The Research Of Subcritical Water Chromatography

The chromatographic behavior of some phenols on a PRP-1 column was investigated by using subcritical water as mobile phase. Differences in the properties of subcritical water, conventional acetonitrile/water and methanol/water mobile phase for reversed phase separations are explored. The transfer enthalpies and entropies of hydroxyl and nitryl in different mobile phase systems were compared by van't Hoff curve. Results suggest that the presence of acetonitrile and methanol in the mobile phase may decrease interaction of solute and stationary phase with respect to subcritical water, thereby reducing entropy contribution to the retention. Retention mechanisms of phenolic compound appear to be more similar in subcritical water and water/methanol systems on the PRP-1 column. Hydrogen bond in subcritical water system plays a very important role in the retention of the phenols.The diffierence on separation behavior of phenols in 1% methanol-water, 5% methanol-water, 1% acetonitrile-water, and 5% acetonitrile-water systems was explored at 110 ? and 130 ?. Much less retation times of phenols and symmetrical peak was found with organic entrainer. The transfer enthalpies and entropies of phenols, hydroxyl and nitryl in SubWC systems modified by different entrainers were analytical by van't Hoff curve. Results suggest that the presence of 1% methanol or 1% acetonitrile influences the ?H0 and ?S0 of phenols little, while 5% acetonitrile gives higher ?H0 and ?S0. It is concluded organic entrainer has little effect on the ?H0 and ?S0 of hydroxyl. But adding 5% methanol or 5% acetonitrile elevate those of nitryl.Six phenols were better separated using temperature programming on PRP-1 column. Temperature programming allows one to improve SubWC selectivity to a large degree, to separate complex samples, and inprove peak pattern and column efficiency.The effect of adding methanol or ethanol into pure water on separating phenols by temperature programming was studied. Relative to pure water SubWC, the one modified by two factors can separate phenols better at lower temperature faster.