The effect of pressure and mobile phase velocity on the retention properties of small analytes and large biomolecules in ultra-high pressure liquid chromatography

► The effects of very high pressure (up to 1100 bar) on retention were evaluated in both isocratic and gradient mode. ► The effect of pure pressure was separated from heat effects (frictional heating). ► Significant differences in retention behaviours were observed, depending on the type/size of the analyte. ► Possibly the conformational properties of large biomolecules play important role in their retention properties.