SEPARATION OF GLUCOSE POLYMERS BY HYDROPHILIC INTERACTION CHROMATOGRAPHY ON AQUEOUS SIZE-EXCLUSION COLUMNS USING GRADIENT ELUTION WITH PULSED AMPEROMETRIC DETECTION

Maltooligosaccharides were submitted to hydrophilic interaction chromatography on three aqueous size-exclusion columns. When mobile phase compositions were 0% to 40% (v/v) acetonitrile in water, the chromatographic mechanism was by size exclusion on all three columns; at concentrations greater-than-or-equal-to 50% (v/v) acetonitrile, the carbohydrates were fractionated by partition chromatography (0.88 > k' > 143; where k' is the solute capacity factor), and the order of elution was reversed. When maltooligosaccharides were eluted from the three columns using isocratic mobile phases in which the concentration of acetonitrile was varied from 50% to 75% (v/v), a negative linear relationship (R2 > -0.973) existed between retention and solvent strength; retention increased as the polarity of the mobile phase was decreased. When the composition of the mobile phase was 65% acetonitrile in water, a correlation (R2 > 0.99) was found in all three columns between the degree of polymerization and the retention of the oligosaccharide. With gradient elution, the Protein-Pak 60 column resolved N-acetylneuraminic acid, rhamnose, arabinose and a mixture of commercially available glucose polymers; the between-run precision of the retention times (n = 16) for the chromatography varied from 0.09 to 0.64% (relative standard deviation). The chromatography was applied to the analysis of enzyme-hydrolyzed starch digests.