Water-rich Mixtures Research Articles

Solubility and Preferential Solvation of Sulfanilamide, Sulfamethizole and Sulfapyridine in Methanol + Water Mixtures at 298.15 K

The equilibrium solubilities of sulfanilamide, sulfamethizole and sulfapyridine in methanol + water mixtures at 298.15 K were determined and the preferential solvation parameters were derived from their thermodynamic solution properties by means of the inverse Kirkwood–Buff integrals. In all cases the drug solubility was the lowest in neat water and highest in neat methanol. The preferential solvation parameters for methanol (δx 1,3) are negative in water-rich mixtures but positive in compositions from 0.32 in mole fraction of methanol to pure methanol. Based on these results it is conjecturable that in the former case hydrophobic hydration around the aromatic rings plays the main role in the drug’s solvation. The higher solvation by methanol in mixtures of similar cosolvent compositions and in methanol-rich mixtures can be explained in terms of the higher basic behavior of this co-solvent interacting with the Lewis acidic groups of the drugs. Besides, the drugs’ solubilities were mathematically represented by using the Jouyban–Acree model obtaining average percentage deviations lower than 2.6 % for correlative studies.

Viscosity coefficients of KCl, NaCl, NaI, KNO3, LiNO3, NaBPh4 and Bu4NI in water-rich binary mixtures containing propan-2-ol at 298.15 K

ABSTRACTViscosities of KCl, NaCl, NaI, KNO3, LiNO3, NaBPh4 and Bu4NI solutions (from ~0.01 M to ~0.05 M) in water (1) + propan-2-ol) (2) binary mixtures with mole fractions of propan-2-ol, x2 = 0.01, 0.02, 0.05, 0.075, 0.10 and 0.15, were determined at 298. 15 K. The relative viscosity data have been analysed and interpreted in terms of the Jones–Dole equation, ηr = A∙c1/2 + B∙c. The obtained results allowed to determine the values of B± coefficients for individual ions using the assumption about the equality . All the results presented in this article have been discussed in terms of ion–solvent interactions.

Solubility of phenobarbital in aqueous cosolvent mixtures revisited: IKBI preferential solvation analysis

ABSTRACTThe preferential solvation parameters of phenobarbital in aqueous binary mixtures of 1,4-dioxane, t-butanol, n-propanol, ethanol, propylene glycol and glycerol were derived from solution thermodynamic properties by using the IKBI method. This drug is sensitive to preferential solvation effects in all these mixtures. The preferential solvation parameter by the cosolvent (δx1,3) is negative in almost all the water-rich mixtures but positive in mixtures with similar proportions of solvents and cosolvent-rich mixtures, except in 1-propanol + water mixtures, where negative values are also found in mixtures with x1 ≥ 0.70. Hydrophobic hydration around the non-polar ethyl and phenyl groups of this drug in water-rich mixtures could play a relevant role in drug solvation. Otherwise, in mixtures of similar solvent compositions and in cosolvent-rich mixtures the preferential solvation by cosolvent could be due to the acidic behaviour of the drug.

Vapor-liquid interface properties of diethyl sulfoxide-water and ethyl methyl sulfoxide-water mixtures: Molecular dynamics simulations and quantum-chemical calculations

Senior sulfoxides, such as diethyl sulfoxide (DESO) and ethyl methyl sulfoxide (EMSO), are prospective cryoprotectants. These liquids are either applied in the form of their mixtures with water or mix with water inside the living cell. This work reports vapor-liquid equilibrium (VLE) properties of the senior sulfoxide-water mixtures over an entire composition range. Negative deviations from an ideal behavior were found for both sulfoxides in their aqueous mixtures. The inter-molecular interactions in the mixtures are predominantly electrostatic. A strong hydrogen bond exists between DESO (EMSO) and water, whereas water does not coordinate the methylene groups. Thanks to their hydrophobic chains, DESO and EMSO exhibit elevated densities at the vapor-liquid interface. Both DESO and DMSO act rather efficiently as surfactants decreasing surface tension of the water-rich mixtures. The reported results confirm stability of the aqueous mixtures of sulfoxides and foster their emerging applications.

Preferential solvation of etoricoxib in some aqueous binary cosolvent mixtures at 298.15 K

ABSTRACTPreferential solvation parameters of etoricoxib in several aqueous cosolvent mixtures were calculated from solubilities and other thermodynamic properties by using the IKBI method. Cosolvents studied were as follows: 1,4-dioxane, N,N-dimethylacetamide, 1,4-butanediol, N,N-dimethylformamide, ethanol and dimethyl sulfoxide. Etoricoxib exhibits solvation effects, being the preferential solvation parameter δx1,3, negative in water-rich and cosolvent-rich mixtures but positive in mixtures with similar proportions of both solvents. It is conjecturable that the hydrophobic hydration in water-rich mixtures plays a relevant role in drug solvation. In mixtures of similar solvent proportions where etoricoxib is preferentially solvated by the cosolvents, the drug could be acting as Lewis acid with the more basic cosolvents. Finally, in cosolvent-rich mixtures the preferential solvation by water could be due to the more acidic behaviour of water. Nevertheless, the specific solute–solvent interactions in the different binary systems remain unclear because no relation between preferential solvation magnitude and cosolvent polarities has been observed.

A systematic study on solubility and solvation of bioactive compound chrysin in some water + cosolvent mixtures

The equilibrium solubility of flavonoid chrysin was evaluated using UV–Vis spectrophotometric method in various mixed solvents comprising 0–100% (v/v) dimethylformamide (DMF) and tetrahydrofuran (THF) in water and constant temperature (25.0±0.1) °C. From solubility data, the Gibbs free energy changes involved with the dissolution process of chrysin were also determined. The obtained results showed that the solubility of chrysin increases by increasing the DMF and THF proportion in solution. Furthermore, the preferential solvation parameters of the solute chrysin by co-solvents DMF and THF, δxcosolv,S, were derived using the inverse Kirkwood-Buff integrals (IKBI) approach. From the δxcosolv,S data, it was found that water is the preferred solvent in the solvation shell of chrysin in water-rich mixtures but the co-solvents DMF and THF are preferred in intermediate compositions to pure co-solvent. The variation of this parameter in the binary mixtures studied is discussed based on types of intermolecular solute-solvent interactions and structural characteristics of flavonoid chrysin.

Micellar Properties for Propoxylated Surfactants in Water/Alcohol Solvent Mixtures and Their Antibacterial and Polyester Fabric Antistatic Performances

AbstractTwo propoxylated quaternary amine surfactants characterized by two and six average PO adduct numbers (PO‐2 and PO‐6 QA surfactants) were synthesized to investigate the micellar properties of propoxylated cationic surfactants in water/alcohol mixtures. The effect of PPO groups on micelle formation was explored using conductivity, UV–vis spectroscopy, dynamic light scattering techniques. Regular or reverse micellization occur with water or alcohol rich solvent mixtures, respectively. For intermediate composition no micellization occurs. Also the performances in antibacterial and antistatic fabrics were studied. PO‐2 QA surfactant has excellent antibacterial activities against both the Gram‐negative bacterium Escherichia coli and the Gram‐positive bacterium Staphylococcus aureus while both surfactants have good antistatic activity over polyester fabric.

SOME NUMERICAL ANALYSES ON THE SOLUBILITY OF VANILLIN IN CARBITOL® + WATER SOLVENT MIXTURES

In this communication some reported solubility values of vanillin (component 3) in 2-(2-ethoxyethoxy)ethanol (Carbitol ® , component 1) + water (component 2) mixtures at five temperatures from 298.15 to 318.15 K were correlated with the Jouyban-Acree model combined with van’t Hoff or Apelblat equations, obtaining models in second degree regarding the mixtures compositions. Mean percentage deviations were near to 6.0%. On the other hand, by means of the inverse Kirkwood-Buff integrals it was demonstrated that vanillin is preferentially solvated by water in water-rich mixtures (with a minimum δx 1,3 value in the mixture x 1 = 0.05, i.e. –4.29 x 10 –2 ) but preferentially solvated by the cosolvent in mixtures with compositions 0.12 < x 1 < 1.00 (with a maximum δx 1,3 value equal to 3.61 x 10 –2 in the mixture x 1 = 0.25). It is conjectural that hydrophobic hydration plays a relevant role in the first case, whereas, in the second case, vanillin would be acting as Lewis acid with Carbitol ® .

Solution thermodynamics and preferential solvation of sulfamethazine in (methanol + water) mixtures

The solubility of sulfamethazine (SMT) in {methanol (1)+water (2)} co-solvent mixtures was determined at five different temperatures from (293.15 to 313.15)K. The sulfonamide exhibited its highest mole fraction solubility in pure methanol (δ1=29.6MPa1/2) and its lowest mole fraction solubility in water (δ2=47.8MPa1/2) at each of the five temperatures studied. The Jouyban–Acree model was used to correlate/predict the solubility values. The respective apparent thermodynamic functions Gibbs energy, enthalpy, and entropy of solution were obtained from the solubility data through the van’t Hoff and Gibbs equations. Apparent thermodynamic quantities of mixing were also calculated for this drug using values of the ideal solubility reported in the literature. A non-linear enthalpy–entropy relationship was noted for SMT in plots of both the enthalpy vs. Gibbs energy of mixing and the enthalpy vs. entropy of mixing. These plots suggest two different trends according to the slopes obtained when the composition of the mixtures changes. Accordingly, the mechanism for SMT transfer processes in water-rich mixtures from water to the mixture with 0.70 in mass fraction of methanol is entropy driven. Conversely, the mechanism is enthalpy driven in mixtures whenever the methanol composition exceeds 0.70mol fraction. An inverse Kirkwood–Buff integral analysis of the preferential solvation of SMT indicated that the drug is preferentially solvated by water in water-rich mixtures but is preferentially solvated by methanol in methanol-rich mixtures.

Solubility and preferential solvation of some non-steroidal anti-inflammatory drugs in methanol + water mixtures at 298.15 K

ABSTRACTThe equilibrium solubilities of naproxen (NAP), ketoprofen (KTP), and ibuprofen (IBP) in methanol + water binary mixtures at 298.15 K were determined and the preferential solvation parameters were derived by means of the inverse Kirkwood–Buff integrals (IKBI) method. These drugs are very sensitive to specific solvation effects. The preferential solvation parameters by methanol δx1,3 are negative in water-rich mixtures but positive in compositions from 0.32 in mole fraction of methanol to pure methanol. It is conjecturable that in the former case the hydrophobic hydration around aromatic rings and/or methyl groups plays a relevant role in the solvation. The higher solvation by methanol in mixtures of similar co-solvent compositions and in methanol-rich mixtures could be explained in terms of the higher basic behaviour of this co-solvent interacting with the hydroxyl group of the drugs. Moreover, drug solubilities were correlated by using the modified nearly ideal binary solvent/Redlich–Kister model obtaining average percentage deviations (APDs) lower than 9.0%.

Thermodynamic Study of the Solubility of Naproxen in Some 2-Propanol + Water Mixtures

The equilibrium solubilities of the anti-inflammatory drug naproxen (NPX) in 2-propanol + water mixtures were determined at several temperatures from 298.15 to 313.15 K. The Gibbs energy, enthalpy, and entropy of solution and of mixing were obtained from these solubility data. The solubility was maximal in φ1 = 0.90 and very low in pure water at all the temperatures studied. A non-linear plot of ∆solnH° vs. ∆solnG° with negative slope from pure water up to 0.20 in volume fraction of 2-propanol and positive beyond this composition up pure 2-propanol was obtained at the mean temperature, 305.55 K. Accordingly, the driving mechanism for NPX solubility in the water-rich mixtures was the entropy, probably due to water-structure loss around non-polar moieties of the drug and for the 2-propanol-rich mixtures it was the enthalpy, probably due to its better solvation of the drug.

Preferential solvation of nifedipine in some aqueous co-solvent mixtures

ABSTRACTPreferential solvation parameters of nifedipine (NIF) in ethanol (EtOH) + water and propylene glycol (PG) + water mixtures were obtained from their thermodynamic properties in solution using the inverse Kirkwood–Buff integrals. Preferential solvation parameter (δx1,3) by both co-solvents is negative in the water-rich mixtures but positive in almost all the other compositions at 293.2, 303.2 and 313.2 K. Nevertheless, in EtOH-rich mixtures the values of δx1,3 are also negative. It can be assumed that in water-rich mixtures the hydrophobic hydration around the non-polar groups of NIF plays a relevant role in the solvation. The higher drug solvation by co-solvent in mixtures of similar solvent proportions and in co-solvent-rich mixtures could be due mainly to polarity effects. Moreover, in these mixtures the drug could be acting as a Lewis acid with the co-solvents molecules. Finally, in EtOH-rich mixtures the drug could be acting as a Lewis base with water molecules.

Solubility and preferential solvation of acetaminophen in methanol + water mixtures at 298.15 K

ABSTRACTThe equilibrium solubility of acetaminophen in methanol + water binary mixtures at 298.15 K was determined and correlated with the Jouyban–Acree model. Preferential solvation parameters by methanol (δx1,3) were derived from their thermodynamic solution properties by means of the inverse Kirkwood–Buff integrals method. δx1,3 values are negative in water-rich mixtures but positive in compositions from 0.32 in mole fraction of methanol to pure methanol. It is conjecturable that in the former case, the hydrophobic hydration around non-polar groups plays a relevant role in the solvation. The higher solvation by methanol in mixtures of similar cosolvent compositions and methanol-rich mixtures could be explained in terms of the higher basic behavior of this cosolvent.

Preferential solvation of indomethacin in 1,4-dioxane + water mixtures according to the inverse Kirkwood–Buff integrals method

ABSTRACTThe preferential solvation parameters (δx1,3) of indomethacin (IMC) in 1,4-dioxane + water binary mixtures were derived from their thermodynamic properties by means of the inverse Kirkwood–Buff integrals method. δx1,3 is negative in water-rich and 1,4-dioxane-rich mixtures but positive in cosolvent compositions from 0.17 to 0.69 in mole fraction of 1,4-dioxane at 298.15 K. It is conjecturable that in water-rich mixtures, the hydrophobic hydration around the aromatic and methyl groups of the drug plays a relevant role in the solvation. The higher solvation by 1,4-dioxane in mixtures of similar cosolvent compositions could be mainly due to polarity effects. Finally, the preference of this drug for water in 1,4-dioxane-rich mixtures could be explained in terms of the higher acidic behavior of water molecules interacting with the hydrogen-acceptor groups present in IMC.

Preferential Solvation of Indomethacin in Some Aqueous Co-Solvent Mixtures

The preferential solvation parameters for indomethacin (IMC) in ethanol (EtOH) + water and propylene glycol (PG) + water binary mixtures were obtained from their thermodynamic properties by means of the inverse Kirkwood–Buff integrals (IKBI) and the quasi-lattice quasi-chemical (QLQC) methods. According to IKBI method, the preferential solvation parameter by co-solvents, (δx1,3), is negative in the water-rich mixtures of both binary systems but positive in the other compositions at temperatures of 293.15, 303.15, and 313.15 K. It is conjecturable that in water-rich mixtures the hydrophobic hydration around the aromatic rings and methyl groups of the drug plays a relevant role in the solvation. The higher drug solvation by co-solvent in mixtures of similar solvent proportion and in co-solvent-rich mixtures could be due mainly to polarity effects. Here IMC would be acting as a Lewis acid with the EtOH or PG molecules because these co-solvents are more basic than water.

Solubility and saturation apparent specific volume of some sodium sulfonamides in propylene glycol + water mixtures at 298.15 K

Equilibrium solubility of sodium sulfadiazine (Na.SDZ), sodium sulfamerazine (Na.SMR), and sodium sulfamethazine (Na.SMT), was determined in aqueous binary mixtures of propylene glycol (PG) at 298.15K. If the solubility values expressed in both concentration scales are considered, i.e. mole fraction and molarity, in water-rich mixtures the solubility decrease as: Na.SDZ>Na.SMT>Na.SMR, whereas, in PG-rich mixtures the observed order is: Na.SMT>Na.SDZ>Na.SMR. In all cases the solubility in neat water is higher than those in neat PG. Correlation of the solubility data obtained was made by means of the Jouyban–Acree model for all the sodium sulfonamides. Otherwise, apparent specific volumes (ϕVsp) of sodium sulfonamides at saturation were also calculated in all the mixtures. The average ϕVsp values are as follows: 0.663cm3g−1 for Na.SDZ, 0.723cm3g−1 for Na.SMR, and 0.740cm3g−1 for Na.SMT, with a variation lower than 5.0% in each case.

Preferential Solvation of the Antioxidant Agent Daidzein in some Aqueous Co-Solvent Mixtures according to IKBI and QLQC Methods

The preferential solvation parameters by ethanol (EtOH) or propylene glycol (PG) of daidzein were derived from their solution thermodynamic properties by means of the inverse Kirkwood-Buff integrals and the quasi-lattice-quasi-chemical (QLQC) methods. According to IKBI method, the preferential solvation parameter by the co-solvent, δx1,3, is negative in water-rich mixtures but positive in co-solvent-rich mixtures in both kinds of systems. This could demonstrate the relevant role of hydrophobic hydration around the aromatic rings in the drug solvation in water-rich mixtures. Furthermore, the more solvation by co-solvent in co-solvent-rich mixtures could be due mainly to polarity effects and acidic behavior of the hydroxyl groups of the compound in front to the more basic solvents present in the mixtures, i.e. EtOH or PG. Otherwise, according to QLQC method, this drug is preferentially solvated by the co-solvents in all the mixtures in both kind of systems.

Solution Thermodynamics and Preferential Solvation of Sulfamerazine in Methanol + Water Mixtures

The solubility of sulfamerazine (SMR) in methanol + water co-solvent mixtures was measured at five temperatures from 293.15 to 313.15 K. The mole fraction solubility of this sulfonamide was maximal in pure methanol (δ 1 = 29.6 MPa1/2) and minimal in water (δ 2 = 47.8 MPa1/2) at all the temperatures studied. The apparent thermodynamic functions Gibbs energy, enthalpy, and entropy of solution were obtained from these solubility data by using the van’t Hoff and Gibbs equations. Apparent thermodynamic quantities of mixing were also calculated by using the ideal solubilities reported in the literature. A non-linear enthalpy–entropy relationship was observed for SMR in the plot of enthalpy versus Gibbs energy of mixing. This plot shows two different trends according to the slopes obtained when the mixture’s composition changes. Accordingly, the driving mechanism for the SMR solution process in water-rich mixtures is the entropy whereas it is the enthalpy in mixtures with mass fractions of methanol greater than 0.20. Additionally, the preferential solvation of this drug by the solvents was analyzed by means of the inverse Kirkwood–Buff integrals, which indicate that it is preferentially solvated by water in water-rich mixtures but preferentially solvated by methanol in methanol-rich mixtures.

Preferential solvation of some n-alkyl p-substituted benzoates in propylene glycol + water cosolvent mixtures

The preferential solvation parameters by propylene glycol (PG) of the homologous series of the n-alkyl esters of p-hydroxybenzoic and p-aminobenzoic acids, namely, methyl, ethyl, propyl and butyl derivatives, were derived from their thermodynamic properties of solution by means of the inverse Kirkwood–Buff integrals (IKBI) method. The preferential solvation parameters by the cosolvent, δx1,3, are negative in water-rich mixtures, but positive in PG-rich mixtures, and the relative magnitudes of δx1,3 are proportional to the alkyl chain length despite of the solvent involved in the preferential solvation, i.e. PG or water. It is possible that the hydrophobic hydration around aromatic ring and/or methylene groups plays a relevant role in the drugs solvation in water-rich mixtures. The more solvation by PG in PG-rich mixtures could be due mainly to polarity effects and acidic behaviour of the hydroxyl or amine groups of the compounds in front to the more basic solvent present in the mixtures, i.e. PG.

Solubility and preferential solvation of sulfadiazine, sulfamerazine and sulfamethazine in propylene glycol + water mixtures at 298.15 K

The equilibrium solubility of sulfadiazine, sulfamerazine and sulfamethazine in propylene glycol (PG)+water binary mixtures was determined at 298.15K and the preferential solvation parameters were derived from their thermodynamic solution properties by means of the inverse Kirkwood–Buff integrals method. It is found that these sulfonamides are sensitive to specific solvation effects. The preferential solvation parameters by PG (δx1,3) are negative in water-rich mixtures but positive in mixtures with compositions from 0.20 in mole fraction of PG to pure PG. It is conjecturable that in the former case the hydrophobic hydration around aromatic rings and/or methyl groups plays a relevant role in the solvation. The more solvation by PG in mixtures of similar co-solvent compositions and in PG-rich mixtures could be explained in terms of the bigger basic behavior of this co-solvent interacting with hydrogen-donor groups of the drugs.