The retention mechanisms of small mols. on a wide range of stationary phases using different mobile phase compositions are one of the most discussed topics in current state-of-the-art supercritical fluid chromatog. (SFC).

Although various theories have been published on retention behavior, prediction, and stability over time, an in-depth insight into the mechanisms is still lacking.

Our study focused on the description of the retention mechanisms on columns with amine moieties, i.e., 2-ethylpyridine, 2-picolylamine, 1-aminoanthracene, and diethylamine, dedicated to SFC, using three different compositions of organic modifier, i.e., methanol, methanol + 10 mmol/L NH₃, and methanol + 2% H₂O, in CO₂.

An extensive set of analytes characterized by more than 200 mol. descriptors was used.

The importance of the effect of each mol. descriptor on the retention behavior was determined by artificial neural networks.

Thus, the descriptors increasing and/or decreasing retention on individual columns using different mobile phase compositions were defined.

The data collected over one year of column use were statistically evaluated to describe the retention behavior of small mols. on the tested stationary phases using three organic modifiers and to describe the changes in retention behavior over time.

As the development of the SFC method can be laborious and time-consuming, this publication offers a detailed description of the interactions taking place between the analyte and the SFC stationary phase.

Understanding these fundamental processes will enable faster development of SFC methods using quality-by-design principles.