Influence of pressure on solute retention in liquid chromatography

Although the mobile phase is generally considered to be incompressible in liquid chromatography, the local pressure appears to have a significant effect upon solute retention. In this investigation, laser fluorescence detection was utilized to measure solute retention directly along a reversed‐phase packed capillary column with a methanol mobile phase. For derivatized fatty acids, n ‐C 10:0 to n ‐C 20:0 , the capacity factors increased systematically by +9.3% to + 24.4% under normal operating pressure conditions (1,500 to 5,000 psi). Whereas the magnitude of this increase in solute retention seems surprising, it appears to correlate well with the unified theoretical model developed by Martire.