Influence of pressure on solute retention in liquid chromatography

Abstract

Confirming recent, independent experimental results, simple considerations of thermodynamics show that the logarithm of the retention factors of solutes vary linearly with increasing pressure, in the pressure range most commonly used (0–200 atm). The coefficient of this dependence increases linearly with the difference between the partial molar volumes of the solute in the stationary and the mobile phases. For homologues, this coefficient increases linearly with the number of carbon atoms and with the difference, Δ V CH 2 , between the partial molar volumes of a CH 2 group in the two phases. The pressure dependence of the retention factor may be significant because for a C 18—methanol system Δ V CH 2 / V CH 2 is of the order of 6%.