Utilizing experimentally estimated capacity factors and calculated activity coefficients of the solutes in the mobile phase, as well as octadecylsilica stationary phases of varying coverage, the selectivity of separation in a reversed-phase liquid chromatographic system is studied. The retention times were measured for n-alkanes (C5-C7), n-alcohols (C5-C7) and benzene derivatives in methanol - water mobile phases. A strictly linear relationship between the experimentally determined selectivity factor (#x3B1;) and the calculated selectivity factor in the mobile phase (#x3B1;m) is observed. The relative retention in the stationary phase (#x3B1;s) is independent of the mobile phase strength and the silica surface coverage, i.e., #x3B1;sis merely a function of the molecular structure of related solutes. Therefore, a change in surface coverage does not lead to a change in #x3B1;.
展开▼
