Solubility-Modifying Power of Zwitterionic Salts

The separation of small, hydrophilic molecules from aqueous solutions on one side and the dissolution of hydrophobic organic molecules in water on the other are nowadays among the most difficult challenges in chemical and bio-technology. Even though these two tasks are seemingly of opposite nature, it is demonstrated herein that both processes can be facilitated by addition of zwitterionic salts, a new class of compounds that can act either as a solubility enhancer or a phase-separation promoter depending on the structure of the solute dissolved in an aqueous solution. At a more fundamental level, this study investigates the salting in/out propensity of the ions and supports the importance of both salt-solute interaction and their concentration.