Separation of sulphonamides and determination of the active ingredients in tablets by micellar electrokinetic capillary chromatography.

The separation and determination of seven sulphonamides and trimethoprim by micellar electrokinetic capillary chromatography were successfully achieved, employing sodium dodecyl sulphate (SDS) as a micellar phase and tetrabutylammonium bromide as additive. The effects of surfactant and modifier concentrations, pH and applied voltage on the retention behaviour of the solutes and the column efficiency were studied. The migration time of sulponamides increase with increasing SDS concentration and decreasing the applied voltage, but varies only slightly with pH. There is an optimum applied voltage at which a higher theoretical plate number is achieved, in contrast to the sulphonamides, the retention behaviour of trimethoprim gave a more obvious response to changes in the experimental conditions. The determination of three active ingredients in tablets was performed using sulphathiazole as an internal standard with good results. The theoretical plate number ranged between 2.0 x 10(5) and 2.8 x 10(5) with a 50-cm capillary.