Separations of Carbohydrates on Charcoal Columns in the Presence of Molybdate

Abstract

THE elution of certain carbohydrates from charcoal– ‘Celite’ columns by aqueous ethanol is accelerated when the column is impregnated with, and the eluent contains, borate ions in an alkaline environment¹. Only those carbohydrates which form strong complexes with borate ions are appreciably affected in this manner. A wider applicability of this technique for fractionating carbohydrate mixtures would ensue if complexing agents other than borate ions could be employed in neutral and acidic media. It is known² that chromate, molybdate and tungstate ions react with polyalcohols and cause changes in their specific rotations. The influence of pH on the specific rotations of aqueous solutions of mannitol which separately contain these ions has been investigated. By far the greatest change in the specific rotation occurs in the presence of molybdate ions, and it is a maximum at pH less than about 2.5 (Fig. 1). A maximum of two molybdate ions may complex with each mannitol molecule (Fig. 1) (cf. ref. 2).