Separation and Quantification of Fructan (Inulin) Oligomers by Anion Exchange Chromatography

Abstract

ABSTRACT Accurately quantifying inulins according to their degree of polymerization (DP) has long challenged fructan researchers. This paper describes recent advances in anion exchange chromatographic separation and improved quantification of inulin oligomers up to DP 8. Pure inulin standards were prepared by fractionating water-soluble carbohydrate extracts of Jerusalem artichoke ( Helianthus tuberosus L.) tubers using gel permeation chromatography. Samples of each pure inulin oligomer were freeze-dried and used to prepare aqueous standards of known concentrations. Elution times in a Dionex anion exchange (HPAE) system run isocratically increased non-linearly with increasing DP. Separation times for polysaccharides up to DP 40 were reduced by the use of a sodium acetate gradient. Responses by the pulsed amperometric detector (PAD) per μ g of inulin decreased in a regular manner as DP increased. Inulin polysaccharides become increasingly difficult to quantify as DP increases. In spite of this limitation, high-performance anion exchange chromatography with pulsed amperometric detection provides a convenient and rapid method to separate and quantify inulins of low to moderate DP.