Pentane-Methanol Mixture as a Model of the Stationary Phase in Reversed-Phase Liquid Chromatography Using Octadecyl-Bonded Silica Gel and Methanol

Abstract

A pentane-methanol mixture was taken as a convenient model of practical stationary phase functioning in the reversed-phase liquid chromatography (RPLC) system consisting of octadecyl-bonded silica gel (ODS) and methanol. The capacity factor (k′) of tris(β-diketonato)chromium(IH) or bis(β-diketonato)palladium(II) observed in the ODS/methanol system was compared with the ratio of the solubility of the complex in a pentane-methanol mixture to that in methanol. A pentane-methanol mixture, containing methanol in a mole fraction range 0.42-0.66, was found to be a medium comparable to the stationary phase in the RPLC, because the distribution of the complex was similar. Furthermore, the incorporation of methanol into alkyl-moiety of ODS was confirmed experimentally. The above facts suggest that the stationary phase functioning in the RPLC consisting of ODS and methanol is a mixed phase of the alkyl-moiety of ODS and methanol incorporated from the mobile phase into the moiety for the complex tested.