2 research outputs found
Predicting the Aqueous Solubility of Pharmaceutical Cocrystals As a Function of pH and Temperature
The
solubility of pharmaceutical cocrystals in aqueous solution
is influenced by pH-dependent dissociation and salt formation which
complicates the design of cocrystal formation and purification processes.
To increase the efficiency of those processes, the aqueous solubility
of pharmaceutical cocrystals was predicted in this work using perturbed-chain
statistical associating fluid theory (PC-SAFT). Modeling results and
experimental data of pH-dependent solubilities were compared for the
weak base nicotinamide, the weak acid succinic acid, their 2:1 cocrystal,
as well as for all occurring salts at 298.15 and 310.15 K. It was
found that the pH-dependent acid–base equilibria of nicotinamide
and succinic acid directly influence the solubility of their cocrystal
and their salts. By accounting for the thermodynamic nonideality of
the components in the cocrystal system, PC-SAFT is able to predict
the solubility behavior of all above-mentioned components in good
agreement with the experimental data
Predicting the Effect of pH on Stability and Solubility of Polymorphs, Hydrates, and Cocrystals
Cocrystal
formation processes from aqueous solutions are often
affected by pH-dependent dissociation, polymorphic transitions, and
formation of hydrates and salts. To enhance the efficiency of those
processes, the aqueous stability and solubility of pharmaceutical
cocrystals were predicted in this study using the perturbed-chain
statistical associating fluid theory (PC-SAFT). The solubilities in
the binary systems caffeine/water and oxalic acid/water were modeled
including hydrate formation and polymorphic transitions between the
corresponding anhydrate forms I and II. Moreover, pH-dependent solubilities
of these hydrate-forming components, their 2:1 cocrystal, and all
appearing salts were measured and modeled at 298.15 K. It was found
that the pH-dependent acid–base equilibria of caffeine and
oxalic acid directly influence the stability and solubility of their
cocrystal, their hydrates, and salts. In consideration of the thermodynamic
nonideality of the components in the cocrystal system, PC-SAFT enables
solubility predictions of the before-mentioned components as well
as if any cocrystal is formed at given conditions of pH and temperature