DETERMINATION OF OLIGOSACCHARIDES BY CAPILLARY ZONE ELECTROPHORESIS

Oligosaccharides occur in various biological materials, and the alpha-galactosides raffinose, stachyose, verbascose and ajugose are important in relation to the quality or nutritive value of legume seeds. A simple technique for the isolation and group separation of oligosaccharides was developed as an appropriate purification step prior to determination of the individual oligosaccharides by high-performance capillary electrophoresis (HPCE). The HPCE technique adapted to the separation of alpha-galactosides was based on capillary zone electrophoresis (CZE) in berate buffers with UV detection at 195 nm. The influence of various separation conditions, including voltage, pH, temperature and buffer composition, on the resolution, migration times, number of theoretical plates and peak areas was studied by the use of galactinol and the mono-, di-, tri- and tetra-alpha-galactosides of sucrose. Up to about 375 000 plates/m were obtained with the described CZE method. Tests of repeatability and linearity and the use of internal standards and relative response factors were used for evaluations of the qualitative and quantitative aspects of the method. With the combined technique of group separation, purification and CZE, a rapid and efficient method for the determination of naturally occurring oligosaccharides is now available for even complex mixtures of these carbohydrates.