Capillary Electrophoresis for Monitoring Chemical Reactions: Sulfation and Synthetic Manipulation of Sulfated Carbohydrates

Abstract

The lack of a simple and rapid method for the analysis of structurally similar, highly charged, carbohydrates has made monitoring their chemical modification much more difficult than in traditional synthetic reactions where thin-layer chromatography (TLC) is used. High-performance liquid chromatography (HPLC), frequently used in the analysis of reaction mixtures, requires substantial sample preparation and long analysis times. Capillary electrophoresis (CE) allows rapid, repetitive, high-resolution analysis with little, if any, sample preparation. The use of CE as an analytical tool for a large variety of chemical compounds has seen a rapid increase in recent years [ 1]. CE separates analytes in a narrow fused silica capillary (50-100/zm × 0.5-1 m) under high voltage (5-25 kV) [2]. Under normal polarity separations, a small amount of concentrated sample in a basic buffer is applied at the anode and detected at the cathode. Negative analytes, such as sulfated sugars, are prevented from migrating under electro horesis toward the anode by the bulk flow of solvent towards the cathode. This electroosmotic flow is caused by the applied voltage across the charged silinol residues (resulting from the basic buffer) of the capillary column [ 1,2]. Applications for carbohydrates have included analysis and separation of highly charged glycosaminoglycans and their derivatives, sialic acid containing oligosaccharides, and carbohydrates derivatized with charged groups [ 2 ]. The utility of CE to follow chemicalreactions of highly charged carbohydrates of very similar structure has not yet been reported.