Analytical Sciences

Adsorption-Partition Switching of Retention Mechanism in Ice Chromatography with NaCl-doped Water-Ice

Yuiko TASAKI and Tetsuo OKADA

Department of Chemistry, Tokyo Institute of Technology, Meguro, Tokyo 152-8551, Japan

A liquid phase is coexistent with water-ice prepared from a brine solution at any temperature above the eutectic point of the system. Ice chromatographic measurements have provided information on the liquid phase in an ice particle prepared from NaCl. The growth of the liquid phase causes the alternation of the dominant separation mechanism from the adsorption on the ice surface to the partition into the liquid phase, resulting in an increase in the retention of a water-soluble probe. When the liquid phase is developed, the retention is well explained by the partition coefficient determined with bulk solvents, suggesting that all of the liquid pools in a water-ice particle are connected to each other. In contrast, only a part of the liquid pools act as a stationary phase when the volume of the liquid phase is small. A model, which assumes the homogenous distribution of a salt in an ice particle and spherical shapes of a liquid pool, has allowed the estimation of its size.

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