RETENTION MECHANISM IN REVERSED-PHASE LIQUID-CHROMATOGRAPHY - SPECIFIC EFFECTS OF PROPIOPHENYL AND MULTIFUNCTIONAL (CYANOPROPYL-OCTADECYL) BONDED SILICAS

Accurate measurements of the retention of homologous series were made on a phenyl-3-propyl-bonded silica and on a multifunctional silica (si multaneously bonded with n-octadecyl and cyanopropyl groups). It is sh own that the retention of these types of phases is governed by their h ydrocarbonaceous part, as on pure n-alkyl-bonded silicas. Energetic co nsiderations gained from plots of log k' vs. log k' allow one to chara cterize global effects of an organic modifier on the chromatographic e quilibrium. In particular, the influence of pi-pi interactions on rete ntion is shown. These types of curves enable one also to compare diffe rent columns in RPLC. In a general way it is shown that the specific e ffects are superimposed on the effect of hydrocarbonaceous parts, whic h is always predominant, The mechanism of insertion of the solute is a lways valid and multifunctional phases are intermediate between pure a lkyl-bonded silica and functionalized phases.