Carbohydrate Membrane Desalter

The Dionex CMD-I Carbohydrate Membrane Desalter is a cation-exchange membrane device that removes sodium ions from the eluent stream after oligosaccharide detection.

This device exchanges >99% of eluent sodium ions (up to 0.35 M at 1.0 mL/min) for hydronium ions, generating dilute acetic acid that can then be quantitatively removed by vacuum evaporation.

The CMD-I automatically reduces the eluent pH and removes sodium ions online following high pH anion-exchange chromatography with pulsed amperometric detection (HPAE-PAD). HPAE-PAD detects carbohydrates at low picomole levels with good recoveries (75-100%) without the need for derivatisation.

At high pH, and at ionic strengths up to 0.25 M sodium acetate, neutral and charged oligosaccharides are resolved on the basis of branch, linkage, and positional isomerism using a CarboPac PA-100 column.

The postcolumn use of the CMD-I eliminates the need for dialysis steps and minimises sample handling before subsequent MS or enzymatic analyses of HPAE-PAD purified oligosaccharides.