Novel way of separating polyfluorocarboxylic acids by ion-exclusion chromatography.

Ion-exclusion chromatography has been successfully applied to the separation of a number of polyfluorocarboxylic acids. The separation of various mono- and dibasic polyfluorocarboxylic acids having a different alkyl group was investigated using a polymethacrylate-based weakly acidic cation-exchange resin (TSK gel OApak-A) in the H -form and conductimetric detection. When water was used as the eluent, polyfluorocarboxylic acids could not be resolved. When an aqueous solution of sulfuric acid, benzoic acid, o-phthalic acid, 1,3,5-benzenetricarboxylic acid, 1,2,4,5-benzenetetracarboxylic acid, and tartaric acid was used, the separation of polyfluorocarboxylic acids occurred for monobasic ones. While, for fluorine-containing dibasic acids, imperfect separation of peaks occurred. In order to improve their separation, the effect of an addition of organic modifiers such as methanol, 2,2,2-trifluoroethanol and 2H-hexafluoro-2-propanol in the eluent was also investigated.