Analysis of oligosaccharides by MEKC with aminobenzoic alkyl esters as derivatization agents

Oligosaccharides derivatized with various aminobenzoic esters and aminobenz onitrile were separated by micellar electrokinetic capillary chromatography (MEKC) with sodium dodecyl sulfate (SDS). Methyl, ethyl and butyl aminoben zoates as well as aminobenzonitrile were used as the derivatization agents for homologous maltodextrins and the oligosaccharides from human milk. The polarity of the label had a significant influence on the partition between the aqueous and the micellar phases. Butyl aminobenzoate derivatives exhibi ted the longest retention times and the best resolution of the sugars. In c ontrast, derivatives of aminobenzonitrile gave the poorest separations owin g to their relatively high polarity. The retention times of the oligosaccha rides are inversely related to the degree of polymerization (DP) of the car bohydrates. Malto-oligosaccharides up to a DP of 10 could be resolved. The separation method was optimized with respect to the SDS concentration and t he capillary temperature. Optimal resolution was found with a buffer consis ting of 20 mM phosphate, pH 7.0, with 50 mM SDS at a temperature of 30 degr ees C. Oligosaccharides from human milk could be separated by the optimized method. The separation by MEKC showed a similar profile as that obtained b y reversed-phase capillary HPLC, which demonstrates the analogy of the rete ntion mechanism of both techniques.