Abstract
A mixed retention mechanism was studied in gas-liquid chromatography of some hydrocarbons and dialkyl ethers using packed columns of silica gel beads coated with different amounts of tricresyl phosphate (TCP). Two adsorption equilibria, on solid surface of silica gel and on organic surface of a monolayer of TCP dominantly contribute to solute retention until the silica gel surface is completely covered with a monolayer of TCP. For hydrocarbons, adsorption on solid surface of silica gel is promoted by formation of a weak 1:1 solute-TCP adduct through lateral interaction between adsorbed solute and TCP molecules. An excess of TCP over an amount necessary for formation of the monolayer on the whole of silica gel surface forms a bulk liquid on the deactivated surface of silica gel, so that bulk solution partition concurrently contributes to solute retention, together with adsorption on the TCP monolayer. Distribution constants of these sorption equilibria could be calculated as reasonable values for any solute.
