In Hydrophobic Interaction Chromatography (HIC) the sample interacts, at high mobile phase salt concentration, with a hydrophobic stationary phase.
It is eluted from the stationary phase by decreasing the salt concentration. Almost all biological molecules have hydrophobic patches which, under physiological conditions, are shielded by hydrophilic or ionic groups.
HIC is particularly attractive for protein purification when the sample is solved in high salt concentration.
In contrast to reverse phase chromatography (RPC), the biological activity of the eluted molecules is maintained in HIC. It is used increasingly as a substitute for ammonium sulfate precipitation because of higher throughput and greater recovery of enzymatic activity.
The strength of HIC is influenced strongly by the nature of the salt component in the mobile phase.