Characterization of the polarity of subcritical water.

The polarity of subcritical water was studied solvatochromically with betaine dye (33) across a temperature range of 30°C-180°C and a pressure range of 13.8bar (200psi) to 124bar (1800psi). It was observed that temperature has a greater effect than pressure on the polarity of subcritical water. In addition, subcritical water was compared with traditional hydro-organic mobile phases and the polarity of subcritical water was found to be comparable to a range of 30%-50% methanol/water and a range of 20%-30% acetonitrile/water mobile phases. It was concluded that subcritical water is more suited to separations involving slightly polar and polar compounds than more nonpolar analytes.