Full length articleThe use of Ościk's equation to describe the retention in reversed phase liquid chromatography

- Everett's equation describes the composition of a surface phase in RP LC system.
- Ościk's equation describes in sufficient detail the retention in the RP LC system.
- In RP LC system adsorption determines the formation of a surface phase.
- Distribution of a solute in RP LC proceeds according to the partition mechanism.

The Ościk's equation based on the theory of conformal solutions was used to describe the chromatographic process in RP-HPLC. Theoretically calculated values of the logarithms of retention factors (logk) were compared with experimental values for a group of aromatic substances, i.e. alkylbenzenes, PAHs, and polar benzene derivatives. Studies were conducted using two columns: RP-18 and RP-4, as well as water-methanol and water-acetonitrile mixtures as mobile phases.The applicability of Everett's equation to describe the composition of surface phase was also verified. For this purpose, the excess methanol adsorption isotherm on LiChrospher RP-18e, was experimentally determined.