TEMPERATURE PROGRAMMING IN MACROCYCLE-BASED ION CHROMATOGRAPHY

The well documented affinity of macrocyclic ligands for alkali and alkaline earth metal cations has been exploited in performing chromatographic separations of both cations and anions. It is shown that because the complexation reaction of metal ions with macrocycles is exothermic, the column capacity, and hence the retention of ions, is decreased as the column temperature is increased. While ion retention in classical ion exchange is also a function of temperature, the effect is less pronounced than in macrocycle-based systems. Temperature gradient elution of anions on macrocycle-based columns is performed based on the decrease of column capacity as the temperature is increased, showing improvements over separations performed under isothermal conditions.