Buffered superheated water as an eluent for reversed-phase high performance liquid chromatography

Inorganic buffers have been used to control the pH of a superheated water eluent for reversed-phase liquid chromatography. Using a temperature gradient from 70–190 °C, the relative order of elution of a series of sulfonamides on a polystyrene-divinyl benzene column was determined at pH 3, 7 and 11. The separations were compared with conventional reversed-phase separations on polymer and ODS-bonded silica columns. The apparent pKa values of selected sulfonamides at elevated temperatures were determined from their retention factors across in a range of superheated buffers and the values were compared to those reported at room temperature.