Hydrophobic Interaction Chromatography (HIC) is a gentle technique compared to reversed-phase LC for the binding and desorption of hydrophobic proteins. The use of aqueous mobile phases in HIC is less likely to disturb protein conformation and results in better activity recovery. Biomolecules adsorb to a weak hydrophobic surface at high salt concentrations and are eluted by a decreasing salt gradient. As a result, hydrophobic interaction chromatography combines the gentleness of salt precipitation with the precision of chromatography, for excellent recovery of protein activity. TSKgel BioAssist Phenyl columns are constructed from PEEK (polyether ether ketone).