Studies on the long-term thermal stability of stationary phases in subcritical water chromatography

The long-term thermal stability of five commercially available reversed-phase columns has been evaluated under subcritical water conditions (100 and 150 °C). The five columns included Zorbax RX-C8, Nucleosil C18 AB, Hypersil BDS C18, PRP-1 (poly(styrene–divinylbenzene)), and ZirChrom-PS (polystyrene) columns. Retention factors, plate numbers, and peak areas were monitored over a prolonged period of time. Comparing the three silica-based columns, the Zorbax RX-C8 column was the most stable followed by the Nucleosil C18 AB column. The Hypersil BDS C18 column was the least stable under subcritical water conditions. The ZirChrom-PS column was stable at 100 °C for at least 7600 column volumes. Of all five columns, the polymeric PRP-1 column was the most stable under subcritical water conditions.