Isolation of ibuprofen enantiomers and racemic esters through electrodialysis

Abstract

The electrodialysis of pure rac-ibuprofen and the products of the enzymatic kinetic resolution of the profen were investigated in order to establish the best conditions for the separation of the ibuprofen from the ethyl esters. The enzymatic esterification of rac-ibuprofen with ethanol (used as solvent and acyl-aceptor) was catalyzed with Novozym®435 at the optimum conditions investigated previously. The reaction product mixtures possess about 60% of ibuprofen (enriched in the S-enantiomer) and 40% of the racemic esters.An electrodialysis cell composed by four compartments separated by cation-, anion- and cation-exchange membranes was developed allowing the selective migration of ibuprofen avoiding its decomposition on the electrodes. In fact, the stainless steel electrodes submerged in ammonium formate solutions were separated from the compartments containing the profen (~200 ppm in ethanol, pH 6.81–6.34) with cation-exchange membranes. The best separation performance was reached after 6 h of operation at 60 V with an anion-exchange membrane that led up to 57% extraction of ibuprofen from the products of the enzymatic esterification in ethanol media. The membrane allowed the selective migration of both stereoisomers and a negligible quantity of the ethyl esters.