EFFECT OF COVERAGE DENSITY ON THE RETENTION MECHANISM IN REVERSED-PHASE HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY

The chromatographic properties of reversed-phase high-performance liquid chromatographic (RP-HPLC) packings with chemically bonded C18 groups of controlled coverage were characterized by correlation of the capacity factor and the composition of the mobile phase, taking physico-chemical properties of the packings into account. On the basis of a cylindrical model of pores and the dependence of retention on density and homogeneity of the surface coverage with alkylsilyl ligands, an attempt was made to describe the retention mechanism in the RP-HPLC system. It was found that packings with a coverage density higher than 3.8 μmol/m2 were dense, homogeneous and shielded the unblocked surface silanol groups sufficiently. © 1990.