ADDITION AND MEASUREMENT OF METHANOL IN CARBON-DIOXIDE MOBILE-PHASE FOR SUPERCRITICAL-FLUID CHROMATOGRAPHY

A simple method for the addition of methanol to supercritical CO2 is d escribed. Carbon dioxide, the most widely used mobile phase in supercr itical fluid chromatography, is a relatively non-polar fluid, and henc e addition of small amounts of polar modifiers could be necessary to m igrate polar solutes. In this paper, a new mixing device was developed , in which high porous stainless steel filters were used to generate m ethanol-modified carbon dioxide mobile phase. When supercritical CO2 g oes through the mixing device, the modifiers held within the small por es of filters can be dissolved in the pressurized supercritical fluids . High porous stainless steel filter with 2 mu m porosity was used in our mixing device. To measure the amount of methanol dissolved in supe rcritical CO2 after the mixing device, a fuel cell type modifier senso r, which was made by depositing gold and platinum on a porous plastic disc was used.