ELECTROOSMOTICALLY DRIVEN ELECTROCHROMATOGRAPHY OF ANIONS HAVING SIMILAR ELECTROPHORETIC MOBILITIES BY ION-PAIRING

Anions of similar electrophoretic mobility are separated using an electrochromatographic technique which involves partitioning the anions, with the aid of the ion-pairing agent, tetrabutylammonium (TBA) cation, onto the surface of a reversed-phase open-tubular capillary liquid chromatographic (OTCLC) column. The anions separate based on differences in retention rather than differences in electrophoretic mobility. Resolution is easily controlled by varying the concentration of TBA in the buffer. Complete separation of anions having similar mobilities is achieved with as little as 600-mu-M TBA. Mass transfer broadening is inherently smaller for this electroosmotically driven system than that for pressure-driven OTCLC. The efficiency achieved for such a separation in a 40-cm column (N = 140 000) is twice that for a similar chromatographic separation and nearly equal to that for a similar, but poorly resolved, capillary zone electrophoretic separation.