High-speed Liquid Chromatography of Sugar Acids on An- Ion-exchange Resins

Mixtures of aldonic and aldaric acids are difficult to analyse. Aldonic acids can be separated in a satisfactory way on anion-exchange resins with a solution of sodium chloride as eluent. Under these circumstances, however, aldaric acids show unacceptably long elution times and peak broadening. The ability of aldaric acids to form non-adsorbable complexes with magnesium ions lowers their elution times, particularly of the low-molecular-weight acids, by up to 25 fold. This effect can be controlled by adjusting the magnesium ion concentration in the eluent. It is thus possible to achieve rapid, accurate analysis of mixtures of aldonic and aldaric acids by a proper choice of the magnesium and chloride ion concentrations in the eluent.