Addition and measurement of water in carbon dioxide mobile phase for supercritical fluid chromatography

A method for the addition of water to supercritical CO2 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 small amounts of polar modifiers could be necessary to migrate polar solutes. In this work, supercritical CO2 is delivered from the pump to a µ-Porasil column that is saturated with water. After passing through the µ-Porasil column, supercritical CO2 is changed to a new mobile phase with different polarity, and it is possible to separate polar samples by using this new mobile phase. The amount of water dissolved in supercritical CO2 is measured by an amperometric microsensor, which is prepared from a thin film of perfluorosulfonate ionomer.