Die sorption organischer moleküle an verestertem siligakel : I. Sorptionswärmen als schlüssel zu einem sorptionsmodell

Abstract

Adsorption of organic molecules on esterified silica gel. I. Heat of adsorption as a key to a model of adsorption Silica gel was dehydrated at high temperatures and the remaining silanol groups were esterified with polyethylene glycol 200. Good stationary phases for gas chromatography were obtained by this method, differing in the surface density of the surface-bonded alcohol molecules. Heats of adsorption of different organic molecules were determined by gas chromatographic methods. A linear relationship between heat of adsorption and surface density of the esterified alcohol molecules was found. From these data a model for the adsorption mechanism was assumed: Generally the strength of the surface field of the silica gel determines the adsorption. This field is more or less weakened depending on the size and surface density of the esterified alcohol molecules. The nature of the alcohol affects the adsorption only if it contains a polar functional group in the ω-positiom which differs essentially from the silanol groups.