Use of the LeVan—Vermeulen isotherm model for the calculation of elution band profiles in non-linear chromatography

Abstract

The two-term LeVan—Vermeulen isotherm is the simplest competitive isotherm based on the ideal adsorbed solution model. It applies when both components follow individually the single-component Langmuir isotherm model. It takes into account the influence of the difference in the column saturation capacity for these two components. Individual band profiles calculated with this isotherm are in qualitative agreement with experimental results. They exhibit a stronger displacement effect, a weaker tag-along effect and a higher degree of band separation than predicted by the Langmuir competitive isotherm when the column saturation capacity is larger for the second component than for the first. Conversely, when the column saturation capacity is larger for the first component than for the second, the displacement effect is less intense and the tag-along effect is stronger than with the competitive Langmuir isotherm and the separation deteriorates. When the sample size is increased, a reversal of the elution order is observed.