A new adsorption-partition model of solute retention in chromatographic systems with chemically bonded stationary phases

This paper describes an attempt to derive a new model of solute retention f or liquid chromatography (LC) with chemically bonded stationary phases. In our new model we intended to reflect the physicochemical nature of the proc ess more closely than in any of the approaches currently used, To this end we intended to derive a retention model capable of quantitative description of contributions of two complementary processes occurring in parallel duri ng the course of solute migration through the stationary phase bed. One of these can be described as intermolecular interactions of a solute with the chemically bonded organic ligands; in our new model this first contributory mechanism has been quantified in the spirit of the classical Snyder model of solute retention. The other consists in intermolecular interactions of a solute with the free (i.e. nonbonded) silanols on the surface of the silic a matrix. In our approach this second contributory mechanism was modeled wi th aid of a simple stoichiometric isotherm, taking into account the adsorpt ion of the molecules of a solute and of the components of a mixed eluent. T he overall (i.e. mixed) mechanism of solute retention was ultimately given as a sum of the two contributions. The performance of our new model was extensively tested with abundant exper imental results originating from the literature. For verification we used r etention data, obtained for 3-cyanopropyl silica (normal-phase (NP) TLC), o ctadecylsilica (reversed-phase (RP) TLC), dimethylsilica (RPTLC), and dimet hylsilica also impregnated with paraffin oil (RPTLC). The outcome of this t est led to the general conclusion of a remarkably good fit of the experimen tal results to the master equation of our new model.