Insight into a direct solid–solid transformation: a potential approach for the removal of residual solvents

Here we report two new crystal forms of adenosine 3',5'-cyclic monophosphate sodium and the discovery of the direct solid-solid transformation process from its methanol trihydrate (solvate) to its pentahydrate form (hydrate) that is only mediated by humidity. These findings provide a potential approach for the removal of residual solvents in the manufacturing of pharmaceuticals and food additives.