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

A new device to accurately deliver a small amount of methanol into supercritical carbon dioxide fluid is described. Carbon dioxide, the most widely used mobile phase in supercritical fluid chromatography, is a relatively non-polar fluid, and hence the addition of a small amount of methanol could change the solvent strength of the mobile phase. In this work, supercritical CO2 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 chamber, supercritical CO2 is changed to a new mobile phase with different polarity. 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.