended to a multicomponent system without including any ternary (or multicomponent) parameters. The good capability of the equation in data reduction is shown by many illustrative examples for various kinds of strongly nonideal binary and ternary mixtures.     

Efficient Reduction of CO2 into Formic Acid on a Lead or Tin Electrode using an Ionic Liquid Catholyte Mixture

Highly efficient electrochemical reduction of CO₂ into value‐added chemicals using cheap and easily prepared electrodes is environmentally and economically compelling. The first work on the electrocatalytic reduction of CO₂ in ternary electrolytes containing ionic liquid, organic solvent, and H₂O is described. Addition of a small amount of H₂O to an ionic liquid/acetonitrile electrolyte mixture significantly enhanced the efficiency of the electrochemical reduction of CO₂ into formic acid (HCOOH) on a Pb or Sn electrode, and the efficiency was extremely high using an ionic liquid/acetonitrile/H₂O ternary mixture. The partial current density for HCOOH reached 37.6 mA cm^?2 at a Faradaic efficiency of 91.6 %, which is much higher than all values reported to date for this reaction, including those using homogeneous and noble metal electrocatalysts. The reasons for such high efficiency were investigated using controlled experiments.     

Determination of Tiopronin in Human Plasma by SPE then Reversed-Phase HPLC–UV

An accurate, simple and sensitive method based on reversed-phase high-performance liquid chromatography with UV detection has been developed for determination of tiopronin (TP) in human plasma. TP in plasma was reacted with p-bromophenacyl bromide (p-BPB) to give the TP-p-BPB adduct and this derivative was then extracted from the plasma on a silica gel cartridge. Potential interfering compounds were removed by washing with water, and the TP-p-BPB adduct was then eluted with acetonitrile. The organic phase obtained was evaporated to complete dryness under a stream of nitrogen. The residue was dissolved in acetonitrile and this solution was injected on to a reversed-phase ODS HPLC column. The mobile phase was usually the ternary mixture acetonitrile–water–trifluoroacetic acid, 40:59.88:0.12 (v/v). The retention times of TP-p-BPB and the internal standard adduct were 14.4 and 17.9 min, respectively. No interfering peaks were encountered in several blank plasma samples examined. The limit of detection for TP was 12 ng mL^?1. Extraction recovery exceeded 70%. The calibration plot for the TP derivative was linear in the range 40?4000 ng mL^?1, regression coefficient 0.9989, and the coefficient of the variation of the points of the calibration plot was below 10%. The method was validated appropriately and successfully applied to the determination of TP in human plasma.     

Determination of sulfonamides in swine muscle after salting-out assisted liquid extraction with acetonitrile coupled with back-extraction by a water/acetonitrile/dichloromethane ternary component system prior to high-performance liquid chromatography

A salting-out assisted liquid extraction coupled with back-extraction by a water/acetonitrile/dichloromethane ternary component system combined with high-performance liquid chromatography with diode-array detection (HPLC–DAD) was developed for the extraction and determination of sulfonamides in solid tissue samples. After the homogenization of the swine muscle with acetonitrile and salt-promoted partitioning, an aliquot of 1 mL of the acetonitrile extract containing a small amount of dichloromethane (250–400 μL) was alkalinized with diethylamine. The clear organic extract obtained by centrifugation was used as a donor phase and then a small amount of water (40–55 μL) could be used as an acceptor phase to back-extract the analytes in the water/acetonitrile/dichloromethane ternary component system. In the back-extraction procedure, after mixing and centrifuging, the sedimented phase would be water and could be withdrawn easily into a microsyringe and directly injected into the HPLC system. Under the optimal conditions, recoveries were determined for swine muscle fortified at 10 ng/g and quantification was achieved by matrix-matched calibration. The calibration curves of five sulfonamides showed linearity with the coefficient of estimation above 0.998. Relative recoveries for the analytes were all from 96.5 to 109.2% with relative standard deviation of 2.7–4.0%. Preconcentration factors ranged from 16.8 to 30.6 for 1 mL of the acetonitrile extract. Limits of detection ranged from 0.2 to 1.0 ng/g.     

A refined physico-chemical model of solute retention in reversed-phase high-performance liquid chromatography with ternary mobile phases

Summary In our previous publication we have introduced a new model of solute retention in RP-HPLC systems with ternary mobile phases of the B+AB₁+AB₂ type (B: acetonitrile or tetrahydrofuran; AB₁: methanol; AB₂: water). That model proposed no stoichiometric differentiation between acetonitrile and tetrahydrofuran, alternatively present in the solvent system; moreover, it made some very rough assumptions only as to the intermolecular interactions among the mobile phase constituents.This paper introduces a significant refinement to the already established retention model, which is based on the simple quantitative relationships between acetonitrile and tetrahydrofuran, and the remaining components of the ternary liquid system. The refined model is tested with same experimental data.     

Vapour—liquid equilibria. IV. The ternary system carbon tetrachloride—methanol—chloroform at 293.15 K

Total vapour pressure measurements made by the modified static method for the ternary system carbon tetrachloride—methanol—chloroform and constituent binaries at 293.15 K are presented. The different expressions for G^E suitable for correlation of these data are tested. The prediction of ternary VLE from constituent binaries is studied. Our results are compared to literature data.     

Low-temperature liquid extraction as a method of the pretreatment of phenol samples for reversed-phase HPLS

A new procedure was developed for the liquid—liquid extraction of phenols from aqueous solutions With acetonitrile. It is based on the ability of aqueous acetonitrile systems to form immiscible phases in the temperature range 271—269 K. The resulting duration of analysis is 40–45 min, the partition coefficient is 45–140, and the recovery is 97.8–99.2%. The procedure was proved applicable for sample pretreatment followed by determination by reversed-phase HPLC.     

Determination of autoprotolysis constants of ternary water—dioxane—methanol solvent systems at 25°C

The thermodynamic autoprotolysis constant K₅ (the sum of the autoprotolysis constants of H₂O and CH₃OH) of various ternary water—dioxane—methanol and the corresponding binary solvent systems (water—dioxane, water—methanol) were determined by potentiometric measurements with a combined glass—calomel electrode. In the ternary mixtures, the results show that the composite medium effect on the pK₅ values, expressed by a parameter b = dpK₅/d_u (u being avariable expressing the solvent composition), depends on the ratio of the organic solvent concentrations. In these mixtures, superposition of the various effects detected in the corresponding binary solvents allows the calculation of the pK₅ value of any ternary mixture by means of a simple equation.