Partial solvation parameters (PSP) have much in common with the Hansen solubility\nparameter or with a linear solvation energy relationship (LSER), but there are advantages based on\nthe sound thermodynamic basis. It is, therefore, surprising that PSP has so far not been harnessed\nin pharmaceutics for the selection of excipients or property estimation of formulations and their\ncomponents. This work introduces PSP calculation for drugs, where the raw data were obtained from\ninverse gas chromatography. It was shown that only a few probe gases were needed to get reasonable\nestimates of the drug PSPs. Interestingly, an alternative calculation of LSER parameters in silico did\nnot reflect the experimentally obtained activity coefficients for all probe gases as well, which was\nattributed to the complexity of the drug structures. The experimental PSPs were proven to be helpful\nin predicting drug solubility in various solvents and the PSP framework allowed calculation of the\ndifferent surface energy contributions. A specific benefit of PSP is that parameters can be readily\nconverted to either classical solubility or LSER parameters. Therefore, PSP is not just about a new\ndefinition of solvatochromic parameters, but the underlying thermodynamics provides a unified\napproach, which holds much promise for broad applications in pharmaceutics.
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