High-performance anion-exchange chromatography for carbohydrate analysis

Although anion-exchange chromatography of innately anionic carbohydrates (such as glycosaminoglycans, polyuronic acids, and polysialic acids) have been performed previously, this review will concentrate on the aspects of chromatography of the neutral carbohydrates under alkaline conditions.For high-performance liquid chromatography of carbohydrate materials in general, the readers are referred to the excellent reviews by Honda (1) and Hicks (2).In 1959, Frahn and Mills (3) showed that hydroxyl groups of carbohydrates can be ionized in strong alkali.This fact was not utilized for anion-exchange chroma-, tography of carbohydrates until 1963.When the strong anion-exchange resins first became commercially available, they were used to "remove" reducing mono-and oligosaccharides (e.g., (4)) and chromatographic separation of reducing carbohydrates were not even considered.Reducing sugars were, however, chromatographed as borate complexes in borate buffers of pH 8-10 (e.g., (5,6)).Chromatography by borate complexing has been quite useful for analytical (7,8) as well as preparative purposes (e.g., ( 9)) until very recently.Austin et al. ( 10) reported chromatographic separations of anomeric glycosides using a strong anion-exchange resin eluted with water.Structurally related antibiotics consisting of amino sugars were successfully separated on Dowex 1 (OH-form) using only water as eluent (11).Dekker (12) separated nucleosides on the same column, using a methanol-water mixture.Subsequently methyl glycoside anomers of neutral and amino sugars were separated on Dowex 1 (OH-form) (13,14).Commercially available strong anion-exchange resins used in these applications were of high capacity, capable of handling hundreds of milligrams on a resin bed of