Solvation characteristics of pressurized hot water and its use in chromatography

The influence of temperature in the range 75-180 degrees C on the solvation properties of pressurized water is studied by use of chromatography for a varied group of compounds on a porous polymer sorbent PLRP-S 100, The solvation parameter model is used as the basis of a quantitative comparison of the influence of temperature and solvent composition variation on the elution strength and selectivity of the mobile phase. The predominant influence of increasing temperature on the solvation properties of water is to reduce its cohesion and capacity for hydrogen-bond interactions. Even at 189 degrees C, however, hot water retains sufficient of its room temperature properties to remain a relatively weak eluting solvent in reversed-phase chromatography compared with aqueous mixtures of miscible organic solvents. Changes in selectivity accompanying composition variation for acetonitrile, methanol, and propan-2-ol are quantitatively different from those demonstrated for temperature variation of pressurized water, indicating that for method development the two processes are complementary rather than redundant.