Optimization of the separation of polycarboxylic acids by capillary zone electrophoresis

The optimization of electrolyte systems for the separation and detection of polycarboxylic acids using capillary zone electrophoresis is described. A borate buffer in the pH range 9-10 was chosen for the separation. The factors affecting separation selectivity include the addition of complexing reagents, such as alkaline earth metal ions and cyclodextrins, to the carrier electrolyte. A model can be developed that is based on the chemical complexation equilibria and allows the prediction of migration times and optimum carrier electrolyte compositions. Five experiments were found to be sufficient for establishing optimum separation conditions for 18 di- and tricarboxylic acids. UV detection at 185 nm was feasible for both aromatic and aliphatic carboxylic acids. The technique can be applied to the determination of the carboxylic acid composition of alkyd resins and similar technical products.