Organic electrolytes with negatively chargeable functional groups such as benzoic acid (BA, weak acid), benzenesulfonic acid (BSA, strong acid), and p-aminobenzoic acid (p-ABA, ampholyte) were concentrated through polyethylene (PE) films photografted with 2-(dimethylamino)ethyl methacrylate (DMAEMA) by electrotransport. The permeabilities of DMAEMA-grafted PE (PE-g-PDMAEMA) films to BA and BSA were considerably increased by the application of direct current at pH 6. BA and BSA could be selectively permeated from the respective binary BA/phenyl-1,2-ethandiol (PhED, neutral) and BSA/PhED mixtures by making use of the difference in their permeabilities. In addition, BSA was selectively permeated from the binary BSA/BA mixtures. The organic electrolytes mentioned above were transported against their concentration gradient toward the anode side and their degrees of concentration went up to 90% by the continuous application of direct current. The degrees of concentration for organic electrolytes obtained by electrotransport in this study were slightly higher than those obtained by the uphill transport using the PH difference across the PE-g-PDMAEMA film, and the concentration time was considerably shortened. It was made clear that the electrotransport through the PE-g-PDMAEMA films is one of the effective techniques to selectively separate or concentrate organic electrolytes with negatively chargeable functional groups. (C) 2003 Wiley Periodicals, Inc.