New device for controlling the amount of methanol in carbon dioxide mobilephase for supercritical fluid chromatography

A new device to accurately deliver a small amount of methanol into supercri tical carbon dioxide fluid is described. Carbon dioxide, the most widely us ed mobile phase in supercritical fluid chromatography, is a relatively non- polar fluid, and hence the addition of a small amount of methanol could cha nge the solvent strength of the mobile phase. In this work, supercritical C O2 and methanol are delivered from the pump to a 100-mu1 mixing chamber in which a small magnetic bar is rotating. After passing through the mixing ch amber, supercritical CO2 is changed to a new mobile phase with different po larity. The modified mobile phase was successfully used for the separations of polar compounds and polyaromatic hydrocarbons (PAHs). (C) 2001 Elsevier Science B.V. All rights reserved.