SEPARATION OF BENZENE POLYCARBOXYLIC ACIDS BY PACKED-COLUMN SUPERCRITICAL FLUID CHROMATOGRAPHY USING METHANOL CARBON-DIOXIDE MIXTURES WITH VERY POLAR ADDITIVES

Packed column supercritical fluid chromatography (SFC) can be used to separate much more polar solutes than is generally recognized. Polyfunctional benzene carboxylic acids, including benzene mono-, di-, tri-, tetra-, and hexacarboxylic acids, are rapidly separated using packed columns. Mobile phases consist of small amounts of a very polar additive, like citric acid or trifluoroacetic acid dissolved in methanol and mixed with carbon dioxide. Without the additive, few of the solutes elute and peak shapes tend to be poor. The hexacarboxylic acid is rapidly eluted with a modifier concentration below 10%.