A crossover of the solid substances solubility in supercritical fluids: what is it in fact?

Journal of Molecular Liquids. 2021. Vol. 334. Article 115997.

Kalikin N., Oparin R. D., Kolesnikov A. L., Budkov Y., Kiselev M. G.

We investigate a well-known phenomenon of the appearance of the crossover points, corresponding to the
intersections of the solubility isotherms of the solid compound in supercritical fluid. Opposed to
the accepted understanding of the existence of two fixed crossover points, which confine the region of
the inverse isobaric temperature dependence of the solubility, we have found that these points tend to shift
with the change of the temperature and in the limit of the certain threshold value they converge to a single
point. We demonstrate this analyzing the solubility data of a set of poorly soluble drug compounds, which
have been computed in a wide area of the phase diagram via the approach, based on the classical density
functional theory. Thorough analysis of the available in the literature experimental solubility data is found
to be in an agreement with our conclusions, as one can find that the wider temperature region of the experimental
study is, the more pronounced effect of the crossover points drift can be observed.

Keywords: Classical density functional theory, сверхкритические флюиды, Solubility, Supercritical fluids, Растворимость, Теория классического функционала плотности