Experimental and thermodynamic analyses of supercritical CO2-Solubility of minoxidil as an antihypertensive drug

A major challenge in the production of micro/nano-sized drug particulates is to understand the solubility behavior of the drug in a supercritical fluid (SCF). In the present study, solubility of Minoxidil, an antihypertensive drug, in SC-CO2 was measured statically under various sets of operating conditions in terms of temperature (308-338 K) and pressure (120-270 bar), leading to solubilities in the range of 0.24 x 10(-6) to 3.39 x 10(-6). Next, three different approaches were followed to estimate, rather than actually measure, the solubility, where models based on two equations of state (i.e., Soave-Redlich-Kwong (SRK) and Peng-Robinson (PR)) combined with either Wong Sandler (WS) or van der Waals (vdW2) mixing rules, semi-empirical equations (Mendez-Santiago and Teja (MST), Bartle et al., Chrastil, Kumar and Johnston (K-J)), and the activity coefficient (UNIQUAC and modified Wilson models) were adopted to model the experimental data. The semi-empirical models were proved to be self-consistent upon performing the respective self-consistency tests. Eventually, results were devised to calculate estimates of the vaporization (Delta H-vap), solvation (Delta H-sol) and total enthalpies (Delta H-total). (C) 2020 Elsevier B.V. All rights reserved.