Because the Dionex ERD 500 is a cation-exchange device, it will remove any cation, and most zwitterions passing through it. The only remedy for cationic carbohydrate recovery is to convert the cationic saccharide to a non-cationic form (e.g., conversion of an amino sugar to an N-acetamido sugar by N-acetylation).
Another cause of poor recovery is excessive residence time in the Dionex ERD 500. This results when low flow-rates are used. Lower flow-rates allow time for greater diffusion of saccharides (especially neutral saccharides) across the Dionex ERD 500 cation exchange membranes.
Under the condition recommended in this manual, (1.0 mL/min) the residence time of a carbohydrate in the Dionex ERD 500 is ≤ 4 seconds where neutral and acidic oligosaccharide recovery is typically 75–100%.