Capillary zone electrophoresis of derivatized acidic monosaccharides

A new and specific precolumn derivatization reaction for acidic monosaccharides was introduced and evaluated in the separation and sensitive detection of carbohydrates by capillary electrophoresis. The derivatization reaction involved the attachment of sulfanilic acid (a UV absorbing tag) or 7‐aminonaphthalene‐1,3‐disulfonic acid (a UV absorbing and fluorescing tag) via a condensation reaction between the amino group of the derivatizing agent and the carboxyl group of the sugar in the presence of a water‐soluble carbodiimide. The derivatization reaction replaced the weak carboxylic acid of the sugar by a strong sulfonic acid, which is fully ionized at all pH. This allowed the electrophoresis of the sugar derivatives over a wide pH range and permitted the determination of acidic carbohydrates at very low femtomole levels by UV and fluorescence detection.