Nonlinear liquid-liquid chromatography: Modeling of the influence of the operating parameters on the elution profiles of cannabinoids.

In liquid-liquid chromatography (LLC), the volume of the stationary phase and the contact area between the mobile and stationary phases depend on the mobile phase flow rate and rotational speed (i.e., the g-force) applied to keep the liquid stationary phase in the column while pumping the mobile phase. Additionally, the volume and concentration of the injected mixture influence the separation resolution. The potential of mechanistic models for the selection of operating conditions in LLC remains untapped. In this study, the effects of the operating conditions on the elution peak shape of two model compounds, cannabidiol (CBD) and cannabigerol (CBG), were systematically investigated using hexane/methanol/water as the solvent system. The elution profiles of the solutes were modeled with Martin and Synge's equilibrium cell model. CBD and CBG distribution equilibria for the upper phase as the stationary phase were described using an anti-Langmuir-type correlation. The model provided very good predictions of the elution profiles in both the linear and nonlinear ranges of the distribution equilibria under the studied operating conditions. The results of this work highlight the potential of mathematical modeling for LLC process parameter selection.