A Kinetic and Quantitative Approach to Peak Splitting Phenomena When Using 2-Propanol as Modifier in Adsorption HPLC

Abstract

When using 2-propanol as a modifier in adsorption chromatography, a “satellite” peak is observed if a shight excess of a polar chlorinated hydrocarbon, such as CH₂Cl₂, is injected.

This satellite peak whose appearance is related to the presence of 2-propanol, has been identified as a part of the CH₂Cl₂ injected. The satellite peak behaves chromatographically mainly as a normal solute peak and its area is proportional to both the amount of CH₂Cl₂ injected and the concentration of 2-propanol in the mobile phase and on the other hand inversely related to the flow-rate and the concentration of CH₂Cl₂ in the mobile phase.

A physico-chemical model is proposed based on the perturbance of the dynamic equilibrium when the sample enters the column. The model is compatible with the experimental results and explains the origin of the satellite peak as well as its chromatographic behaviour. It also allows a better understanding of the role of a modifier related to its adsorption-desorption process.