Differential Scanning Microcalorimetry Technique Research Articles

Physicochemical and thermodynamic properties of the {1-alkyl-1-methylpiperidinium bromide [C1Cn=2,4PIP][Br], or 1-butylpyridinium bromide, [C4Py][Br], or tri(ethyl)butylammonium bromide [N2,2,2,4] [Br] + water} binary systems

This work is a continuation of our comprehensive study of ionic liquids, ILs (including organic salts with melting temperature above 100 °C) and their aqueous solutions as a novel alternative working pair for the absorption heat pump. A series of organic salts: 1-ethyl-1-methyl-piperidinium bromide, [C1C2PIP][Br], 1-butyl-1-methyl-piperidinium bromide, [C1C4PIP][Br], 1-butylpyridinium bromide, [C4Py][Br] and tri(ethyl)butylammonium bromide, [N2,2,2,4][Br] have been synthesized. The structures of compounds have been confirmed using NMR spectra. The basic thermal characterization of pure organic salts, including temperature and enthalpy of phase transition (Ttr, ΔtrH), temperature and enthalpy of melting (Tfus, ΔfusH) have been measured using a differential scanning microcalorimetry technique (DSC). The physico-chemical properties that are: density (ρ) and dynamic viscosity (η) of the tested binary systems have been determined at wide temperature and composition range. From experimental densities data, the apparent molar volumes (Vϕ,1) were calculated. In order to obtain limiting apparent molar volumes (Vϕ,10), the concentration dependence of apparent molar volumes was correlated with Redlich–Mayer type equation. Additionally, the limiting molar expansibilities (Eϕ0) and isobaric thermal expansion coefficients (αP) have been calculated. Temperature dependence of the dynamic viscosity has been correlated using VFT equation. The solid−liquid phase equilibria (SLE) have been determined using a dynamic method and correlated using NRTL equation. The influence of the alkyl chain length in the piperidinium cation substituent, as well as the cation structure, on investigated properties are presented and discussed.

Ionic Liquids as Efficient Extractants for Quercetin from Red Onion (Allium cepa L.)

The solubility of Quercetin in alcohols, esters and in 1-ethyl-3-methylimidazolium trifluoroacetate, [EMIM][TFA] ionic liquid (IL) using the dynamic method was measured at constant pH in a range of temperature 233-373 K and compare to the literature data. The experimental solubility data have been correlated by means of commonly known GE models,UNIQUAC and NRTL with the assumption that the systems studied here present simple eutectic behaviour. The basic thermal properties of Quercetin, i.e., fusion temperature and the enthalpy of fusion have been measured with differential scanning microcalorimetry technique (DSC).The application of alcohols, esters and ionic liquids (ILs) as alternatives to conventional organic solvents in the liquid-liquid extraction of Quercetin from different medicinal plants, flowers and frozen red onion (Allium cepa L.) was investigated. The parameters affecting the extraction yield using ILs such as chemical structures of the IL cation and anion, the phase volume ratio of extracting solvent, time of extraction and the Quercetin form of sample and concentration were evaluated. Specific Quercetin composition was performed through HPLC measurements. Using the most effective ILs in extraction, the 14.3±0.1g.kg-1 and 5.9±0.1g.kg-1of Quercetin from frozen pure red onion was obtained with N,N-diethyl-N-methyl-N-(2-methoxyethyl)ammonium tetrafluoroborate, [N2,2,1,2OCH3][BF4] and 1-ethyl-3-methylimidazolium trifluoroacetate, [EMIM][TFA], respectively.

Studying of drug solubility in water and alcohols using drug-ammonium ionic liquid-compounds

Synthesis of three mefenamic acid (MEF) derivatives - ionic liquid compounds composed of MEF in an anionic form and ammonium cation (choline, MEF1), or {di(2-hydroxyethyl)dimethyl ammonium (MEF2)}, or {tri(2-hydroxyethyl)methyl ammonium compound (MEF3)} is presented. The basic thermal properties of pure compounds i.e. fusion temperatures, and the enthalpy of fusion of these compounds have been measured with differential scanning microcalorimetry technique (DSC). Molar volumes have been calculated with the Barton group contribution method. The solubilities of MEF1, MEF2 and MEF3 using the dynamic method were measured at constant pH in a range of temperature from (290 to 370) K in three solvents: water, ethanol and 1-octanol. The experimental solubility data have been correlated by means of three commonly known GE equations: the Wilson, NRTL and UNIQUAC with the assumption that the systems studied here present simple eutectic behaviour. The activity coefficients of pharmaceuticals at saturated solutions in each binary mixture were calculated from the experimental data. The formation of MEF-ionic liquid compounds greatly increases the solubility in water in comparison with pure MEF or complexes with 2-hydroxypropyl-β-cyclodextrin. The development of these compounds formulations will assist in medication taking into account oral solid or gel medicines.

Physicochemical and thermodynamic properties of the {1-alkyl-1-methylmorpholinium bromide, [C1Cn=3,4,5MOR]Br, or 1-methyl-1-pentylpiperidinium bromide, [C1C5PIP]Br + water} binary systems

In this study, the density, ρ, dynamic viscosity, η, (solid+liquid), SLE and (vapor+liquid), VLE phase equilibria of four binary systems (ionic liquid, IL+water) are determined. Heat capacities, Cp of (organic salt+water) mixtures were studied as well. In this work, a series of organic salts namely: 1-mehyl-1-propylmorpholinium bromide, [C1C3MOR]Br, 1-mehyl-1-butylmorpholinium bromide, [C1C4MOR]Br, 1-mehyl-1-pentylmorpholinium bromide, [C1C5MOR]Br and 1-methyl-1-pentylpiperidinium bromide, [C1C5PIP]Br have been synthesized. The structure of the synthesized compounds were confirmed by 1H NMR, 13C NMR and elemental analysis. The thermophysical characterization of pure organic salts, including: temperature of phase transition (Ttr), enthalpy of phase transition (ΔtrH), melting temperature (Tm) and enthalpy of melting (ΔmH) have been determined using differential scanning microcalorimetry technique (DSC) at atmospheric pressure. Additionally, the thermogravimetry technique (TG/DTA) was used to determine the decomposition temperature. The influence of the alkyl chain length in the morpholinium cation as well as the cation structure on the physicochemical and thermodynamic properties presented in this work are discussed.

Solubility of pharmaceuticals in water and alcohols

The aim of this study was to examine the phase equilibria in binary systems: {pharmaceutical, Ph (1)+water, or alcohol (2)}. This work was carried out for four pharmaceuticals, Phs: aminophylline and (−) lobeline hydrochloride, perphenazine and indomethacin. Solubility of tested Phs was determined in three solvents. Water, the main component of any living organism. Ethanol, substance corresponding to the transport of the Ph in the body, and 1-octanol, a model compound of human cell and skin membrane. All studied Phs have aromatic structure and functional groups typical for drugs.The differential scanning microcalorimetry technique, DSC was used to measure basic thermal properties of pure drugs, i.e., temperatures of fusion, enthalpy of fusion, glass-transition temperatures and heat capacity change at the glass-transition temperature. Molar volumes have been calculated with Barton group contribution method. The Bates–Schwarzenbach method enabled us to determinate the pKa of used Phs. These values are important because it may designate the Phs dosage and the activity at the certain pH. The pKa experimental values are slightly different than the literature data which was already published as a results of different experimental methods. In this work, altogether 12 binary systems {Ph (1)+solvent (2)} were studied with the use of dynamic and spectrophotometric method. Three GEx thermodynamic models were used to correlate the experimental data: Wilson equation, NRTL equation and UNIQUAC equation.

Phase equilibria study of binary systems comprising an (ionic liquid + hydrocarbon)

In this study, the interaction of two ionic liquids with hydrocarbons has been investigated. With this aim, (solid+liquid) equilibria (SLE) and (liquid+liquid) equilibria (LLE) for binary systems of {1-methyl-1-propyl-pyrrolidinium triflate [PMPyr][CF3SO3]+heptane, or benzene, or thiophene, or benzothiophene} and {N-butyl-4-cyanopyridinium tricyanomethanide [BCN4Py][TCM]+heptane, or toluene, or 2-methylthiophene, or benzothiophene} were measured at ambient pressure. A dynamic method was used over a broad range of mole fractions and temperatures from (T=270 to 370)K. An upper critical solution temperature (UCST) was detected for all mutually immiscible systems. The immiscibility gap for [BCN4Py][TCM] in benzene and thiophene is larger than those for [PMPyr][CF3SO3]. Conversely, in heptane it is slightly larger for [PMPyr][CF3SO3]. The basic thermal properties of the pure ILs, i.e. melting and glass-transition temperatures as well as the enthalpy of fusion have been measured using a differential scanning microcalorimetry technique (DSC). The well-known NRTL model has been used to correlate the experimental SLE data points.

Physicochemical and thermodynamic characterization of N -alkyl- N -methylpyrrolidinium bromides and its aqueous solutions

Abstract This work is a continuation of our research of ionic liquids to investigate the physicochemical and thermodynamic properties of (ionic liquid + water) binary mixtures as a novel alternative working pair for the absorption heat pump cycle. In this work, a series of organic salts: N-propyl-N-methyl-pyrrolidinium bromide, [C1C3PYR]Br; N-butyl-N-methylpyrrolidinium, [C1C4PYR]Br and N-pentyl-N-methylpyrrolidinium bromide, [C1C5PYR]Br have been synthesized. The structures of new compounds have been confirmed using NMR spectra and elementary analysis. The basic thermal characterization of pure ILs, including temperature and enthalpy of phase transition (Ttr, ΔtrH), temperature and enthalpy of melting (Tm, ΔmH) have been measured using a differential scanning microcalorimetry technique (DSC). Decomposition temperature of the tested ILs were detected by the simultaneous TG/DTA experiments. The effect of temperature on the density (ρ) and dynamic viscosity (η) is reported over a wide temperature range from 298.15 to 343.15 K at ambient pressure. From experimental density data, the excess molar volumes (VE) were calculated and correlated using Redlich–Kister equation. The isothermal vapour–liquid phase equilibria (VLE) have been measured by an ebulliometric method at wide temperature range from 328.15 to 368.15 K and pressure up to 85 kPa. Experimental data have been correlated by means of NRTL equation. The solid–liquid phase equilibria (SLE) for the tested binary mixtures have been determined over whole composition range using dynamic method. The NRTL equation using parameters obtained from the VLE gives good description of SLE data. The influence of the alkyl chain length in the pyrrolidinium cation on the presented physicochemical and thermodynamic properties were discussed.

Density, viscosity and phase equilibria study of {ethylsulfate-based ionic liquid+water} binary systems as a function of temperature and composition

Abstract This paper is a continuation of our investigation on physicochemical and thermodynamic properties of ionic liquids and its aqueous solutions. In this work the density, ρ and dynamic viscosity, η have been determined for binary mixtures of the ionic liquids: 1-ethyl-1-methyl-piperidinium ethylsulfate, [EMPIP][EtSO4], 1-ethyl-1-methylmorpholinium ethylsulfate, [EMMOR][EtSO 4 ] and 1-ethyl-1-methylpyrrolidinium ethylsulfate, [EMPYR][EtSO4] with water at wide temperature and composition range at atmospheric pressure. From experimental values of the density, ρ and dynamic viscosity, η the excess molar volumes, VE and viscosity deviations, Δη were calculated and correlated using Redlich–Kister polynomial equation. The (solid + liquid) phase equilibria, SLE for the tested binary mixtures have been determined by well-known dynamic method at a wide range of composition and temperature at atmospheric pressure. For comparison, the SLE data for {[EMPYR][EtSO4] + water} binary mixtures have been determined using DSC technique. The experimental SLE data have been correlated by means of NRTL, UNIQUAC and Wilson equations. Additionally, the basic thermal properties of the pure ILs, that is, the glass-transition temperature, Tg,1 as well as the heat capacity at the glass-transition temperature, ΔCp(g),1, melting temperature, Tm and enthalpy of melting, ΔmH have been measured using a differential scanning microcalorimetry technique (DSC). Decomposition of the ILs was detected by the simultaneous TG/DTA experiments. The choice of the ionic liquids allowed to determine the effect of cation structure on physicochemical and thermodynamic properties.

Measurements, Correlations, and Predictions of Thermodynamic Properties of N-Octylisoquinolinium Thiocyanate Ionic Liquid and Its Aqueous Solutions

N-Octylisoquinolinium thiocyanate, [C8iQuin][SCN], has been synthesized in our laboratory from [C8iQuin][Br] as a substrate. The compound was characterized using 1H-NMR, 13C-NMR, and elemental analysis. Karl Fisher titration was used to determine the water content. The density and viscosity of pure ionic liquid were determined over a wide temperature range from (288.15 to 348.15) K. The basic thermal properties of the pure IL have been measured using by means of a differential scanning microcalorimetry technique (DSC). Decomposition of the IL was detected by the simultaneous TG/DTA experiments. (Liquid + liquid) phase equilibria (LLE) have been measured for binary mixtures {[C8iQuin][SCN] (1) + water (2)} using a dynamic method at atmospheric pressure. The experiments have been done over a broad range of ionic liquid mole fraction, x1, and temperatures from 250 K to the boiling point of water. Experimental heat capacities and excess enthalpies were determined for {[C8iQuin][SCN] (1) + water (2)} binary mixtures for different IL mole fractions at a wide range of the temperature at ambient pressure. The influence of temperature and composition was assessed, and suitable equations were used to correlate the experimental data. The experimental results were compared with data for other ionic liquids available in the open literature.

Phase Equilibria Study of the Binary Systems (N-Hexylisoquinolinium Thiocyanate Ionic Liquid + Organic Solvent or Water)

Liquid-liquid phase equilibria (LLE) of binary mixtures containing a room-temperature ionic liquid N-hexylisoquinolinium thiocyanate, [HiQuin][SCN] with an aliphatic hydrocarbon (n-hexane, n-heptane), aromatic hydrocarbon (benzene, toluene, ethylbenzene, n-propylbenzene), cyclohexane, thiophene, water, and 1-alcohol (1-ethanol, 1-butanol, 1-hexanol, 1-octanol, 1-decanol) have been determined using a dynamic method from room temperature to the boiling-point of the solvent at ambient pressure. N-hexylisoquinolinium thiocyanate, [HiQuin][SCN] has been synthesized from N-hexyl-isoquinolinium bromide as a substrate. Specific basic characterization of the new compound including NMR spectra, elementary analysis, and water content have been done. The density and viscosity of pure ionic liquid were determined over a wide temperature range from 298.15 to 348.15 K. The mutual immiscibility with an upper critical solution temperature (UCST) for the binary systems {IL + aliphatic hydrocarbon, cyclohexane, or water} was detected. In the systems of {IL + aromatic hydrocarbon or thiophene} an immiscibility gap with a lower critical solution temperature (LCST) was observed. Complete miscibility in the liquid phase, over a whole range of ionic liquid mole fraction, was observed for the binary mixtures containing IL and an 1-alcohol. For the tested binary systems with immiscibility gap {IL + aliphatic hydrocarbon, aromatic hydrocarbon, cyclohexane, thiophene, or water}, the parameters of the LLE correlation have been derived using the NRTL equation. The basic thermal properties of the pure IL, that is, the glass-transition temperature as well as the heat capacity at the glass-transition temperature, have been measured using a differential scanning microcalorimetry technique (DSC). Decomposition of the IL was detected by simultaneous thermogravimetric/differential thermal analysis (TG/DTA) experiments.

Solubility and pKa determination of six structurally related phenothiazines

Solubilities of six structurally related phenothiazines, namely chlorpromazine hydrochloride, fluphenazine dihydrochloride, promazine hydrochloride, thioridazine hydrochloride, trifluoperazine dihydrochloride, and triflupromazine hydrochloride at constant pH were measured in the temperature range from 290K to 350K in three important drugs solvents: water, ethanol and 1-octanol using the dynamic method and UV–vis method. Dissociation constants and corresponding pKa values of drugs were obtained with Bates–Schwarzenbach method at temperature 298.15K in the buffer solutions. Our experimental pKa values for chlorpromazine hydrochloride, fluphenazine dihydrochloride, promazine hydrochloride, thioridazine hydrochloride, trifluoperazine dihydrochloride, and triflupromazine hydrochloride are 9.15, 10.01, 9.37, 8.89, 8.97, and 9.03, respectively. The basic thermal properties of pure drugs i.e. melting and solid–solid phase transition as well as glass-transition temperatures, the enthalpy of melting and phase transitions and the molar heat capacity at glass transition (at constant pressure) were measured with differential scanning microcalorimetry (DSC) technique. Molar volumes were calculated with Barton group contribution method. The experimental solubility data were correlated by means of three commonly known GE equations: the Wilson, NRTL and UNIQUAC with the assumption that the systems studied here have revealed simple eutectic mixtures. The root-mean-square deviations of temperature were used for the precision of the correlation. The activity coefficients of drugs at saturated solutions in each correlated binary mixture were calculated from the experimental data. These new data will help in all prediction-methods and their precision.

Phase behaviour of 1-butyl-1-methylpyrrolidinium thiocyanate ionic liquid

The phase diagrams for the binary systems of {1-butyl-1-methylpyrrolidinium thiocyanate [BMPYR][SCN] + an alcohol (1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, 1-decanol, 1-undecanol, 1-dodecanol), or + water, or + aliphatic hydrocarbons ( n-hexane, n-heptane, n-octane), or + cyclohexane, or + cycloheptane, or + aromatic hydrocarbons (benzene, toluene, ethylbenzene)} have been determined at atmospheric pressure using a dynamic method. The basic thermal properties of pure ILs, i.e. melting temperature and the enthalpy of fusion, the solid–solid phase transition temperature and enthalpy have been measured using a differential scanning microcalorimetry technique. The decomposition of [BMPYR][SCN] was detected. The density and viscosity of the IL at 298.15 K were measured. (Solid + liquid) phase equilibrium diagrams with complete miscibility in the liquid phase region were observed for the systems involving alcohols and water. A decrease in the solubility of [BMPYR][SCN] in alcohols was observed with an increase of the alkyl chain length of an alcohol. (Solid + liquid) phase equilibrium diagrams with immiscibility in the liquid phase region were observed for the systems involving hydrocarbons. As for all ionic liquids (ILs) solubility decreases with an increase of number of carbon atoms in n-alkanes, cyclohydrocarbons, or of substituents at the benzene ring. The correlation of the experimental data has been carried out using the NRTL equation. The data presented here have been compared to the systems published earlier for the thiocyanate based ILs and for ILs with 1-butyl-1-methylpyrrolidinium cation. The influence of the cation and anion on the phase behaviour has been discussed.

Liquid–liquid phase equilibrium of (piperidinium-based ionic liquid + an alcohol) binary systems and modelling with NRHB and PCP-SAFT

The phase diagrams for binary systems of {1-propyl-1-methylpiperidinium bis{(trifluoromethyl)sulfonyl}imide [PMPIP][NTf 2] + an alcohol (butan-1-ol, pentan-1-ol hexan-1-ol, heptan-1-ol, octan-1-ol, decan-1-ol and undecan-1-ol} have been determined at atmospheric pressure using a dynamic method. The influence of an alcohol chain length is discussed for this ionic liquid (IL). A systematic decrease in the solubility is observed with an increase of the alkyl chain length of an alcohol. Liquid + liquid phase equilibrium (LLE) with an upper critical solution temperature was observed. The phase diagrams reported are compared to systems published earlier with the 1-alkyl-1-methylpiperidinium-based ionic liquid. The basic thermal properties of the pure IL, i.e. melting temperature and the enthalpy of fusion, the glass transition temperature and heat capacity at melting temperature have been measured using a differential scanning microcalorimetry technique. The density of [PMPIP][NTf 2] as a function of temperature was measured. The results of the LLE correlation with two models viz. the lattice theory based on non-random hydrogen bonding (NRHB) and the Perturbed-Chain Polar Statistical Associating Fluid Theory (PCP-SAFT) are presented. Both models are capable of describing pure fluid properties of IL (densities and solubility parameters) by using one set of parameters and the LLE in binary systems. This is to our knowledge the first paper presenting the SAFT modelling of binary LLE in ionic liquid systems.

Phase Equilibria Study of {N-Hexylisoquinolinium bis{(trifluoromethyl)sulfonyl}imide + Aromatic Hydrocarbons or an Alcohol} Binary Systems

Isoquinolinium ionic liquid (IL) has been synthesized from N-hexylisoquinolinium bromide as a substrate. Specific basic characterization of the synthesized compound is included, which includes NMR spectra, elementary analysis, and water content. The basic thermal properties of the pure IL, that is, melting and solid-solid transition temperatures, as well as the enthalpy of fusion, or solid-solid transition have been measured using a differential scanning microcalorimetry technique. The density and viscosity as a function of temperature have been measured for the pure IL at temperatures higher than the melting temperature and were extrapolated to T = 298.15 K. The temperature-composition phase diagrams of 8 binary mixtures composed of the IL N-hexylisoquinolinium bis{(trifluoromethyl)sulfonyl}imide, ([HiQuin][NTf(2)]) and an aromatic hydrocarbon (benzene, or toluene, or ethylbenzene, n-propylbenzene) or an alcohol (1-butanol, or 1-hexanol, or 1-octanol, or 1-decanol) have been determined from ambient temperature to the boiling-point temperature of the solvent at ambient pressure. A dynamic method was used over a broad range of mole fractions and temperatures from 270 to 330 K. For the binary systems, the eutectic diagrams were observed with immiscibility in the liquid phase with an upper critical solution temperature (UCST). In the case of the mixture {IL + benzene, or alkylbenzene} the eutectic systems with mutual immiscibility in the liquid phase with very high UCSTs were observed. These points were not detectable with our method and were observed at low IL mole fraction. For mixtures with alcohols, it was observed that with an increasing chain length of an alcohol, the solubility decreases and the UCST increases. The coexistence curves corresponding to liquid-liquid phase equilibrium boundaries and the solid-liquid phase equilibrium has been correlated using the well-known nonrandom two-liquid (NRTL) model.

Solubility of Sparingly Soluble Drug Derivatives of Anthranilic Acid

This work is a continuation of our systematic study of the solubility of pharmaceuticals (Pharms). All substances here are derivatives of anthranilic acid, and have an anti-inflammatory direction of action (niflumic acid, flufenamic acid, and diclofenac sodium). The basic thermal properties of pure Pharms, i.e., melting and glass-transition temperatures as well as the enthalpy of melting, have been measured with the differential scanning microcalorimetry technique (DSC). Molar volumes have been calculated with the Barton group contribution method. The equilibrium mole fraction solubilities of three pharmaceuticals were measured in a range of temperatures from 285 to 355 K in three important solvents for Pharm investigations: water, ethanol, and 1-octanol using a dynamic method and spectroscopic UV-vis method. The experimental solubility data have been correlated by means of the commonly known G(E) equation: the NRTL, with the assumption that the systems studied here have revealed simple eutectic mixtures. pK(a) precise measurement values have been investigated with the Bates-Schwarzenbach spectrophotometric method.

Thermodynamic properties of the N-butylisoquinolinium bis(trifluoromethylsulfonyl)imide

A new isoquinolinium ionic liquid (IL) has been synthesised as a continuation of our work with quinolinium-based ionic liquids (ILs). The work includes specific basic characterization of synthesized compounds: N-isobutylquinolinium bromide, [BiQuin][Br] and N-isobutylquinolinium bis{(trifluoromethyl)sulfonyl}imide [BiQuin][NTf 2] by NMR spectra, elementary analysis and water content. The basic thermal properties of the pure [BiQuin][NTf 2], i.e. melting and glass-transition temperatures, the enthalpy of fusion as well as heat capacity at glass transition have been measured using a differential scanning microcalorimetry technique (DSC). Densities and viscosities were determined as a function of temperature. The temperature-composition phase diagrams of 8 binary mixtures composed of organic solvent dissolved in the IL: {[BiQuin][NTf 2] + aromatic hydrocarbon (benzene, or toluene, or ethylbenzene, or n-propylbenzene), or an alcohol (1-butanol, or 1-hexanol, or 1-octanol, or 1-decanol)} were measured at ambient pressure. A dynamic method was used over a broad range of mole fraction and temperature from (270 to 320) K. For all the binary systems with benzene and alkylbenzenes, the eutectic diagrams were observed with an immiscibility gap in the liquid phase existing at low mole fraction of the IL with a very high upper critical solution temperature (UCST). For mixtures with alcohols, complete miscibility was observed for 1-butanol and also an immiscibility gap with UCST in the liquid phase for the remaining alcohols. The typical dependence was observed that with increasing chain length of an alcohol, the solubility decreases. The well-known NRTL equation was used to correlate experimental (solid + liquid), SLE and (liquid + liquid), LLE phase equilibrium data sets.

Thermophysical properties and phase equilibria study of the binary systems { N-hexylquinolinium bis(trifluoromethylsulfonyl)imide + aromatic hydrocarbons, or an alcohol}

The new quinolinium ionic liquid has been synthesised as a continuation of our work with quinolinium-based ionic liquids (ILs). The work includes specific basic characterisation of synthesized compounds: N-hexylquinolinium bromide, [HQuin][Br] and N-hexylquinolinium bis{(trifluoromethyl)sulfonyl}imide [HQuin][NTf 2] by NMR spectra, elementary analysis and water content. The basic thermal properties of the pure [HQuin][NTf 2] i. e. melting and glass-transition temperatures, the enthalpy of fusion as well as heat capacity have been measured using a differential scanning microcalorimetry technique (DSC) and thermal analysis instrument (TA). Densities and viscosities were determined as a function of temperature. Phase equilibria for the binary systems: {[HQuin][NTf 2]) + aromatic hydrocarbon (benzene, or toluene, or ethylbenzene, or n-propylbenzene), or an alcohol (1-butanol, or 1-hexanol, or 1-octanol, or 1-decanol)} have been determined at ambient pressure. A dynamic method was used over a broad range of mole fractions and temperatures from (270 to 320) K. For all the binary systems with benzene and alkylbenzenes, the eutectic diagrams were observed with immiscibility gap in the liquid phase beginning from (0.13 to 0.28) mole fraction of the IL with very high an upper critical solution temperature (UCST). For mixtures with alcohols, the complete miscibility was observed for 1-butanol and immiscibility with UCST in the liquid phase for the remaining alcohols. The typical dependence was observed, that with increasing chain length of an alcohol the solubility decreases. The well-known NRTL equation was used to correlate experimental (solid + liquid), SLE and (liquid + liquid), LLE phase equilibria data sets. For the systems containing immiscibility gaps, (IL + an alcohol) parameters of the LLE correlation were used to the prediction of SLE.

Physico-chemical properties and phase behaviour of piperidinium-based ionic liquids

The sufficient review of the existing literature of the 1-alkyl-1-methylppiperidinium-based ionic liquids has been presented. The phase diagrams for the binary systems of {1-butyl-1-methylpiperidinium thiocyanate [BMPIP][SCN] + an alcohol (1-hexanol, 1-heptanol, 1-octanol, 1-nonanol, 1-decanol, 1-dodecanol), or + water, or + aliphatic hydrocarbons ( n-hexane, n-heptane, n-octane), or + cyclohexane, or, + cycloheptane, or + aromatic hydrocarbons (benzene, toluene, ethylbenzene)} and for the binary systems of {1-ethyl-1-methylpiperidinium bis{(trifluoromethyl)sulfonyl}imide [EMPIP][NTf 2] + an alcohol (ethanol, 1-propanol, 1-butanol, 1-hexanol, 1-heptanol, 1-octanol, 1-nonanol), or + water} have been determined at atmospheric pressure using a dynamic method. The influence of an alcohol chain length was discussed for these ionic liquids. A systematic decrease in the solubility was observed with an increase of the alkyl chain length of an alcohol. (Solid + liquid) phase equilibria with complete miscibility in the liquid phase region were observed for the systems involving water and the alcohols for the thiocyanate-based ionic liquid. Opposite, the bis{(trifluoromethyl)sulfonyl}imide-based ionic liquid reveal the immiscibility gap in the liquid phase. The correlation of the experimental data has been carried out using the NRTL equation. The phase diagrams reported here have been compared to the systems published earlier with the 1-alkyl-1-methylpiperidinium-based ionic liquids. The influence of the cation and anion on the phase behaviour has been discussed. The basic thermal properties of pure ILs, i.e. melting temperature and the enthalpy of fusion, the solid–solid phase transition temperature and enthalpy have been measured using a differential scanning microcalorimetry technique.

Modelling, solubility and pKa of five sparingly soluble drugs

Drug solubility is an important aspect of drug development. The objective of this investigation was to measure solubilities of five drugs (cimetidine, phenylbutazone, fenbufen, nitrofurantoin, triamterene) at constant pH in range of temperature from 270 to 340K in three solvents: water, ethanol and 1-octanol with the dynamic-visual method and the saturation shake-flask method using spectrophotometric analysis. The Barton group contribution method was used for the calculations of molar volumes of solutes. The thermodynamic description of the solubility curves was made using the thermophysical properties obtained with the differential scanning microcalorimetry technique (DSC). The DSC measurements have shown different than existing in the literature enthalpies of melting for phenylbutazone and fenbufen. The experimental solubility data also differ from the literature data, normally measured at one, or two temperatures only. The solubility data have been correlated by means of three commonly known excess Gibbs energy, GE equations. The activity coefficients of drugs at saturated solutions were calculated from the experimental data. Reexamination of the pKa values using diluted solutions was made with the Bates–Schwarzenbach method for the pKa measurements. The association constants and corresponding pKa values of drugs were close to the most of the literature data. We hope that our new solubility data, thermophysical data, and pKa values will improve all prediction-methods and their precision.

Solubility and p Ka of select pharmaceuticals in water, ethanol, and 1-octanol

Solubilities of six pharmaceuticals, namely nadolol, atenolol, bifonazole, nimesulide, estrone, mefenamic acid at constant pH, were measured over the range of temperature from (240 to 340) K in three important for drug solvents: water, ethanol, and 1-octanol using the dynamic method and spectroscopic UV–Vis method. Dissociation constants and corresponding p K a values of the drugs were obtained with the Bates–Schwarzenbach method using UV–Vis Perkin–Elmer Lambda 35 Spectrophotometer at temperature 298.15 K in the buffer solutions. Our experimental p K a values for nadolol, bifonazole, nimesulide, and mefenamic acid are 9.3, 5.85, 7.34, and 3.88, respectively. The basic thermal properties of pure drugs i.e. fusion and glass-transition temperatures, as well as the enthalpy of fusion and the molar heat capacity at the glass-transition (at constant pressure) have been measured using the differential scanning microcalorimetry technique (DSC). Molar volumes have been calculated with the Barton group contribution method. The experimental solubility results have been correlated by means of three commonly known G E equations: the Wilson, NRTL, and UNIQUAC with the assumption that the systems studied here are simple eutectic mixtures. The activity coefficients of pharmaceuticals in saturated solutions in each correlated binary mixture were calculated from the experimental results. Prediction of solubility in water at T = 298.15 K was made by the group contribution method.