Solubility and solid phase studies of isomeric phenolic acids in pure solvents

• Published in: Journal of molecular liquids Vol. 272; pp. 1048 - 1057
• Main Authors: Vilas-Boas, Sérgio M., Brandão, Paula, Martins, Mónia A.R., Silva, Liliana P., Schreiner, Tatiana B., Fernandes, Luciano, Ferreira, Olga, Pinho, Simão P.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.12.2018
• Subjects: Melting; NRTL-SAC; Phenolic acids; Solubility; X-ray diffraction; X-ray diffraction; NRTL-SAC; Melting; Phenolic acids; Solubility
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/j.molliq.2018.10.108

The solubilities of gallic, protocatechuic, gentisic or α-resorcylic acids were measured in nine pure solvents (water, methanol, ethanol, 1-propanol, 2-propanol, 2-butanone, ethyl acetate, acetonitrile and dimethylformamide) at 298.15 K and 313.15 K, using the analytical isothermal shake-flask method. Additionally, solid phase studies of the selected phenolic acids were carried out using differential scanning calorimetry (DSC) and X-ray diffraction (XRD), giving access to important data on melting properties as well as on the structure of the solid phase before and after the dissolution. The NRTL-SAC model coupled to the reference solvent approach (RSA) were applied to correlate the solubility data in a set of seven solvents and, after used to predict the solubility in 1-propanol and dimethylformamide. Average relative deviations (ARD) between 28 and 40% for the correlation and between 16 and 59% for the predictions were obtained. These values are within the order of magnitude usually found for such type of semi-predictive models, using a limited set of data. [Display omitted] •Solubility of four phenolic acids in nine solvents was measured at 298.15 and 313.15 K.•Phenolic acids melting temperature and enthalpy were estimated.•New solid phases were identified by X-ray diffraction.•An extensive comparative analysis shows the relevance of the new data.•Modelling approach calls for new developments for such a vast family of compounds.