Application of Ocik's Equation for Description of Solute Retention in RP HPLC and Calculation of Retention Factor in Water

Ocik's Equation, assuming the partition displacement model for a chromatographic process is proposed, for the description of solute retention in reversed phase liquid chromatography. Moreover, a numerical method of calculation of solutes retention factors in water, derived from the linear form of this Equation is presented. Theoretical investigations are applied to the literature of the RP HPLC results obtained for a group of model solutes, i.e., alkyl benzene homologues and test substances of different polarities chromatographed using three chemically bonded stationary phases: RP-8 (octylsilyl-silica), ODS (octadecylsilyl-silica) and PLRP-S (polystyrene-divinylbenzene polymer, PS-DVB) and water-methanol and/or water-acetonitrile mixtures as effluents. Calculated chromatographic parameters were analyzed as hydrophobicity indices and related to experimental and calculated log P values.