Properties of subcritical water as an eluent for reversed-phase liquid chromatography—Disruption of the hydrogen-bond network at elevated temperature and its consequences

The use of subcritical water as an eluent for reversed-phase liquid chromatography is further explored. Shape selectivity as well as thermodynamic values for solute transfer were measured and compared to those seen with traditional ambient methanol/water and acetonitrile/water mobile phases. Linear solvation energy analysis was also used to analyze extrapolated values of the retention factor in pure water at ambient temperatures ( k ′ w ) for subcritical water and ambient hydroorganic mobile phases. Results indicate that it is likely that a large disruption in the hydrogen-bonding network of water at high temperatures causes unique chromatographic selectivity, as well as prohibits accurate extrapolation from high temperature to ambient conditions using pure water. Additionally, subcritical water was not found to be a suitable mobile phase for determining k ′ w for use in estimating octanol/water partition coefficients.