Separation and pulsed amperometric detection of alditols and carbohydrates by anion exchange chromatography using alkaline mobile phases modified with Ba(II), Sr(II), and Ca(II) ions

The effect of some divalent nonelectroactive cations (DNCs) in the anion-exchange chromatographic separations with alkaline mobile phases of carbohydrates and alditols was investigated; the ions examined at a typical concentration of 1 mM were Ca(II), Ba(II), and Sr(II). The use of these cations in the eluent as their corresponding acetates or nitrates has been found to yield at least a twofold effect. First, the peak symmetry and concurrently the column efficiency is greatly improved. Second, the presence of Ba(II) or Sr(II) significantly enhances the response of all analytes investigated in pulsed amperometry at a gold working electrode. The action of the DNCs on the separation seems to be related to a very effective removal of carbonate ion from the alkaline eluent and, especially, their ability to complex cyclic and acyclic polyhydroxy compounds. Efficiency estimated from data calculated at 10% of peak height can increase by as much as 25% with a comparably lower RSD (15%, n = 9), From the viewpoint of the separation efficiency and reproducibility of chromatographic data, all divalent inorganic ions employed were well-behaved. However, only the use of Ba(II) or Sr(II) is recommended since alkaline mobile phases containing Ca(II) ion negatively affect the gold electrode response of some analytes.