Abstract
The separations of eleven thiazide and related sulfonamide diuretics using superheated water chromatography at up to 200 A degrees C on an XBridge C18 column were compared with conventional liquid chromatography at ambient temperature. Most of the sulfonamide diuretics were thermally stable, but many of the thiazides were degraded. The most sensitive were the dihydrothiazides, including cyclopenthiazide and hydrochlorothiazide, which were converted to the corresponding aminobenzenedisulfonamides in the pre-column heater. The N-methyl thiazides, including methyclothiazide, appeared to be more stable but degraded on the column and of the thiazides, chlorothiazide eluted largely unchanged although some on-column degradation was observed for benzthiazide. The results confirmed that in superheated water chromatography problems may be encountered with analytes with low storage stability at ambient temperature.