Comparison of elution strength, column efficiency, and peak symmetry in subcritical water chromatography and traditional reversed-phase liquid chromatography Original Research Article

In this study, the elution strength of subcritical water has been investigated by matching the retention times of catechol, aniline, and pyridine using subcritical water, acetonitrile–ambient water, or methanol–ambient water mixtures as the eluent. Separations were performed on Chromatorex C-18, Zorbax RX-C-18, and poly(styrene-divinylbenzene) columns. The separation temperature ranged from 60 to 200 °C depending on columns used. It was found that a temperature rise of 40 °C for pure water mobile phase resulted in shortening retention time of at least the last eluting solute in each mixture by approximately 50%. The column efficiency study showed that subcritical water separation was more efficient than traditional separations using organic solvent–ambient water mixtures on the PRP-1 column. When temperature was increased, peak symmetry in subcritical water separation was mostly improved. This tendency was observed for separations on all three columns.