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 solva tion parameter model is used as the basis of a quantitative comparison of t he influence of temperature and solvent composition variation on the elutio n strength and selectivity of the mobile phase. The predominant influence o f increasing temperature on the solvation properties of water is to reduce its cohesion and capacity for hydrogen-bond interactions. Even at 189 degre es C, however, hot water retains sufficient of its room temperature propert ies to remain a relatively weak eluting solvent in reversed-phase chromatog raphy compared with aqueous mixtures of miscible organic solvents. Changes in selectivity accompanying composition variation for acetonitrile, methano l, and propan-2-ol are quantitatively different from those demonstrated for temperature variation of pressurized water, indicating that for method dev elopment the two processes are complementary rather than redundant.