Optimization of resolution in micellar electrokinetic chromatography via computer-aided variation of concentrations of sodium dodecyl sulfate and acetonitrile as modifier

A computer-aided method is presented, that permits optimizing simultaneously the concentrations of an anionic surfactant (sodium dodecyl sulfate) and the modifier acetonitrile in the separation buffer in micellar electrokinetic chromatography (MEKC) on the basis of four test runs. The presented method was developed for the separation of non-polar solutes. The underlying algorithm takes into account that resolution in MEKC is dependent on selectivity, retention factor and the ratio hold-up time/migration time of the micelles (t(O)/t(M)). It is shown that with high surfactant concentrations and high acetonitrile concentrations a nearly infinite elution range is approached. The presented optimization method is applied to the separation of biogenic amines derivatized with dansyl chloride. It is shown that under the conditions usually employed in MEKC up to a volume fraction of acetonitrile in the separation buffer of 0.20 the critical micellar concentration of the surfactant investigated is increased only to a small extent.