End-label, free-solution capillary electrophoresis of highly charged oligosaccharides.

The effect of fluorescent tags on the separation of negatively charged oligosaccharides, derived from a partially hydrolyzed kappa-carrageenan, was studied. When the charge-to-friction ratio of oligosaccharides is increased by the end-label, the migration order is from smaller to larger oligomers, and the resolution of larger oligomers could be improved by using a sieving medium. The migration order can be entirely reversed when the charge-to-friction ratio of the solute is decreased by the end-label. The experimental electrophoretic mobilities obtained in this work are in excellent agreement with the recently reported theoretical model (Mayer, P.; Slater, G. W.; Drouin, G. Anal. Chem. 1994, 66, 1777-1780). The maximum number of separated oligomers (Mmax) as a function of applied voltage and injection time was also studied, but no strong dependencies were found. Resolution between small oligomers could be significantly improved by following this separation principle.