Ice Chromatographic Characterization of Thin Liquid Layer at the Interface between Water-Ice and Organic Solvent

The quasi-liquid layer (QLL) on the surface of water-ice has been studied by ice chromatography, in which water-ice particles are used as a stationary phase. We have, in previous papers, demonstrated that solutes are retained on the ice stationary phase with hexane-based mobile phases and have revealed that the hydrogen bonds between a solute and the dangling bonds on the surface of water-ice are responsible for retention at such low temperatures as −12.0 to −5.0 °C. However, increasing the temperature allows the shift of the principal retention mechanism from the hydrogen-bond adsorption to the partition into the QLL; this has been confirmed by drastic changes in the retention of probe solutes. The threshold temperature, at which the retention shift occurs, depends on the concentration and type of a polar component added to the mobile phase. Thus, the QLL developed in the present system contains not only water but also a polar component added to the mobile phase. This phenomenon occurs at a temperature much lower than that predicted from the lowering of the freezing point due to the dissolution of a polar component in water and, thus, is a surface process rather than a bulk phase transition.