Isomeric distinction of small oligosaccharides: a bottom-up approach using the kinetic method.

Isomeric distinction of di- and tri-saccharides could be efficiently achieved by using data previously obtained while performing experiments aimed at discriminating monosaccharides using trimeric ion dissociation with data analysis by the kinetic method. This study shows that effects observed for lower homologues when one of the partners is changed in the metal/reference system (typically a transition metal divalent cation associated to amino acids) can be extrapolated to upper homologues, at least for the tested analyte series. Systems allowing galactose, glucose, and fructose distinction were used as starting conditions to resolve cellobiose, lactose, maltose, and saccharose disaccharides. When a unique dissociation reaction was observed from the trimeric clusters, a new reference was selected based on its propensity to favor the analyte or the reference release, as revealed from monosaccharide experiments, depending on the desired effect. The same approach could be implemented from data obtained for disaccharides to select efficient metal/reference systems to distinguish cellotriose, isomaltotriose, maltotriose, and panose trisaccharides. As a result, method optimization is greatly improved due to an enhanced rationalization of the search for discriminant systems. While 40 systems had to be tested for monosaccharides, by screening five transition metals and eight amino acids, the proposed approach allowed efficient metal/reference systems to be found for disaccharides after testing 18 combinations; then, only four systems had to be scrutinized to achieve trisaccharide distinction. Accurate quantitative analyses could be performed in binary mixtures using three-point calibration curves to correct for competition effects between analytes for the formation of the trimeric clusters.