Understanding the Solubility behaviour of Ibuprofen and Xylitol in Natural Deep Eutectic Systems through Hansen Solubility Parameters and Physicochemical Properties

• The solubility behaviour of Xylitol and Ibuprofen various Natural Deep Eutectic systems (NADES) was explored. • Hansen Solubility Parameters (HSPs) were correlated with the experimental data of the solubility. • Theoretical models help screen good/bad NADES for solutes, but 1D HSPs affinity success doesn’t ensure the same in 2D. • Except for the dispersion parameter (δ d ), all the other HSPs showed a good correlation with solubility. • Surface tension, density and molar volume showed good correlations with the solubility data. Most of the recent studies have been praising the peculiar ability of deep eutectic systems (DES), especially the natural-based ones (designated by NADES), in dissolving a wide variety of compounds. Despite their remarkable physicochemical properties, it is still true that little is known about the factors that would help to comprehend their interesting behaviour when they are used as solvents. Hence, it is important to gather as many tools as possible that can be useful for understanding it. First, the affinity degrees between the two selected compounds (Ibuprofen and Xylitol) and the various NADES, were analysed using Hansen Solubility Parameters (HSPs), which confirmed to be a good tool for screening good and bad NADES for solubilising Ibuprofen and Xylitol. Although, in general, the empirical models (EM) such as the one proposed by Hoftyzer-Van Krevelen and Fedors (HKF) and Yamamoto (Ymt) performed better than the semi-empirical models (SEM), when it came to assessing affinity, it was found that this actually depends on the type of assessment carried out, i.e., if it is in 1- or 2-dimension. Furthermore, it was also found that, except for the dispersive parameter (δ d ), all the others play a significant role in the interaction between the two compounds and NADES, especially the total solubility parameter (δ t ). Finally, the correlations between a set of physiochemical properties of NADES and the solubility data were evaluated in this work where it was possible to conclude that surface tension, density and molar volume are those that present the highest contribution for the variations in the solubility.