Browsing by Author "Teixeira, Gabriel"
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- Designing type V deep eutectic solvents with antimalarial pharmaceutical ingredientsPublication . Teixeira, Gabriel; Brandão, Paula; Ferreira, Ana I.M.C. Lobo; Abranches, Dinis O.; Santos, L.uís M.N.B.F.; Ferreira, Olga; Coutinho, João A.P.This work studies the formation of deep eutectic solvents formed by one active pharmaceutical ingredient (quinine, pyrimethamine, or 2-phenylimidazopyridine) and a second component potentially acting as an excipient (betaine, choline chloride, tetramethylammonium chloride, thymol, menthol, gallic acid, vanillin, acetovanillone, 4-hydroxybenzaldehyde, syringaldehyde, propyl gallate, propylparaben, or butylated hydroxyanisole), aiming to address challenges regarding drug solubility, bioavailability, and permeability. A preliminary screening was carried out using the thermodynamic model COSMO-RS, narrowing down the search to three promising excipients (thymol, propyl gallate, and butylated hydroxyanisole). Nine solid–liquid equilibrium (SLE) phase diagrams were experimentally measured combining the three model drugs with the screened excipients, and using a combination of a visual melting method and differential scanning calorimetry. Negative deviations from thermodynamic ideality were observed in all nine systems. Furthermore, a total of four new cocrystals were found, with powder and single crystal X-ray diffraction techniques being employed to verify their unique diffraction patterns. In the thermodynamic modelling of the SLE diagrams, two COSMO-RS parametrizations (TZVP and TZVPD-FINE) were also applied, though neither consistently delivered a better description over the other.
- Estimating the melting temperatures of type V deep eutectic solventsPublication . Teixeira, Gabriel; Abranches, Dinis O.; Ferreira, Olga; Coutinho, João A.P.The recently proposed category of type V deep eutectic solvents (DESs), composed only of non-ionic species, has attracted great interest in the literature. However, despite their importance in solvent design, measuring the solid−liquid equilibrium (SLE) diagrams of all possible type V DES precursor combinations is unfeasible. Therefore, a reliable computational tool must be found to estimate SLE phase diagrams and, thus, the melting points of type V DESs. In this work, a total of 134 different binary eutectic systems (1744 datapoints) were gathered from the literature, and the calculation capabilities and accuracy of three different models COSMO-RS, UNIFAC of Dortmund, and Group and Group-Interaction Contribution method (GGIC) were evaluated. UNIFAC and COSMO-RS were, by far, the best performing models, with average absolute deviations (AADs) of, respectively, 6.9 K for 94 systems and 7.4 K for 133 systems. Due to a lack of group interaction parameters, UNIFAC could only describe 94 systems, a severe disadvantage over COSMO-RS. Moreover, despite being able to describe all 134 systems, the GGIC model resulted in an AAD of 37 K. Finally, the effect of using the different parametrizations or multiple conformers in COSMO-RS predictions was also evaluated, and the validity of neglecting heat capacity terms when performing SLE calculations was verified.
- Imidazolium chloride ionic liquid mixtures as separating agents: fuel processing and azeotrope breakingPublication . Vilas-Boas, Sérgio M.; Martins, Mónia A.R.; Tentor, Fabio Ribeiro; Teixeira, Gabriel; Sgorlon, Juliana; Coutinho, João A.P.; Ferreira, Olga; Pinho, SimãoRelevant chemical separations for the petrochemical and chemical industries include the removal of aromatic hydrocarbons from aliphatics, the desulfurization and denitrification of fuels, and the separation of azeotropic mixtures containing alkanols. In an attempt to contribute to the development of novel technologies, the potentialities of imidazolium chloride ionic liquid (IL) mixtures as separation agents were investigated. Selectivities, capacities, and solvent performance indices were calculated through the activity coefficients at infinite dilution of organic solutes and water in the imidazolium chloride IL: [C8mim]Cl, [C12mim]Cl, and the equimolar mixture of [C4mim]Cl and [C12mim]Cl. Results show that the imidazolium chloride IL might be appropriately tailored for specific purposes, in which an increase in the proportion of cations containing larger alkyl chains tends to increase the overall affinity with organic solutes. The IL designer solvent concept was explored by comparing the IL equimolar mixture results with the intermediary [C8mim]Cl. The COSMO-RS thermodynamic model was also applied, showing it to be a promising tool for a fast qualitative screening of potential separation agents for specific separation processes.
- Ionic liquids as entrainers for terpenes fractionation and other relevant separation problemsPublication . Vilas-Boas, Sérgio M.; Teixeira, Gabriel; Rosini, Sabrina Barbosa; Martins, Mónia A.R.; Gaschi, Priscilla S.; Coutinho, João A.P.; Ferreira, Olga; Pinho, SimãoThis work discusses the potential of two phosphonium-based ionic liquids (ILs), [P6,6,6,14]Cl and [P6,6,6,14][(C8H17)2PO2], and one methylimidazolium-based IL, [C4mim][OAc], as entrainers in the fractionation of terpene mixtures, in the desulfurization and denitrification of fuel oils, and in the separation of aromatics from aliphatic hydrocarbons. To this aim, the activity coefficients at infinite dilution of 45 solutes were obtained by gas-chromatography in the temperature range (333.15–458.15) K. Selectivities and capacities were calculated showing that [P6,6,6,14]Cl is adequate for the fractionation of (−)-menthone/L-(−)-menthol mixture, being also a suitable option for the deterpenation of citrus essential oil, and the removal of thiophene and pyridine from aliphatic hydrocarbons. To complement the experimental measurements COSMO-RS model was tested, demonstrating good potential to screen separation agents and give insights for several important separation problems, including the removal of contaminants from fuels and the isolation, fractionation and purification of terpenes mixtures.
- Liquefying flavonoids with terpenoids through deep eutectic solvent formationPublication . Teixeira, Gabriel; Abranches, Dinis O.; Silva, Liliana P.; Vilas-Boas, Sérgio M.; Pinho, Simão; Ferreira, Ana I.M.C. Lobo; Santos, Luís M.N.B.F.; Ferreira, Olga; Coutinho, João A.P.The formation of deep eutectic solvents (DES) is tied to negative deviations to ideality caused by the establishment of stronger interactions in the mixture than in the pure DES precursors. This work tested thymol and menthol as hydrogen bond donors when combined with different flavonoids. Negative deviations from ideality were observed upon mixing thymol with either flavone or flavanone, two parent flavonoids that only have hydrogen bond acceptor (HBA) groups, thus forming non-ionic DES (Type V). On the other hand, the menthol systems with the same compounds generally showed positive deviations from ideality. That was also the case with the mixtures containing the more complex hydroxylated flavonoid, hesperetin, which resulted in positive deviations when mixed with either thymol or menthol. COSMO-RS successfully predicted the behavior of the solid-liquid phase diagram of the studied systems, allowing for evaluation of the impact of the different contributions to the intermolecular interactions, and proving to be a good tool for the design of DES.
- Using Molecular Conformers in COSMO-RS to Predict Drug Solubility in Mixed SolventsPublication . Cordova, Isabella Weber; Teixeira, Gabriel; Ribeiro-Claro, Paulo J.A.; Abranches, Dinis O.; Pinho, Simão; Ferreira, Olga; Coutinho, João A.P.This work explores the impact of solute conformers on the conductor-like screening model for real solvents (COSMO-RS) solubility predictions of vanillin and ethyl vanillin in water, short alcohols, and their mixed solvents. Two major conformers of these solutes and changes with solvent polarity were experimentally established by Raman spectroscopy and further confirmed by density functional theory calculations. The COSMO-RS predictions using the individual conformers show a poor description of the solubilities. Estimation with the COSMO-RS default conformer distribution gave better predictions and an intermediate behavior between the predictions obtained using each individual conformer. To further improve the description of the solubilities, the weight of each conformer was fitted to the experimental solid-liquid equilibrium data of the solute in a pure solvent at different temperatures. Better solubility predictions in ternary systems describing solubility maxima were found, suggesting a semipredictive approach to COSMO-RS. This method can predict the liquid-liquid oiling-out effect in the studied binary and ternary systems.