Solubility of amiodarone hydrochloride in aqueous co-solvent mixtures revisited: IBKI preferential solvation analysis

Abstract

The preferential solvation parameters (δx1,3) of amiodarone hydrochloride (AMDH) in three binary solvent mixtures of ethanol (1)+water (2), N-methyl pyrrolidone (NMP) (1)+water (2) and propylene glycol (1)+water (2) were derived from their available solubility data by using the inverse Kirkwood–Buff integrals method. The values of δx1,3 varied non-linearly with the co-solvent (1) proportion in all the aqueous mixtures. For the system of ethanol+water, the values of δx1,3 were negative in water-rich mixtures and co-solvent-rich mixtures, but positive in intermediate compositions. However, for the propylene glycol (1)+water (2) mixtures with composition 0.167<x1<1 and NMP (1)+water (2) mixtures with composition 0.20<x1<1, the δx1,3 values were positive indicating that AMDH is preferentially solvated by co-solvent. The positive δx1,3 values could be explained on the basis of the higher acidic behavior of AMDH molecules interacting with the hydrogen acceptor groups present in co-solvent.