3-Aminopropyl-bonded-phase silica, thin-layer chromatographic plates: Their preparation, and application to sugar resolution

Commercially available, precoated plates of silica gel have been derivatized by reaction with (3-aminopropyl)triethoxysilane (3-APTS). The aminopropyl-bonded-phase plates prepared from Adsorbosil-Plus-1, soft-layer prekotes (Alltech Associates, Inc.2) provided optimal resolution of a variety of closely related sugars. Plates were immersed in a 1.0% solution of 3-APTS in hexane for 15 min, washed with hexane, and then dried. The resulting, bonded-phase silica contained 9.7% of 3-aminopropyl groups. Further derivatization could be obtained, but optimal resolution of sugars occurred at this level of aminopropyl substitution. Acetonitrile—water mixtures were used as mobile phases; normal phase chromatography resulted, because increasing the proportion of water resulted in increased mobility of the sugars. Closely related mono-, di-, and tri-saccharides have been resolved more effectively than in such traditional approaches as t.l.c. on plates of cellulose or underivatized silica. Also, significantly less time is required for irrigation of the plates than is normally encountered in the t.l.c. of sugars. “Anomalous” behavior was observed for aldotetroses, aldopentoses, and some aldohexoses and deoxy sugars; these remain at the origin. Two sugars of this series, xylose and rhamnose, have been shown to interact covalently with the amino groups on the derivatized plates.