ABSTRACT
High performance liquid chromatographic (HPLC) separations of complex carbohydrates are now sufficiently developed that isomeric species in com plicated mixtures can be resolved as single peaks (for review, see Ref. 1). The term oligosaccharide mapping has been applied to such higher resolu tion chromatographic analyses and different HPLC methods, singly or in combination, are currently employed [2-8], High pH anion-exchange chro matography (HPAEC) with pulsed amperometric detection (PAD) has of ten been used for “mapping” complex carbohydrates from glycoproteins [2-4,6-8]. The method has the distinct advantage that not only can oligo saccharides be separated according to size, charge, and linkage isomerism, but also that low nanomole amounts of carbohydrates can be detected in column effluents without derivatization (for review, see Refs. 9 and 10). However, artifactual peaks occur from several sources in HPAEC-PAD chromatograms. A duplicity of peaks results from base-catalyzed epimeri zation of the reducing GlcNAc residue of N-linked oligosaccharides [11]. Oligosaccharides with 3-O-substituents on the reducing end residue readily undergo base-catalyzed elimination from the 0 carbon [12,13], which can be avoided by preparation of the alditol form before chromatography [11,14,
♦Current affiliation: Astra Draco AB, Lund, Sweden.
