Interfacial behavior of selected biologically and technologically relevant ions is studied using
molecular dynamics simulations employing polarizable potentials. Propensities of choline,
tetraalkylammonium (TAA), and sodium cations, and sulfate and chloride anions for the air/water
interface are analyzed by means of density profiles. Affinity of TAA ions for the interface increases
with their increasing hydrophobicity. Tetramethylammonium favors bulk solvation, whereas cations
with propyl and butyl chains behave as surfactants. The choice of counter-anions has only a weak
effect on the behavior of these cations. For choline, sodium, chloride and sulfate the behavior at the
air/water interface was compared to the results of our recent study of segregation of these ions at
protein surfaces. No analogy between these two interfaces in terms of ion segregation is found.